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Our study objectives were to evaluate the effects of divergent rates of body weight (BW) gain during early gestation in beef heifers on F0 performance, metabolic and endocrine status, colostrum immunoglobulins, and subsequent F1 calf characteristics, growth performance, concentrations of hormones and metabolites, and response to vaccination. Angus-based heifers (n = 100; BW = 369 ± 2.5 kg) were adapted to individual feeding for 14 d and bred using artificial insemination with female-sexed semen. Heifers were ranked by BW and assigned to either a basal diet targeting 0.28 kg/d gain (low [LG], n = 50) or the basal diet plus an energy/protein supplement targeting 0.79 kg/d gain (moderate gain [MG], n = 50) until day 84 of gestation. Dam BW and blood samples were collected at 6 time points during gestation; body composition was evaluated on days -10 and 84; and fetal measurements were taken on days 42, 63, and 84. At calving (LG, n = 23; MG, n = 23), dam and calf BW were recorded; and colostrum, calf body measurements, and blood samples were collected. Cow-calf pairs were managed on a common diet from calving to weaning, followed by a common postnatal development period for all F1 female offspring. Growth performance, hormone and metabolite profiles, feeding behavior, and reproductive performance were assessed from birth to prebreeding in F1 heifers. Offspring were vaccinated against respiratory disease and bovine viral diarrhea pathogens on days 62.3 ± 4.13 and 220.3 ± 4.13 postcalving. By design, MG dams were heavier (P < 0.0001) than LG on day 84, and the BW advantage persisted until subsequent weaning of F1 calves. Concentrations of serum IGF-1 and glucose were increased throughout gestation (P < 0.001) in MG dams, whereas concentrations of NEFA were decreased (P < 0.001) in LG dams. Calves from MG dams were 2.14 kg heavier (P = 0.03) and had larger chest circumference (P = 0.04) at birth compared with LG cohorts. Heifers from MG dams continued to have greater (P ≤ 0.03) BW gain and feed efficiency during the development period, but no differences were observed (P ≥ 0.13) in body composition, concentrations of hormones and metabolites, feeding behavior, puberty attainment, and response to vaccination in F1 offspring. Hence, early gestation rate of gain impacted BW and concentrations of glucose and IGF-1 throughout gestation in the F0 dam, resulting in altered F1 calf BW and measurements at birth and increased gain and efficiency during the development period., (© The Author(s) 2024. Published by Oxford University Press on behalf of the American Society of Animal Science. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

The objective of this research was to evaluate effects of replacing sorghum × Sudangrass hay with ground juniper in gestating ewe supplements on pre- and postpartum growth performance, serum metabolites and hormonal concentrations, milk fatty acid composition, and progeny preweaning performance. In a completely randomized design, commercial Rambouillet ewes (age = 3 to 5 yr; initial BW = 65.2 ± 1.6 kg) on a base diet of long-stem sorghum × Sudangrass hay were assigned to 1 of 4 dietary supplements in which ground juniper replaced 0% (CNTL), 33% (18JUN), 66% (36JUN), or 100% (54JUN) of the ground sorghum × Sudangrass hay in a pelleted supplement with ground juniper from d 38 ± 4 of gestation to 2 d postpartum. Treatment DM diet intake overall (g/kg BW) in ewes receiving no juniper was similar ( ≥ 0.38) to that of those receiving increasing concentrations of juniper. Changes in ewe BW and BCS were similar ( ≥ 0.24) in ewes throughout gestation. All serum metabolites and hormones were within normal clinical ranges; however, serum IGF-1 decreased linearly ( = 0.003), alanine increased (linear; = 0.003), and serum Na decreased (linear; = 0.049) as the percentage of juniper increased in the diet. Ewe milk fatty acid composition was similar ( > 0.05) for the majority of fatty acids across treatment groups, with the exception of arachidonic acid (C20:4n6) being greater ( < 0.02) in 54JUN vs. CNTL ewe milk. Lamb birth weights were similar ( = 0.13), whereas lamb ADG tended to differ (quadratic; = 0.06) from d 0 to 14, with 18JUN being the least. At weaning, BW tended ( = 0.09) to linearly decrease in lambs born to ewes consuming greater concentrations of juniper but were not different ( = 0.26) between CNTL and 18JUN, 36JUN, and 54JUN. Results indicated that feeding increasing levels of ground juniper in supplements did not negatively alter ewe performance or serum metabolites and hormones measured pre- and postpartum. Lamb birth weight and preweaning performance appeared unaffected by maternal consumption of ground juniper containing supplements. Results also provide novel information regarding the effects of plant secondary compound consumption throughout pregnancy on ewe and progeny performance and health.

The aim of this study was to assess the effect of GnRH vaccination in boars (BO), barrows (BA), and gilts (GI) slaughtered at an average BW of 133 kg. Forty BO, 40 BA, and 40 GI were housed individually, fed ad libitum, and divided into 2 groups of 20 pigs per sex, a control group (CON) and a GnRH vaccinated group (IC). The IC group received 2 injections of GnRH vaccine (Improvac) at 70 and 105 kg. In BA, GnRH vaccination had minor effects on performance. Observed effects in BO and GI are therefore probably not caused by the GnRH vaccination itself but by the subsequent withdrawal of gonadal hormones. In BO, the increased feed intake after GnRH vaccination ( < 0.001), accompanied by a fall in estradiol and testosterone levels, led to faster growth ( = 0.014), increased back fat thickness ( = 0.021), and a tendency for a decreased meat percentage ( = 0.052). GnRH vaccination of BO decreased the boar taint-related sensory attribute scores similar to the levels of BA and GI ( < 0.001). In GI, the increased feed intake after GnRH vaccination ( < 0.001), accompanied by low progesterone levels, led to faster growth ( < 0.001), increased back fat thickness ( = 0.018), decreased meat percentage ( = 0.032), and a decreased shear force ( = 0.002) without significant differences in the sensory profile.

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.

Gestating Angus, nonlactating, spring-calving cows were used to determine variation in maintenance energy requirements (MR); to evaluate the relationship among MR and cow and calf performance, plasma concentrations of IGF-I, T4, glucose, insulin, and ruminal temperature; and to describe the LM proteome and evaluate protein abundance in cows with different MR. Cows (4 to 7 yr of age) with a BCS of 5.0 ± 0.2 and BW of 582 ± 37 kg in the second to third trimester of gestation were studied in 3 trials (trial 1, n = 23; trial 2, n = 32; trial 3, n = 38). Cows were individually fed a complete diet in amounts to meet predicted MR (Level 1 Model of NRC), and feed intake was adjusted weekly until constant BW was achieved for at least 21 d (maintenance). Cows were classified on the basis of MR as low (>0.5 SD less than mean, LMR), moderate (±0.5 SD of mean, MMR), or high (>0.5 SD more than mean, HMR) MR. Blood samples were taken at maintenance and at 2 mo postpartum in trial 2. Muscle biopsies were taken from LMR and HMR after cows consumed actual MR for 28 d (trial 2) or 21 d (trial 3). Proteins from LM were separated by 2-dimensional difference gel electrophoresis and were identified, and abundance was quantified and compared. The greatest differences in MR between cows were 29%, 24%, and 25% in trials 1, 2, and 3, respectively. Daily MR (NEm, kcal·BW(-0.75)·d(-1)) averaged 89.2 ± 6.3, 93.0 ± 4.9, and 90.4 ± 4.6 in trials 1, 2, and 3, respectively. Postpartum BW and BCS, calf birth and weaning weights, postpartum luteal activity, and ruminal temperature were not influenced by MR of the cows. Concentrations of IGF-I were greater (P = 0.001) in plasma of MMR compared with LMR cows consuming predicted MR diets, and MR was negatively correlated with concentrations of IGF-I in plasma (r = -0.38; P = 0.05) at 2 mo postpartum. A total of 103 proteins were isolated from LM; 52 gene products were identified. Abundance of specific proteins in the LM was not influenced (P > 0.11) by MR. Variation in MR of cows will make it possible to improve feed efficiency by selection. Identification of biomarkers for MR will allow selection of more efficient cows, which consume less feed and produce calves with similar weaning weights. Productive cows that require less feed for maintenance will improve efficiency of production and enhance sustainability of the environment.

This study used an endocrinological approach to explain the differences between sows that have higher vs. lower preweaning mortality in a group-farrowing system. The association between sows that had 2 or more piglets die within the first 72 h postfarrowing (high risk) or sows that had 1 or no piglets die within the first 72 h postfarrowing (low risk) with changes in serum hormone concentrations was investigated. Multiparous sows (n = 63; parity 2 to 7) from 4 contemporary breeding groups, each mated within a week, were used. Sows were housed in a group-farrowing system where 8 sows farrowed in individual pens and shared a communal feeding and dunging area in each room. Reproductive performance, including total born, born alive, and stillborn per litter, individual weight of piglets at birth and weaning (at 5 wk postfarrowing), litter size at weaning, preweaning mortality of piglets, and sow BW before farrowing and after weaning, were recorded for all sows. Of these sows, 14 sows from 2 breeding groups were selected randomly for blood sampling through an indwelling ear vein catheter. A blood sample was collected daily from each sow 2 d prefarrowing through 2 d postfarrowing. Serum samples were analyzed for prolactin, oxytocin, cortisol, and urocortin concentrations using RIA. Among the 14 sows, 7 sows lost 2 or more piglets during the first 72 h after farrowing and were classified as high risk sows, and the other 7 sows lost 0 or 1 piglet during the same period and were classified as low risk sows. Catheters in 11 sows (5 high risk sows and 6 low risk sows) remained functional for the entire sampling period. Results indicate that high risk sows farrowed larger litters (live born = 13.8 ± 0.50 vs. 11.3 ± 0.48 piglets; P = 0.03) with lighter piglets (1.4 ± 0.04 vs. 1.7 ± 0.05 kg; P < 0.001) compared with low risk sows. In addition, high risk sows had greater oxytocin concentrations (0.09 vs. 0.07 ng/mL; SE = 0.02, P = 0.01), which might be associated with larger litters farrowed, compared with low risk sows. There were no differences between high risk and low risk sows (P > 0.30) in terms of serum prolactin, cortisol, or urocortin concentrations. These results suggest that litter size and birth weight of piglets played an important role in preweaning mortality of piglets and hormone concentrations in sows were not associated with piglet mortality in the group-farrowing system used.

Heat stress-induced reduction in feed intake is an annoyance of the poultry industry. Feed intake is regulated by complex mechanisms in which brain-gut neuropeptides are involved, but the changes in such neuropeptides in broiler chickens during heat exposure remain unclear. In this study, we investigated the effects of acute heat stress (35°C, 6 h, and 65% relative humidity) on the gene expression of appetite-regulating peptides in the hypothalamus and gastrointestinal tract of broiler chickens at 42 d of age. The hypothalamic mRNA levels of neuropeptide Y, agouti-related peptide, pro-opiomelanocortin, cocaine- and amphetamine-regulated transcript, corticotropin-releasing hormone, melanocortin 4 receptor, melanin-concentrating hormone, prepro-orexin, cholecystokinin (CCK), and ghrelin did not significantly change (P>0.05) in the heat-exposed broiler chickens. However, the mRNA levels of ghrelin in the glandular stomach, duodenum, and jejunum significantly increased and the mRNA level of CCK in the duodenum significantly decreased. The results indicate that acute heat stress had no effect on the gene expression of central appetite-regulating peptides under current experimental conditions; however, some gastrointestinal tract peptides (e.g., ghrelin and CCK) might play a role in the regulation of appetite in acute heat-exposed broiler chickens. Furthermore, ghrelin in the glandular stomach, duodenum, and jejunum might be the main regulative target of acute heat stress induced anorexia.

Heat stress (HS) causes seasonal infertility in sows and decreases reproductive efficiency. The objective was to examine thermoregulation, metabolic responses, and reproduction in sows exposed to HS or thermoneutral (TN) conditions during different phases of a production cycle (gestation, lactation, and breeding). Fifty-eight first-parity Landrace (n = 26) or Landrace × Large White F1 (n = 32) sows were rotated through environmental chambers for 57 d beginning in late gestation. The ambient temperature sequences included either TN (18°C to 20°C) or HS (24°C to 30°C) for each production phase with the following treatment groups: TN-TN-TN (n = 15), TN-HS-TN (n = 14), HS-TN-HS (n = 14), and HS-HS-HS (n = 15) for gestation-farrowing-breeding (20, 24, and 13 d, respectively). Regardless of the temperature treatment, rectal temperatures were greater (P < 0.001) during lactation (39.36°C ± 0.01°C) than during the gestation (38.27°C ± 0.01°C) or the breeding period (38.77°C ± 0.01°C). The increase in rectal temperature (P < 0.001) and respiration rate (P < 0.001) in response to the HS was greatest during lactation. There was an effect of day (P < 0.001) on serum IGF-1 and insulin concentrations because both insulin and IGF-1 increased after farrowing. Compared with HS sows, the TN sows had greater feed intake (P < 0.001) and greater serum concentrations of insulin (early lactation; P < 0.05) and IGF-1 (late lactation; P < 0.05) when they were lactating. The effects of HS on sow BW, back fat, and loin eye area were generally not significant. Average BW of individual piglets at weaning was approximately 0.5 kg lighter for the sows in the HS farrowing room (P < 0.05). Weaning-to-estrus interval, percentage sows inseminated after weaning, subsequent farrowing rate, and subsequent total born were not affected by treatment. In summary, regardless of ambient temperature, sows undergo pronounced and sustained changes in rectal temperature when they transition through gestation, lactation, weaning, and rebreeding. The effects of HS on rectal temperature, respiration rate, feed intake, and metabolic hormones were greatest during lactation. The controlled HS that we imposed affected piglet weaning weight, but rebreeding and subsequent farrowing performance were not affected.

This project aimed to determine the effect of Se as inorganic Na-selenite (MSe) or organic Se-yeast (OSe) on antioxidant status, hormonal profile, reproductive performance, and embryo development in first-parity gilts. Forty-nine gilts were allocated to 1 of the 3 dietary treatments starting at first pubertal estrus and lasting up to 30 d after AI: control [CONT: basal diet (Se = 0.2 mg/kg) without added Se; n = 16], MSe (CONT + 0.3 mg/kg of MSe; n = 16), and OSe (CONT + 0.3 mg/kg of OSe; n = 17). Blood was collected from all gilts on the day after each onset of estrus and on d 30 after AI. Blood was also collected daily from d -4 to d +4 of the third onset of estrus (d 0) in 8 CONT, 9 MSe, and 8 OSe cannulated gilts. Gilts had received, after d 14 and 15 of their third estrus, a hormonal challenge to induce super-ovulation. At slaughter, embryos and corpora lutea (CL) were weighed and measured. Blood Se was less (P < 0.01) in CONT than in Se gilts and greater in OSe than in MSe (P < 0.01) from the first estrus until d 30 of gestation. At the same time, blood Se-dependent glutathione peroxidase (GSH-Px) decreased for CONT gilts, whereas it increased for both Se groups. The increase was greater in MSe than in OSe gilts (treatment × time, P = 0.02). Plasma 3,3',5-triiodothyronine and thyroxine concentrations for MSe tended to be less than for OSe gilts (P < 0.06). In cannulated gilts, plasma FSH tended to change among treatments (treatment × time, P = 0.06), and plasma estradiol-17β (E(2)) was less (P = 0.01) for MSe than for OSe. There was no treatment effect on mean litter size or embryonic antioxidant status. The Se content of individual embryos was greater for Se-treated than for CONT gilts (P = 0.03), and Se content of individual embryos and total litter was greater for OSe than for MSe gilts (P < 0.01). The length, weight, and protein content of embryos were greater in OSe than in MSe gilts (P < 0.05). There was no treatment effect on weight, length, Se content, and ferric reducing antioxidant power of CL, but GSH-Px in CL was greater for Se than for CONT gilts (P = 0.02). In summary, the Se status response of gilts to dietary Se was affected by both the quantity and the source of Se dietary supplements. Moreover, the uterine transfer of Se to embryos was improved with OSe as compared with MSe, and this was concomitant with an enhanced development of embryos.

Seventy-two barrows (Landrace × Large White, initial BW of 4.9 ± 0.3 kg and 17 ± 3 d old) were used to determine if dietary chito-oligosaccharides can replace antibiotics as a means to reduce signs associated with infection in weaned pigs challenged with Escherichia coli. Pigs were assigned to 1 of 4 treatments in a randomized complete block design using 6 pens per treatment with 3 pigs per pen. The treatments consisted of pigs fed the unsupplemented corn-soybean meal diet challenged or unchallenged with E. coli K88 and pigs fed the same diet supplemented with 160 mg of chito-oligosaccharides or 100 mg of cyadox/kg and challenged with E. coli K88. On d 7, 1 group of pigs fed the unsupplemented diet, as well as all pigs fed diets containing chito-oligosaccharides or cyadox, were orally dosed with 30 mL of an alkaline broth containing E. coli K88. Another group of pigs fed the unsupplemented diet was orally dosed with 30 mL of sterilized alkaline broth. Fecal consistency was visually assessed each morning from d 7 to 14. Blood samples were collected at 0, 24, 48, and 168 h postinfection. On d 14 postchallenge, all pigs were killed to evaluate intestinal morphology and determine E. coli concentrations in the intestine. During the postchallenge period (wk 2), unsupplemented pigs challenged with E. coli had decreased (P < 0.05) BW gain, feed intake, fecal consistency, villus height, villus height:crypt depth ratio, and plasma IGF-1, and increased (P < 0.05) diarrhea incidence, E. coli counts in the intestine, plasma interleukin-1β, plasma IL-10, and IGA-positive cells in the jejunal and ileal lamina propria, compared with unchallenged pigs. Supplementation with cyadox largely mitigated these effects. Although chito-oligosaccharide reduced the incidence of diarrhea, the growth performance of E. coli-challenged pigs supplemented with chito-oligosaccharide was not better than that of unsupplemented pigs challenged with E. coli. Therefore, chito-oligosaccharide, at the amount used in this experiment, does not seem to be an effective substitute for antibiotics as a growth promoter for newly weaned pigs challenged with E. coli.

Provision of additional floor heating (33 to 34 degrees C) at birth and during the early postnatal hours is favorable for newborn piglets of domestic sows (Sus scrofa). We investigated whether this relatively high temperature influenced sow behavior and physiology around farrowing. One-half of 28 second-parity pregnant sows were randomly chosen to be exposed to floor heating 12 h after onset of nest building and until 48 h after birth of the first piglet (heat treatment), whereas the rest of the sows entered the control group (control treatment) with no floor heating. Hourly blood sampling from 8 h before and until 24 h after the birth of the first piglet was used for investigation of temporal changes in plasma concentrations of oxytocin, cortisol, and ACTH. In addition, occurrence and duration of sow postures were recorded -8 to +48 h relative to the birth of the first piglet. There was a clear temporal development in sow behavior and hormone concentrations (ACTH, cortisol, and oxytocin) across parturition (P < 0.001), independent of treatment. In general, hormone concentrations increased from the start to the end of farrowing. The observed oxytocin increase and peak late in farrowing coincided with the passive phase where sows lie laterally with an overall reduced activity. Floor heating increased the mean concentration of cortisol (P = 0.02; estimated as 29% greater than in controls) and tended to increase the mean concentration of ACTH (P = 0.08; estimated as 17% greater than in controls), but we did not find any treatment effect on mean oxytocin concentrations, the course of parturition, or the behavior of sows. Behavioral thermoregulation may, however, have lost some function for the sows because the floor was fully heated in our study. In addition, exposure to heat decreased the between-sow variation of plasma oxytocin (approximately 31% less relative to control) and ACTH (approximately 46% less relative to control). Whether this decreased variation may be indicative of acute stress or linked to other biological events is unclear. In conclusion, inescapable floor heating (around 33.5 degrees C) may be considered a stressor for sows around farrowing, giving rise to elevated plasma concentrations of cortisol, but without concurrent changes in oxytocin or behavioral activity.

The current study was performed to clarify the effects of GHRH treatment on milk production and plasma hormones and metabolites in lactating Japanese Black cows (a beef breed) under negative energy balance (EB). Ten multiparous lactating beef cows were offered a normal-energy diet daily (110% of ME requirements for maintenance and lactation) until 5 d in milk (DIM) to standardize the cows before dietary treatment. From 6 DIM to the final days (63 DIM) of the experiment, the cows were allotted to experimental dietary treatments: 5 cows were offered a diet formulated for 130% [high-energy diet (HED)] and the remaining 5 cows were offered a diet formulated for 80% [low-energy diet (LED)] of ME requirements for maintenance and lactation. In addition, all cows received daily subcutaneous injections of 3 mg of bovine GHRH from 36 to 56 DIM (GHRH treatment period). Differences in BW of HED- and LED-fed cows at 63 DIM were +28.4 and -7.2 kg compared with BW at 6 DIM, and HED- and LED-fed cows were under positive EB (+23.7 MJ/d) and negative EB (-11.6 MJ/d) throughout the experiment period. Treatment with GHRH increased (P<0.01) the average daily milk yield to 6.2 kg in HED-fed cows compared with a milk yield of 5.3 kg for 7 d before the GHRH treatment period (pretreatment period); LED-fed cows had no increase in milk production from GHRH treatment. Plasma GH, IGF-1, insulin, and glucose concentrations increased (P<0.05) after GHRH treatment in both HED- and LED-fed cows; GHRH treatment also induced an increase (P<0.05) in the net area under the curve of plasma insulin after glucose challenge in both HED- and LED-fed cows. Plasma urea N concentrations were decreased (P<0.05) by GHRH treatment in HED-fed cows, but not in LED-fed cows. Plasma NEFA concentration was unaffected by GHRH treatment in both HED- and LED-fed cows. We conclude that GHRH treatment of lactating Japanese Black cows stimulates endogenous GH and subsequent IGF-1 secretion and might induce an increase in insulin resistance, irrespective of EB; however, compared with lactating dairy cows, both galactopoietic and lipolytic effects of GHRH might be insufficiently exerted under negative EB in lactating beef cows.

Metabolic demand for sulfur-containing AA increases during inflammation in nonruminants. Therefore, Met supplementation may alleviate the negative effects of infection on N balance. Effects of gram-negative bacterial lipopolysaccharide (LPS) and supplemental dietary Met on N balance, serum hormones and haptoglobin, and plasma urea-N and AA were evaluated in 20 Angus-cross steers (BW = 262 +/- 6.3 kg). Treatments (2 x 2 factorial) were infusion of no LPS (-LPS) or a prolonged low dose of LPS (+LPS) and dietary supplementation of no (-MET) or 14 g/d (+MET) of rumen-protected Met (providing 7.9 g/d of dl-Met). Steers were adapted to a roughage-based diet (DMI = 1.4% of BW daily) and supplemental Met for 14 d, and were then infused (1 mL/min via intravenous catheter) with LPS on d 1 (2 microg/kg of BW) and 3 (1 microg/kg of BW) of a 5-d collection period. Blood was collected on d 1, before LPS infusion, and at 2, 4, 6, 8, 10, 12, and 24 h after LPS challenge. Diet samples, feed refusals, feces, and urine were collected daily for 5 d. Rectal temperature and serum concentrations of cortisol, prolactin, tumor necrosis factor-alpha, and haptoglobin increased, whereas thyroxine and triiodothyronine decreased for +LPS vs. -LPS steers (LPS x h; P < 0.01). Plasma urea-N was greater for +LPS than -LPS steers (LPS; P = 0.03), and serum IGF-1 was not affected (P > or = 0.26) by LPS or Met. Plasma concentrations of Thr, Lys, Leu, Ile, Phe, Trp, Asn, Glu, and Orn decreased, plasma Ala increased, and Gly and Ser initially increased, then declined in +LPS vs. -LPS steers (LPS x h; P < or = 0.04). Plasma Met was greater for +MET than -MET steers before LPS infusion, but declined in +MET steers after LPS infusion (LPS x Met x h; P < 0.01). By design, DMI was not different, but DM digested was less (P = 0.04) for +LPS than -LPS steers. Infusion of LPS did not affect (P > or = 0.24) N intake, fecal N excretion, or N digested, but resulted in greater (P < 0.01) urinary N excretion and less (P < 0.01) N retention. The absence of an LPS x Met interaction (P = 0.26) for N retention indicates that supplemental Met does not improve the N utilization of growing beef steers exposed to a gram-negative bacterial endotoxin. Decreases in plasma concentrations of several essential AA in +LPS steers suggest that metabolic demand for these AA likely increased in steers exposed to endotoxin.

This study was conducted to investigate individual metabolic and endocrine adaptation to lactation under conditions of identical housing and feeding conditions in high-yielding dairy cows. Forty-five cows were studied on a research farm under standardized but practical conditions. From wk 2 before calving until wk 14 postpartum, blood samples were collected at weekly intervals and assayed for blood chemistry and various metabolites and hormones. Body weight, BCS, and backfat thickness were also recorded weekly. Milk yield, milk composition, and feed intake and energy balance were accordingly measured during the postpartum phase. The animals were retrospectively classified according to their plasma concentration of beta-hydroxybutyrate (BHB): cows in which a BHB threshold of 1 mM was exceeded at least once during the experiment were classified as BHB positive (BHB+); cows with BHB values consistently below this threshold were classified as BHB negative (BHB -). Using this classification, differences for NEFA and glucose concentrations were observed, but the mean calculated energy balance did not differ between the groups during the experimental period (-22.2 MJ of NE(1)/d +/- 4.7 for BHB+ and -18.9 MJ of NE(1)/d +/- 4.9 for BHB-). In BHB+ cows, the peripartum decrease (P < 0.05) of BW, BCS, and backfat thickness was more pronounced than in BHB- cows. Mean milk yields did not differ between groups. However, BHB+ cows had greater milk fat and lesser milk protein contents (P < 0.05), resulting in a greater (P < 0.05) fat:protein ratio than in BHB- cows. Thus, to some extent, cows were able to compensate for the negative energy balance by adjustments in performance. Milk acetone concentrations followed BHB concentrations in blood. Insulin-like growth factor-I and leptin concentrations were greater (P < 0.05) in BHB- cows during the time of observation than in the BHB+ cows. Comparing the reproductive variables recorded (first increase of progesterone, first service conception rate, number of services per conception, interval from calving to first AI, interval from first AI to conception, and days open) between the 2 groups yielded no significant differences. Our findings imply that despite comparable energy balance, there is considerable individual variation of the adaptive ability of cows during early lactation based on a variety of metabolic and endocrine variables.

There are several different milking management systems in Latin America, because Gir cattle are reputed to be easily stressed and not well adapted to machine-milking. This paper, therefore, provides an overview of hormone release and behavior during suckling and milking in Gir cows and their cross-bred offspring. Several experiments were performed to study oxytocin release during exclusive suckling or exclusive hand- and machine-milking, oxytocin, and prolactin release during a mixed suckling-milking system and oxytocin release after weaning. Cortisol concentrations and behavior were also examined. Concentration of oxytocin, released during suckling, and both types of milking were high, but the maximum concentration measured during suckling was significantly greater than that observed during exclusive milking. In the mixed suckling-milking system, the greatest oxytocin and prolactin releases were measured during suckling. Cortisol concentrations measured before, during, and after milking demonstrated that Gir x Holstein and Holstein cows were not stressed. On the other hand, although Gir had greater concentrations of cortisol, the percentage of residual milk for Gir cows was less than for dairy cows exposed to different stressful situations. In general, Gir cows and their crossbred offspring adapted to machine-milking, although these breeds can react negatively to milkers. Gir, Gir x Holstein, and Holstein cows all had similar cortisol levels during and after milking.

The objective of this study was to determine the effects of castration on short-term growth performance, hormone profiles, and behavior in pigs at 3, 6, 9, or 12 d of age. Ninety intact male pigs were assigned randomly to a treatment age by litter [3, 6, 9, or 12 d of age; n = 9 to 13 pigs per treatment (age) group]. Pigs within a single litter were then assigned to noncastrated (NC) or castrated (CAS) treatment groups according to BW. Pigs were nonsurgically fitted with jugular catheters, and blood samples were drawn immediately before castration (0 h) and at 0.5, 1, 1.5, 2, 24, and 48 h after castration. Body weights were obtained when pigs were catheterized and again at 24 and 48 h after castration. Serum samples were analyzed for cortisol, porcine corticosteroid-binding globulin, and dehydroepiandrosterone sulfate (DHEA-S). No differences were detected in initial BW of pigs, and there was no overall treatment effect on growth performance of pigs at 24 or 48 h posttreatment. A time x treatment interaction was detected (P < 0.01) for serum cortisol concentrations, such that cortisol was greater in CAS pigs than in NC pigs. No overall effect of age at castration was observed on cortisol concentrations. At 24 h after castration, serum cortisol concentrations returned to baseline in all treatment groups; however, at 48 h after castration, overall cortisol concentrations were elevated (P < 0.01) in the 6-, 9-, and 12-d-old pigs in both the CAS and NC groups compared with baseline concentrations. Total cortisol and porcine corticosteroid-binding globulin were used to calculate the free cortisol index (FCI). A time x treatment interaction was observed (P < 0.01) for FCI, such that FCI was greater in CAS males than in NC males. The FCI was also affected by age (P < 0.01). There was a time x treatment x age interaction (P < 0.01) for serum DHEA-S, such that DHEA-S concentrations decreased in CAS animals but increased in NC animals, and DHEA-S concentrations increased with age. During the first 2 h after castration, there was an overall age effect (P = 0.01) on the time that pigs spent standing, such that 3-d-old pigs stood more than 6-, 9-, or 12-d-old pigs. Treatment did not influence the time that pigs spent nursing, lying, standing, or sitting, although there was a trend (P = 0.08) for CAS pigs to be less active than NC pigs. These data indicate that castration is stressful regardless of age; however, the stress associated with handling seems to increase as pigs age.

To determine the effects of BCS at parturition and postpartum lipid supplementation on blood metabolite and hormone concentrations, 3-yr-old Angus x Gelbvieh beef cows, which were nutritionally managed to achieve a BCS of 4 +/- 0.07 (479.3 +/- 36.3 kg of BW) or 6 +/- 0.07 (579.6 +/- 53.1 kg of BW) at parturition, were used in a 2-yr experiment (n = 36/yr). Beginning at 3 d postpartum, cows within each BCS were assigned randomly to be fed hay and a low-fat control supplement or lipid supplements with either cracked high-linoleate or high-oleate safflower seeds until d 61 of lactation. The diets were formulated to be isonitrogenous and isocaloric, and the safflower seed supplements were formulated to achieve 5% DMI as fat. On d 31 and 61 of lactation, blood samples were collected preprandially and then hourly postprandially (at 0, 1, 2, 3, and 4 h). Serum insulin (P = 0.27) and glucose (P = 0.64) were not affected by BCS at parturition. The mean concentrations of plasma NEFA (P = 0.08) and beta-hydroxybutyrate (P = 0.08) tended to be greater, and serum IGF-I was greater (P < 0.001) in BCS 6 than BCS 4 cows. Conversely, serum GH was greater (P = 0.003) for BCS 4 cows, indicating that regulation of IGF by GH may have been uncoupled in BCS 4 cows. The postpartum diet did not affect NEFA (P = 0.94), glucose (P = 0.15), IGF-I (P = 0.33), or GH (P = 0.62) concentrations. Oleate-supplemented cows had greater (P = 0.03) serum insulin concentrations, whereas control cows had greater (P = 0.01) plasma beta-hydroxybutyrate concentrations. Concentrations of NEFA (P = 0.05) and glucose (P < 0.001) were greater, and beta-hydroxybutyrate tended (P = 0.07), to be greater at d 3, whereas serum IGF-I was greater (P = 0.003) at d 6 of lactation. Similar concentrations of NEFA, glucose, GH, and IGF-I indicate that the nutritional status of beef cows during early lactation was not influenced by lipid supplementation. However, perturbations of the somatotropic axis in BCS 4 cows indicate that the influence of energy balance and BCS of the cow at parturition on postpartum performance should be considered when making managerial decisions.

Effects of different feeding frequencies on growth performance, preprandial metabolic parameters, and endocrine traits were studied in calves up to 28 d after birth and respective postprandial changes were investigated on d 3 and 7. Calves were fed with a computer-programmed automate that allowed frequent daily intakes (GrA; n = 7) or were fed twice daily by bucket (GrB; n = 7) the same daily amounts (pair-feeding) of colostrum and milk. Weight gains did not differ significantly between groups. Plasma protein was higher (P < 0.01) from d 14 to 28 in GrB than in GrA. Plasma glucose increased postprandially in GrB on d 3 and 7 but in GrA only on d 3, and there was a significant treatment x time interaction on d 3 and 7 after feed intake. For plasma triglycerides there was a significant postprandial treatment x time interaction on d 3, and triglycerides were higher (P < 0.05) in GrA than in GrB before feed intake on d 7. For insulin concentrations on d 7 the treatment x time interaction was significant and concentrations 8 h after feed intake were higher (P < 0.05) in GrA than GrB. For concentrations of growth hormone on d 7 during an 8-h period the treatment x time interaction was significant and concentrations from 320 to 340 min after feed intake were higher (P < 0.05) in GrB than in GrA. Plasma IGF-I concentrations were higher (P < 0.05) in GrA than in GrB on d 7. The hematocrit and concentrations of immunoglobulin G, albumin, urea, creatinine, L-lactate, nonesterified fatty acids, cholesterol, glucagon, and thyroxine did not differ between groups. In conclusion, feed intake at high frequency by an automate transiently changed some metabolic and endocrine traits (glucose, triglyceride, insulin, and IGF-I) but had no significant effects on growth performance during the first 4 wk of life.

To determine the effects of dietary lasalocid and increased dietary fat on reproduction, multiparous Brahman cows (n = 68), body condition score (BCS) of 6.2 +/- 0.7 and BW of 500.9 +/- 42.6 kg, were randomly assigned within sex of calf to receive one of four rations. All treatment groups grazed Coastal bermudagrass overseeded with rye-ryegrass and were given ad libitum access to hay and water. The control (n = 17) group received 4.17 kg x d(-1) x cow(-1) of 4:1 corn:soybean meal. The rice bran (n = 17) group received 4.35 kg x d(-1) x cow(-1) of 3:1:1 corn:soybean meal:rice bran (5.2% dietary fat). The lasalocid (n = 17) group received the Control diet with the addition of 200 mg of lasalocid x d(-1) x cow(-1). The rice bran-lasalocid (n = 17) group received the rice bran diet with the addition of 200 mg of lasalocid x d(-1) x cow(-1). Diets were fed once daily from d 1 after parturition through the detection of first estrus. Weight and BCS of cows and BW of calves were recorded at 14-d intervals from d 1 after parturition through detection of first estrus and at weaning. Cows were bled on d 1, 3, 5, 7, and 14 and at weekly intervals until estrus and on d 7 and d 10 after estrus. Ovarian follicular populations were monitored by transrectal ultrasonography weekly from d 14 after parturition through detection of first estrus. Plasma 13-14-dihydro-15-ketoprostaglandin-F2alpha (PGFM) and progesterone (P4) concentrations were quantified using RIA. Concentrations of PGFM from d 1 to 7 and P4 concentrations on d 7 and 10 after estrus were not influenced (P > 0.10) by diet or sex of calf. Changes in BW and BCS were not affected (P > 0.10) by diet. The number of medium-sized follicles tended to be greater (P < 0.06) in Controls than in cows on lasalocid or rice bran + lasalocid treatments on d 21. Cumulative return to estrus with a functional corpus luteum by d 60 postpartum was greater (P < 0.02) in the rice bran (70.6%) and lasalocid groups (76.5%) than in Controls (52.9%) or the group given rice bran + lasalocid (25.0%). Normal first estrous cycles were less likely (P < 0.07) to be exhibited in cows given rice bran + lasalocid than in other groups. Intervals from calving to corpus luteum formation, functional corpus luteum, and first P4 > or = 1 ng/mL were longer (P < 0.02) in cows given rice bran + lasalocid than in other cows. Combining increased dietary fat (5.2%) with lasalocid lengthened the time to reproductively important events.

In vitro digestion and growth studies were conducted to evaluate the effects of level of soybean oil inclusion in forage-based diets. In Exp. 1, diets were bromegrass hay (H), bromegrass hay and corn-soybean meal supplement (C), C with 3% added soybean oil (O3), and C with 6% added soybean (O6). Diets containing supplements were formulated to be isonitrogenous and isocaloric. Treatment means were compared using a single-degree-of-freedom contrast (H vs C, O3, and O6) and orthogonal polynomial contrasts within diets C, O3, and O6. Diet H had the lowest (P = .0003) IVDMD and a linear decline (P = .0001) in IVDMD was observed from C to O6, but 24-h IVDMD disappearance was greatest (P = .001; quadratic) for O3. Total VFA increased from C to O3 and then decreased from O3 to O6 (quadratic; P = .001), and acetate:propionate ratio decreased linearly (P = .0001) from C to O6. Changes in long-chain fatty acids reflected biohydrogenation by ruminal microbes; however, only 18:3 was hydrogenated to the same extent across all diets. In Exp. 2, 36 Angus x Gelbvieh heifers (260.0 +/- 6.0 kg initial BW) were individually fed C, O3, or O6 as mixed rations for 104 d. Diets were formulated to be isonitrogenous and provide ADG of .91 kg. Feed efficiency and ADG was greatest (P < .02; quadratic) for O3 heifers. Serum NEFA increased linearly (P = .02) and serum glucose (P = .02), cholesterol (P = .002), and GH (P = .04) showed a quadratic response to level of dietary soybean oil. Plasma proportions of 16:0, 16:1, 18:0, and 18:1 increased quadratically (P < .03), and 18:2 increased linearly (P < .001) from C to O6. In Exp. 3, 42 Angus x Gelbvieh heifers (288.7 +/- 6.6 kg initial BW) were divided into six pens (two pens/treatment) in a randomized complete block designed experiment. Rations were delivered as hay plus a top-dressed supplement (C, O3, or O6). Heifers fed O3 conceived 10 d earlier (quadratic; P = .06) than heifers fed C and O6. Other production estimates did not differ (P > or = .10) among dietary treatments. Inclusion of soybean oil at 3% of a forage-based diet increased total VFA, many blood metabolites, ADG, and feed efficiency, and it decreased time to conception. Adding soybean oil as 3% of a forage-based diet is an acceptable feeding strategy for developing beef heifers.

Ruminally protected choline (RPC) was evaluated in two experiments. In Exp. 1, beef steers (n = 160; average initial BW = 350.9 kg) were fed a 90% concentrate diet with either 0, .25, .5, or 1.0% RPC (DM basis) for 112 to 140 d. Feeding .25% RPC increased ADG 11.6% compared with 0% RPC, but responses diminished with increasing RPC level (cubic response, P < .10). Daily DMI was not affected by RPC level, but feed:gain was improved 6.8% with .25% RPC compared with 0% RPC, and responses diminished with increasing RPC level (cubic response, P < .10). Carcass yield grade increased linearly (P < .10) as RPC level increased, but marbling score was lower for all three RPC-containing diets than for the 0% RPC diet (quadratic response, P < .05). In Exp. 2, 20 Suffolk lambs (initial BW = 29.8 kg) were fed an 80% concentrate diet for 56 d with the same RPC levels as in Exp. 1. Serum triglycerides (TG) and cholesterol (CLSTRL) were measured in weekly blood samples, and intensive blood samples were collected on d 28 and 56 to evaluate serum insulin (INS), GH, and NEFA. For the 56-d feeding period, ADG responded quadratically (P < .10) to RPC level, but DMI and feed:gain were not affected. Serum INS and NEFA concentrations increased linearly (P < .05) and serum GH responded cubically (P < .05) to RPC level on d 28, but no differences were noted on d 56. Serum TG concentrations in weekly samples increased linearly (P < .10) with RPC level, but, averaged over all weeks, serum CLSTRL concentrations did not differ (P > .10) among treatments. Quantities of carcass mesenteric (P < .05) and kidney fat (P < .10) increased linearly, but longissimus muscle and liver fat contents did not differ (P > .10) among RPC levels. Supplementing RPC in high-concentrate diets improved performance, but results were not consistent among RPC levels or between cattle and sheep. Potential effects of RPC might be mediated through alterations in fat metabolism and(or) metabolic hormones related to fat metabolism.

Primiparous beef cows (n = 35 Bos taurus, average initial BW of 498 kg) were allotted to treatments in a split-plot designed experiment to determine the effects of supplemental ruminally protected amino acids on cow and calf productivity and metabolic changes in the cows. Cows were fed chopped annual rye hay at 1.5% of BW. The following treatments were used: 1) .8 kg soybean hulls, 1.4 kg ground corn, .6 kg soybean meal (CON); 2) 1.4 kg ground corn, 1.4 kg soybean meal (PRO); 3) PRO plus ruminally protected methionine and lysine (supplied 5 and 10 g, respectively; PRO1); and 4) PRO with twice the level of ruminally protected amino acids in PRO1 (PRO2). Cow weight gain was not different (P > .26) among treatments and averaged 1.2 kg/d for the 45 + 6 d before parturition. After parturition, cow weight gain did not differ (P > .47) between CON and PRO treatments, but it decreased quadratically (P < .01) with increasing level of ruminally protected amino acids. Total milk yield, protein, and fat (4 h) were greater (P < .05) for cows consuming PRO supplements than for CON, whereas CON cattle tended (P = .11) to lose less body condition. Total milk protein showed a quadratic increase (P < .05) in response to level of ruminally protected amino acids that was the inverse of the quadratic response noted for cow weight gain. Serum urea N concentration was greater (P = .07) for cattle consuming additional protein. Metabolic hormones were not affected (P > .18) by dietary treatment, but they responded (P < .05) to changes in physiological state. Supplements with additional protein supported greater (P = .0001) milk urea N concentration and output. Milk urea N concentration increased (P < .05) and milk IGF-I decreased (P < .05) as the lactation period progressed. The measurement of CON and PRO diets revealed that supplements with additional soybean meal had greater (P < .05) DM and N degradation; the extent of forage DM and NDF degradation was similar (P > .05) among treatments. Production shifted away from body weight gain to increased milk protein production when daily supplementation of ruminally protected methionine and lysine increased from 5 and 10 to 10 and 20 g, respectively. This shift in production was not reflective of changes in the metabolic regulators measured.

Multiparous Brahman cows (n = 21) were randomly assigned during late fall within BW and body condition score (BCS) to receive either 3.0 mL of corn oil (C; n = 7), 3.0 mg/(cow x d) triiodothyronine (T3) s.c. in 3.0 mL of corn oil (HYPER; n = 7), or 4.0 mg/(kg x d) 6-n-propyl-2-thiouracil (PTU; fed with concentrate) plus 3.0 mL/d corn oil (HYPO; n = 7). Water, minerals, and Coastal bermudagrass hay were available free choice, and all cows received 3.2 kg x cow(-1) x d(-1) of 5:1 corn:soybean meal concentrate. The feeding period extended through three normal estrous cycles. Blood samples were collected weekly during the first and second estrous cycle, or until d 42 for anestrous cows, and daily throughout the third cycle. Also, between d 9 and 14 of the third cycle, or after d 35 in anestrous cows, intensive samples were collected at 2-h intervals for 24 h. Serum T3, thyroxine (T4), and progesterone (P4) were measured in weekly and intensive samples, and cortisol, insulin, GH, and thyroid-stimulating hormone (TSH) were measured in intensive samples. The altered thyroid status of HYPER and HYPO cows was evident (P < .001) during the third estrous cycle in mean daily T3, T4, and intensive TSH (P < .001) concentrations. Changes in BW and BCS were influenced by treatment (P < .001). A greater (P < .001) proportion of HYPER cows exhibited abnormal cycle length, and three of seven cows became anestrous. For cows that continued normal cycles, treatment did not affect (P > .05) the number of follicular waves, diameter of the dominant follicle, diameter of the ovulatory follicle, or P4 profiles during the third cycle. Insulin and GH concentrations did not differ (P > .05) among treatments in intensive samples, but, mean cortisol was greatest (P < .02) in HYPER cows. For Brahman cows that maintained normal estrous cycles, induced hyper-or hypothyroid status did not influence ovarian function.

A 2 x 3 factorial arrangement of treatments was used to elucidate the mechanism(s) by which prenatal androgenization improves postnatal rate and efficiency of growth and composition of gain in beef heifers. Fifteen control (C) and 15 prenatally androgenized (PA) Angus x Simmental heifers (prenatal treatment, Pretrt) received no (N), estrogen (E), or estrogen and testosterone (ET) implants postnatally (postnatal treatment, Posttrt) to evaluate whether the postpubertal growth response after prenatal androgenization could be induced in prepubertal heifers. Blood was collected from the heifers at 6 +/- 1, 9 +/- 1, and 12 +/- 1 mo of age and analyzed from serum concentrations of growth hormone (GH), IGF-I, IGF-II, insulin, thyroxine (T4), and triiodothyronine (T3). Season of the year had a greater effect on hormone concentrations than either Pretrt or Posttrt, and there were no Pretrt x Posttrt interactions. Prenatal treatment, PA, had no effect on GH; however, Posttrt E and ET increased (P < .001) GH concentrations. Prenatal treatment, PA, increased (P < .05) IGF-I concentrations, and there was a nonsignificant increase (P = .11) in IGF-I concentrations with Posttrt E and ET. Concentrations of IGF-II were unaffected by Pretrt PA; however, they were lower (P < .01) in the Posttrt E and ET groups. Insulin, T4, T3, BW, and ADG were not affected by Pretrt and Posttrt. Concentrations of GH and IGF-I were increased in heifers that received Pretrt PA and(or) Posttrt E and ET in a manner to support improved growth performance; however, BW and ADG were similar. In prepubertal beef heifers, factors in addition to increased GH and IGF-I seem to be necessary for improved growth performance.

Ovulation rate, serum hormone concentrations, follicular fluid (FFL) concentrations of steroids and IGF, IGF binding protein (IGFBP) activity in FFL, and follicular IGF-I and -II mRNA were compared during the follicular phase among five genotypes of ewes: Finn (F), Composite III (C), 1/2 Booroola Merino (B) x 1/2 F (B x F), 1/2 F x 1/2 C (F x C), 1/2 B x 1/2 C (B x C). Composite III ewes were a Columbia x Suffolk x Hampshire crossbred. Ovulation rates for F (n = 7), C (n = 5), B x F (n = 6), F x C (n = 3), and B x C (n = 8) ewes were 3.1, 1.6, 3.8, 2.9, and 2.9 (Pooled SEM = .5), respectively. Concentrations of IGF-I in FFL were 53% greater (P < .05) in large (> or = 4.1 mm) than in small (< 4.1 mm) follicles but did not differ (P > .10) among genotypes. In contrast, FFL IGF-II concentrations were greater (P < .05) in B x C and B x F ewes than in C or F x C ewes but did not differ between small and large follicles. Ligand blotting revealed that IGFBP activity of three species (34, 27 to 29, and 24 kDa) were lower (P < .05) in FFL of large than in FFL of small follicles but did not differ (P < .10) among genotypes. Follicular wall IGF-I mRNA and IGF-II mRNA was detected in 5 and 32% of the samples from preovulatory follicles, respectively, using reverse transcriptase-PCR and ethidiumbromide staining. Ovarian IGF-I mRNA levels, assessed by Northern analysis, in B x F and B x C ewes were greater (P < .05) than those in C ewes; ovarian IGF-I mRNA levels in F and F x C ewes were intermediate and did not differ (P > .10) from those in C ewes. Small follicles from B x C and B x F ewes had severalfold greater (P < .05) estradiol concentrations than those from F or C ewes, whereas large follicles from B x F ewes had twice (P < .05) the estradiol concentrations of follicles from F or C ewes. Progesterone in FFL did not differ among genotypes. Serum LH, FSH, inhibin, IGF-I, and progesterone did not differ (P > .10) among genotypes.(ABSTRACT TRUNCATED AT 400 WORDS)

Forty-eight Holstein dairy heifers (98.9 kg BW; 3 mo old) were subjected for 246 d to twice-daily s.c. injections of saline (CTL) or human growth hormone-releasing hormone (GRH; 5 micrograms/kg BW) and to photoperiods of 8 h of light (L): 16 h of dark (D) or 16L:8D according to a 2 x 2 factorial arrangement of treatments. Jugular blood samples were collected from 16 heifers at 3, 4, 8, and 11 mo of age to monitor prolactin, growth hormone, and estradiol-17 beta. Plasma progesterone concentrations were monitored weekly in all heifers as an index of puberty (> 1 ng/mL). Growth hormone release was induced by GRH (P < .001) throughout the trial; area under the GH curve (AUC) averaged 1,582 vs 3,643 ng.min-1.mL-1 in CTL vs GRH heifers. However, GRH-induced GH response was less (P < .05) after the second daily injection. There was also an interaction (P = .08) between GRH, photoperiod, and days of treatment on GRH-induced GH response; AUC was greater in GRH-16L:8D than in GRH-8L:16D heifers at 3 mo but less at 8 mo of age. The PRL concentrations were similar for both photoperiods at 3 mo (36.4 vs 41.7 ng/mL) and 8 mo (16.2 vs 12.8 ng/mL) of age but were greater in 16L:8D vs 8L:16D heifers at 4 mo (18.4 vs 39.3 ng/mL) and 11 mo (26.3 vs 44.1 ng/mL) of age (photoperiod x day interaction, P < .001). Photoperiod of 16L:8D vs 8L:16D reduced (P < .01) weight at puberty in CTL heifers (251 vs 303 kg BW) and to a lesser extent in GRH-treated heifers (271 vs 284 kg BW; GRH x photoperiod interaction, P = .10). In conclusion, GH response is maintained throughout 8 mo of GRH treatment, and a 16L:8D photoperiod will reduce age and weight at puberty in heifers. Furthermore, refractoriness to photoperiod-induced PRL changes was detected.

Changes in serum metabolic hormones, carcass composition, and body weight gains were examined in 21 Angus bulls (9 mo old) subjected to feed restriction and realimentation. They were allotted to three feeding regimens: 1) control (CON); 2) restricted (REST); and 3) realimented (REAL). The CON group was fed 3.2% of their body weight; the REST group was fed 1.5%. The REAL group was fed the restricted diet (1.5% BW) for 84 d then fed the control diet (3.2% BW) until slaughter. The CON and REAL groups were slaughtered at approximately 400 kg and the REST group at 346 kg. For the experiment, average daily gains (kg/d) were different (P < .05) (CON = 1.60; REAL = 1.35; REST = .64). Bulls were bled every 20 min for 6 h on d 14, 70, 98, and 127 of the experiment. Overall carcass characteristics (yield grade, muscle area, marbling) and chemical analysis of 9-10-11 rib sections indicated changes in quantity and percentages of protein and fat commensurate with the dietary intake treatments. The REST group had the least lean and fat (P < .05); the REAL group had less fat than (P < .05) but the same amount of lean (P > .05) as the CON group. Serum GH was higher in the REST than in the CON group (P < .05). In the REAL group, serum GH values rose to a level similar to that of the REST group; realimentation lowered serum GH (P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

To determine the effect of low protein intake on boar libido, semen characteristics, and plasma hormone concentrations, 20 crossbred boars (1 yr of age) were divided into 10 littermate pairs, and boars from within pairs were fed 44 g/kg of BW.75 per day of either a low-protein diet (7% CP) or a control diet (16% CP) with the same energy content (3.41 Mcal of ME/kg). During the first 16 wk and from wk 19 to 23, semen was collected two times per week. During wk 17 and 18, boars were subdivided within dietary treatment and semen was collected either two or seven times per week. Blood samples were collected at 12-min intervals for 6 h before and 1 h after an intravenous injection of GnRH (375 ng/kg of BW) during wk 24. All plasma samples were analyzed for LH and pooled samples were analyzed for estradiol-17 beta and testosterone. Boars with low protein intakes required more time to start ejaculation (P = .11, wk 0 through 7; P < .04, after wk 7), had a shorter duration of ejaculation (P < .09, wk 19 through 23), and had reduced semen volumes (P < .01, after wk 7) compared with boars on the control treatment. There was no interaction between dietary treatment and semen collection frequency (P > .39) for any of the semen or libido measurements. Testosterone and LH concentrations were not affected by protein intake (P > .5). However, concentration of estradiol-17 beta was greater in boars fed the control diet than in boars fed the low-protein diet (582 vs 202 pg/mL, respectively; P < .08). Estrogen concentrations in boars were negatively correlated with the time required for the boar to start ejaculating (r2 = .72). Boars with low protein intakes had reduced libido and semen volume. This reduction in libido and semen volume may be a result of a decrease in estradiol-17 beta concentration in circulation.

To determine the effect of energy and protein intakes on boar libido, semen characteristics, and plasma hormone concentrations, 24 crossbred boars (1 yr of age) were allotted to one of three dietary treatments. Two protein levels (7.7 and 18.1 g/d of lysine) and two energy levels (6.1 and 7.7 Mcal/d of ME) were combined to create 1) low-energy and low-protein (ep), 2) low-energy and high-protein (eP), and 3) high-energy and high-protein (EP) treatments. Semen was collected two times per week for 27 wk. During wk 28, blood samples were collected before and after a intravenous injection of GnRH (375 ng/kg of BW). The EP boars had higher (P < .01) ADG than the eP boars (373 vs 169 g), which had higher (P < .01) ADG than the ep boars (169 vs 92 g). Fewer EP and eP boars (zero of eight and two of eight, respectively) than ep boars (five of eight) consistently refused to mount the collection dummy (P < .05). During the final 20 wk of the semen-collection period, EP and eP boars had 33% longer durations of ejaculation (P < .04), had 60% greater semen and gelatinous fraction volumes (P < .03), but had 25% lower sperm concentration in their semen (P < or = .12) than ep boars. The EP boars produced 38% more sperm than the ep boars (P < .10). Baseline LH concentration, LH pulse frequency, LH pulse amplitude, testosterone concentration, and estradiol-17 beta concentrations were not affected by treatment (P > .10).(ABSTRACT TRUNCATED AT 250 WORDS)

Experiment 1 was conducted to characterize the concentrations of prolactin, growth hormone (GH), cortisol, insulin, glucagon, glucose, nonesterified fatty acids (NEFA), urea N, and 10 indispensable amino acids in the plasma of mares (n = 8) and stallions (n = 8) during the last 4 h of a 19-h period of feed deprivation and for 8 h after a noon meal. Experiment 2 was similar to Exp. 1 except that only stallions (n = 8) were used, and they were either fed (n = 4) or not fed (n = 4) at noon in a 2 x 2 Latin square design conducted over two sampling days 7 d apart. In Exp. 1, increases (P < .01) after feeding were observed for plasma concentrations of prolactin, cortisol, insulin, glucagon, glucose, urea N, and all amino acids except methionine; NEFA concentrations decreased (P < .01) after feeding. Episodic increases in GH concentrations were observed for most horses but were not associated with either feeding or gender (P > .1). Plasma urea N concentrations were higher (P < .025) overall in stallions than in mares, and the rise in prolactin concentrations after feeding was greater (P < .01) in stallions than in mares. In Exp. 2, meal-associated increases (P < .01) were observed for plasma concentrations of prolactin, insulin, glucagon, and glucose; NEFA concentrations decreased (P < .01). Except for cortisol, no hormone or metabolite varied with time across days when the stallions were not fed (P > .1), indicating that there was no inherent diurnal or feeding schedule-associated fluctuations in their concentrations. Cortisol concentrations varied (P < .02) over time but did not differ (P > .1) between fed and nonfed stallions. Again, GH concentrations were episodic but did not differ (P > .1) between fed and nonfed stallions. The lack of feeding effects on GH secretion in horses is similar to the response in pigs but differs from that in ruminants, in which GH concentrations generally decline after feeding.

The effect of serving sows at first or second estrus after weaning was determined using 114 Camborough sows (Parities 1 to 8). Eighty sows were paired according to weaning-to-estrus interval and parity. One sow of each pair was bred at first and the other at second estrus after weaning. A further 27 sows were catheterized on d 3 after weaning or d 20 of the first estrous cycle and bred at first or second estrus, respectively. Blood samples were taken every 30 min from 0800 to 1330 on the day after catheterization, every 6 h from catheterization until 1 d after standing estrus, and every 12 h for a further 3 d. Of the 80 sows, litter size increased (P < .002) by breeding Parity 1 and 2 sows at second rather than at first estrus (10.4 vs 12.8 total pigs born). These increases in litter size were achieved in the absence of any significant changes in sow weight or backfat during lactation and between weaning and breeding, and predicted changes in fat and protein during lactation. Similar but nonsignificant results (P = .15) were observed for the 27 catheterized sows. Plasma progesterone concentrations measured 50 h after the preovulatory LH surge were higher in Parity 1 and 2 sows bred at second rather than at first estrus (5.4 +/- .7 vs 3.7 +/- .3 ng/mL, P < .04). Sows of Parity 1 and 2 bred at first rather than at second estrus had higher plasma IGF-I (P < .05) and glycerol (P < .001) concentrations and tended to have lower preprandial insulin concentrations (P = .09).(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of selection for lean tissue growth on the metabolic and physiological state (i.e., level of maturity) of the pig at birth have been examined on newborns from three breeds that markedly differ with respect to birth weight and postnatal muscle growth potential: a primitive Chinese breed (Meishan, MS), a European breed (Large White, LW), and a composite line (CL) highly selected for high rate of gain. Within each breed, 40 pigs from eight litters were used for whole carcass and tissue sampling, blood sampling, and for a fat tolerance test at 2 h of age. The CL pigs were heavier (P < .001) than the LW and MS pigs at birth but exhibited lower percentages of carcass protein, fat, mobilizable fat, and ash than the MS pigs (P < .05). In addition, MS pigs had larger adipose tissue adipocytes than pigs from the two other breeds (P < .001). Despite their 31% higher RNA capacity in longissimus muscle (higher RNA:protein ratio, P < .05), CL pigs exhibited a lower percentage of muscle protein (P < .05) than did MS pigs. Relative liver weight was higher for LW than for CL pigs (P < .05), which had the lowest percentage of liver phospholipids (P < .01). The CL pigs exhibited lower hematocrit (P < .01), glucose (P < .01), albumin (P < .01), cortisol (P < .01), and thyroxine (P < .05) levels than the MS pigs.(ABSTRACT TRUNCATED AT 250 WORDS)

Three generations of selection for 56-d blood cholesterol concentrations were used to establish low and high cholesterol lines of pigs in which cholesterol concentrations differed by 39% in the last generation. Litter size (number of fully formed pigs born per litter) diverged with each successive generation of selection and, at the third generation, litter size differed between the low and high line by two pigs (high line = 8.5 +/- .6; low line = 10.5 +/- .5; P < .05). A random selection of offspring (gilts, n = 109; boars, n = 46; barrows, n = 94) from the third generation and a control line maintained throughout the experiment were monitored for hormonal and anatomical relationships that might provide insight into the mechanisms that altered fecundity. Ovulation rate (number of corpora lutea) as determined on d 60 of pregnancy was increased in the low (n = 29) compared with the high cholesterol line (n = 38; 11.8 +/- .3 vs 9.8 +/- .3, respectively; P < .05), and litter size continued to be increased in the low cholesterol line (P < .05). No differences were noted between lines in kidney, ovarian, or total corpora lutea weight. Empty uterine weight and adrenal weight were increased in the high cholesterol line (P < .05) in randomly selected offspring of the third generation, and liver weight increased in the low line (P < .05). Associated with increased concentrations of cholesterol were increased serum concentrations of progesterone (gilts) and testosterone (boars) in the high cholesterol line (P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

The objective of this study was to determine the maintenance requirements in metabolizable energy (MEm) of adult, nonlactating, nonpregnant Charolais cows. A feeding trial was conducted using 12 cows fed at one of two feeding levels (75 [L] and 113 [H] kcal of ME.kg BW-.75.d-1) for 116 d. Body composition was estimated from subcutaneous adipocyte diameter. Body weight changes averaged -468 and +46 g/d, respectively. Diet DM digestibility averaged .496. The L cows spent less time eating and ruminating but had other behavioral characteristics similar to those of H cows. Estimates of MEm were calculated from BW or body composition changes and amounted to 109 and 124 kcal of ME.kg BW-.75.d-1, respectively. Heat production (HP) was then measured over 67 d in a second trial on two L and two H cows from the feeding trial and planes of feeding were switched after 14 d. Estimates of MEm varied from 112 to 105 kcal.kg BW-.75.d-1. Within animal, day-to-day variations in heat production were high (4.6% on average) and prevented the detection of any precise changes of HP with time on treatment. None of the trials showed any significant effect of level of feeding on MEm.

Twenty barrows were designated as fast-growing (FG) and their littermates designated as slow-growing (SG) based on birth, weaning, and 56-d weight. Half of each group received 70 micrograms of porcine somatotropin (pST)/kg BW daily beginning at 40 kg BW. At 60 and 105 kg BW, blood was collected every .5 h for 12 h beginning 1 h before pST injection, fat biopsies were taken for in vitro lipogenic activity, and insulin erythrocytes were isolated for receptor binding. Swine treated with pST had elevated ADG (.95 vs .88 kg/d; P < .1) and reduced days to slaughter (61 vs 67; P < .1). The pST-treated pigs had less average backfat (2.73 vs 3.96 cm; P < .01), larger longissimus muscle areas (32.3 vs 28.2 cm2; P < .05), and a higher percentage of muscle (56.3 vs 50.3%; P < .01) than control pigs. Exogenous pST increased protein (17.4 vs 13.2%; P < .05) and decreased fat (22.9 vs 37.1%; P < .05). The FG pigs had higher ADG (.98 vs .86 kg/d; P < .01) and required fewer days to slaughter (57 vs 71; P < .01) than SG pigs. Administration of pST increased (P < .01) average pST levels (1.7 vs 14.0 ng/mL) in FG and SG pigs at 60 kg BW. At 105 kg BW, pST was higher (P < .01) in pST-FG than in pST-SG swine (46.0 vs 19.3 ng/mL) but was not different between FG and SG control swine (1.9 vs 1.8 ng/mL). Administration of pST increased concentrations of IGF-I (510.0 vs 160.0 ng/mL) and nonesterified fatty acids (182 vs 109 muEq/L, P < .01) in FG and SG swine. Over sample periods and growth rates, pST reduced (P < .05) CO2 production and lipid synthesis (.345 and 1.85 vs .575 and 2.71 mumol of glucose incorporated.g-1.2 h-1). At 60 kg BW, FG swine had less (P < .01) CO2 production and lipid synthesis (.299 and 1.83 vs .921 and 3.61 mumol.g-1.2 h-1) than did SG swine. Exogenous pST increased (P < .05) binding to insulin erythrocyte receptors (7.25 vs 6.34%).

Four Suffolk wether lambs were used in a crossover design to determine the effects of a 3-d feed and water deprivation period on metabolic and hormonal responses to a glucose load. During each period of the crossover design all lambs were limit-fed a 36% concentrate diet for 16 d then two lambs were deprived of feed and water for 3 d. All lambs were then limit-fed the 36% concentrate diet. Glucose loading tests were performed before feeding on d 1, 5, and 9 of the realimentation period. Ten milliliters of a 2.5 M glucose solution were infused into the right jugular vein and blood samples were obtained from the left jugular vein at intervals for 4 h after infusion. Plasma or serum samples were analyzed for insulin, growth hormone (GH), somatostatin, prolactin, glucose, free fatty acids (FFA), and urea N. At the end of the period in which feed was withheld, fed lambs had greater (P < .09) serum insulin and lower plasma FFA (P < .01) and somatostatin (P < .05). On d 1 of realimentation, previously unfed lambs had greater postinfusion GH (P < .01), FFA (P < .01), and glucose (P < .04) concentrations. Previously unfed lambs also had a slower (P < .01) glucose fractional removal rate and longer (P < .02) glucose half-life than fed lambs on d 1 of realimentation, but they had a shorter (P < .13) glucose half-life than fed lambs on d 5 of realimentation.(ABSTRACT TRUNCATED AT 250 WORDS)

Four experiments were conducted to examine effects of GnRH administered at estrus on various reproductive characteristics in repeat-breeding dairy cows (eligible for third service). In Exp. 1, cows (n = 8 per group) received (i.m.) either saline or 50, 100, or 250 micrograms of GnRH at 12 h after onset of estrus. There was a positive linear (P < .05) effect of dose on concentrations of LH, but not of FSH, in serum at 2 h after the injection. Concentrations of progesterone (P4) were higher (P = .10) through 16 d after estrus in nonpregnant cows that returned to estrus 18 to 24 d after GnRH treatment than in nonpregnant cows given saline. Likewise, among cows with elevated concentrations of P4 through 30 d after estrus (diagnosed pregnant by increased concentrations of pregnancy-specific protein B; PSPB), P4 was higher (P = .10) in those given GnRH than in those given saline. In Exp. 2, concentrations of LH, FSH, and estradiol-17 beta (E2) were similar among 12 cows during the periestrual period before they received (i.m.) 100 micrograms of GnRH or saline at estrus. Concentrations of P4 after estrus were increased 2 d earlier (P < .05) in GnRH- than in saline-treated cows. Among cows with elevated concentrations of P4 and PSPB through 40 d after AI, P4 was higher (P < .05) in those given GnRH than in those given saline. In Exp. 1 and 2, a greater proportion (43 vs 14%; P = .07) of cows given GnRH was pregnant 42 to 56 d after estrus than of those given saline, but calving rate was similar (27 vs 14%). In Exp. 3, average number of LH pulses per 8 h was similar between saline- and GnRH-treated cows on d 1, 3, and 8, but overall concentrations of LH were reduced (P < .05) in GnRH-treated cows. Concentrations and number of pulses of FSH were increased (P < .05) on d 8 after treatment with GnRH. Concentrations of P4 were increased earlier (P < .05) after estrus in GnRH-treated (69 +/- 12 h) than in saline-treated cows (126 +/- 12 h), with higher (P < .05) concentrations of P4 on d 4 to 8. In Exp. 4, eight cows received either 100 micrograms of GnRH or saline at 12 h after onset of estrus (d 0) in a cross-over design.(ABSTRACT TRUNCATED AT 400 WORDS)

Blood collected from 54 sows over 2 to 8 d of the periparturient period was assayed for progesterone, insulin, and prolactin to determine whether the sows' hormonal state was correlated with perinatal pig mortality and weight gain. Sows with larger litters had higher concentrations of progesterone and prolactin and a lower concentration of preprandial insulin during the 48 h preceding parturition. Pig mortality was higher in larger litters and involved pigs of lower birth weight. Most pigs that died lost weight during the 24 to 48 h that preceded their deaths. Litters with lower weight gain during the first 24 h postpartum tended to have higher mortality during the next 48 h. For some sows, progesterone remained elevated during the 48 h postpartum and litters of these sows had lower than average 3-d weight gains. Low milk intake by pigs is a major cause of death and poor growth, and we suggest that poor milk production by the sow is one contributing factor. Elevated postpartum progesterone may inhibit lactogenesis and contribute to poor pig performance.

Thirty-two crossbred barrows were used to determine the effects of frequency of administration of equivalent total dosages of recombinant porcine somatotropin (rpST) on growth performance, tissue accretion rates, and hormone and metabolite status of pigs. Treatments were control (buffer-injected daily), 60 micrograms/kg BW daily (4 injections/4 d), 120 micrograms/kg BW injected every other day (2 injections/4 d), or 240 micrograms/kg BW given every 4th d (1 injection/4 d). Treatments were initiated at 35 BW and continued until each pig had consumed a total of 440 Mcal of DE intake. Pigs were fed a diet that contained 16% CP, 1.2% lysine, and 3.5 Mcal of DE/kg at 85% of calculated ad libitum intake. Feed intake and rpST dose were adjusted at 8-d intervals. The 240 micrograms/kg BW treatment did not decrease appetite beyond the 15% restriction already imposed in the experimental design. Treatment groups responded to rpST in a frequency-dependent manner. Average daily gain was improved by 10, 23, and 36%, respectively, as injection frequency was increased from 1/4 to 2/4 to 4/4 d. Muscle weights were increased uniformly (15% on average) on a BW basis by all rpST treatments. Carcass (21, 42, and 63%), visceral (43, 65, and 112%), and empty body (22, 43, and 65%) protein accretion rates were increased by rpST treatment in a frequency-dependent fashion, respectively. Lipid accretion also was reduced in carcass and empty body (31% on average) by all rpST injection schemes relative to controls; however, visceral lipid accretion was increased by 59% by rpST. Protein utilization efficiency increased linearly by 24, 45, and 65% as the frequency of injection of rpST was increased from 1/4 to 2/4 to 4/4 d. Hormones and metabolites exhibited frequency-related profiles as well. These results suggest that frequency of administration greatly influences the magnitude of responsiveness to rpST and that optimal benefit would be realized by a delivery system that mimicked a daily surge, at minimum, of rpST.

Previous studies have documented the effectiveness of porcine somatotropin (pST) administered by daily injection in promoting lean tissue growth in lean and obese pigs and the influence of sex and genotype. The present study examined the accretive responses in pigs of different lines and sexes to a slow release formulation of pST (pST-SR). Implants that deliver 2.0 mg of pST/d were implanted in genetically lean and obese barrows and gilts at 65 +/- .7 kg BW (mean +/- SE). Pigs received no, one, or two implants (i.e., doses of 0, 2.0, and 4.0 mg of pST/d). Pigs (four per line x sex x dose) were housed individually and continuously supplied with fresh water and a 19% CP diet containing 1.08% lysine. Pigs were slaughtered on d 0 (four per line x sex) and at the end of the trial (approximately 42 d after implantation) for estimation of initial composition and calculation of accretion rates. Blood samples were collected at d 0, 7, 14, 28, and 42 to measure endocrine and metabolite responses to pST-SR. Sustained-release pST elevated (P < .05) circulating pST throughout the trial with peak concentrations at d 7. On d 7, serum pST concentrations in the pigs given 2.0 mg of pST-SR per day were 16-fold greater than those in control pigs, and in pigs given 4.0 mg of pST-SR per day pST concentrations were 33-fold greater than in controls. Elevated serum pST resulted in increased (P < .05) serum concentrations of insulin-like growth factor (IGF)-I, IGF-II, insulin, and glucose and in reduced (P < .05) concentrations of urea nitrogen and IGF binding protein (IGFBP)-2. Gain was not influenced by pST-SR dose; however, feed consumption was reduced (P < .05) and efficiency of gain was increased (P < .05). Accretion of all body components except cold carcass weight, cecum, and untrimmed Boston butt and ham were changed (P < .05) with pST-SR administration. Heart and stomach were the only components of the carcass and offal whose accretion was not affected by line or sex. Increases in accretion of carcass components (< 75%) induced by sustained-release pST were considerably less than those measured in the organs (liver, 157%; lungs, 748%). The pST-SR treatment resulted in elevated serum concentrations of pST and its mediators and improved efficiency and composition of gain.(ABSTRACT TRUNCATED AT 400 WORDS)

Forty-five Large White barrows were injected daily i.m. with either excipient from 30 to 100 kg BW (CTRL), excipient from 30 to 60 and porcine somatotropin (pST; 100 micrograms/kg BW) from 60 to 100 kg BW (pST-60), or pST (100 micrograms/kg BW) from 30 to 100 kg BW (pST-30). Somatotropin accelerated overall growth rate (+4 and +9% for pST-60 and pST-30, respectively), increased longissimus (+10.3 and +14.7%) and semitendinosus (+17 and +13%) muscle weights, and decreased backfat (-49 and -58%) and leaf fat (-49 and -53%) weights. The administration of pST resulted in a similar increase in muscle fiber size for all fiber types in both longissimus (LM) and semispinalis (SS) muscles (+21%). Somatotropin had otherwise little effect on muscle fiber types and biochemical traits of LM, whereas dramatic changes were observed in SS. The relative area occupied by Type IIB fibers was increased (+22 and +29%) and that of Type I fibers was decreased (-10 and -15%). In pST-30 animals, myosin ATPase activity (+15%) and native myosin fast isoform proportion (+10%) were augmented, and energy metabolism was more glycolytic (lactate dehydrogenase: +25%) and less oxidative (citrate synthase: -13%; beta-hydroxyacyl-CoA dehydrogenase: -21%). Compared to CTRL animals, administration of pST increased muscle water concentration (LM: +.8 and +1.1%: SS: +3.3 and +3.3%) and decreased intramuscular fat (LM: -29 and -27%; SS: -39 and -50%). The pH measured 45 min and 24 h postmortem, glycogen content, reflectance, and index of light diffusion were mostly not affected by pST treatment. In conclusion, pST had a very favorable effect on growth performance without any important effect on meat quality traits except for the reduction in intramuscular lipid content. The results indicated that the effects of pST on muscular histochemical and biochemical characteristics were different in LM and SS muscles.

Sixteen crossbred beef heifers were used to determine the efficacy of serum clinical profiles as diagnostic tools for detection of early stages of locoweed toxicity and to test the ability of two mineral supplements for prevention or therapy of toxicosis. Dietary treatments were (DM basis) 1) 100% sorghum sudangrass hay, 2) 80% sorghum sudangrass hay:20% locoweed, 3) 80% sorghum sudangrass hay:20% locoweed plus 100 g of Silent Herder Mineral Mix (a mineral supplement reported to alleviate locoweed toxicity), and 4) 80% sorghum sudangrass hay:20% locoweed plus 100 g of clinoptilolite (a natural zeolite clay). Diets were fed at 1.5% of BW for 28 d, after which heifers had ad libitum access to sorghum sudangrass hay for 14 d. Jugular blood was sampled before feeding every 7 d, and at 2, 4, 6, and 8 h after feeding on d 28. Compared with controls, heifers fed locoweed had elevated (P less than .01) serum alkaline phosphatase activities from d 7 through 35. On d 42, alkaline phosphatase activities in heifers previously fed locoweed were lower (P less than .05) than in control heifers. Serum glutamic oxaloacetic transaminase activities were elevated (P less than .01) in heifers fed locoweed from d 7 through 42 compared with control heifers. In heifers fed locoweed, serum Fe concentrations were less (P less than .01) on d 7 through 28, but no treatment effects were noted (P greater than .10) on d 35 or 42.(ABSTRACT TRUNCATED AT 250 WORDS)

Forty-one primiparous beef heifers were used over 2 yr to evaluate the effect of prepartum administration of a growth hormone-releasing factor analog (GRF-A) or growth hormone-releasing factor (GRF(1-29)-NH2) on somatotropin (ST), insulin-like growth factor I (IGF-I), milk production, heifer BW, and postpartum (PP) return to ovarian activity. Beginning on d -11 +/- 1 from parturition, heifers were administered (s.c.) GRF-A ([desNH2-Tyr1,D-Ala2,Ala15]GRF(1-29)-NH2, 2.5 micrograms/kg; Yr 1) or GRF(1-29)-NH2 (12.5 micrograms/kg; Yr 2) (GRF; n = 17) or vehicle (CON; n = 24) for seven consecutive days. Blood samples were collected at 20-min intervals from -60 to 300 min from the first and fourth injections. Samples were also collected at 20-min intervals for 6 h on d 25 and 69 +/- 1 PP. Area under the curve of ST (nanograms.minute-1.milliliter-1) was greater (P less than .01) in GRF than in CON heifers (9,671 +/- 677 vs 2,611 +/- 237). Increases in ST after GRF-A or GRF(1-29)-NH2 were similar. On d 25 +/- 1 PP, frequency of ST release (pulses per 6 h) was greater (P less than .01) in CON (3.3 +/- .2) than in GRF (2.1 +/- .2) heifers. Milk production was similar (P greater than .1) for the two treatments. Heifer BW loss from d -16 to 81 after parturition was greater (P less than .01) in GRF (88 +/- 5) than in CON (68 +/- 5) heifers. Postpartum return to ovarian activity (progesterone greater than 1 ng/mL for two consecutive weeks) was delayed (P less than .05) in GRF (97 +/- 14) vs CON (71 +/- 8) heifers. After accounting for variation due to treatment and year, a negative (P less than .02) correlation (r = -.39) was detected between concentrations of IGF-I during the first 30 d PP and PP interval to ovarian activity. These results indicate that prepartum administration of GRF altered the release pattern of ST after parturition and was associated with greater PP BW loss and delayed PP return to ovarian activity in heifers.

Effects of growth hormone-releasing factor (GRF) and intake on arterial concentrations and net visceral metabolism of hormones were measured in six growing Hereford x Angus steers using a split-plot design with 4-wk injection periods within 8-wk intake periods. Steers were fed a 75% concentrate diet at two intakes and were injected s.c. twice daily with saline or GRF (10 micrograms/kg of BW). Arterial concentrations of growth hormone (GH) were measured on d 1 and d 8 to 10 of injections. Eleven measurements, obtained at 30-min intervals, of arterial concentration and net flux of hormones across portal-drained viscera (PDV) and liver were obtained on d 8 to 10 of injections (six hourly measurements were used for insulin-like growth factor-I [IGF-I] and somatostatin). The area under the GH curve and average and peak GH concentrations were increased (P less than .01) by GRF and were greater (P less than .10) at low than at high intake. Liver removal of GH was not affected by GRF or intake. Arterial IGF-I concentration was increased (P less than .05) by GRF and not affected by intake. Treatments did not affect IGF-I flux across the liver. Arterial insulin concentration was greater (P less than .05) at high than at low intake, in part because of greater (P less than .01) PDV release. Increased (P less than .10) arterial insulin concentration in GRF-treated steers was not attributable to significant changes in PDV or liver net flux. Arterial glucagon concentration was greater (P less than .01) at high than at low intake, in part because of greater (P less than .05) PDV glucagon release and decreased (P less than .10) liver extraction ratio. Effects of intake on arterial concentration of insulin and glucagon were in part due to changes in visceral metabolism, but GRF did not affect PDV or liver hormone metabolism.

Eleven crossbred barrows were housed in environmentally controlled rooms with an 8-h photoperiod. Pigs in one room received control illumination of 113 1x (CON; n = 6), and pigs in the other room received intense illumination of 1,783 1x (INT; n = 5) fluorescent light. Pigs were given at least 20 d of exposure to the environment before blood samples were taken every 3 h for 48 h. Data were analyzed by split-plot analysis of variance. Except for prolactin, no treatment x time interactions were noted for the hormone profiles evaluated (P greater than .10). Pigs in INT had greater (P less than .05) concentrations of prolactin in serum than pigs in CON at every sampling time. Concentrations of ACTH and cortisol in plasma were similar for INT (33.9 +/- 3.2 pg/mL of ACTH and 24.4 +/- 3.4 ng/mL of cortisol, respectively) and CON (34.9 +/- 3.0 pg/mL of ACTH and 31.3 +/- 3.1 ng/mL of cortisol, respectively). Within the INT treatment, serum melatonin concentrations were more than doubled (P less than .05) during darkness (66.8 +/- 9.3 pg/mL) compared with during light (30.4 +/- 9.3 pg/mL); however, within the CON treatment, concentrations during light and darkness did not differ (38.4 +/- 9.3 pg/mL and 42.9 +/- 9.3 pg/mL, respectively). Results indicate that light of greater intensity is required to entrain circadian rhythms of melatonin in serum of pigs. Furthermore, pigs may respond to bright light with greater secretion of prolactin, even under constant duration of photoperiod.

To compare the effects of time of daily protein supplementation on grazing behavior, forage intake, digesta kinetics, ruminal fermentation, and serum hormones and metabolites, 12 ruminally cannulated Holstein steers (449 and 378 kg average initial and final BW, respectively) were allotted to three groups. Treatments consisted of CON = no supplement, AM = cottonseed meal (.25% of BW) at 0600, and PM = cottonseed meal (.25% of BW) at 1200. Steers grazed a dormant (1.1% N) intermediate wheatgrass (Thinopyrum intermedium Host) pasture. Sampling trials occurred in December, January, and February. Supplementation altered (P = .01) time spent grazing; CON steers grazed approximately 1.5 h longer than supplemented steers. Supplemented steers lost less (P = .02) BW (-40 kg) than CON steers (-75 kg) did. Supplementation did not alter (P greater than .15) forage OM intake; however, total OM intake was greater (P = .01) for supplemented steers (22.3 g/kg of BW) than for CON (18.4 g/kg of BW) steers. Supplementation did not affect (P greater than .15) digesta kinetics. Extent of in situ NDF (96 h) and rate (%/h) of disappearance for supplemented steers was greater (P = .01) than for CON steers. Across all periods, ruminal NH3 N and total VFA concentrations were lower (P = .01) for CON steers than for supplemented steers. Serum insulin (ng/mL) concentration was lower (P = .03) and concentration of serum growth hormone (ng/mL) was higher (P = .02) for CON steers than for supplemented steers. Cottonseed meal supplementation enhanced utilization of intermediate wheatgrass; however, supplementation time had minimal effects on the variables measured.

Our objective in this study was to determine endocrine responses and changes in ovarian structures after a single injection of a GnRH agonist in Holstein dairy heifers (n = 38). Heifers were inseminated and received (i.m.) either saline or 200 micrograms of fertirelin acetate once on d 11, 12, or 13 after estrus (d 0). Blood was collected at 15- to 30-min intervals for 6 h after the injection to determine concentrations of LH, FSH, estradiol (E), and progesterone (P) in serum and once daily for 8 to 12 d after the injection to determine concentrations of E and P. Pregnancy rates were 58% (11 of 19) in both treatment groups. Diameter of the corpus luteum and numbers and appearance of ovarian follicles were determined by real-time ultrasonography on d-1 through 5 after injection. No treatment-induced ovulations or changes in the number of ovarian follicles were observed after the injection of the GnRH agonist. More (P less than .05) of the largest follicles within heifers receiving fertirelin acetate showed changes in their appearance on at least the 1st d after injection (6 of 10 vs 1 of 9 control heifers). Fertirelin acetate induced release of LH and FSH from the pituitary within 15 min of injection; both hormones reached peak concentrations at 120 min and then returned to pretreatment concentrations by 300 to 360 min after injection.(ABSTRACT TRUNCATED AT 250 WORDS)

This study investigated the responsiveness of the pituitary-ovarian axis of prepubertal gilts to hourly injections (i.v.) with GnRH. Six gilts each at 70, 100, 150, and 190 d of age were assigned either to treatment with GnRH or saline. Treatments were given until gilts showed estrus or for 7 d, whichever came first. Hourly pulsing with GnRH resulted in gradually increasing concentrations of estradiol-17 beta (E2), a preovulatory surge of LH, and subsequently increased progesterone (P4) concentrations. The increase in serum P4 was preceded by ovulation and corpora lutea (CL) formation in two gilts 70 d of age and all older gilts. The interval (h) from start of GnRH treatment to peak E2 (88 +/- 3), peak LH (103 +/- 3), and concentrations of P4 greater than or equal to 1 ng/mL (144 +/- 4) did not differ (P greater than .50) for 18 gilts between 100 and 190 d of age. In two ovulating, 70-d-old gilts, the interval from onset of GnRH treatment to peak E2 (171 +/- 6), peak LH (186 +/- 0), and P4 greater than or equal to 1 ng/mL (216 +/- 4) was lengthened (P less than .001). Peak concentrations of E2 (pg/mL) were higher (P less than .01) at 190 d (48 +/- 2) and 150 d (49 +/- 2) than at younger ages and lower (P less than .01) in gilts 70 d of age (31 +/- 1) than in gilts 100 d of age (41 +/- 2). Peak LH (nanograms/milliliter) was higher (P less than .01) in gilts 100 d of age (12.7 +/- 6) than in older gilts. Concentrations of P4 were similar (P greater than .20) for all ovulating gilts. The number of CL (12.7 +/- .7) did not differ (P greater than .20) for 18 gilts 100 d of age or older but was higher (P less than .01) than that (4.5 +/- 1.1) for two gilts 70 d of age. Corresponding endocrine responses or ovulations were not observed in four 70-d-old gilts treated with GnRH or in gilts given saline. These findings indicate that the functional integration of the pituitary-ovarian axis is completed between 70 and 100 d of age. Hourly treatment with GnRH is an adequate stimulus to induce ovulation in prepubertal gilts as early as 70 d of age. Also, the number of follicles reaching ovulatory competency was similar (P greater than .20) in gilts between 100 and 190 d of age, when GnRH was given on a BW basis.

The effects of superovulatory treatment (FSH-P vs human menopausal gonadotropin, HMG) and of route of administration (i.m. vs. i.v.) of prostaglandin F2 alpha (PGF2 alpha) on hormonal profiles were determined in 32 Angus x Hereford heifers. Heifers were superstimulated with either FSH-P (total of 26 mg) or HMG (total of 1,050 IU) beginning on d 9 to 12 of an estrous cycle and PGF2 alpha (40 mg) was administered at 60 and 72 h after the beginning of superovulatory treatments. Heifers were artificially inseminated three times at 12-h intervals beginning 48 h after PGF2 alpha treatment. Blood serum samples were collected immediately before treatments began, at 12-h intervals during the first 60 h, each 4 h during the next 96 h, and each 12 h until day of embryo collection. Concentrations of LH and FSH were not affected by hormone treatments, route of PGF2 alpha injection, or interactions between them. Estradiol-17 beta (E2-17 beta) levels were higher (P less than .05) in HMG- than in FSH-P-treated heifers 60 h after gonadotropin treatment. Peak concentration of E2-17 beta occurred earlier (P less than .05) in HMG- than in FSH-P-treated heifers and earlier in heifers injected with PGF2 alpha i.m. than in those injected i.v. Progesterone concentrations were not influenced by treatment or route of PGF2 alpha administration, but were affected (P less than .01) by the interactions between treatment and route of PGF2 alpha administration. Progesterone declined to basal levels earlier in the FSH-P- than in the HMG-treated heifers.(ABSTRACT TRUNCATED AT 250 WORDS)

Ten lighthorse stallions were used to determine 1) whether prolactin (PRL) and cortisol responses previously observed after acute exercise in summer would occur in winter when PRL secretion is normally low, 2) whether subsequent treatment with a dopamine receptor antagonist, sulpiride, for 14 d would increase PRL secretion and response to thyrotropin-releasing hormone (TRH) and exercise, and 3) whether secretion of LH, FSH, and cortisol would be affected by sulpiride treatment. On January 11, blood samples were drawn from all stallions before and after a 5-min period of strenuous running. On January 12, blood samples were drawn before and after an i.v. injection of GnRH plus TRH. From January 13 through 26, five stallions were injected s.c. daily with 500 mg of sulpiride; the remaining five stallions received vehicle. The exercise and secretagogue regimens were repeated on January 27 and 28, respectively. Before sulpiride injection, concentrations of both cortisol and PRL increased (P less than .05) 40 to 80% in response to exercise; concentrations of LH and FSH also increased (P less than .05) approximately 5 to 10%. Sulpiride treatment resulted in (P less than .05) a six- to eightfold increase in daily PRL secretion. The PRL response to TRH increased (P less than .05) fourfold in stallions treated with sulpiride but was unchanged in control stallions. Sulpiride treatment did not affect (P greater than .05) the LH or FSH response to exogenous GnRH.(ABSTRACT TRUNCATED AT 250 WORDS)