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We hypothesize that syncytin-Rum1, bovine endogenous retrovirus-K1 (BERV-K1), pregnancy-specific protein-B (PSP-B), and interferon-τ (IFN-τ) will be influenced by maternal nutrient restriction and be differentially expressed during key stages (day 16, 34, and 50) of the establishment of gestation when fed to meet industry standards. Commercial crossbred heifers (n = 49) were maintained on a total mixed ration and supplemented with dried distillers grains with solubles. All heifers were subjected to 5-d CO-Synch + CIDR estrus synchronization protocol. Non-pregnant, non-bred control (NP-NB) heifers (n = 6) were ovariohysterectomized on day 16, and the remaining heifers were AI to a single Angus sire (day of breeding = day 0). On the day of breeding, heifers were randomly assigned to dietary treatments. One half were assigned to control treatment (CON) targeted to gain 0.45 kg/d, and the remaining half were assigned to restricted treatment (RES), which received 60% of control diets. Heifers were subjected to ovariohysterectomy on day 16, 34, or 50 of gestation. Utero-placental tissues were obtained from the uterine horn ipsilateral (P) and contralateral (NP) to the corpus luteum and separated into maternal caruncle (CAR), maternal endometrium, inter-caruncle, (ICAR), and fetal membrane (FM). There were no interactions between stage of gestation and nutritional treatment for syncytin-Rum1 or PSP-B (P > 0.22). Expression of BERV-K1 was influenced by a treatment × stage of gestation interaction (P = 0.03) in NP-CAR. On day 50, heifers fed the CON diet had greater BERV-K1 expression compared with CON heifers on day 16 and 34 and RES heifers at all sampling time points. There was a treatment × stage of gestation interaction (P < 0.01) for IFN-τ in FM tissue. On 16 d, mRNA expression of IFN-τ was greater (P < 0.01) compared with day 34 and 50 for both CON and RES heifers, but RES FM had greater (P < 0.01) IFN-τ expression compared with CON FM. In P-CAR, PSP-B expression increased (P < 0.01) by 18 000-fold on day 50 compared with NP-NB heifers. In P-ICAR, expression of syncytin-Rum1 in P-ICAR was greater (P = 0.01) on day 16 with a 14.14-fold increase compared with relative expression on day 34 and 50; whereas, PSP-B was increased (P < 0.01) on day 34 and 50 compared with day 16. In conclusion, 40% nutrient restriction had limited influence on mRNA of ERVs, PSP-B, and IFN-τ but stage of gestation differences reinforced the importance of these genes during the establishment of pregnancy.

A 2 × 2 factorial experiment was conducted to evaluate the effects of dietary corn type (waxy corn [WC] vs. nonwaxy corn [NC]) and fasting period (2 h vs. 12-16 h) before slaughter on growth and plasma index in weaning pigs. Twenty-four crossbred barrows (8.26 ± 0.47 kg) were allotted to 4 treatments with 6 replications of 1 pig per replicate metabolism cage. Waxy corn contained less fat, a lower amylase:amylopectin ratio, more CP, and more starch than NC. Pigs fed the WC diet had lower jejunum digesta pH compared with those fed the NC diet ( < 0.05). Maltase activity in the jejunum and ileum mucosa ( < 0.01), sucrose activity in the ileum mucosa ( < 0.01), and amylase activity in the pancreas and jejunum digesta ( < 0.05) were increased in pigs fed the WC diet relative to those fed the NC diet. But the total tract apparent digestibility (TTAD) of starch and CP was lower for the WC group ( < 0.05). Ingestion of the NC diet resulted in higher ( < 0.05) ADG and ADFI in the second week but did not affect ADG ( = 0.091) and the feed:gain ratio (F:G; = 0.077) during the whole experiment period. The plasma glucose ( < 0.01) concentration was higher and high-density lipoprotein cholesterol (HDL-C; < 0.01) concentrations was lower in the hepatic portal vein in pigs fed the WC diet relative to those fed the NC diet. Fasting 2 h before slaughter decreased the jejunum and ileum digesta pH compared with the 12-h fasting group ( < 0.01). Villus height increased in the duodenum ( < 0.01) and jejunum ( < 0.05) and the villus height:crypt depth ratio increased in the duodenum ( < 0.05) of pigs after shortening the fasting period before slaughter. Shortening the fasting time before slaughter resulted in higher plasma glucose ( < 0.05) concentrations and a higher HDL-C:low-density lipoprotein cholesterol (LDL-C) ratio ( < 0.05) whereas the LDL-C ( < 0.05) concentrations were reduced in the hepatic portal vein. The results of this experiment indicate that although the production performance of both WC and NC diets is equal, the glucose concentration is higher and HDL-C is lower in the portal vein for the WC diet, and fasting time before slaughter has an influence on the plasma index and intestinal morphology in weaning pigs.

Compensatory growth in response to feed restriction (FR) affects deposition rates of lean and adipose tissues. It is, however, unclear whether pigs with low birth weight differ from their counterparts with normal birth weight with regard to compensatory growth. Female littermate pigs with low (UW; 1.1 kg) and normal (NW; 1.5 kg) birth weight were fed to appetite (control, CON) or feed restricted (RES) at 60% of DMI of the CON group between 78 and 98 d of age and subsequently refed at the level of the CON group until 131 d of age. Subgroups of pigs were slaughtered at 75, 98, 104, and 131 d of age to compare BW and body composition. Blood samples were taken at 98 and 119 d of age to analyze plasma metabolites and hormones. At birth UW pigs were shorter and had lower BW until 131 d of age than NW pigs ( < 0.05). Feed intake per kilogram of BW was greater in UW than in NW pigs ( < 0.01). The UW and NW pigs differed in carcass composition as indicated by greater relative subcutaneous fat at 75 d ( < 0.1), greater shoulder back fat ( < 0.05) at 98 d, and lower carcass weight at 131 d with greater abdominal and subcutaneous neck back fat in UW compared with NW pigs ( < 0.05). During FR, BW gain of RES pigs was lower than in NW pigs. The RES pigs showed greater feed intake after termination of FR until 131 d than CON pigs ( < 0.01). At 98 d RES pigs were leaner than CON pigs ( < 0.05). After 6 d of refeeding (104 d) relative fat depot weights were still smaller ( < 0.03) in RES pigs than in CON pigs. After 5 wk of refeeding, RES pigs had lower abdominal fat weights and greater plasma cortisol levels than CON pigs ( < 0.05). Regarding the plasma metabolite and hormone response, at 98-d fasting levels of plasma NEFA and glycerol were greater in RES than in CON pigs ( < 0.05), and after the drop in their levels after morning feeding ( < 0.001), plasma NEFA and glycerol and also triacylglycerol increased until the next meal in RES vs. CON pigs ( < 0.01). Plasma cortisol was greater in RES pigs after 3-wk FR ( < 0.05), whereas only a trend for increased plasma adrenalin concentrations in RES pigs at the end of the FR period and after 5 wk of refeeding was found ( < 0.1). In conclusion, UW pigs at 75 d of age (20 to 23 kg BW) had greater subcutaneous fat, whereas at 131 d (61 to 68 kg BW) they showed greater abdominal fat than NW pigs, suggesting that subcutaneous fat is deposited earlier than abdominal fat. The FR caused similar changes in body composition, plasma lipids, and stress hormones in UW and NW pigs.

The impact of acute stressors (24-h feed or water deprivation) on growth performance, intestinal characteristics, and serum stress markers in weaned pigs was evaluated. Pigs (6.21 ± 0.29 kg) were allotted in a randomized complete block design to 4 treatments on the basis of BW at the time of weaning. There were 8 mixed-sex pigs in each of 12 pens per treatment. Treatments were arranged as a 2 × 2 factorial and consisted of a feed or water stressor that included a 0- or 24-h deprivation period postweaning, and pigs were subsequently allowed access to feed and water. Growth performance was measured 1, 7, 14, and 28 d postweaning. Serum and intestinal samples were taken 1 and 7 d postweaning. Serum was analyzed for cortisol and corticotrophin-releasing factor, and villus height, crypt depth, and mast cell density were measured in the jejunum and the ileum. Expression of mucin (MUC2), tumor necrosis factor α (TNF-α), interleukin 6 (IL-6), claudin 1 (CL-1), occludin (OC), and zonula occludens 1 (ZO-1) genes were measured on d 1 and 7 postweaning in the jejunum and ileum by real-time PCR. There was a decrease (P < 0.05) in ADG with the water stressor 1 d postweaning, although subsequently, there were improvements (P < 0.05) in ADG and feed efficiency. Furthermore, the water stressor reduced ADFI during the last 14 d of the trial and cumulatively (P < 0.05). Seven days postweaning there was an increase (P < 0.05) in jejunal villous height to depth ratio due to the feed stressor and a decrease (P < 0.05) in the ileal villous height to depth ratio due to the water stressor. There was an increase (P < 0.05) in serum cortisol levels due to the water stressor both 1 and 7 d postweaning. Furthermore, there was an increase in serum corticotrophin-releasing factor 1 d but not 7 d postweaning due to the water stressor (P < 0.05). The feed stressor reduced (P < 0.05) TNF-α gene expression, and the water stressor reduced (P < 0.05) OC gene expression in the jejunum 1 d postweaning. In the ileum, there was a reduction in CL-1 and ZO-1 gene expression (P < 0.05) due to the water stressor 7 d postweaning. The results from the current investigation showed that a 24-h feed or water deprivation at the time of weaning has negative impacts on growth performance, intestinal characteristics, and serum stress responses immediately following the stress event and throughout the nursery period.

The effects of feed withdrawal time before slaughter on finishing pig carcass composition were evaluated in 2 studies. In Exp. 1, 728 pigs (BW = 128.9 ± 1.2 kg) were allotted to 1 of 4 treatments in a randomized design with number of pigs per pen and location within barn balanced across treatment. The 4 treatments were feed withdrawal times of 8, 24, 36, or 48 h and there were 12 replicate pens per treatment. Before feed withdrawal, pigs were fed a standard corn-soybean meal diet containing dried distillers grains with solubles (DDGS), bakery coproducts, and 5.0 mg/kg ractopamine HCl. Feed withdrawal time decreased (linear; P < 0.02) live weight, HCW, and backfat while increasing percentage yield (quadratic; P < 0.01) and fat-free lean index (FFLI; linear; P < 0.001). In Exp. 2, 843 pigs (BW = 125.4 ± 1.6 kg) were used to determine the impact of feed withdrawal on growth, carcass, blood lactate, and meat quality. There were 4 treatments: withholding feed for 8, 12, 24, or 36 h, with 10 replicates per treatment. Pigs were fed a common corn-soybean meal-based diet containing 20% DDGS and 5.0 mg/kg ractopamine HCl. Withholding feed decreased (linear; P < 0.001) live weight, ultimately resulting in decreased (P < 0.01) HCW. There were no differences in FFLI or backfat, but percentage yield (linear; P < 0.001) increased with longer withdrawal times. Carcass contaminations by stomach contents escaping from the oral cavity after shackling (leaking ingesta) or visible fecal contamination of the exterior of the carcass (runny bung) were also measured. Although withholding feed did not affect runny bung, it increased (linear; P < 0.001) the incidence of leaking ingesta, whereas blood lactate, visual color score, and purge loss were unaffected. Withholding feed increased 45-min pH (quadratic; P > 0.02) and ultimate pH (linear; P < 0.01) and increased (quadratic; P < 0.03) visual marbling score. Withholding feed decreased (linear; P < 0.001) feed intake, resulting in feed savings of up to 3 kg/pig. Although several heavyweight pigs were removed before trial commencement and the variable number of remaining pigs per pen may have influenced the response to feed withdrawal, the present data indicates that finishing pigs can experience between 24 and 36 h of feed withdrawal without negatively affecting carcass composition. However, the increased incidence of leaking ingesta beyond 12 h of feed withdrawal is concerning.

The objectives were to evaluate the effects of nutrient restriction during early to midgestation followed by realimentation on maternal performance and organ mass in pregnant beef cows. On d 30 of pregnancy, multiparous, nonlactating cows (initial BW = 620.5 ± 11.3 kg and BCS = 5.1 ± 0.1) were assigned to 1 of 3 dietary treatments: control (CON; 100% NRC; n = 18) and restricted (RES; 60% NRC; n = 30). On d 85, cows were slaughtered (CON, n = 6; R, n = 6), remained on control (CC; n = 12) and restricted (RR; n = 12), or were realimented to control (RC; n = 11). On d 140, cows were slaughtered (CC, n = 6; RR, n = 6; RC, n = 5), remained on control (CCC, n = 6; RCC, n = 5), or were realimented to control (RRC, n = 6). On d 254, all remaining cows were slaughtered. Cows were weighed before slaughter and all maternal organs were dissected and weighed. The diet consisted of grass hay to meet 100 or 60% NEm recommendations for fetal growth and to meet or exceed recommendations for other nutrients. At d 85 slaughters, BW and empty BW (EBW) were not affected (P ≥ 0.84) by maternal nutrition. However back fat was decreased (P = 0.05) in RES vs. CON cows. Large intestine and abomasum mass were increased (P ≤ 0.05) in RES cows vs. CON. At d 140, BW was decreased (P = 0.05) and EBW tended to be decreased (P = 0.10) in RRC cows vs. CCC and RCC being intermediate. Liver mass was decreased (P = 0.02) in RR vs. CC with RC being intermediate. Ruminal mass was decreased (P = 0.003) in RR vs. CC and RC cows. At d 254, BW and EBW were similar (P ≥ 0.78) across treatments. We observed partial changes in maternal weight and organ masses due to different lengths of maternal nutrient restriction followed by realimentation. It appears that the dam undergoes some adaptations during an early to midgestation nutrient restriction and becomes more efficient in the utilization of nutrients after being realimented and as gestation advances.

Cattle weights can be highly variable and are influenced by many factors, including time of weighing, ambient temperature, feed intake, and cattle handling. A protocol of limit feeding has been in use since the 1980s that was designed to reduce variation in gut fill due to differences in intakes. Cattle are penned and fed a 50% hay, 50% wet corn gluten feed or grain diet (DM basis) at an estimated 2% of BW for at least 5 d, after which weights are taken on 2 consecutive d and averaged for a limit-fed BW (LFW). For this analysis, full-fed weights (FFW) also were taken before the limit-feeding period while cattle had ad libitum intakes. Data from 18 experiments were used to analyze differences within 2-d LFW and between LFW and FFW. For 10 of the 18 experiments, FFW also were measured on 2 consecutive d. Cattle included in this summary were grazing cornstalks, smooth bromegrass pasture, Bermuda grass pasture, fescue pasture, native range, or in a dry lot on a 70% forage diet. The largest differences between FFW and LFW for individual cattle were -39 to +44 kg over all 18 experiments. Differences between 2 consecutive d of LFW were -23 to +24 kg for all 18 experiments. Differences between 2 d of FFW were -14 to +34 kg in the 10 experiments measuring FFW on 2 consecutive d. There was not a clear relationship between FFW and LFW; each weighing scenario had unique environmental conditions that led to different relationships. Differences in both beginning and ending BW were compounded when calculating ADG. Average daily gain was calculated for 15 of the experiments on the basis of either LFW or FFW. Differences between LFW and FFW ADG were -0.29 to +0.31 kg/d. The maximum ADG based on FFW was 1.62 kg/d. This large ADG, on a forage based diet, was likely due to changes in gut fill rather than tissue gain. These data suggest that handling cattle in a similar manner when weighing is more important than limiting intakes to decrease variance between weights. However, limiting intake before collection of beginning and ending BW better estimates empty body weight of cattle, allowing for a more accurate determination of actual body tissue weight gain. Measuring weights accurately becomes especially crucial when evaluating multiple components within a system (e.g., cornstalks to pasture to feedlot). Feeding a standard diet between these components of the system minimizes differences in gut fill due to treatment and allows for a more accurate determination of each component's contribution to the total system.

The objective of this study was to evaluate the effects of the forage-to-concentrate ratio (F:C) of diets fed before and during short-term feed restriction (FR) on rumen fermentation, absorptive capacity of the reticulorumen, and apparent total tract digestibility. Twenty ovariectomized and ruminally cannulated Angus × Hereford heifers were blocked by BW and individually penned in box stalls (9 m(2)), having free access to water throughout the study. Heifers were randomly assigned to 1 of 2 dietary treatments, receiving either a high forage diet (HF; F:C of 92:8) or a moderate forage diet (MF; F:C of 60:40). Diets were fed ad libitum for 14 d before 5 d of baseline measurements (BASE) followed by 5 d of FR where heifers were restricted to 25% of ad libitum DMI relative to BASE. Dry matter intake was measured daily and ruminal pH was recorded every 2 min throughout the study. Ruminal fluid and blood samples were collected on d 3 of BASE and FR whereas short-chain fatty acid (SCFA) absorption was assessed in vivo using the isolated washed reticulorumen technique on d 5 of BASE and FR. Indigestible NDF was used as a marker to estimate apparent total tract digestibility. Diet × period interactions (P = 0.030 and 0.025) were detected for DMI and ruminal SCFA concentration, respectively. The interaction was the result of greater DMI and numerically greater SCFA concentration for MF than HF during BASE, with a reduction observed for both during FR, although treatment effects were no longer present. Period effects (BASE vs. FR) but not treatment effects (P > 0.05) were detected for mean ruminal pH (P < 0.001) and the total SCFA absorption rate (mmol/h; P = 0.038). During BASE, mean pH was reduced (6.4 vs. 6.9) and the SCFA absorption rate was greater relative to FR (674.5 vs. 554.8 mmol/h). Diet (P < 0.001) and period (P < 0.001) effects were detected for DM and OM digestibility with greater digestibility occurring for heifers fed MF than HF (70.5 vs. 63.3% for DM and 73.0 vs. 66% for OM) and greater digestibility during FR than BASE (69.5 vs. 64.3% for DM and 71.7 vs. 67.2% for OM). During FR, NDF digestibility was also greater than during BASE (P < 0.001; 62.4 vs. 55.8%). The effect of FR on serum NEFA differed by diet (diet × period, P < 0.001) with NEFA being greater for heifers fed HF than MF during FR (474.4 vs. 377.7 μEq/mL, respectively) with no differences observed between HF and MF during BASE. It can be concluded that severe short-term FR had a negative impact on ruminal SCFA absorption and energy balance and that altering the F:C of the diet does not mitigate these effects.

The objective of this study was to determine if the forage-to-concentrate ratio (F:C) of diets fed prior to and during (PRE) feed restriction (FR) and diets fed post-FR (POST) affect the recovery for DMI, ruminal fermentation, and short-chain fatty acid (SCFA) absorption following FR. Twenty ovariectomized and ruminally cannulated Angus × Hereford heifers were used in this study and were fed (ad libitum) either a high forage (HF; F:C = 92:8) or a moderate forage (MF; F:C = 60:40) diet for 19 d. Heifers were then exposed to a 5-d FR period where feed was restricted to 25% of ad libitum intake relative to that measured during the previous 5 d. After FR, heifers were provided feed ad libitum with one half of the HF and MF heifers receiving the HF or MF diet during the 3-wk recovery period (REC1, REC2, and REC3). This resulted in 4 treatment combinations separated over time (PRE-POST): HF-HF, HF-MF, MF-HF, and MF-MF. The PRE × POST interaction was not significant for any of the measured variables, and the PRE × POST × period interaction was only significant for the molar proportion of ruminal butyrate. For heifers fed HF PRE, DMI increased from REC1 to REC3 whereas DMI did not differ among periods for heifers fed MF PRE (PRE × period, P = 0.045). The duration that pH < 5.5 (PRE × POST; P = 0.003) was numerically greater during REC1 for heifers fed HF than MF PRE (191 vs. 98 min/d), with duration decreasing from REC1 to REC2 for heifers fed HF PRE. Total ruminal SCFA concentration and absorption rate were not affected by the diet fed PRE (P > 0.05) or period (P > 0.05). For heifers fed MF POST, DMI increased from REC1 to REC3 whereas DMI did not differ among POST periods for heifers fed HF POST (POST × period, P = 0.033). The duration that ruminal pH was <5.5 was greater for heifers fed MF than HF POST (274.9 vs. 14.1 min/d; POST × period, P < 0.001) with MF heifers decreasing duration from REC1 to REC2 whereas duration did not differ among periods for HF. Ruminal SCFA concentration and rate of absorption were not affected (P > 0.05) by diet fed POST. It is concluded that feeding a MF diet prior to and during FR improves the recovery response for DMI. Irrespective of the prefeeding, however, a HF diet is beneficial in the POST-restriction period because it most effectively alleviated ruminal pH reduction and hastened DMI recovery.

Drought and other weather-related disasters impact the amount and quality of grains and forages available to beef cattle. The impact of nutrient restriction at specific gestational timeframes on fetal skeletal muscle growth was examined. Crossbred beef cows were fed to NRC recommendations (CCC) or restricted to 60% of said levels for the first 85 or 140 d of pregnancy followed by realimentation to recommended protein and energy levels (RCC and RRC, respectively). Fetal infraspinatus (INF) morphometrics and gene expression analyses were performed at d 85, 140, and 254 of gestation. Results demonstrate that fetal primary myofibers are larger (P < 0.05) after 85 d of maternal caloric restriction by comparison to controls. Realimentation of pregnant dams at d 85 causes an increase (P < 0.05) in RCC INF cross-sectional area (CSA) by comparison to RRC at d 140 but the fibers remain smaller (P < 0.05) than CCC muscle cells. Returning nutrient load to recommended levels at d 140 of pregnancy increases RRC CSA equivalent to CCC fibers at d 254 (343.4 ± 5.2 and 345.2 ± 5.3 μm(2), respectively). Fetal RRC and CCC muscle fibers are smaller (P < 0.05) than RCC fibers at d 254 suggesting the later experienced compensatory growth. Numbers of Paired box 7 (Pax7) immunopositive cells were fewer (P < 0.05) in the nutrient restricted fetuses at d 85 suggesting a loss of muscle progenitor cells. Moreover, mRNA content for the collagen crosslinking enzymes, lysyl oxidase and bone morphogenetic protein 1, were greater (P < 0.05) in the d 85 nutrient restricted fetal INF than CCC suggesting increased connective tissue cell numbers and/or activity. Because myogenesis is acutely regulated by the IGF, mRNA content of these growth factors and their receptors was examined. Fetal IGF1 mRNA content was lower in the d 85 nutrient restriction fetuses (P < 0.05) by comparison to CCC. Levels of INF IGF2 mRNA were greater (P < 0.05) in d 85 NR fetuses than CCC. Continued nutrient restriction through d 140 resulted in a reduction (P < 0.05) in IGF2 expression by comparison to CCC. No treatment effect on IGF1R or IGF2R mRNA content was noted. In summary, NR for 85 d causes an increase in primary INF fiber size that may be a result of increased IGF2 transcription and Pax7-immunopositive cell fusion. Realimentation of NR beef cows supports compensatory growth of the fetal musculature such that normal muscle fiber size and muscle progenitor numbers are achieved before birth.

Our objective was to determine if the severity of short-term feed restriction (FR) affects the timeline for recovery of the absorptive function of the reticulo-rumen and barrier function of the total gastrointestinal tract in beef cattle. Eighteen ruminally cannulated and ovariectomized Angus × Hereford heifers were housed in individual pens. Heifers were blocked by initial BW into 3 blocks and, within block, randomly assigned to 1 of 3 treatments that differed in the severity of FR: heifers were restricted to 75, 50, or 25% of ad libitum intake. Treatments were imposed during a 5-d period of FR followed by 3 consecutive wk of recovery (REC1, REC2, and REC3). Throughout the experiment heifers were fed the same diet (60% forage:40% concentrate) for ad libitum intake (except during FR) and water was available at all times. Dry matter intake was measured daily and ruminal pH was recorded every 2 min during FR and recovery periods. Ruminal fluid and blood samples were collected on d 3 of the FR and d 5 of REC1 and REC3. Short-chain fatty acid (SCFA) absorption rates were evaluated on the last day of FR, REC1, and REC3 using the temporarily isolated and washed reticulo-rumen technique. On d 2 of FR and d 4 of REC1 and REC3, a 1 L solution of Cr-EDTA (180 mM) was dosed into the rumen followed by 48 h of total urine collection. Dry matter intake (% BW) increased rapidly in REC1 for heifers restricted to 75 and 50%; however, heifers restricted to 25% needed at least 2 wk to recover (treatment × period; P < 0.001). Regardless of the severity of FR, the duration that pH < 5.5 was the highest during REC1 (period P < 0.001). However, an interaction was found for the acidosis index, with pH × min/kg of DMI being greatest in heifers restricted to 25% on d 1 of the recovery period. A treatment × period interaction was found for the absolute absorption rate (mmol/h) of total SCFA (P = 0.009). The total SCFA absorption rate was not different for heifers restricted to 75 and 50% across periods, whereas an increase from FR and REC1 to REC3 was detected for heifers restricted to 25% of ad libitum intake. A treatment effect was observed for urinary Cr output (P = 0.027) indicating that heifers previously restricted to 25% of ad libitum intake had greater Cr excretion in urine during FR and recovery. This study indicates that severe FR negatively affects the time required for recovery of reticulo-rumen absorptive function and total tract barrier function. Another important finding is that regardless of severity, FR increases risk for ruminal acidosis when heifers have free access to feed after FR.

The objective of this study was to evaluate whether different severities of short-term feed restriction (FR) affect the absorptive function of the reticulo-rumen and total tract barrier function in beef cattle. Eighteen ruminally cannulated and ovariectomized Angus × Hereford heifers were blocked by BW into 3 blocks, with blocks conducted sequentially. Treatments were imposed during the 5-d FR period by restricting heifers to 75 (FR75), 50 (FR50) or 25% (FR25) of the ad libitum feed intake measured during a 5-d baseline period (BASE) occurring immediately before FR. Throughout the study, heifers were housed in individual pens (9 m(2)) and were fed the same diet (60% forage:40% concentrate) with free access to water. Dry matter intake was measured daily and ruminal pH was measured every 2 min throughout the study. Ruminal fluid and blood samples were collected on d 3 of the BASE and FR periods, and the temporarily isolated and washed reticulo-rumen technique was used to evaluate short-chain fatty acid (SCFA) absorption on d 5 of the BASE and FR periods. Total tract barrier function was evaluated starting on d 2 of the BASE and FR periods using a pulse dose of Cr-EDTA followed by 48 h of total urine collection. Data were analyzed using the Proc Mixed procedure of SAS with the fixed effects of block, treatment, period, and the treatment × period interaction, the random effect of cow nested in block with period included as a repeated measure. Dry matter intake did not differ among treatments during BASE but, as imposed by the experimental model, DMI during FR relative to BASE equated to 70, 49, and 25%, which was close to the targeted values of 75, 50, and 25% (treatment × period, P < 0.001). A treatment × period interaction (P < 0.001) was also detected for ruminal SCFA concentration with the concentration decreasing as the severity of FR increased, whereas there were no differences during BASE. Mean ruminal pH increased during FR with increasing severity of FR, but was not different during BASE (treatment × period, P < 0.001). Absorption of SCFA across the reticulo-rumen tended to decrease with increasing severity of FR (P = 0.08). For individual SCFA, acetate absorption (mmol/h) tended (P = 0.057) to be less for FR25 and FR50 when compared with FR75 and decreased (P = 0.05) by almost 70 mmol/h at FR25 and FR50 relative to BASE (322mmol/h). Heifers restricted to 25% (FR25) feed had greater urinary Cr recovery during FR than BASE, whereas no changes were detected for FR75 and FR50. This study indicates that moderate severities of short-term FR decrease the absorptive function of the reticulo-rumen, but more severe FR is required to compromise total tract barrier function in beef cattle.

Seventy-four Angus and Angus × Hereford heifers were used in 2 successive years (yr 1, n = 43; yr 2, n = 31) to determine if luteal function of heifers during acute submaintenance feeding is related to variation in utilization of feed as determined by residual feed intake (RFI). Residual feed intake was determined for heifers beginning at 12.3 ± 0.1 mo of age in yr 1 and at 9.1 ± 0.1 mo of age in yr 2. Heifers were assigned to dry-lot pens (n = 6 to 9 heifers/pen) with electronic gates to measure individual feed intake of a total mixed ration for 70 and 72 d in yr 1 and 2, respectively. Residual feed intake was calculated as the difference between actual DMI and expected DMI from linear regression of DMI on mid-test BW(0.75) and ADG. At 14.4 ± 0.1 mo of age, all heifers were provided a restricted amount of feed to supply 40% of their maintenance energy requirements for 21 d. Estrous cycles of heifers were synchronized with PGF(2α) on d -10, 0, and 11 relative to start of restriction. Concentrations of progesterone in plasma on d 14 to 21 of restriction were used to determine if heifers ovulated. Overall ADG and ADFI were 0.83 ± 0.02 and 7.37 ± 0.67 kg/d, respectively, for yr 1; and 0.50 ± 0.02 and 5.66 ± 0.09 kg/d, respectively, for yr 2. There was no correlation between RFI and BW, ADG, ADFI, or ultrasound measure of backfat, nor was RFI related to concentrations of IGF-I in plasma. All heifers lost BW and had reduced backfat (P < 0.001) at the end of restricted feeding. All heifers had reproductive cycles before dietary restriction started. During acute nutritional restriction, 4 heifers became anovulatory. Sixteen heifers had concentrations of progesterone in plasma during restricted feeding that were atypical of normal luteal function. There was no relationship between luteal function during nutrient restriction and RFI of heifers. Circulating IGF-1 was greater at weaning and after restricted feeding in heifers with a smaller RFI (>0.5 SD below the mean) than heifers with a greater RFI (>0.5 SD above the mean). It is concluded that RFI is not related to luteal function during acute submaintenance feeding, but that short-term restriction of nutrient intake can alter luteal function that may compromise fertility, even in heifers that exhibit estrus and ovulate.

Sixteen Boer goat doelings, 16 Spanish doelings, and 8 Angora doelings and 8 wethers, 283, 316, and 330 d of age initially (SEM = 5.0), respectively, were used to evaluate effects of nutrient restriction on heat energy (HE). During the first and second 10-wk phases, 8 animals of each breed were fed a 50% concentrate pelletized diet at a level adequate for maintenance and moderate energy accretion (CONT). Other animals were fed approximately 50% of these amounts in phase 1 relative to initial BW, followed by the greater level of feeding in phase 2 based on initial or actual BW when greater (REST). Average daily gain was 43, -20, 16, -78, 8, and -48 g in phase 1 (SEM = 5.0) and 26, 44, 50, 65, 27, and 32 g in phase 2 (SEM = 3.5) for Angora-CONT, Angora-REST, Boer-CONT, Boer-REST, Spanish-CONT, and Spanish-REST, respectively. Total HE was greater for CONT vs. REST in both phases (P < 0.001), greater in phase 1 for Angora than for Boer (P < 0.01) and Spanish (P < 0.01), and greatest (P < 0.01) in phase 2 among breeds for Angora [481, 347, 430, 356, 424, and 338 kJ/kg of BW(0.75) per day in phase 1 (SEM = 11.1), and 494, 479, 445, 397, 444, and 406 kJ/kg of BW(0.75) per day in phase 2 (SEM = 11.3) for Angora-CONT, Angora-REST, Boer-CONT, Boer-REST, Spanish-CONT, and Spanish-REST, respectively]. Equations describing the temporal pattern of HE (kJ/kg of BW(0.75) per day), expressed as a percentage of the wk-0 value and corrected for corresponding breed × week CONT means, in phase 1 were 95.8 ± 2.43 - (8.18 ± 1.144 × week) + (0.655 ± 0.1098 × week(2)) for Angora (R(2) = 0.58), 95.3 ± 2.63 - (4.34 ± 1.237 × wk) + (0.271 ± 0.1187 × wk(2)) for Boer (R(2) = 0.41), and 97.4 ± 2.21 - (4.69 ± 1.068 × wk) + (0.282 ± 0.1021 × wk(2)) for Spanish (R(2) = 0.53). Phase 2 equations were 78.9 ± 2.22 + (8.74 ± 1.036 × wk) - (0.608 ± 0.0095 × wk(2)) for Angora (R(2) = 0.60), 77.5 ± 2.10 + (3.30 ± 0.978 × wk) - (0.153 ± 0.0942 × wk(2)) for Boer (R(2) = 0.39), and 80.6 ± 2.50 + (4.50 ± 1.165 × wk) - (0.208 ± 0.1122 × wk(2)) for Spanish (R(2) = 0.43). These equations indicate that changes in HE in response to nutrient restriction and realimentation were more rapid and of greater magnitude in Angora vs. Boer and Spanish. The temporal pattern of decline in HE by Boer and Spanish during restriction was similar, but the subsequent rise with realimentation was slower and smaller for Boer. In conclusion, most appropriate methods of predicting change in the maintenance energy requirement during and after periods of limited feed intake may differ among breeds of goats.

In a previous study with limit-fed gestating gilts, we observed that gilts fed 6 times/d had greater ADG than those fed the same amount over 2 feedings. To confirm these earlier responses, we used finishing pigs as a model in two 42-d trials and two 28-d trials to evaluate the effects of restricted feed intake and feeding frequency (2 vs. 6 times/d, floor fed) on pig performance between 68 and 114 kg. In all experiments, pigs (10/pen) were housed in 1.8 × 3.1 m pens with a half-solid, half-slatted concrete floor. Pigs were fed a corn- and soybean meal-based diet formulated to 1.15% standardized ileal digestible Lys and 3,294 kcal of ME/kg. In Exp. 1 to 3, energy and Lys were supplied to pigs according to NRC (1998) calculations to target an ADG of 0.80 kg. In Exp. 4, the diet was supplied to pigs to target an ADG of 0.80 kg (low feed intake) or 0.95 kg (high feed intake) to determine if the amount of energy above the maintenance requirement and feeding frequency affected pig performance. Pigs were fed by dropping similar amounts of feed onto the solid concrete floor either 2 (0700 or 1400 h) or 6 times (3 meals within 2 h at the morning and afternoon feedings) per day with an Accu-Drop Feed Dispenser (AP Systems, Assumption, IL). In Exp. 1 and 2, pigs fed 6 times daily had increased (P < 0.02) ADG and G:F compared with pigs fed 2 times per day. Greater feeding frequency increased (P < 0.05) the duration of time spent feeding and standing and reduced the lying time. In Exp. 3, a third treatment was included to determine whether the improvements in performance were due to decreased feed wastage. This treatment was designed to minimize feed wastage by dropping feed closer to the floor for pigs fed 2 times per day. Pigs fed 6 times daily had improved (P < 0.05) ADG and G:F compared with pigs in either treatment fed 2 times per day. No difference (P > 0.05) in performance was observed between pigs fed 2 times per day when feed was dropped from the feed drop or by the modified method. In Exp. 4, increasing the feeding frequency from 2 to 6 times per day improved (P < 0.01) ADG and G:F for pigs fed the low feed intake and tended to increase (P < 0.06) ADG and improved (P < 0.05) G:F for pigs fed the high feed intake. In limit-feeding situations, increasing the frequency of feeding from 2 to 6 times per day improved pig performance, which confirmed our earlier findings in gestating gilts.

The present study evaluated whether feed deprivation can increase reactivity to stressful events, such as those that can occur at slaughter. Therefore, effects of 30 h of feed deprivation on behavior, including reactions to psychological stressors, and physiological status in cattle were determined. Sixteen Holstein cows (Exp. 1) and 32 Holstein heifers (Exp. 2) were either fed (FE) or 30-h feed deprived (FD). Throughout the first day of feed deprivation and during evening feed distribution to control animals, FD heifers and cows were more active than controls (P < 0.05). In Exp. 1, during a feeding test, in response to a sudden air blast arising from the bucket from which the cow was feeding, FD cows showed a longer latency to return to feed (P = 0.0002), spent less time in the bucket air blast zone (P = 0.008) and less time motionless (P = 0.03), and tended to withdraw over a longer distance (P = 0.07) than FE cows. In Exp. 2, during a reactivity test, FD heifers spent more (P = 0.0001) time motionless in response to social isolation than FE heifers. In Exp. 2, one-half of the FE and FD heifers were subjected to an additional physical and psychological stressor just before the reactivity test by driving them for 5 min through a labyrinth. Within heifers subjected to the additional stressor, FD heifers were less accepting of being detained (P = 0.05) and stroked (P = 0.003) by a familiar stockperson in a corner of the test arena. Compared with FE animals, FD heifers and FD cows had greater plasma cortisol concentrations (P < 0.05). Feed-deprived cows also had reduced β-hydroxybutyrate concentrations (P = 0.02) compared with FE cows. Thus, in cattle, FD influenced some of the classical indicators of energy metabolism and exacerbated reactivity to sudden events. In addition, when additional stressors were applied, FD cattle were more reluctant to accept handling. Results indicate that a multifactorial origin of stressors during the slaughter period may synergistically increase psychological stress of cattle.

Pyruvate carboxylase (PC; EC 6.4.1.1) is a critical enzyme for gluconeogenesis and maintenance of tricarboxylic acid (TCA) cycle intermediates, and expression of PC mRNA is increased at calving and during feed restriction. The bovine PC gene contains 3 promoters (3, 2, and 1 from 5' to 3') that produce 6 mRNA 5' variants (A through F). Products of promoter 1, untranslated region (UTR) variants A, B, C, and F are specifically expressed in glucogenic and lipogenic tissues. The objective of this study was to develop a quantitative PCR-based assay for bovine PC 5' UTR variants that would permit simultaneous characterization of PC variant expression and to determine the pattern of PC variant expression during the transition to lactation and during feed restriction. Primer combinations specific to the coding region of PC and the 5' UTR for variants D, E, and F were used with Taqman probes in a real-time PCR multiplex assay to simultaneously determine total PC mRNA and expression of each UTR variant. The intraassay and interassay CV were less than 2 and 10%, respectively. Total PC mRNA and PC 5' UTR variant profile was determined for liver biopsy samples collected from Holstein cows (n = 8) at -28, +1, and +28 d relative to calving (DRTC) and from mid-lactation Holstein cows subjected to either feed restriction (n = 8) or fed for ad libitum intake (n = 8). The expression of PC mRNA corresponding to the coding region of PC and PC 5' UTR variant regions A, B, C, and F increased (P < 0.05) 4-fold with feed restriction and 6-fold at calving. Nuclei isolated from liver biopsy samples and used to determine the rates of PC gene transcription indicate changes in the abundance of PC 5' mRNA variants A, B, C, and F that are due to corresponding changes in the rate of transcription of the bovine PC gene. The data support the use of the multiplex assay described here as a proxy measure of the activity of bovine PC promoter 1. The increased PC mRNA expression observed at calving and during feed restriction is the result of specific increases in 5' UTR variants A, B, C, and F due to increased transcriptional activity of promoter 1 of the PC gene.

The effects of dietary energy source and feed withdrawal on muscle glycolytic potential (GP) and blood acid-base responses to handling were investigated in slaughter-weight pigs (initial BW 94.7 ± 1.01 kg). Crossbred pigs (n = 96; 48 barrows, 48 gilts) were used in a randomized complete block design with a 4 × 2 × 2 factorial arrangement of treatments: l) diet [control, high fat (10% supplemental fat), low-digestible carbohydrate (20% total starch), and high-fat/low-digestible carbohydrate (10% supplemental fat and 20% total starch)]; 2) feed withdrawal (0 and 36 h); and 3) sex (barrow and gilt). Diets were fed for 28 d before the feed withdrawal treatment was applied, at the end of which all pigs were individually moved through a 12.20-m-long × 0.91-m-wide passageway for 16 laps (195 m total distance), with the assistance of an electric goad (2 times per lap). Longissimus muscle biopsies were collected at the beginning of the feeding and feed withdrawal periods and immediately after and 4 h after the handling procedure. Venous blood was collected 2 h before and immediately after the handling procedure to measure acid-base responses. At the end of the feeding period, pigs fed the control and high-fat diets were heavier (P < 0.001) than those on the low-digestible carbohydrate and the high-fat/low-digestible carbohydrate diets (129.8, 130.9, 114.0, and 122.1 kg, respectively; SEM 1.91). Diet, feed withdrawal, and sex did not affect (P > 0.05) blood acid-base responses to handling. Muscle GP at the end of the feeding period and 4 h posthandling was least (P < 0.05) for pigs fed the high-fat diet and similar for the other 3 diet treatments. Pigs subjected to 36 h compared with 0 h of feed withdrawal had less GP (P < 0.05) immediately after and 4 h after the handling procedure. There was an interaction between diet and feed withdrawal treatments for changes in GP from the start of feed withdrawal to 4 h posthandling. The reduction in GP was greater (P < 0.05) for fasted than for fed pigs receiving the control and high-fat diets, but was similar (P > 0.05) for fasted and fed pigs receiving the 2 low-digestible carbohydrate diets. In conclusion, neither dietary energy source nor fasting affected blood acid-base responses to handling; however, fasting-induced changes in LM GP were diet dependent.

The overall objective was to compare reproductive performance through 4 parities of gilts developed with ad libitum access to feed or with restriction of energy to 75% of ad libitum intake. Effects on growth and pubertal development are reported. The experiment was a 2 × 2 factorial with 661 gilts. One-half of the gilts (n = 330) were allowed ad libitum access to feed from weaning to breeding at 235 d of age (AL), and 331 littermates were developed with ad libitum access to feed to 123 d of age and then restricted to 75% of ad libitum intake to 235 d of age (Res). Diets for gilts on regimen AL were formulated to meet requirements for growth. All nutrients except energy and selenium were increased in the diet fed to gilts on regimen Res so that nutrient intake per unit of BW was expected to be similar to that of gilts on regimen AL. Sires of all gilts were from an industry maternal line. Dams were either an industry Large White-Landrace cross, or Nebraska selection Line 45, producing gilts denoted as LW/LR and L45X, respectively. Traits were recorded every 2 wk. Recording of feed intake and BW began at 53 d of age, and recording of backfat (BF) and LM area (LMA) began at 123 d of age. Estrus detection began at 140 d of age to determine age at puberty (AP). The G:F ratio from 123 to 235 d of age for gilts on the AL regimen was greater (0.269 vs. 0.257, P < 0.01) than for gilts on the Res regimen; the greatest difference occurred in the first 2-wk period following feed restriction. The LW/LR gilts were heavier, had less BF, and had greater LMA than L45X gilts, but interactions with feeding regimen and period of development existed. Feed restriction reduced BW, BF, LMA, and ratio of BF to BW, but had little effect on ratio of LMA to BW. More L45X gilts than LW/LR gilts (98 vs. 93%, P < 0.01) and more gilts developed on regimen AL than regimen Res (98 vs. 91%, P < 0.01) expressed estrus. Mean age at puberty was 178.6 d for LW/LR and 173.0 d for L45X gilts (P < 0.01) and 174.1 d for regimen AL and 177.5 d for regimen Res (P < 0.05). The Res regimen delayed pubertal development. Subsequently, it will be important to determine effects on reproduction through 4 parities.

During marketing, cattle may be exposed to periods of water deprivation. The impact of water and feed access and health status on the physiological well-being and carcass characteristics of Holstein slaughter cows during preslaughter marketing was studied through analysis of serum components, BW loss percentage, and fresh meat composition. Ninety-one multiparous Holstein cows (609 ± 89 kg mean BW, 2.9 ± 0.5 mean BCS, varying stage of lactation) were purchased over 3 wk in 3 groups (n = 31, 29, and 31) at a terminal market in central Wisconsin. Each cow was screened to determine health status (sick or not sick) and randomly assigned to 1 of 3 water and feed withdrawal treatment pens (AL, ad libitum access to water for 36 h; 18H, 18 h of ad libitum access to water followed by 18 h of water withdrawal; 36H, 36 h of water withdrawal; all 3 treatments included 36 h of feed withdrawal) in a randomized complete block arrangement with repeated measures for serum components. Blood samples were collected by tail venipuncture at 0, 9, 18, 27, and 36 h of each treatment. Ambient temperatures were 1.9 ± 6.2°C during the trial period, which occurred over a 3-wk period in March and April 2007 near Arlington, WI. No difference (P > 0.05) was observed in mean serum cortisol in AL (18.41 ± 2.17 ng/mL) or 36H (22.98 ± 2.17 ng/mL). Mean serum glucose was greater (P < 0.05) in 36H pens (78.15 ± 0.77 mg/dL) than AL (75.91 ± 0.77 mg/dL). Mean serum creatinine was greater (P < 0.05) in 36H pens (0.71 ± 0.03 mg/dL) than AL (0.60 ± 0.03 mg/dL). The 36H pens also displayed increased (P < 0.05) serum albumin, anion gap, Ca, Cl, Na, cholesterol, and aspartate aminotransferase over AL. Greater (P < 0.05) mean percentage BW loss was observed in 36H pens (5.2 ± 0.6%) than AL (3.1 ± 0.6%). Mean muscle protein (%) was greater (P < 0.05) in 36H (22.2 ± 0.4%) than 18H (21.3 ± 0.4%). Mean muscle moisture (%) was greater (P < 0.05) in AL and 18H (75.3 ± 0.4% and 75.2 ± 0.4%) than 36H. Mean 24-h pH values were 5.92 (AL), 5.92 (18H), and 5.81 (36H; SE = 0.04) and were not different (P < 0.05). Observed pH and color values indicated a borderline dark-cutter state across all cattle in the study, regardless of water and feed access treatment. Based on these results, water and feed withdrawal in lairage should not exceed 18 h during the marketing of Holstein slaughter cows acclimated to springtime conditions to maintain BW, serum component concentrations, and fresh meat composition.

Twelve mature Angora does were used in a replicated 3 × 3 Latin square to determine effects of feeding level on energy utilization. Fiber growth and change in tissue (nonfiber) mass were determined in the first 4 wk of 6-wk periods, preceded by 14 or 18 d of adaptation. Determination of ME intake and gas exchange measures occurred in wk 4, followed by feeding near maintenance, then fasting in wk 5 and 6 to determine the ME requirement for maintenance (ME(m)). A 60% concentrate diet was fed at levels to approximate 100, 125, and 150% of assumed ME(m) [low, medium (med), and high, respectively]. Digestibilities and diet ME/GE were not affected by treatment with different amounts of feed offered and subsequent intake near ME(m). Heat energy during fasting (261, 241, and 259 kJ/kg of BW(0.75); SEM = 8.7) and efficiency of ME used for maintenance (71.6, 69.6, and 69.2%; SEM = 2.29) were similar among treatments, although ME(m) differed (P < 0.04) between med and high (365, 344, and 377 kJ/kg of BW(0.75) for low, med, and high, respectively; SEM = 10.3). Tissue gain was less (P < 0.01) for low than for the mean of med and high (MH; -0.6, 23.7, and 29.8 g/d), although clean fiber growth only tended (P < 0.09) to differ between low and MH (5.60, 6.57, and 7.36 g/d for low, med, and high, respectively; SEM = 0.621). Intake of ME was greater (P < 0.01) for MH than for low (6.87, 8.22, and 8.41 MJ/d for low, med, and high, respectively). Total heat energy was less (P < 0.02) for low vs. MH and tended (P < 0.07) to be greater for high than for med (6.03, 6.31, and 6.77 MJ/d); mobilized tissue energy was low but greater (P < 0.02) for low vs. MH (0.16, 0.01, and 0.04 MJ/d for low, med, and high, respectively). Efficiency of ME use for fiber growth was similar among treatments (17.2, 16.3, and 17.7% for low, med, and high, respectively; SEM = 1.61). In conclusion, efficiency of ME use for fiber growth was similar to the NRC recommendation regardless of feeding level, although ME(m) was decreased perhaps because of experimental conditions used. Energy appeared partitioned to fiber growth, but preferential usage was not complete possibly because energy metabolism for tissue accretion reached a plateau with the greatest feeding level.

Angus x Hereford heifers (15 mo and AI to a single sire) were used to evaluate the effect of prenatal nutritional restriction on postnatal growth and regulation of glucose in plasma. Dams (d 32 of gestation) were stratified by BW and BCS and allotted to low [LN, 55% of NRC (1996) requirements, n = 7] or moderate nutrition [MN, 100% of NRC (1996) requirements, n = 7]. After 83 d of feeding, dams were commingled and received a diet in excess of requirements. Dams were allowed to calve naturally, and bull calves were castrated at birth. Dams and calves were maintained as a group until weaning, and calves were maintained as a group after weaning. Calves (15 mo of age) were adapted to a similar diet during 2 wk; catheters were placed in both jugular veins; and calves were confined in stalls. Two days later, calves were subjected to an intravenous glucose challenge and the next day to an insulin challenge. Dams had similar (P = 0.31) BW at the beginning of the experiment. At the end of restriction, LN dams weighed less (P ≤ 0.01) and had less BCS (P < 0.001) compared with MN dams. Length of gestation was not affected by prenatal nutritional treatment. Nutrient restriction during gestation did not influence birth weight or postnatal growth. Concentrations of glucose (P = 0.49) and insulin (P = 0.29) were not different in plasma of LN and MN calves before glucose infusion. Plasma concentrations of glucose, after intravenous administration of glucose, decreased more rapidly (P = 0.05) in LN compared with MN calves. Concentrations of glucose (P = 0.68) and insulin (P = 0.55) in plasma of LN and MN calves were similar after infusion of insulin. Nutritional restriction of dams during early gestation did not influence postnatal growth, but altered clearance of glucose after a bolus infusion of glucose.

Angus x Hereford heifers (15 mo and artificially inseminated to a single sire) were used to evaluate the effect of prenatal nutritional restriction on postnatal growth and development. At d 32 of gestation, dams were stratified by BW and BCS and allotted to a low-nutrition [55% of NRC (1996) requirements, n = 10] or moderate-nutrition [100% of NRC (1996) requirements, n = 10] diet. After 83 d of feeding, dams were commingled and received a diet in excess of requirements. Dams were allowed to calve naturally, and birth weights and growth of calves were recorded. Bulls were castrated at birth. Steers (16 mo of age, 5 per treatment) received a high-concentrate diet ad libitum to a constant age (88 ± 1 wk). Steers were slaughtered and weights of the empty body and organs were recorded. Samples of organs, muscle (complexus), and perirenal and subcutaneous adipose tissue were stored at -80 degrees C, and then DNA and protein concentrations were quantified and expression of genes associated with fatty acid metabolism and glucose uptake were measured in adipose and muscle tissue. Dams had similar (P > 0.33) BW and BCS at the beginning of the experiment. At the end of restriction, dams on the low-nutrition diet weighed less (P ≤ 0.01) and had less BCS (P < 0.001) than those on the moderate-nutrition diet. Length of gestation was 274 ± 2 d for dams in the low-nutrition treatment and 278 ± 2 d (P = 0.05) for dams in the moderate-nutrition treatment. Nutrient restriction during gestation did not influence birth weight or postnatal growth of calves. Lungs and trachea of steers whose dams were fed the low-nutrition diet weighed less (P = 0.05) at slaughter than those of steers whose dams were fed the moderate-nutrition diet; weights of other organs were not influenced by treatment. Complexus muscle from steers whose dams were fed the low-nutrition diet had a greater (P = 0.04) concentration of DNA and larger muscle fiber area compared with steers whose dams were fed the moderate-nutrition diet. Abundance of mRNA for fatty acid binding protein 4, fatty acid translocase, and glucose transporter 4 was less in perirenal adipose tissue of steers whose dams were fed the low-nutrition diet compared with those whose dams were fed the moderate-nutrition diet. Nutritional restriction of dams during early gestation did not alter postnatal calf growth. However, concentrations of DNA in muscle tissue and muscle fiber area were greater in steers from dams exposed to restricted nutrient intake during early gestation.

The objectives were to evaluate effects of maternal nutrient restriction and stage of gestation on maternal and fetal visceral organ mass and indices of jejunal growth and vascularity in beef cows. Thirty multiparous beef cows (BW = 571 +/- 63 kg; BCS = 5.4 +/- 0.7) carrying female fetuses (d 30 of gestation) were allocated to receive a diet of native grass hay (CON; 12.1% CP, 70.7% IVDMD, DM basis) to meet NRC recommendations for BW gain during early gestation or a nutrient-restricted diet of millet straw (NR; 9.9% CP, 54.5% IVDMD, DM basis) to provide 68.1% of NE(m) and 86.7% of MP estimated requirements. On d 125 of gestation, 10 CON and 10 NR cows were killed and necropsied. Five remaining CON cows received the CON diet, and 5 NR cows were realimented with a concentrate supplement (13.2% CP, 77.6% IVDMD, DM basis) and the CON hay to achieve a BCS similar to CON cows by d 220 of gestation. Remaining cows were necropsied on d 245 of gestation. Cow BW and eviscerated BW (EBW) were less (P < 0.01) for NR than CON at d 125 but did not differ (P > 0.63) at d 245. Cows fed the CON diet had greater (P < 0.09) total gastrointestinal (GI) tract, omasal, and pancreatic weights. Stomach complex, ruminal, and liver weights were greater for CON than NR cows (P < 0.09) on d 125. Total GI, stomach complex, and pancreatic weights increased (P < 0.001) with day of gestation. Restricted cows had decreased (P = 0.09) duodenal RNA:DNA compared with CON. Duodenal DNA was less (P = 0.01) and jejunal RNA:DNA (P = 0.09) was greater for cows at d 125 vs. 245. Cow jejunal capillary area density increased with day of gestation (P = 0.02). Fetal BW and EBW were unaffected by dietary treatment (P > or = 0.32). Total GI tract and all components increased in mass with day of gestation (P < 0.001). Fetuses from NR dams had greater (P = 0.003) reticular mass at d 245 than CON fetuses. Fetuses from NR cows had greater (P = 0.02) percent jejunal proliferation at d 125 and greater (P = 0.03) total intestinal vascularity (mL) at d 245. Fetal jejunal DNA decreased (P = 0.09), RNA:DNA increased (P = 0.05), and total jejunal proliferating cells increased (P < 0.001) with day of gestation. Jejunal capillary area density, number density, and surface density were greater (P < 0.008) during late gestation. Results indicate that maternal and fetal intestines undergo changes during gestation, which can be affected by nutrient restriction and may partially explain differences observed in fetal development and postnatal performance.

The roles of pancreatic polypeptide (PP) have not been determined in ruminant animals. The aim of the present study was to examine the role of PP in the regulation of ghrelin secretion in sheep. Two experiments were conducted using four 2-yr-old Suffolk wethers fed a maintenance diet of alfalfa hay cubes. In Exp. 1, the effects of feeding on blood ghrelin and PP concentrations were examined in scheduled-fed sheep. Blood samples were collected every 10 min from 30 min before to 360 min after feeding. Plasma PP concentrations were transiently increased from the preprandial average value to the values from 30 to 60 min after feeding and gradually decreased (P < 0.05) to stable values from 150 to 180 min. The values from 30 to 60 min were greater (P < 0.05) than those from 150 to 360 min. In contrast, plasma ghrelin concentrations were gradually decreased (P < 0.01) by feeding. The values from 60 to 360 min were less (P < 0.01) than the preprandial average value. In Exp. 2, the effects of continuous PP infusion on ghrelin secretion were examined in feed-deprived sheep. The animals were deprived of feed for 48 h before PP infusion. The PP-treated group intravenously received synthetic bovine PP at a rate of 10 pmol.kg(-1 )of BW.min(-1) for 180 min. Blood samples were collected every 10 min from 30 min before to 180 min after the commencement of PP infusion. Plasma PP concentrations reached a plateau within 30 min after the commencement of PP infusion. Plasma ghrelin concentrations were decreased (P = 0.002, 0.016, 0.007) by PP infusion at 160, 170, and 180 min, respectively. In conclusion, plasma ghrelin and PP concentrations were decreased and increased, respectively, in response to feeding in ruminant animals. Furthermore, PP could depress ghrelin secretion.

Primiparous ewes born as singletons to Rambouillet x Columbia crossbred ewes fed either 100% of NRC recommendations (control, Con; n = 7) or 50% of NRC (nutrient restricted, NR; n = 7) from d 28 through 78 postmating were utilized for this study. At 1 yr of age, a subset of ewes born to Con (n = 4) and NR (n = 4) mothers received jugular catheters and were subjected to a corticotrophin-releasing hormone (CRH)/arginine vasopressin (AVP) challenge, an ACTH challenge, and an isolation stress test, in which ACTH and cortisol responses were determined. A week after these challenges, estrus was monitored twice daily in all ewes from Con (n = 7) and NR mothers (n = 7). Once estrus was observed (d 0), daily blood samples were collected from ewes for progesterone through the subsequent estrus. Estrous detection and daily blood sampling were repeated during an estrous cycle in the next year, ewes were hand mated at the second estrus, and pregnancy was determined by delivery of a live lamb(s). Ewes from NR mothers tended (P = 0.10) to have a greater peak ACTH response after an intravenous CRH/AVP injection than ewes from Con mothers. The cortisol response of ewes to a CRH/AVP or ACTH challenge was not influenced by maternal nutrition. In contrast, ewes from Con mothers tended (P = 0.10) to release more ACTH in response to the isolation stress test and showed a greater (P = 0.04) cortisol release than ewes from NR mothers. Ewes from NR mothers exhibited decreased (P < 0.05) plasma progesterone in both yr 1 and 2 of the study compared with ewes from Con mothers. Furthermore, fewer (P < 0.0001) ewes from NR mothers produced a lamb (1 of 7) than ewes from Con mothers (7 of 7) during yr 2 of the study. These findings indicate that maternal undernutrition during early gestation may affect stress responses by the offspring, but has limited impact on hypothalamo-pituitary-adrenal sensitivity. Furthermore, offspring of NR ewes exhibited reduced progesterone secretion during the luteal phase of their estrous cycles and a markedly reduced fertility compared with offspring from Con ewes.

A study was conducted to evaluate the extent and dynamics of whole body protein deposition and changes in chemical and physical body composition after a period of AA intake restriction in growing barrows with medium lean tissue growth potentials. Forty Yorkshire barrows (initial BW 14.4 +/- 1.6 kg) were scale-fed at 75% of estimated voluntary daily DE intake up to 35 kg of BW and assigned to 1 of 2 diets: AA adequate (AA+; 20% above requirements; NRC, 1998) and AA deficient (AA-; 40% below requirements; restriction phase). Thereafter (re-alimentation phase), pigs from both dietary AA levels were scale-fed or fed ad libitum diets that were not limiting in AA. Body weight gain and body composition, based on serial slaughter, were monitored during the 34-d re-alimentation phase. During the restriction phase AA intake restriction reduced BW gains (556 vs. 410 g/d; P < 0.001; AA+ and AA-, respectively). At 35 kg of BW, AA intake restriction increased whole body lipid content (11.1 vs. 17.5% of empty BW; P < 0.05) and the whole body lipid to body protein ratio (0.65 vs. 1.20; P < 0.01) and reduced body protein content (17.1 vs. 14.6% of empty BW; P < 0.01) and body water content (68.2 vs. 63.9%; P < 0.05). The relationships between body protein vs. body water and body protein vs. body ash content were not altered by previous AA intake restriction or by feeding level during the re-alimentation phase (P > 0.10). Throughout the re-alimentation phase, there were no interactive effects of time, feeding level, and previous AA intake level on growth performance, body protein, and body lipid content (P > 0.10). During the re-alimentation phase, body protein deposition, derived from the linear regression analysis of body protein content vs. time, was not affected by feeding level and previous AA intake level (P > 0.10; 156 g/d for AA- vs. 157 g/d for AA+). Based on BW and body protein content, it can be concluded that no compensatory body protein deposition occurred in barrows, with medium lean tissue growth potential after AA intake restriction between 15 and 35 kg of BW. It is suggested that the upper limit to body protein deposition was the main factor that limited the extent of compensatory body protein deposition in this population of pigs. The concept of an upper limit to body protein deposition may be used to explain why compensatory growth is observed in some studies and not in others.

A study was conducted to evaluate the extent and dynamics of whole body protein deposition (Pd) and changes in chemical and physical body composition after a period of AA intake restriction in entire male pigs with high lean-tissue growth potentials. Fifty-eight entire male pigs (initial BW 15.8 +/- 0.9 kg) were allotted to 1 of 3 dietary AA levels between 15 and 38 kg of BW: control (15% above requirements), AA-15% (15% below requirements), and AA-30% (30% below requirements). Thereafter, pigs were fed diets not limiting in AA content. Throughout the experiment, pigs were scale-fed at 90% of estimated voluntary daily DE intake. Representative pigs were slaughtered at 15, 38, 53, 68, or 110 kg of BW to monitor changes in body composition. Between 15 and 38 kg of BW, restriction of AA intake reduced BW gain (P < 0.01; 794, 666, and 648 g/d for control, AA-15%, and AA-30%, respectively). At 38 kg of BW, AA intake restriction increased whole body lipid (LB) content (P < 0.01; 11.3, 14.3, 17.5% of empty BW), and the LB-to-whole body protein (PB) ratio (LB/PB; P < 0.02; 0.68, 0.88, 1.10 for control, AA-15%, and AA-30%, respectively). Relationships between PB versus whole body water and PB versus whole body ash were not affected by dietary treatments (P > 0.10). At 110 kg of BW and based on BW, PB, and LB/PB, complete compensatory growth (CG) was achieved. Body weight gain between 38 and 110 kg of BW was inversely related to previous dietary AA levels (P < 0.01; 1,089, 1,171, and 1,185 g/d for control, AA-15%, and AA-30%, respectively). For pigs on the control diet, and based on N-balance data, Pd increased with BW, from 172 g/d at 40 kg of BW to 226 g/d at 82 kg of BW. At 40 kg of BW, Pd was greater (P < 0.05) for pigs on the AA-15% (205 g/d) and AA-30% (191 g/d) diets than pigs on the control diet (172 g/d). These findings indicate that pigs with high lean-tissue growth potentials are more likely to express compensatory Pd and their genetically determined upper limit to Pd (PdMax) after a period of AA intake restriction. This study confirms previous findings that BW effects on PdMax are small in growing pigs between 40 and 80 kg of BW. It is suggested that CG and compensatory Pd after a period of AA intake restriction is constrained by the pig's PdMax and is driven by a target LB/PB. Combined with previous observations in our laboratory, these results suggest that CG after a period of AA intake restriction tends to occur only when pigs are within the energy-dependent phase of lean-tissue growth and not when the genetically determined upper limit to lean-tissue growth, or PdMax, determines growth performance.

The physiological and metabolic effects of prophylactic treatment with osmolytes were investigated using twenty-four 2.5-yr-old Bos indicus steers. Animals were allocated to 1 of 4 treatment groups: 1) control, feed and water deprived for 48 h (n = 6); 2) transported, transported for 48 h (n = 6); 3) glycerol, dosed with glycerol (2 g/kg of BW) and then transported for 48 h (n = 6); and 4) betaine, dosed with betaine (0.25 g/kg of BW) then transported for 48 h (n = 6). Body water, electrolytes, blood pH and gases, plasma lactate, glucose, albumin, total protein, anion gap, strong ion difference, total weak acids, and BW were determined at the conclusion of 24 and 48 h of transportation. The glycerol group had greater body water volumes than the control (P = 0.05) and transported (P = 0.02) groups. The glycerol, transported, and betaine groups had lower (P = 0.02) plasma Mg concentrations than the control group at 24 h, whereas the glycerol group maintained lower (P = 0.04) plasma concentrations of Ca than the control group. The betaine group had lower (P = 0.04) hematocrit than the control group at 24 and 48 h. Plasma bicarbonate and pCO2 were 13 and 17% greater (P = 0.01 and 0.04, respectively) in the glycerol group at 24 h compared with control and transported groups. However, the ratio of [HCO3]/[CO2] in the glycerol group did not differ from the other groups and thereby maintained pH. The glycerol group maintained a 30% greater (P < 0.001) plasma concentration of glucose than the control group, and 14% greater (P = 0.05) than the transported and betaine groups. In contrast, betaine had little effect on increasing blood glucose compared with glycerol. Glycerol-linked hyperhydration at 24 h may not only help to conserve water loss during long distance transportation, but the increased blood glucose may have an important protein-sparing effect due, in part, to greater insulin concentrations inhibiting the breakdown of muscle proteins, thus, countering the amino-acid mobilizing effect of cortisol after 24 h. Therefore, the osmolyte glycerol shows promise as a prophylactic treatment for attenuating the effects of long distance transportation by maintaining body water, decreasing the energy deficit, and preserving health and muscle quality.

The effect of early gestation maternal undernutrition followed by realimentation on placentomal vascular growth and angiogenic factor expression was determined in multiparous beef cows bred to the same bull. Cows gestating only female fetuses (n = 30) were fed in equal numbers to meet the NRC requirements (control) or were fed below the NRC requirements to lose BW (nutrient restricted; NR) from d 30 to 125 of gestation. After slaughter on d 125 of gestation, 10 control and 10 NR cows were necropsied. The remaining NR cows (n = 5) were then fed to achieve a BCS equal to their control group contemporaries (n = 5) by d 220 of gestation. All cows were fed the control diet from d 220 until 250 of gestation, when the remaining control and NR cows were slaughtered and necropsied. At necropsy, placentomes were fixed via perfusion of the caruncular and cotyledonary arteries to determine capillary vascular density. Cotyledonary (fetal placental) and caruncular (maternal placental) tissues also were snap-frozen in liquid nitrogen, and mRNA concentrations of vascular endothelial growth factor and its 2 specific receptors, fms-like tyrosine kinase and kinase insert domain containing receptor, as well as placental growth factor, were determined. There was no effect of diet or day of gestation on the percentage of proliferating caruncular cells. Although diet did not impact cotyledonary cellular proliferation, there was an increase (P < 0.05) in the percentage of proliferating cells on d 250 compared with d 125 of gestation. Nutrient restriction from d 30 to 125 increased (P < or = 0.10) placental mRNA concentrations of placental growth factor and fms-like tyrosine kinase; however, there was no alteration in vascularity. By d 250 of gestation, NR cows had increased (P < 0.05) caruncular capillary surface density and decreased (P < 0.05) cotyledonary capillary area density, capillary number density, and capillary surface density compared with control cows. Although nutrient restriction had little effect on placental vascularity by d 125, upon realimentation, alterations in vascularity became apparent by d 250 of gestation, suggesting a placental programming effect.

Two experiments were conducted to evaluate effects of out-of-feed events on nursery and grow-finish pig performance. An out-of-feed event is a period of time that pigs do not have access to feed as a result of late feed delivery or bridging in bulk bins, feed lines, or feeders. In these studies, we created an out-of-feed event by removing the feeders from pens or preventing access to the feeder. In Exp. 1, 190 pigs (initially 6.4 +/- 1.6 kg and 21 +/- 3 d of age) were used in a 35-d growth study. Treatments involved a 20-h feed withdrawal for 1, 2, or 3 randomly selected times or a control treatment where feeders were never withdrawn. Feeders were withdrawn on d 11 for pigs with 1 out-of-feed event, d 8 and 23 for pigs with 2 out-of-feed events, and d 9, 14, and 20 for pigs with 3 out-of-feed events. There was a treatment (P < 0.06) effect only during weeks in which an out-of-feed event occurred. Growth rate was lower (P < 0.05) for pigs with 1 out-of-feed event (d 11) compared with control in the d 8 to 14 period. During the same period, those pigs with the first of 2 (d 8) or 3 (d 9) out-of-feed events had intermediate ADG. In the d 15 to 21 period, only pigs with the second and third of 3 out-of-feed events (d 15 and 20) had lower growth performance compared with control pigs, whereas growth performance was similar to the control for those with 1 or 2 out-of-feed events. Pigs with 3 out-of-feed events had greater ADG and G:F (P < 0.05) compared with the other 3 treatments for the d 22 to 28 period. For the overall study (d 0 to 35), there were no differences (P > 0.86) in growth performance among pigs with 0, 1, 2, or 3 out-of-feed events. In Exp. 2, 479 pigs (initially 41.6 +/- 4 kg) were used in an 85-d growth study. Treatments involved feed withdrawal (20 h) weekly for the duration of the study; feed withdrawn weekly from d 45 to 85; or a control treatment where pigs had access to feed for the duration of the experiment. Feed withdrawal occurred on a randomly selected day with the exception of Saturday, Sunday, or a day before a weigh day (usually a Thursday every other week). From d 0 to 45, 46 to 85, and the overall d 0 to 85 period, there were no differences (P > 0.12) in ADG, ADFI, G:F, or average final BW among treatments. Results suggest that out-of-feed events of 20 h or less have no long-term detrimental effects on growth performance in nursery or grow-finish pigs.

Two experiments were conducted to determine whether the decreased proportion of fast muscle fibers seen previously in 2-wk-old lambs from ewes that were dietary restricted from d 30 to 70 of gestation are still evident in older lambs and what the consequences may be in terms of growth rates and carcass composition. Throughout both experiments, ewes were fed on an individual basis according to the recommended dietary allowance throughout pregnancy relative to metabolic BW (BW(0.73)). Control groups were fed as above, and the treatment groups had their nutrient supply reduced to 50% of this recommended allowance from d 30 to 70 (Exp. 1) or d 30 to 85 (Exp. 2) of gestation, after which they were returned to the same level of nutrition as the control group. All twin lambs were kept with their dams, and at 2 wk were given access to creep. After weaning, lambs were individually housed and fed ad libitum to 24 or 17 wk of age for Exp. 1 and 2, respectively. Although not significant (P = 0.18), growth to 24 wk (Exp. 1) resulted in a small decrease in the protein content and therefore an increase in the fat:lean ratio in the carcass of lambs subjected to maternal dietary restriction. This was not apparent when animals were slaughtered at 17 wk (Exp. 2; P > 0.68). Few significant effects of maternal dietary restriction on the fiber type composition of muscles were observed. In Exp. 1 the number of fast fibers increased (P < 0.008) with no effect on slow fiber number in LM. In Exp. 2 an increase in the total number of fibers in male lambs and an increase in type II (A and B) fibers in female lambs were observed in the LM, and an increase in IIB fiber number was observed in semitendinosus (ST) muscle from male lambs. Prenatal maternal dietary restriction during the time of muscle differentiation demonstrated an increase in type IIB muscle fibers and increase in intramuscular fat; although significant, effects on subsequent carcass quality of lambs were relatively small. These data suggest that the lambs adapted to changes in muscle fiber composition previously observed at 2 wk. However, lambs in this study were well fed during postnatal growth. Whether offspring would still have been able to compensate if they had received poor nutrition postnatally and whether that failure to compensate would have influenced carcass composition remain to be determined.

A restriction/realimentation feeding strategy was applied to pigs to increase the age at market weight and final ADG, modify protein and lipid deposition rates at carcass and muscle levels, and thereby improve eating quality of the pork. A total of 126 Duroc x (Large White x Landrace) pigs (females and castrated males) were used. At the average BW of 30 kg, within litter and sex, pairs of littermates (blocked by BW) were randomly assigned to ad libitum (AL) feeding during growing (30 to 70 kg of BW) and finishing (70 to 110 kg of BW) periods (AL, n = 56), or restricted feeding at 65% of the ADFI of the AL pigs, on a BW basis, during the growing period and AL feeding during finishing (compensatory growth, CG; n = 56). In each feeding regimen, 15 pigs were slaughtered at 70 kg of BW, and 41 pigs were slaughtered at 110 kg of BW. Additionally, 14 pigs were slaughtered at 30 kg of BW to calculate tissue deposition rates. The CG pigs showed decreased ADG (-35%, P = 0.001) during growing but increased ADG (+13%, P = 0.001) during finishing (i.e., compensatory growth) due to greater (P = 0.001) ADFI and G:F. Hence, CG pigs were 19 d older at 110 kg of BW than AL pigs. The CG pigs were leaner at 70 kg of BW than AL (e.g., 11.7 vs. 13.5 mm of average backfat thickness for CG and AL pigs, respectively, P = 0.023), whereas the differences were reduced at 110 kg of BW (20.6 vs. 21.0 mm of average backfat thickness for CG and AL pigs, respectively, P = 0.536). At 70 kg of BW, intramuscular fat (IMF) content of LM did not differ between CG and AL pigs (1.25 vs. 1.49%, respectively, P = 0.118), whereas CG pigs had less IMF in LM at 110 kg of BW (2.19 vs. 2.53% for CG and AL pigs, respectively, P = 0.034). Feeding regimen influenced the composition of weight gain. From 30 to 70 kg of BW, feed restriction reduced (P = 0.001) lean and adipose tissue deposition at the carcass level and protein and lipid deposition at the muscle level. From 70 to 110 kg of BW, the CG feeding strategy increased (P = 0.016) deposition of adipose but not of lean tissue at the carcass level. However, lipid and protein deposition at the muscle level were not affected. Thus, realimentation promoted deposition of subcutaneous fat over IMF. Feeding regimen hardly affected technological meat quality at 110 kg of BW. The CG feeding strategy decreased (P = 0.014) the meat juiciness score in relation to the decreased IMF but did not influence other sensory traits. Elevated IMF content and improved pork quality might be achieved by modifying the onset or duration of the restriction and realimentation periods.

Recommendations for transportation of lambs, horses, calves, and pigs from a committee of the European Commission, which required rest stops of 6 or 24 h, every 8 h, were evaluated using Rambouillet x Suffolk lambs. The lambs of 17.6 +/- 0.5 kg of BW were randomly assigned to 1 of 3 treatments: transported for 22 h (continuous; n = 15); transported for 8 h, unloaded and rested for 6 h, transported for 8 h, unloaded and rested for 24 h, transported for 6 h (rested, n = 15); or remained in the home pasture throughout the study (control, n = 16). Off-trailer rest with food and water occurred in novel pens. Food deprivation in the continuous lambs was reflected by a decrease (P < 0.001) in plasma concentrations of glucose and an increase (P < 0.02) in plasma concentrations of blood urea nitrogen, creatinine, and total bilirubin relative to rested or control lambs. Electrolytes varied within and among all 3 treatments (P < 0.05), but no distinct pattern indicating dehydration was evident. Serum concentrations of cortisol were elevated in continuous and rested lambs compared with control lambs at 22 h (P < 0.05). Plasma immunoglobulin G antibody response to ovalbumin was suppressed (P < 0.05) in the continuous and rested lambs relative to the control lambs. Differences (P < 0.05) between continuous and rested lambs indicated the rest stops were sufficient to maintain BW during transport; however, these results were confounded by the control lambs losing a similar (P = 0.50) percentage of their initial BW as the continuous lambs at 22 h. The rest stops eliminated the physiological indicators of food deprivation and maintained BW but did not alleviate evidence of immunosuppression, and 52 h was required to complete the otherwise 22-h-long trip.

Dramatic changes in the livestock industry have brought about widespread concern regarding the welfare of animals in terms of the hunger that they may experience. Despite this concern, animal science has not been able to provide a methodology that can objectively determine whether the welfare of animals is compromised by hunger. The current work sought to provide data that characterized the physiological and behavioral responses of animals experiencing 57 h of food deprivation. For this purpose, 2 separate experiments were conducted, in which physiological or behavioral measures were collected from swine deprived of feed for 21 to 57 h or fed normally (physiology, n = 20/treatment; behavior, n = 8/treatment). Treatment x time interactions were found (P < 0.02) for insulin, beta-hydroxybutyrate, NEFA, drinking, standing, inactivity, lying sternal, lying lateral, and total lying. Animals appeared to adjust appropriately to the metabolic challenge imposed, as suggested by increases in alternative energy substrates (NEFA, beta-hydroxybutyrate). Additionally, feed-deprived animals appeared less active than control animals until after 45 h of feed deprivation, when the former appeared to be more active. Our results suggest that feed deprivation of finishing pigs for durations greater than 45 h produced behavioral changes that may be related to increased sensations of hunger and which possibly are dependent on the use of alternative energetic substrates. Our data link behavioral and physiological changes after the imposition of feed deprivation.

An experiment was carried out to evaluate the metabolic utilization of energy in crossbred barrows during feed restriction and subsequent refeeding. Ten pigs, initially weighing 52 kg, were used in 5 blocks of 2 littermates each. A 7-d adaptation period (P1) was used in which pigs were offered feed at 2.60 MJ of ME.kg of BW(-0.60).d(-1). This adaptation period was followed by a 7-d period (P2), in which 1 pig of each block continued to receive feed at the same level of feeding, whereas for its littermate a 40% reduction in feed intake was imposed (i.e., 1.55 MJ of ME.kg of BW(-0.60).d(-1)). During the subsequent 7-d period (P3), both pigs were offered feed at 2.60 MJ of ME.kg of BW(-0.60).d(-1). After P3, pigs were fasted for 1 d. Heat production (HP) was measured for all pigs during the last 3 d of P1 and on all days for P2 and P3. Heat production was measured using an open-circuit respiration chamber. Energy and N balances were determined for P1, P2, and P3. The HP was partitioned into HP due to physical activity, the short-term thermic effect of feeding, and resting HP. Feed restriction during P2 decreased (P < 0.01) total HP, resting HP, short-term thermic effect of feeding, and retained energy, whereas HP due to physical activity was not affected by feed restriction (P = 0.50). Likewise, fecal and urinary N loss, protein gain, lipid gain, and ADG were reduced during feed restriction (P < 0.01). There were no differences in components of HP and metabolic utilization of energy between the 2 groups during P1 and P3. Nevertheless, urinary N loss was decreased (P < 0.05) and ADG increased (P < 0.01) during P3 for pigs that were restricted in P2. Compensatory growth after a period of feed restriction does not seem to be related to a change in the metabolic utilization of energy for gain but more likely is due to gain in water and gut contents.

The objective of this study was to determine the influence of the level of feed intake and a 2-d feed restriction period on the postweaning adaptation of pancreatic exocrine secretions. At 33 d of age, 18 piglets fitted with 2 permanent catheters (for pancreatic juice collection and reintroduction) were weaned and allocated to 1 of the following 2 dietary treatments for 5 d: restricted feed allocation (restricted) or gradually increasing feed allocation (control). Pancreatic juice was collected daily during both basal and prandial periods. The basal period was defined as the period from 1400 to 1700 h (i.e., 5 to 8 h after the morning meal), whereas the prandial period was defined as the period from 30 min before to 60 min after the morning meal (given at 0900). Digestive enzyme activities and antibacterial activity were determined. Pancreatic protein secretion was 44% less (P < 0.05) in restricted piglets than in control piglets during the basal period. Trypsin secretion was affected by feed-restriction of piglets. The meal did not affect protein and trypsin secretions in restricted piglets, whereas at d 3 postweaning, protein and trypsin secretions and trypsin specific activity in control piglets were 9-, 105-, and 25-fold greater (P < 0.001) during the first 30 min after the meal than before the meal. Lipase and amylase secretions were not affected by variations in feed intake. The secretion of antibacterial activity in restricted piglets was greater (P < 0.05) than that of control piglets only at d 5. The extended feed restriction period increased the basal secretion of antibacterial activity (P = 0.09) and postprandial secretion of amylase (P = 0.05). In conclusion, a low level of feed intake during the early postweaning period decreased pancreatic protein and trypsin secretions, whereas a 2-d feed restriction period enhanced secretions of amylase and antibacterial activity. In addition, our results indicate that during periods of dietary adaptation, such as at weaning, measurements of enzyme activities in the tissue do not accurately reflect the enzyme secretion.

We hypothesized that adaptation of heat production in the realimented cow would occur over an extended period, and the length of time would be influenced by the level of feed. Our objectives were to quantify the changes in heat production of cows after feed restriction and to quantify the effect of level of realimentation on the dynamics of heat production in lightweight cows. Forty 4-yr-old nonpregnant, nonlacting cows (4-breed composite: 1/4 Hereford, 1/4 Angus, 1/4 Red Poll, and 1/4 Pinzgauer) were randomly assigned to receive 1 of 4 levels of a common alfalfa hay source. All cows were feed-restricted [50.0 g of DM/metabolic body size (MBS, kg of BW(0.75)); period 1], and individual fed heat production measurements were taken 0, 7, 13, 28, 56, and 91 d after feed restriction (period 1). In period 2, cows were fed their assigned feed level for their treatment after d 91 of restriction: 50.0 (T50.0), 58.5 (T58.5), 67.0 (T67.0), and 75.5 (T75.5) g of DM/MBS. Measures were taken at 7, 13, 28, 42, 56, 91, 119, and 175 d. In period 3, all cows were fed 75.5 g of DM/MBS after their 175-d measurement, and measures were taken at 7, 14, 28, 56, and 112 d later. In period 1, heat production decreased rapidly during the first 7 d of feed restriction, and heat production continued to decrease during the 91-d restriction. Heat production increased rapidly within the first 7 d, but chronic adaptation continued for T75.5 and T67.0 cows. In period 3, heat production increased rapidly during the first 7 d. Heat production scaled for metabolic body size tended to differ among treatments (P = 0.11). Daily heat production increased by 2.5 kcal/d. These data suggest that there is not a lag in heat production during realimentation and that increased recovered energy is associated with a rapid increase in heat production.

Sixteen female pigs (Duroc x Landrace x Large White) were divided into 2 groups, which had either free access to the diet (control group) or were feed-restricted from d 28 to 80 and then had free access to the diet (compensatory growth group). The sensory analysis showed that the pigs exhibiting compensatory growth produced meat with increased tenderness compared with control pigs (P < 0.05). To gain further knowledge of the influence of compensatory growth on meat tenderness, the sarcoplasmic protein fraction of muscle tissue was studied at the time of slaughter and 48 h postmortem using proteome analysis. At slaughter, 7 different proteins were found to be affected by compensatory growth: HSC70, HSP27, enolase 3, glycerol-3-phosphate dehydrogenase, aldehyde dehydrogenase E2, aldehyde dehydrogenase E3, and biphosphoglycerate mutase. The HSC70 and HSP27 both belong to the heat shock family and are known to play a role during muscle development. Hence, they may be affected by compensatory growth and increased protein turnover. Forty-eight hours after slaughter, 8 different proteins were found to be affected by compensatory growth: myosin light chain (MLC) II, MLC III, sulfite oxidase, chloride intracellular channel 1, 14-3-3 protein gamma, elongin B, and phosphohistidine phosphatase 14. The changes observed on MLC II and MLC III could be a consequence of enzymatic cleavage in the neck region of the globular myosin head domain that causes the release of MLC II and MLC III from the actomyosin complex. It has previously been hypothesized that compensatory growth results in an increased postmortem proteolysis; thus it was presumed that the intensity of some protein fragments would be affected by compensatory growth. However, the peptides that were found to be affected at 48 h postmortem were all full-length proteins. The 14-3-3 protein gamma has been proposed to play a role in the contraction of muscle during rigor and may thereby have an effect on meat tenderness. This study reveals some very interesting changes in the muscle proteome affected by compensatory growth, which may be useful in understanding the relationship among compensatory growth, protein turnover, and meat tenderness.

Twelve Angus crossbred cattle (eight heifers and four steers; average initial BW = 594 +/- 44.4 kg) fitted with ruminal and duodenal cannulas and fed restricted amounts of forage plus a ruminally undegradable protein (RUP) supplement were used in a triplicated 4 x 4 Latin square design experiment to determine intestinal supply of essential AA. Cattle were fed four different levels of chopped (2.54 cm) bromegrass hay (11.4% CP, 57% NDF; OM basis): 30, 55, 80, or 105% of the forage intake required for maintenance. Cattle fed below maintenance were given specified quantities of a RUP supplement (6.8% porcine blood meal, 24.5% hydrolyzed feather meal, and 68.7% menhaden fish meal; DM basis) designed to provide duodenal essential AA flow equal to that of cattle fed forage at 105% of maintenance. Experimental periods lasted 21 d (17 d of adaptation and 4 d of sampling). Total OM intake and duodenal OM flow increased linearly (P < 0.001) as cattle consumed more forage; however, OM truly digested in the rumen (% of intake) did not change (P = 0.43) as intake increased. True ruminal N degradation (% of intake) tended (P = 0.07) to increase linearly, and true ruminal N degradation (g/d) decreased quadratically (P = 0.02) as intake increased from 30 to 105%. Duodenal N flow was equal (P = 0.33) across intake levels, even though microbial N flow increased linearly (P < 0.001) as forage OM intake increased. Total and individual essential AA intake decreased (cubic; P < 0.001) as forage intake increased because the supply of nonammonia, nonmicrobial N flow from RUP was decreased (linear; P < 0.001) by design. Total duodenal flow of essential AA did not differ (P = 0.39) across these levels of forage intake. Although the profile of essential AA reaching the duodenum differed (P < or = 0.02) for all 10 essential AA, the range of each essential AA as a proportion of total essential AA was low (11.1 to 11.2% of total essential AA for phenylalanine to 12.3 to 14.3% of total essential AA for lysine). Duodenal essential AA flow did not differ (P = 0.10 to 0.65) with forage intake level for eight of the 10 essential AA. Duodenal flow of arginine decreased linearly (P = 0.01), whereas duodenal flow of tryptophan increased linearly (P = 0.002) as forage intake increased from 30 to 105% of maintenance. Balancing intestinal essential AA supply in beef cattle can be accomplished by varying intake of a RUP supplement.

This study was carried out to evaluate the effect of feed withdrawal and handling intensity on blood acid-base responses and muscle glycolytic potential in slaughter-weight pigs. Sixty crossbred pigs (BW = 107.7 +/- 0.56 kg; 44 barrows and 16 gilts) were used in a randomized complete block design with a 2 x 2 factorial arrangement of treatments: 1) feed withdrawal (0 vs. 24 h), and 2) handling intensity (low vs. high). The high-intensity handling treatment consisted of moving the pigs through a passage (12.2 m long x 0.91 m wide) for eight laps using an electric goad two times per lap. Pigs in the low-intensity handling treatment were moved at their own pace through the passage for eight laps using a livestock panel and paddle. Biopsy samples were collected from the LM at the beginning of feed withdrawal, at the end of the handling procedure, and 4 h after handling. Blood samples were collected 2 h before and immediately after the handling procedure. There were no interactions between feed withdrawal and handling intensity for any of the variables measured. Feed withdrawal decreased (P < 0.05) baseline and posthandling body temperature (38.85 vs. 38.65 degrees C; SEM = 0.060 and 39.70 vs. 39.37 degrees C; SEM = 0.04, respectively) and blood glucose, lowered (P < 0.05) baseline partial pressure of oxygen and partial pressure of carbon dioxide, and increased (P < 0.01) baseline and posthandling plasma free fatty acid concentrations. High-intensity handling produced higher (P < 0.01) posthandling lactate and glucose, and lower (P < 0.01) posthandling blood pH (7.33 vs. 7.18 +/- 0.02, respectively), bicarbonate, base excess, and total carbon dioxide than low-intensity handling. Longissimus muscle glycolytic potential of fasted pigs was lower (P < 0.01) than in fed pigs at the end of the handling procedure (177.2 vs. 137.0 micromol/g of wet tissue; SEM = 10.08, respectively). There was no effect of handling intensity on longissimus muscle glycolytic potential. Feed withdrawal did not attenuate the blood acid-base changes caused by handling; however, the combination of feed withdrawal and handling decreased muscle glycolytic potential.

Two experiments were conducted to determine the effect of feed withholding on carcass and viscera weights and meat quality in grow-finish swine. Experiment 1 included 528 pigs that were marketed from 24 pens and subjected to either 6 (control) or 24 h of feed withholding before marketing. Experiment 2 included 324 pigs that were marketed from 36 pens that were subjected to 6 (control), 16, or 24 h of feed withholding before marketing. In both experiments, pigs from each pen were marketed over a 14-d period in three groups, each 7 d apart. In Exp. 1, withholding feed for 24 h decreased viscera weight, carcass weight and yield, and feed intake during the 14-d marketing period compared with the control group (P < 0.05). Subjective measures of color, firmness, and marbling in fresh pork did not differ for the two treatment groups. In Exp. 2, withholding feed for 16 or 24 h decreased (P < 0.05) viscera weight compared with that of the control group. Withholding feed for 24 h decreased feed intake during the 14-d marketing period compared with intake of the control group. Withholding feed for 16 h did not decrease carcass weight, but carcass weights in the 24-h group were lower than those of the 16-h group in this Exp. 2 (P < 0.05). Color, firmness, marbling, and shear force did not differ among treatment groups in Exp. 2; however, cooking loss in pork from the control group exceeded that of the 24-h treatment. Gain:feed and ADG were not affected by treatment during the marketing period in either experiment. We conclude that withholding feed for either 16 or 24 h decreases viscera weight and feed intake during the marketing phase in finishing swine. These changes could potentially benefit both the producer and the processor with only minimal effects on carcass weight and pork quality.

Expression profiling using microarrays allows for the detailed characterization of the gene networks that regulate an animal's response to environmental stresses. During nutritional restriction, processes such as protein turnover, connective tissue remodeling, and muscle atrophy take place in the skeletal muscle of the animal. These processes and their regulation are of interest in the context of managing livestock for optimal production efficiency and product quality. Here we expand on recent research applying complementary DNA (cDNA) microarray technology to the study of the effect of nutritional restriction on bovine skeletal muscle. Using a custom cDNA microarray of 9,274 probes from cattle muscle and s.c. fat libraries, we examined the differential gene expression profile of the LM from 10 Brahman steers under three different dietary treatments. The statistical approach was based on mixed-model ANOVA and model-based clustering of the BLUP solutions for the gene x diet interaction effect. From the results, we defined a transcript profile of 156 differentially expressed array elements between the weight loss and weight gain diet substrates. After sequence and annotation analyses, the 57 upregulated elements represented 29 unique genes, and the 99 downregulated elements represented 28 unique genes. Most of these co-regulated genes cluster into groups with distinct biological function related to protein turnover and cytoskeletal metabolism and contribute to our mechanistic understanding of the processes associated with remodeling of muscle tissue in response to nutritional stress.

Maternal diet influences fetal growth and postnatal development. We hypothesized that conceptuses gestated in sows provided ad libitum vs. restricted feed intake would differ in the milieu of hormones, growth factors, nutrients, and metabolites associated with growth and metabolism. This hypothesis was tested in two experiments by providing fourth-parity sows (Pig Improvement Co. C15 bred to Line 326 boars) with either 1.81 kg/d (as-fed basis; control) or ad libitum access to gestation diet. In Exp. 1, control (n = 6) or ad libitum (6.4 +/- 0.11 kg/d; n = 9) treatments were provided from d 29 to 45 (onset of estrus is d 0), and sows were slaughtered on d 46. Ad libitum sows gained more weight from d 29 to 45 than controls (34.0 vs. 4.32 kg, respectively; P < 0.01). No differences were observed on d 46 for the number of fetuses, conceptus attachment length, allantoic + amniotic fluid volume, placental weight, fetal weight, and fetal crown-to-rump length. Variation in fetal crown-to-rump length was less (P < 0.03) in sows fed ad libitum. Sows fed ad libitum had greater (P < 0.01) IGF-I and insulin concentrations in plasma than controls on d 43. In Exp. 2, sows were fed 1.81 kg/d (n = 6) or ad libitum (7.0 +/- 0.11 kg/d; n = 4) from d 30 to 56 of gestation, when sows were anesthetized and samples were collected surgically from their gravid uteri. Sows fed ad libitum gained more weight (P < 0.01) than did controls and had more (P < 0.06) IGF-I in their plasma and the plasma collected from umbilical veins of their fetuses. No differences were found for concentrations of insulin or glucose in plasma of sows or fetuses, but urea N concentrations were greater (P < 0.05) in maternal plasma and in the plasma, and allantoic and amniotic fluids of conceptuses from sows fed ad libitum. Combined data from Exp. 1 and 2 revealed a treatment x fetal number interaction (P < 0.05) for average fetal weight. The expected negative relationship between within-litter average fetal weight and the number of fetuses per uterus was observed for control sows (y = 115.4 -1.75 x fetal number; P < 0.05), but litters of ad libitum sows did not show this effect. The hypothesis that providing feed in excess of established requirements in early gestation affects the in utero milieu is supported by these results. Data further reveal that, at least at mid-gestation, the restraint to fetal growth that is exhibited when fetal number increases in control sows is not exhibited when sows are fed ad libitum.

The objectives of this study were to evaluate intestinal cellularity and vascularity in mature ewes in response to dietary restriction and pregnancy status and to quantify the response of these variables to increased nutrient demand of fetal growth. In Exp. 1, 28 mature Dorset x crossbred white-faced ewes (61.6+/-1.8 kg initial BW) were fed a pelleted, forage-based diet. Treatments were arranged in a 2 x 3 factorial, with dietary restriction (60% restriction vs. 100% maintenance for respective states of pregnancy) and pregnancy status (nonpregnant, NP; d 90 and 130) as main effects. Dietary treatments were initiated on d 50 of gestation and remained at 60 or 100% maintenance throughout the experiment. Nonpregnant ewes were fed dietary treatments for 40 d. In Exp. 2, four Romanov ewes were naturally serviced (Romanov fetus and Romanov dam; R/R); two Romanov embryos per recipient were transferred to four Columbia recipients (Romanov fetus and Columbia recipient; R/C), and three Columbia ewes were naturally serviced (Columbia fetus and Columbia dam; C/C). In Exp. 1, dietary restriction and pregnancy status interacted with regard to maternal jejunal DNA concentration (P < 0.01), with restricted ewes having a greater DNA concentration (mg/g; fresh basis) at d 130. Vascularity (percentage of total tissue area) in the jejunum was increased (P < 0.06) as a result of dietary restriction and pregnancy status. Total microvascular volume ofjejunal tissue was not altered by dietary restriction and increased (P < 0.01) at d 130 of pregnancy. In Exp. 2, R/R ewes had less (P < 0.09) DNA (g) in the jejunum compared with R/C and C/C ewes. Jejunal vascularity (%) was increased (P < 0.05) in R/R ewes compared with R/C or C/C ewes, whereas total jejunal microvascular volume remained unchanged. These data demonstrate intestinal vascular density responds to changes in diet and physiological state. In addition, pregnancy increased total jejunal microvascular volume.

The correlated responses in feed intake and G:F ratio with selection for increased growth rate were evaluated by comparing selected (S) and control (C) brown trout (Salmo trutta) reared under conditions known to affect feed efficiency: feed restriction and periods of compensatory growth. Nitrogen and energy requirements for maintenance and growth were also measured. Trout were allotted at comparable BW (3.7+/-0.06 and 3.8+/-0.04 g, for C and S respectively) to triplicate groups per treatment. The experiment lasted a total of 198 d, during which animals were successively submitted to a 116-d feeding phase and fed 10, 30, 50, 70, 100, and 140% of their usual daily ration (UDR), a 35-d phase of food deprivation, and a 47-d refeeding phase. The G:F of C and S were comparable in all experimental conditions tested. During the feeding phase, S grew better than C only when fed 100 and 140% UDR (P < 0.001). This was explained by a higher feed intake capacity. The requirements for growth and maintenance were similar among the lines, which is in agreement with their comparable loss of weight (mean energy loss of -53 and -55 kJ/(kg x d) for C and S, respectively; P > 0.38) observed during the feed deprivation phase and the lack of differences in carcass composition (fat, P > 0.35; protein, P > 0.54). During the refeeding phase, growth performance and G:F were high in all groups. The daily growth coefficient was higher in S than in C (P < 0.001) because of a higher feed intake (P < 0.001). An increase in absolute individual variability in final BW and length was associated with the level of food restriction in both lines; however, it always remained lower in S than in C. In conclusion, fish selected for growth under ad libitum conditions will only exhibit growth superiority when fed diets close to ad libitum, and there was no evidence that selection was associated with an improvement in efficiency of maintenance nor in retention of body tissues.

Calpains are crucial for the degradation of myofibrillar proteins in muscle. Calpastatin is a specific inhibitor of calpains. The objective of this study was to elucidate the effect of nutrient restriction on the activity of calpains and calpastatin in the skeletal muscle of both cows and fetuses. Beginning 30 d after conception, 20 cows were fed either a control diet consisting of native grass hay fortified with vitamins and minerals at recommendations for a mature cow to gain 0.72 kg/d or half the vitamins and minerals and millet straw at 68.1% of NEm requirements. Cows were slaughtered on d 125 of gestation, and the LM was sampled at the 12th rib for calpain and calpastatin measurement. When comparing the muscle samples from nutrient-restricted and control cows, no difference in the activity of calpain I and II was observed; however, there was a significant difference (P < 0.05) in calpastatin activity. Muscle samples from control cows had greater calpastatin content than those of nutrient-restricted cows (P < 0.05); in contrast, the calpastatin content of fetal muscle was greater in fetuses gestated by nutrient-restricted cows than those of control cows (P < 0.05). Further, there were three calpastatin isoforms of 125, 110, and 70 kD detected in fetal muscle, whereas only the110-kD isoform was detected for cow muscle. These results indicate that the activity of the calpain system in skeletal muscle is mainly controlled through the expression of calpastatin. Alternating the calpastatin content in muscle and thereby modulating calpain activity may provide a mechanism for the maintenance of fetal muscle growth during nutrient restriction, whereas skeletal muscle loss in cows is upregulated.

The possible roles of dietary protein level and feed restriction in regulating mammary development of prepubertal gilts were investigated. Cross-bred gilts were fed a commercial diet until 90 d of age and then divided into four nutritional regimens based on two pelleted diets (as-fed basis): a high-protein diet (HP = 13.8 MJ of ME, 1.0% total lysine, 18.7% CP) and a low-protein diet (LP = 13.8 MJ of ME, 0.7% total lysine, 14.4% CP). Nutritional regimens were as follows: 1) HP ad libitum until slaughter (n = 22, T1); 2) HP ad libitum until 150 d of age followed by LP until slaughter (n = 20, T2); 3) LP ad libitum until slaughter (n = 21, T3); and 4) HP with a 20% feed restriction until slaughter (n = 19, T4). Gilts were weighed, their backfat thickness was measured, and jugular blood samples were obtained on d 90, 150, and at slaughter to determine concentrations of prolactin, IGF-I, leptin, and glucose. Gilts were slaughtered 8+/-1 d after their first or second estrus (202.7+/-14.5 d of age). Mammary glands were excised, parenchymal and extraparenchymal tissues were dissected, and composition of parenchymal tissue (protein, fat, DM, DNA, protein/DNA) was determined. The T4 gilts weighed less (P < 0.01) and had less backfat (P < 0.01) than did gilts on other treatments on d 150 and at slaughter. Treatments had no significant effects on prolactin, IGF-I, or glucose concentrations, but there was a treatment x day interaction (P < 0.01) for leptin, with concentrations being lower at slaughter in restricted-fed (T4) vs. LP (T3) gilts (P < 0.05). There was less extraparenchymal mammary tissue (P < 0.01) in T4 gilts than in gilts from the other groups and a tendency (P = 0.13) for the amount of parenchymal tissue to be lower in T4 gilts. In conclusion, a lower lysine intake during prepuberty did not hinder mammary development of gilts, but a 20% feed restriction decreased mass of parenchymal and extraparenchymal tissues. The effect of feed restriction on extraparenchymal tissue is most likely associated with the lower fat deposition.

Four studies were designed to determine whether 1) tumor necrosis factor-alpha (TNF) and the Lipopolysaccharide (LPS) binding ligand, CD14, are produced by sheep adipose tissue; 2) nutritional reserves and/or short-term fasting affect circulating concentrations of TNF; 3) there is a relationship between TNF and metabolic factors in sheep; and 4) inflammation alters circulating concentrations of leptin. In Exp. 1 and 2, ewes were assigned, based on ultrasonic assessments of last-rib subcutaneous fat measurements to fat (fat thickness > 1 cm; mean = 1.52 +/- 0.03 cm) or thin (fat thickness < 1 cm; mean = 0.25 +/- 0.03 cm) groups. Fat and thin ewes were assigned to fed or fasted groups for a total of four groups (fed-fat; fasted-fat; fed-thin; fasted-thin). Fed-ewes had ad libitum access to feed, and fasted-ewes were prohibited feed 48 h before initiation of sample collection. In Exp. 1, subcutaneous fat samples were collected from just above the last rib for detection of TNF and CD14 mRNA, and immunoreactivity. Tumor necrosis factor-alpha-like immunoreactivity in adipocytes was sparse, more pronounced in cells in fed-ewes than fasted-ewes, and localized to membranes between adjacent cells in nucleated regions. Immunoreactivity for CD14 was minimally observed but present in adipocytes and widely expressed in infiltrating monocytes and epithelial vascular cells. Leptin was detected in adipocytes. In Exp. 2, plasma samples collected every 6 h for 24 h were analyzed for plasma concentrations of TNF. Fat ewes had greater plasma concentrations of TNF than thin ewes (P = 0.039). In Exp. 3, wethers were injected i.v. with interleukin-1beta or TNF. Blood samples were collected every 15 min for 8 h following injection. Plasma concentration of leptin was not affected by treatment (P > 0.39). In Exp. 4, wethers were injected with LPS. Blood samples were collected every 15 min for 8 h following injection. Plasma concentration of leptin was not altered by LPS (P > 0.20). These results provide evidence: 1) of TNF-like immunoreactivity within fat tissue; 2) that elements within fatty tissues have CD14 that may allow adipocyte function to be directly affected by LPS; 3) that plasma concentrations of leptin are not altered by LPS treatment; and 4) that circulating concentrations of TNF are elevated with obesity in sheep.

The first objective of this study was to test how well a function that was developed to describe heat production (HP) in growing ewes fit HP data in growing heifers. The second objective was to determine the pattern of adaptation of HP to feed restriction and subsequent realimentation of nutrients. At 234.5 +/- 0.5 d of age, HP was determined by indirect calorimetry on 32 Meat Animal Research Center III heifers. Following the first calorimetry measurement, heifers on the High-High (HH) treatment continued to receive ad libitum access to feed, and daily feed offered to the Low-High (LH) heifers was set at 157 Mcal of ME/kg of BW0.75. Feed restriction of LH heifers continued for 84 d. After 84 d of restriction, LH heifers were allowed ad libitum access to feed. Heat production was determined 4 and 11 wk following feed restriction and 2, 5, 12, and 18 wk following realimentation. There was no residual bias when HP in ad libitum-fed heifers was estimated with an equation form developed in growing ewes: [(kcal/d) = f(BW, matBW) = BW (Ae[k(BW/mature BW)])], nor was there a residual bias when HP was predicted with an allometric equation: [(kcal/d) = f(BW) = A(BWk)]. However, there were residual biases when HP was estimated with an allometric equation that set the exponent to 0.75. Heat production per unit of BW of LH heifers was lower than that of HH heifers at 4 wk of feed restriction (P < 0.001), but HP did not differ between treatments at 11 wk of feed restriction (P = 0.87). At 2 (P = 0.002) and 5 wk (P < 0.001) following the increase in feed offered, HP per unit of BW of the LH heifers was greater than that of the HH heifers. Heat production did not differ between treatments at 12 and 18 wk following refeeding (P < 0.17). Our findings demonstrate that the relationship between HP and BW is described equally well by a logistic and allometric function, but applying a generalized interspecies exponent in an allometric equation to growing heifers results in a bias in estimating HP. The equation form developed in ewes can be used to develop a single equation for the prediction of HP across ages in heifers.