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Total progressive motile sperm count (TPMSC) is a reliable index of fecundity evaluation of bull semen. It is an important determinant frozen semen yield and conception rate of females artificially inseminated. Seminal plasma metabolites and sperm lipids are closely related to sperm survival and motility, but their relationship with TPMSC is not well known. In the present study, Simmental bulls with higher (H, n = 6) or lower (L, n = 6) TPMSC (P < 0.01) were selected from a cohort of 100 animals aged 2 to 5 years based on semen quality. Analysis of semen quality and biochemical markers of seminal plasma revealed that H bulls had greater ejaculate volume (P < 0.05), sperm motility, plasma membrane integrity rate (P < 0.01), seminal plasma neutral α-glucosidase (P < 0.05), alkaline phosphatase, acid phosphatase, cortisol and phosphatidylcholine (P < 0.01), and lower sperm malformation rate (P < 0.05) and reactive oxygen species (ROS) (P < 0.01). Semen metabolites and sperm liposome profiles of H and L groups were compared using LC-MS/MS analysis. A total of 120 differentially abundant metabolites (VIP > 1; P < 0.05) and 59 differentially abundant lipids (VIP > 1; P < 0.05) were identified between H and L groups. Oxidative stress, sperm motility and sperm plasma membrane integrity were among the enriched biological pathways. Cyclic ADP-ribose (cADPR), up-regulated in H bulls, is associated with energy for sperm motility and maintenance of membrane stability. Thymidineglycol (Tg), levanbiose, thymidine (Thd), and CE (3M5) were down-regulated in H bulls, and may have negatively affected sperm motility. Correlation analyses revealed that TPMSC and sperm motility were significantly positively correlated with cADPR, while Tg, Levanbiose, Thd and CE (3M5) were significantly negatively correlated with TPMSC and sperm motility. Thus, we speculate that these molecules may be exploited as potential biomarkers for non-invasive evaluation of TPMSC in bull semen., (© The Author(s) 2025. 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.)

A study involving nine research stations from the NCR-42 Swine Nutrition Committee used a total of 1,978 crossbred pigs to evaluate the effects of dietary ZnO concentrations with or without an antibacterial agent on postweaning pig performance. In Exp. 1, seven stations (IA, MI, MN, MO, NE, ND, and OH) evaluated the efficacy of ZnO when fed to nursery pigs at 0, 500, 1,000, 2,000, or 3,000 mg Zn/kg for a 28-d postweaning period. A randomized complete block experiment was conducted in 24 replicates using a total of 1,060 pigs. Pigs were bled at the 28-d period and plasma was analyzed for Zn and Cu. Because two stations weaned pigs at < 15 d (six replicates) and five stations at > 20 d (18 replicates) of age, the two sets of data were analyzed separately. The early-weaned pig group had greater (P < 0.05) gains, feed intakes, and gain:feed ratios for the 28-d postweaning period as dietary ZnO concentration increased. Later-weaned pigs also had increased (P < 0.01) gains and feed intakes as the dietary ZnO concentration increased. Responses for both weanling pig groups seemed to reach a plateau at 2,000 mg Zn/kg. Plasma Zn concentrations quadratically increased (P < 0.01) and plasma Cu concentrations quadratically decreased (P < 0.01) when ZnO concentrations were > 1,000 mg Zn/kg. Experiment 2 was conducted at seven stations (KY, MI, MO, NE, ND, OH, and OK) and evaluated the efficacy of an antibacterial agent (carbadox) in combination with added ZnO. The experiment was a 2 x 3 factorial arrangement in a randomized complete block design conducted in a total of 20 replicates. Carbadox was added at 0 or 55 mg/kg diet, and ZnO was added at 0, 1,500, or 3,000 mg Zn/ kg. A total of 918 pigs were weaned at an average 19.7 d of age. For the 28-d postweaning period, gains (P < 0.01), feed intakes (P < 0.05), and gain:feed ratios (P < 0.05) increased when dietary ZnO concentrations increased and when carbadox was added. These responses occurred in an additive manner. The results of these studies suggest that supplemental ZnO at 1,500 to 2,000 mg Zn/kg Zn improved postweaning pig performance, and its combination with an antibacterial agent resulted in additional performance improvements.

An experiment was conducted to determine the effect of high dietary intakes of Zn and Cu and their combination on growth performance of weanling pigs with diverse health status and management strategies. Twelve experiment stations cooperated and used a total of 1,356 pigs that averaged 6.55 kg BW and 22.2 d age at weaning. The four dietary treatments, all of which met or exceeded NRC requirements, were 1) control, 2) 3,000 ppm Zn (from Zn oxide), 3) 250 Cu ppm (from Cu sulfate), or 4) 3,000 ppm Zn and 250 ppm Cu. The diets were fed as a complex Phase I diet (1.4% lysine) for 7 d followed by a Phase II diet (1.2% lysine) for 21 d. Chlortetracycline (220 ppm) was added to all diets. Fecal color (1 = yellow to 5 = black) and consistency (1 = very firm to 5 = very watery) were scored daily for 3 wk. At the end of the 28-d study, 412 pigs were bled at five stations, and plasma Cu, Zn, and Fe concentrations were determined at one station with atomic absorption spectrophotometry. Average daily gain (375, 422, 409, 415 g/d), feed intake (637, 690, 671, 681 g/d), and gain/feed (586, 611, 611, 612 g/kg) were improved (P < .01) by the addition of Zn and(or) Cu. Significant Cu x Zn interactions imply that the responses to Zn and Cu were independent and not additive. There were significant (P < .01) Zn and Cu effects and a Zn x Cu interaction on fecal color (3.17, 3.24, 4.32, 3.57) and consistency (2.39, 2.14, 2.14, 2.13). Dietary additions of Cu and Zn resulted in elevated plasma concentrations of Cu and Zn, respectively. These data indicate that pharmacological additions of 3,000 ppm Zn (oxide) or 250 ppm Cu (sulfate) stimulate growth beyond that derived from intakes of Zn and Cu that meet nutrient requirements. However, the combination of Zn and Cu did not result in an additive growth response.

A cooperative research study involving members of a regional committee (North Central Regional Committee on Swine Nutrition [NCR-42]) was conducted to assess the variability in nutrient composition (DM, CP, Ca, P, Se, and amino acids) of corn and soybean meal from 16 sources (15 states, mostly in the Midwest) and to assess the analytical variability in nutrient assays among 22 laboratories (labs; 16 experiment station labs and six commercial labs). Corn samples were obtained from each participating station's feed mill during a 3-yr period (1989, 1990, and 1992), as were soybean meal samples during a 2-yr period (1989 and 1990). Both regular soybean meal (with hulls) and dehulled soybean meal were represented in the study. Samples were analyzed for DM and CP by all 22 labs, for Ca and P by 15 labs, for amino acids by 10 labs, and for Se by 6 labs. Each lab used its own analytical procedures. Samples of corn and soybean meal varied in their nutrient composition depending on the area of origin. The greatest variation among sources was in Se concentration, ranging from .02 to .29 mg/kg in corn and .08 to .95 mg/kg in soybean meal. Crude protein and lysine in corn were positively correlated, but the regression coefficient was low (r2 = .49). The relationship between CP and lysine for the two soybean meals combined was considerably stronger (r2 = .81). Lysine in corn increased by .018 percentage point and lysine in soybean meal (regular and dehulled combined) increased by .063 percentage point for each 1 percentage point increase in CP. Except for CP and Se, the analytical variability among labs was as great as, and in some cases greater than, the variability in nutrient composition among sources of corn and soybean meal. Within-lab analytical variability tended to be less than among-lab variability. Some labs performed certain analyses with considerably less variability and more accuracy than others.

A cooperative experiment involving 501 litters was conducted at four stations to assess the effects of supplemental lysine on lactational performance of sows nursing large litters. Basal diets were formulated to contain .60% lysine from corn or sorghum and soybean meal. Lysine.HCl (78.8% lysine) was substituted for grain to achieve dietary lysine levels of .75 and .90%. First-parity sows nursed a minimum of nine pigs per litter and older sows a minimum of 10 pigs per litter by d 3 of lactation. Overall mean litter size at 21 d of age was 9.7 pigs. Sows remained on treatment for three successive parities unless culled for structural unsoundness or reproductive failure. Dietary lysine did not affect body weight or backfat loss during lactation, sow ADFI, interval from weaning to estrus, or litter size at birth or at 21 d of age. Mean pig weights at birth and at 21 d of age increased quadratically to increasing lysine, with improvements found at all stations from increasing lysine from .60 to .75%. Twenty-one-day pig weights did not increase at the highest lysine level at stations feeding corn, but did improve at the station feeding sorghum, which resulted in a treatment x station interaction (P < .05). The different responses to lysine on different grain sources indicates intake of one or more other amino acid may have limited lactation performance at the highest level of lysine. These data indicate that a 13% CP corn-soybean meal containing .60% lysine is inadequate for sows nursing large litters and that supplemental synthetic lysine beyond .15% additional lysine will not be beneficial due to a deficiency of one or more other amino acids.

Crossbred female swine (n = 393) were used in a multiparity study at five experiment stations to evaluate the effects of dietary supplementation of folic acid (FA) on serum folates status and reproductive performance. The dietary treatments were a corn-soybean meal basal diet (calculated FA, .34 ppm) supplemented with 0, 1, 2, or 4 ppm FA. Experimental diets were fed continuously from a minimum of 21 d before first mating throughout the entire study. At one station, blood samples for radioimmunoassay determination of serum folates concentration were collected by vena cava puncture at mating, d 55 of gestation, d 110 of gestation, and at weaning. Stage of reproduction and dietary FA supplementation affected (P < .005) serum folates concentrations. Serum folates declined from mating to d 55, remained low at d 110, and returned to higher levels at weaning. Linear increases (P < .001) in serum folates with increasing level of dietary FA were observed at each reproductive stage. Over the course of the study, reproductive performance criteria including total pigs born, live pigs at birth and d 21, and individual pig and litter weight at birth and d 21 were not affected (P > .10) by inclusion of FA in the diet. The number of days postweaning to estrus also was not affected by FA treatment. Under the conditions of this experiment, increasing level of FA in the diet had a pronounced effect in attenuating decreased serum folates concentration during gestation but was without benefit to reproductive performance.

This article reviews literature on the highly differentiated nature of the luteal cell types and their regulation in the mid-cycle corpus luteum of ruminants. The blood vessels of the corpus luteum are composed primarily of endothelial cells with few intraluteal arterioles or arteries. Blood flow to the corpus luteum does not seem to be regulated by tropic hormones, metabolic activity, or autonomic nerves, but it is dependent on maintenance of high blood pressure. The density of luteal capillaries and lack of luteal arterioles allows an elevated, relatively unregulated luteal blood flow. Steroidogenesis in the ruminant corpus luteum manifests both dependence on and independence from the actions of LH. Initial luteinization, growth, and development of the corpus luteum is dependent on LH action, but progesterone production by the mid-cycle corpus luteum of ruminants is relatively independent of acute LH stimulation. This apparent enigma may be due to distinct functional properties of the steroidogenic cell types in the corpus luteum. Progesterone production by the large luteal cells is relatively independent of LH action, but the small luteal cells respond to LH stimulation. Much of the progesterone produced by the mid-cycle corpus luteum is produced by the large luteal cells and may not be acutely dependent on LH stimulation. Progesterone production by both cell types is dependent on lipoproteins delivered by the abundant luteal blood supply. Thus, distinct cellular features of the mid-cycle corpus luteum produce considerable steroidogenic capacity.

A regional cooperative study (NCR-42 Committee) evaluated the efficacy of supplemental dried whey and L-lysine.HCl in a corn-soybean meal-based diet for weanling pigs. The experiment involved five research institutions using a total of 960 crossbred pigs weaned between 3 and 4 wk of age. The experiment was conducted as a randomized, complete block design in 15 replications with a minimum of two replicates per station. Two diets were formulated to contain either .95 or 1.10% lysine by altering the ratio of corn:soybean meal (C-SBM). Two other diets were formulated to the same lysine levels but with 20% dried whey (C-SBM-DW). Supplemental L-lysine.HCl was added to each diet mixture as another variable, increasing the lysine level of each diet by .15%. There were station effects (P < .01) for each trait, but no station x treatment interactions (P > .15). Feed intakes and weight gains were greater (P < .01) for pigs fed diets containing dried whey, and there was a greater response (26 vs 10%) to the C-SBM-DW diet that contained 1.10% lysine than to the C-SBM-DW diet at the .95% lysine level. Performance was not improved when L-lysine.HCl was added to either the .95 or 1.10% lysine C-SBM diets, and it elicited a small, but nonsignificant, gain response when it was added to the C-SBM-DW diets. These results suggest that gain and feed performance responses of weanling pigs improved when diets contained dried whey. Lysine was not the limiting factor in either the C-SBM or C-SBM-DW diet formulated to either .95 or 1.10%. Another factor in dried whey was assumed to be responsible for its growth promotion effect.

The mixed-models procedure (MMP) was used to analyze pooled data sets from 12 independent studies conducted during the last 13 yr at nine locations in seven states to provide combined estimates of daily gains by beef steers (Bos taurus) grazing tall fescue (Festuca arundinacea Schreb.) pastures free of (E-) or infested (E+) at different levels with the endophytic fungus Acremonium coenophialum. Treatments included low-infestation (< or = 5% E+), moderate-infestation (> or = 20 to < or = 35% E+), and high-infestation (> or = 50 to < or = 97% E+) tall fescue pastures, and, in tall fescue-clover (Trifolium spp.) mixtures, pastures at the same E+ levels with approximately 25 and 10% clover in spring and summer stands, respectively. Spring, summer, and combined spring+summer data were analyzed separately. The MMP permitted estimation of the fixed effects of treatments over a broad inference space of future years and different tall fescue pastures over a wide geographic range; detected relationships that had not been apparent in the individual studies, such as the interactions between clover presence and E+ infestation levels; and provided a more coherent body of information than did the results obtained from each discrete study. Logistical and financial constraints that force undesirable compromises in the conduct of future grazing and other expensive or time-consuming research may be avoided by using MMP within the context of cooperative projects.

A cooperative research study involving three experiments and 2,318 pigs was conducted at 12 research stations to evaluate the protein (lysine) requirements of barrows and gilts. The two sexes were penned separately and fed fortified corn-soybean meal diets containing protein levels ranging from 12.0 to 17.2%. Lysine levels in these diets ranged from .52 to .90%. Protein levels in Exp. 1 were 12, 14, and 16%; in Exp. 2, protein levels were 13, 14, 15, and 16%; and in Exp. 3, they were 13.2 15.2, and 17.2%. Fat (5%) was added to one-half of the diets in Exp. 3. Each station that participated contributed a minimum of two replicate pens of pigs per diet-sex combination in a given experiment. Average initial and final weights were 35 and 99 kg in Exp. 1 and 51 and 105 kg in Exp. 2 and 3, respectively. At the end of the test period, pigs were slaughtered and hot carcass weight, 10th rib fat depth, and longissimus muscle area were measured. Percentage of carcass muscle was estimated from these data. Overall, barrows gained weight faster than gilts (P < .01), but gilts required less feed per unit of gain (P < .05) and had less backfat, larger longissimus muscle areas, and a greater percentage of carcass muscle (P < .01) than did barrows. Lean growth rate was similar for barrows and gilts (332 vs 329 g/d). Increasing the dietary protein or lysine level resulted in improved rate and efficiency of gain and increased carcass leanness and lean growth rate in gilts, but the increase was less pronounced or did not occur in barrows, resulting in protein level x sex interactions. Feeding low-protein (12 or 13%) diets decreased performance and carcass leanness to a greater extent in gilts than in barrows. The pooled data from the three experiments indicated that most traits tended to reach a plateau at 13% CP (.60% lysine) in barrows, whereas in gilts, weight gains, feed/gain, carcass muscle, and lean growth rate continued to improve, but at a decreasing rate, with up to 17.2% CP (.90% lysine). The results indicate that gilts require higher concentrations of dietary amino acids to maximize lean growth rate than do barrows.

A deterministic computer model was used to predict effects of genetic improvements in performance and of management options on life-cycle flock TDN input per unit of empty body weight (EBW) or carcass lean (CLN) equivalent value of market lamb, cull ewe, and wool output from a pure breeding system of sheep production for sheep fed to maintain normal weight. Relative values per kilogram for market lambs, cull ewes, and clean wool were 1 to .33 to 2.04 in lamb empty body equivalent, but 1 to .33 to 1 in lamb carcass lean equivalent. A 10% increase in lamb viability improved TDN/EBW or CLN by -15 to -20% for high to low lambing rates. Corresponding smaller gains were -7 to -11% for fertility, -3 to -13% for lambing rate, -1 to -3% for wool growth rate, -1 to -5% for milk production without creep feeding, -2 to -1% for mature size to about 70 kg, and -.6 to -.9% for precocity of fertility. Increasing leanness 10% improved TDN/CLN by -3 to -1% but increased TDN/EBW 3% because of higher maintenance requirements of leaner sheep. Higher protein requirements for increased lambing rate, milk production or leanness, or greater increases in non-feed than in feed costs, would mean only slightly less reduction of TDN/output than shown. Creep feeding was beneficial only for prolific, low-milking stock. Flushing reduced adverse effects of restricted feeding. Different values for wool vs meat or for costs of feed vs non-feed inputs would change results. These estimates for relative economic importance of traits apply to derivation of optimum criteria for selection among breeds or crosses, or within-breeds used in rotation crossbreeding, but would differ for specialized terminal-sire or maternal breed roles.

A deterministic computer model of a purebreeding sheep production system was used to simulate effects on life-cycle efficiency from genetic changes in lambing rate (LB), fertility (FERT), precocity of fertility (PREC), and estrus season length (ES) under annual (Y), 4-mo (A), and 73-d (S) breeding intervals. Ewes and lambs of a 1,000-ewe flock were fed to requirement through five yr, beginning with ewe lambs at the optimal breeding season and accumulating feed input (TDN) and market lamb equivalent weight of output (EBW), including cull ewes and wool. For annual lambing, improvement in cost (TDN/EBW equivalence) per 10% increase in genetic potential was -9.8, -8.2, -1.3, and -.8% for LB, FERT, PREC, and ES, respectively. For the A and S lambing intervals, corresponding gains in TDN efficiency were -19 for FERT and -9% for LB when ES was 72 d, but only -6 and -5% when ES was 192 d. Increasing PREC by 10% improved cost -3% under accelerated systems when ES was 72 d, but less than -1% when ES was 192 d. Cost reduction from 10% longer ES under A and S breeding intervals was greater when other reproductive performance was low (-11 and -17%) rather than high (-2 and -3%). Reduction in costs for A and S vs Y lambing intervals was greatest with long ES and was greater with low (-43 and -53%) than with high reproductive performance (-20 and -24%). When ES was 72 d, A and S intervals would reduce costs for high (-9 and -11%) but increase costs for low reproductive traits. Corresponding increases in CP/TDN required in diet would reduce gains in TDN/EBW only slightly. These results should aid in development of optimum selection criteria for stocks used for pure or rotation crossbreeding or as maternal parents of terminal crosses.

A deterministic mathematical computer model was developed to simulate effects on life-cycle efficiency of lamb and wool production from genetic improvement of performance traits under alternative management systems. Genetic input parameters can be varied for age at puberty, length of anestrus, fertility, precocity of fertility, number born, milk yield, mortality, growth rate, body fat, and wool growth. Management options include mating systems, lambing intervals, feeding levels, creep feeding, weaning age, marketing age or weight, and culling policy. Simulated growth of animals is linear from birth to inflection point, then slows asymptotically to specified mature empty BW and fat content when nutrition is not limiting. The ME intake requirement to maintain normal condition is calculated daily or weekly for maintenance, protein and fat deposition, wool growth, gestation, and lactation. Simulated feed intake is the minimum of availability, DM physical limit, or ME physiological limit. Tissue catabolism occurs when intake is below the requirement for essential functions. Mortality increases when BW is depressed. Equations developed for calculations of biological functions were validated with published and unpublished experimental data. Lifetime totals are accumulated for TDN, DM, and protein intake and for market lamb equivalent output values of empty body or carcass lean and wool from both lambs and ewes. These measures of efficiency for combinations of genetic, management, and marketing variables can provide the relative economic weighting of traits needed to derive optimal criteria for genetic selection among and within breeds under defined industry production systems.

Forty-eight Angus and Brangus steers (249 kg initial BW) were used in a randomized complete block design. Steers grazed annual ryegrass (Lolium multiflorum [L.] Lam.) for 107 d and were sampled at 35 and 70 d. Treatments consisted of a corn supplement (C) or corn supplement plus either 80 mg.steer-1.d-1 of lysocellin (L) or 60 mg.steer-1.d-1 of tetronasin (T). When compared with C, ADG of L- and T-fed steers was higher (P less than .05) for the complete 107-d study (1.15 vs 1.25 kg/d). At 35 d, ruminal acetate:propionate ratio tended (P = .07) to be higher for C than for L- and T-fed steers (4.6 vs 3.8). When compared with T, steers fed L tended (P = .11) to have higher acetate:propionate ratios. Ruminal concentrations of ammonia and free amino acids were not affected (P greater than .05) by treatment, but ruminal proteolytic activity tended (P = .13) to be lower for L- and T-fed than for C steers at 70 d. Ionophores did not alter (P greater than .05) ruminal mineral concentrations, but ruminal Mg concentration tended (P = .14) to be higher for T- than for L-fed steers at 70 d. When compared with L- and T-fed steers, C steers had lower (P less than .05) plasma concentrations of Mg (23.7 vs 21.9 mg/liter) and Ca (113.0 vs 104.2 mg/liter) at 35 d. Plasma mineral concentrations were similar (P greater than .05) for L- and T-fed steers. Data are interpreted to indicate that L and T may improve ADG, decrease ruminal acetate:propionate ratio, and alter mineral metabolism.

Twenty calves (7 mo old) were blocked by breed, sex, and weight into five groups of four calves and randomly assigned to either a 90% forage (alfalfa) or a 90% grain (50% sorghum and 50% wheat) diet fed at one (1M) or two (2M) times NEm for 140 d. Samples of ruminal epithelial tissue were collected from the anterior ventral sac, and papillae were cut free by hand and used for in vitro incubations and acyl-CoA synthetase assays. Substrates were acetate (90 mM), propionate (60 mM), butyrate (30 mM), and glucose (20 mM). Net productions of beta-hydroxybutyrate and acetoacetate from acetate were greater (P less than .01) with the 2M feeding; however, 14CO2 production from acetate was greater (P less than .05) with the grain diet. Net production of lactate (P = .09) and pyruvate (P less than .01) from propionate increased with the 2M feeding, whereas net lactate production from glucose decreased (P less than .01). Uptakes of VFA were similar with 1M and 2M feeding and were about 10-fold greater than uptakes of glucose. Production of 14CO2 from propionate was two- to fivefold greater than from acetate, butyrate, or glucose. Oxygen consumption was greater (P less than .01) with 2M feeding and unaffected by substrate. Activities of butyryl-CoA synthetase (nmol.mg of tissue-1.h-1) were greater (P less than .05) for animals consuming the forage diets. Addition of butyrate inhibited acetyl- and propionyl-CoA synthetase activity by 63 and 92%, respectively for all dietary treatments. Overall, metabolism of ruminal epithelial tissue tended to increase with the 2M feeding. Influence of dietary forage content on metabolism and activity of acyl-CoA synthetases was minimal, but the high-forage diet caused slight increases.

Studies were carried out with six barrows (initial BW 50 kg) to determine the effect of two fiber sources on the apparent ileal and fecal N and amino acid digestibilities and bacterial N excretion in feces. The pigs, fitted with a simple T-cannula at the distal ileum, were fed three cornstarch-based diets formulated to contain 16% CP from soybean meal according to a repeated 3 x 3 Latin square design. Diet 1 did not contain additional fiber. Diets 2 and 3 contained 10% powdered cellulose and 10% barley straw (ground through a 2-mm mesh screen), included at the expense of cornstarch, respectively. The pigs were fed 900 g at each meal twice daily, 0800 and 2000. Feces were collected for 48 h after a 10-d adaptation period. Thereafter, ileal digesta were collected for 24 h. Chromic oxide was used as a digestibility marker. With the exception of leucine, the inclusion of fiber did not affect (P greater than .05) the ileal digestibilities of the indispensable amino acids. The values for the average of the ileal digestibilities of the indispensable amino acids were 85.3, 82.9, and 83.2% for diets 1, 2, and 3, respectively. On the other hand, the inclusion of fiber decreased (P less than .05) the fecal digestibilities of all the indispensable amino acids. The values for the average of the fecal digestibilities of the indispensable amino acids were 91.7, 87.4, and 89.1% for diets 1, 2, and 3, respectively. These decreases resulted from an increase (P less than .05) in the excretion of bacterial N, which was measured using 2,6-diaminopimelic acid as a marker. In conclusion, as measured with the ileal analysis method, the inclusion of fiber had little effect on the digestible amino acid supply.

The purpose of this experiment was to determine the ovulation rate after treatment with human chorionic gonadotropin (hCG) in two groups of gilts characterized by different ovarian morphology: grape-type (GT; n = 11) and honeycomb-type (HT; n = 7). At 170 d of age (d 0), gilts were examined by laparoscopy and ovarian type was determined by the distribution of macroscopic follicles present on the ovarian surface. Five to ten minutes after surgery, each gilt received a single injection (i.m.) of 750 IU of hCG. At d 0, GT ovaries had a greater number of large follicles (greater than or equal to 6 mm) than HT ovaries (10.0 +/- .5 vs 2.6 +/- .3; P less than .05), whereas HT ovaries had more small follicles (1 to 3 mm; HT: 42.3 +/- .8 vs GT: 26.7 +/- .9; P less than .05) and total follicles (HT: 59.4 +/- 2.3 vs GT: 52.2 +/- 1.5; P less than .05), although numbers of medium follicles (4 to 5 mm) were similar (GT: 15.6 +/- .8 vs HT: 14.6 +/- 1.7; P greater than .10). Number of induced corpora lutea (CL) per ovary was greater (P less than .05) in gilts with GT ovaries (10.59 +/- 2.9 CL) than in gilts with HT ovaries (5.21 +/- .66 CL). Total weight of luteal tissue (LT) per ovary and serum progesterone concentrations 8 d after induction of ovulation were greater in GT gilts than in HT gilts (GT: 6.37 +/- 1.09 g vs HT: 3.31 +/- .49 g for LT, P less than .05; GT: 21.08 +/- 4.76 ng/ml vs HT: 13.40 +/- 2.05 ng/ml for progesterone, P less than .07).(ABSTRACT TRUNCATED AT 250 WORDS)

Two experiments were performed to determine whether esterification is a major pathway of fatty acid utilization within porcine placenta and to determine what metabolic parameters may limit fatty acid transfer to the fetal pig. Maternal (endometrium) and fetal (chorioallantois) placenta were obtained by Caesarean section at d 110 of gestation in both experiments. Eight gilts were used in the first experiment. Tissue sections were incubated with palmitate at concentrations ranging from .25 to 2.0 mM. Maternal placenta metabolized palmitate at a higher rate than fetal placenta, although fetal placenta was more efficient in esterifying palmitate. Esterification composed the majority of palmitate utilization within fetal and maternal placenta. The second experiment evaluated the effect of dietary lipid on placental fatty acid metabolism and evaluated the ability of placenta to mobilize lipids. Fourteen gilts were divided into two groups of seven and fed a diet containing 15% tallow diet or a diet not supplemented with tallow (control) from d 90 to 110 of gestation. Dietary lipid had no detectable effects on lipoprotein lipase activity, [14C]palmitate metabolism, or lipolysis by the maternal or fetal placenta. Lipolytic activity of placental tissues was minimally affected by incubation with various proposed lipolytic activity of placental tissues was minimally affected by incubation with various proposed lipolytic agents. The data indicate that supply of fatty acids to the fetal pig may be limited by transfer of plasma fatty acids into the cytoplasm of placental cells or by regulatory enzymes for intermediate esterification; both types of limitations have been proposed to be influenced by fatty-acid binding proteins.

The hydrolysis of ochratoxin A (OA) and the corresponding formation of its hydrolysis product, alpha ochratoxin (O alpha), by ruminal digesta and in the rumen of hay-fed and grain-fed sheep were compared. Ruminal contents from sheep fed diets with hay or with grain hydrolyzed OA in vitro; the majority of the activity was associated with the particulate fraction of the ruminal contents. The rate of hydrolysis of OA by ruminal fluid that was adjusted to different pH values was not influenced (P greater than .6) by the pH of the samples (pH was from 5.5 to 7.0). Ruminal fluid obtained from hay-fed animals (pH 7.0) was able to hydrolyze OA in vitro and to produce the hydrolyzed product, O alpha, at a much greater rate (fivefold) than ruminal fluid obtained from grain-fed animals (pH 5.5) (P less than .01). Ochratoxin A was administered intraruminally at a concentration of .5 mg/kg of BW to hay-fed and grain-fed sheep. The half-lives for disappearance of OA from the rumen of sheep fed grain (normal feed intake, rumen pH 5.7), fed grain at a low level (30% of normal feed intake, pH 6.5), and fed hay (pH 7.1) were 3.6, 1.3, and .6 h, respectively. The results suggest that OA is hydrolyzed much faster in the rumen of sheep fed hay than in sheep fed grain, presumably because of the different ruminal microbial population, which in turn influenced the rate of hydrolysis of OA.

Slow-cooled stallion spermatozoa, with and without seminal plasma removed by centrifugation, were diluted in Kenney's extender (KE) containing nonfat dry skim milk with glucose and antibiotics or in KE supplemented by adding a modified high-potassium Tyrode's medium (KMT). Four ejaculates from each of four stallions were collected and divided factorially across these four treatments. Percentage of motile sperm, path velocity, and linearity immediately after treatment (0 h) and after storage at 4 degrees C for 24, 48, and 72 h were evaluated objectively by use of a HTM-2030 sperm motility analyzer. Stallions were a significant source of variation (P less than .01) throughout. After sperm had cooled, effects of stallion, extender, centrifugation, and their interactions were all found to be significant (P less than .01). The motility at 0, 24, 48, and 72 h for centrifuged KE was 74, 47, 39, and 24%; for uncentrifuged KE was 76, 56, 50, and 37%; for centrifuged KMT was 76, 75, 72, and 64%; and for uncentrifuged KMT was 80, 50, 26, and 13%, respectively. The extender x centrifugation interaction, after 24, 48, and 72 h of storage, accounted for half or more of the variation. Whereas centrifugation of semen extended in KE seemed to be harmful to sperm, motility of sperm extended in KMT after centrifugation was remarkably conserved for 72 h and was superior to all other treatments (P less than .05). This extender is promising for preserving liquid stallion semen when it must be transported before use in artificial insemination.

Sixty-four white-faced rams and wethers were dressed with the aid of a commercial pelt puller. The effects of age, castration, and season on difficulty of pelt removal and pelt damage were evaluated. Lambs were divided into two age groups (5 and 12 mo) within gender (ram and whether) and season (spring and fall). A greater force (P less than .05) was required to remove pelts from rams than from wethers in both 5- and 12-mo-old groups. Older lambs slaughtered in the fall required more force (P less than .05) to remove their pelts than did those slaughtered in the spring, but differences by season did not exist for 5-mo-old lambs. The difference between rams and wethers in percentage of live weight that was closely shorn pelt weight was not significant (P greater than .05). The area of grain crack in the flank expressed as a percentage of total area of the skin was lower (P less than .05) for skins from 5-mo-old lambs and ram lambs than it was for skins from 12-mo-old lambs and wether lambs, respectively. Factors involved in difficulty of pelt removal in ram lambs included crosscut shoulder weight, fat firmness, and carcass weight. Difficulty of pelt removal in wether lambs was best predicted by including crosscut shoulder weight and bodywall thickness in multiple regression equations.

Mixed ruminal bacteria (80 mg N/liter) degraded casein and soluble soy protein rapidly (.68 and .72 mg N/[liter.min], respectively), but ammonia was produced at a slower rate (.08 and .10 mg N/[liter.min], respectively). Because there was little increase in cell protein, ammonia production could not account for all the degraded protein. Large quantities of non-ammonia, non-protein nitrogen (NAN-NPN) accumulated, and this NAN-NPN reacted more strongly (2- to 14-fold) with ninhydrin after it was treated with 6 N HCl (110 degrees C, 24 h) or pronase E. Even after 96 h of incubation, 10% of the protein N was still found in the NAN-NPN pool. Monensin had little effect on protein degradation, but it caused a large decrease in ammonia production (P less than .05) and an increase in NAN-NPN (P less than .05). These results indicated that significant quantities of peptide N could not be degraded by ruminal microorganisms and that monensin could increase peptide flow from the rumen. Because 3,3',4',5-tetrachlorosalicylanide, a protonophore that inhibits both Gram-positive and Gram-negative bacteria, did not cause a greater decrease (P greater than .05) in ammonia than monensin, an ionophore that is primarily effective against Gram-positive bacteria, it seemed that the "protein sparing" of monensin could largely be explained by its inhibition of Gram-positive bacteria.

An experiment using a total of 210 crossbred pigs from two farrowing groups evaluated the effects of three weaning weights and their associative starter feeding program on subsequent postweaning performance to 105 kg BW. One group of pigs nursed their dams in outside heated hutches (Trial 1), and a second group was raised in a centrally heated farrowing house (Trial II). The three pig weaning weight groups ranged in weight from 1) 4.1 to 5.0 kg, 2) 5.5 to 6.8 kg, and 3) 7.3 to 8.6 kg. Pigs in Group 1 were fed a high nutrient dense diet (HNDD) for a 2-wk period followed by a corn-soybean meal-dried whey (C-SBM-DW) and then a corn-soybean meal (C-SBM) diet, each for a 2-wk period. Group 2 was fed the same diet sequence except that HNDD was provided for 1 wk, whereas Group 3 was provided only the C-SBM-DW and the C-SBM diets each for 2 wk, consecutively. At the end of the nursery period, pigs were fed C-SBM diet formulations to 105 kg BW. Pigs of Trial I averaged 5.2 d older at weaning than those raised in the central farrowing house, but only a 1.5-d difference existed between light- and heavy-weight groups in both trials. Gains and feed intakes for the three weaning groups were higher as weaning weight increased during both the nursery and the growing-finishing period. There did not seem to be a compensatory growth response for lighter-weight weanling pigs even though they had been fed starter diets containing milk products. Consequently, fewer days (approximately 15) were required for the heavier-weight weanling pig group to reach a final weight of 105 kg than for the light-weight group. The medium-weight group required an intermediate number of days to reach 105 kg.

During the summer and fall of 1987, sows from eight herds in three states were assigned randomly to receive either a combination of 400 IU of pregnant mare's serum gonadotropin with 200 IU of hCG (P.G. 600) or no treatment at weaning. A treatment x parity interaction was observed for days to first estrus after treatment and percentage anestrus (percentage of sows not achieving estrus within 10 d after weaning). Relative to primiparous control sows, primiparous sows given P.G. 600 expressed estrus sooner (P less than .02) after weaning (6.0 vs 7.8 +/- .6 d) and exhibited less (P less than .02) postweaning anestrus (15.6 vs 29.2 +/- 4.0%). Second parity sows that received P.G. 600 showed estrus sooner (P less than .06) than second-parity control sows (4.7 vs 6.4 +/- .7 d). Days to first estrus after treatment did not differ between groups for parity-three and older sows, and percentage anestrus was not different between treatments for parity-two and older sows. The herd X treatment interaction was significant for percentage recycled (percentage of successfully mated sows that returned to estrus), subsequent farrowing rate, and subsequent number of pigs born dead. Number of pigs born alive was lower for sows treated with P.G. 600 than for control sows (10.55 vs 10.10 +/- .18; P less than .02). In summary, treatment of sows weaned in the summer and fall with P.G. 600 had decreased days to postweaning estrus in parity-one and -two sows and reduced frequency of postweaning anestrus in primiparous sows.

In this study, the interactions among breed of cattle, adipose tissue site and specific incubation conditions were investigated. Subcutaneous and i.m. adipose tissues were obtained from 10 Angus and 9 Santa Gertrudis steers immediately postmortem. Adipose tissue explants were incubated acutely for 2 h immediately at slaughter or after being cultured 48 h with or without 1 mU/ml insulin and 30 mg/ml bovine serum albumin; the incorporation of 14C-labeled acetate and glucose (5 mM, plus 5 mM unlabeled lactate) into lipid fractions was measured. AT the same chronological age, Angus steers had a more youthful lean maturity score, higher USDA marbling score and higher USDA quality grade (P less than .05) than did carcasses from Santa Gertrudis steers. The lower marbling score of the Santa Gertrudis steers was paralleled by smaller i.m. adipocytes (P less than .05) relative to Angus steers. Pentose cycle reductase and NADP-malate dehydrogenase activities were greater in Angus i.m. adipose tissue than in Santa Gertrudis i.m. adipose tissue, which would provide more reducing equivalents (NADPH) and glycerol for fatty acid biosynthesis and triacylglycerol esterification. Correspondingly, Angus i.m. adipose tissue exhibited a greater rate of lipogenesis from acetate and glucose (P less than .05) than did Santa Gertrudis i.m. adipose tissue in acute incubations. The presence of insulin resulted in higher rates of lipogenesis from acetate in Angus s.c. adipose tissue than in Santa Gertrudis s.c. adipose tissue after 48 h of explant culture. These data indicate that i.m. and s.c. adipose tissues exhibit aspects of lipid metabolism unique to each tissue and suggest that breed-related differences in adipose tissues may explain the divergent responses to insulin observed in different laboratories.

Performance test records from on-farm tests of young Polish Large White boars and reproductive records of Polish Large White sows from 94 nucleus farms during 1978 to 1987 were used to estimate population parameters for the measured traits. The number of boar performance records after editing was 114,347 from 3,932 sires, 21,543 dams, 44,493 litters and 1,075 herd-year-seasons. Reproductive performance records of sows involved 41,080 litters from 2,348 sires, 18,683 dams and 1,520 herd-year-seasons. Both data sets were analyzed by using restricted maximum-likelihood programs. The model used for the performance records included fixed herd-year-seasons, random sires, dams and error effects, and covariances for the year of birth of sire and year of birth of dam. The model used for the reproduction data set was the same as the performance data with parity as an additional fixed effect. Estimated heritabilities were .27, .29, .26, .07, .06, .06 for average daily gain standardized to 180 d (ADG), backfat thickness standardized to 110 kg BW (BF), days to 110 kg (DAYS), litter size at birth born alive (NBA), litter size at 21 d (N21) and litter weight at 21 d (W21), respectively. Estimated common environmental effects for the same traits were .09, .10, .09, .06, .07 and .08, respectively. Genetic correlations were .25 (ADG and BF), -.99 (ADG and DAYS), -.21 (BF and DAYS), .91 (NBA and N21), .68 (NBA and W21) and .80 (N21 and W21). The respective phenotypic correlations were .23, -.99, -.20, .88, .75, .86. These population parameters for Polish Large White pigs are similar to those for breeds in other countries.

A cooperative experiment to evaluate biotin addition to sow diets was conducted at three research stations using 303 litters. Primiparous and multiparous sows (overall average parity 2.8) were fed a 14% CP corn-soybean meal diet (140 micrograms/kg biotin), with or without supplemental biotin (330 micrograms added biotin per kg feed), throughout gestation and lactation. As many sows as possible were fed their respective diets through three successive parities. During gestation, sows were given from 1.82 to 2.27 kg of feed per day, depending on environmental conditions; during lactation sows had ad libitum access to feed. Supplemental biotin had no effect (P greater than .35) on sow weights at breeding, at d 109 of gestation, at farrowing or at weaning. No differences were found in litter size at birth (P greater than .18), but at d 21 of lactation, sows fed the diet containing supplemental biotin had larger litters than sows fed the unsupplemented diet (9.4 vs 8.7 pigs, respectively; P = .01). Pig weights at birth and d 21 of lactation were not affected (P greater than .20) by dietary treatment. Biotin supplementation did not affect (P greater than .28) the length of the interval from weaning to estrus. No evidence was found that feet cracks or bruises were reduced by biotin supplementation. The results indicate that biotin supplementation of a corn-soybean meal diet during gestation and lactation increased the number of pigs at d 21 of lactation, but it did not decrease the incidence of foot lesions.

Data from 254 crossfostered pigs and 753 noncrossfostered pigs of Duroc and Landrace first-parity litters were used to assess the phenotypic effects of crossfostering on baby pigs. Differences between crossfostered and noncrossfostered pigs in the recipient litter were analyzed. Phenotypic correlations were calculated for selected individual pig traits (n = 1007, combined foster and nonfoster data). Birth weight was correlated positively with improved birth vigor (r = .40; P less than .01), survival to 21 d (r = .34; P less than .01) and weight at 21 d (r = .37; P less than .01). Improved birth vigor was correlated positively with pig survival to 21 d (r = .70; P less than .01) and to weaning (r = .66; P less than .01). These correlations indicate that baby pig size and strength are related and that these two characteristics influence survival and performance. Pigs that were not crossfostered (adjusted for birth vigor) had a 4.8% (P less than .10) higher rate of survival to 21 d and a 6.8% (P less than .05) higher rate of survival to weaning (42 d). However, crossfostered pigs had greater birth vigor (P less than .01). Unadjusted for vigor, crossfostered pigs had an 11.3% (P less than .01) higher rate of survival to 21 d and an 8.6% (P less than .05) higher rate of survival to weaning than noncrossfostered pigs. These results indicate that when average-strength pigs were crossfostered, livability was reduced. However, crossfostered pigs that were stronger than average had greater livability than pigs that were not crossfostered.(ABSTRACT TRUNCATED AT 250 WORDS)

The levels of nonprotein sulfhydryls (NPSH), glutathione disulfide (GSSG), nicotinamide adenine dinucleotide (NAD), hypoxanthine (Hx), xanthine (X) and the extent of lipid (TBA) and pigment oxidation (%MetMb) were determined in longissimus and gluteus medius muscles during storage at 4 degrees C. Muscles were obtained from Holstein and crossbred beef steers. Holstein beef displayed higher values for %MetMb, NAD and TBA and lower values for GSSG and Hx than crossbred beef (P less than .05). These two breed groups did not differ (P greater than .05) in X and NPSH. During storage, GSSG, Hx, X, %MetMb, GSSG/NPSH ratio and TBA value all increased, whereas NAD and NPSH decreased. Compared to the longissimus, the gluteus medius had greater %MetMb, TBA value, GSSG/NPSH ratio and Hx but lower (P less than .05) NAD and NPSH. Differences between Holstein and crossbred animals and between gluteus medius and longissimus muscles in meat color stability may be dependent on inherent metabolic differences.

Data on 2,744 calves produced in Clay Center, Nebraska and Brooksville, Florida were used to evaluate the importance of genotype x location interactions on the reproductive and maternal performance of eight breed groups of F1 crossbred cows. A total of 648 F1 crossbred cows included Bos taurus x Bos taurus (Bt x Bt) crosses: Hereford x Angus reciprocal crossbreds (HA and AH), Pinzgauer x Angus (PA), Pinzgauer x Hereford (PH); and Bos indicus x Bos taurus (Bi x Bt) crosses: Brahman x Angus (BA), Brahman x Hereford (BH), Sahiwal x Angus (SA) and Sahiwal x Hereford (SH). The first calf crop was sired by Red Poll bulls. All remaining calf crops were sired by Simmental bulls. Although the pregnancy rate was 9% higher in Nebraska, the rate of unassisted calvings and calf survival rate were both 4.6% lower in Nebraska. Calf birth and weaning weights were 8.0 and 15.6 kg heavier in Nebraska than in Florida. Bi x Bt dams exceeded (P less than .001) Bt x Bt crossbred dams for all traits except age of calf at weaning and calf-survival rates (P greater than .10). Birth weights of calves from Bi x Bt crossbred dams were 3.4 kg lighter than those from the Bt x Bt crossbred dams. The interaction of location with the breed group comparison of Bi x Bt vs Bt x Bt crossbred dams was significant for pregnancy rate, calf age at weaning, rate of unassisted calving and all weight traits. Adjusted weaning weights of calves from HA, AH, PA, PH, BA, BH, SA and SH cows were as follows: HA, 194 and 222; AH, 202 and 230; PA, 213 and 242; PH, 217 and 245; BA, 251 and 254; BH, 252 and 254; SA, 236 and 238; and SH, 238 and 243 kg, respectively, in Florida and Nebraska. Bos indicus-sired cows (BA, BH, SA and SH) weaned essentially equal-weight calves at both locations, whereas calves from Bt x Bt crossbred cows (HA, AH, PA, PH) were about 28 kg lighter in Florida.

A 3-yr study was conducted to evaluate the effect of dietary biotin supplementation on the reproductive performance of 90 sows and gilts, and on the pre-weaning growth and mortality of 223 litters. Corn-soybean meal-based diets supplemented with either 0 or 440 micrograms/kg d-biotin were fed to sows throughout their reproductive cycle. Biotin supplementation had no beneficial effect (P greater than .10) on 107-d sow weight, sow weight at weaning, weaning to estrus interval, foot lesion score, hair loss score, structural soundness score, number of pigs born, number and percentage of pigs born alive or number and percentage of pigs alive at 21 d of age. Biotin supplementation had no effect (P greater than .10) on pig growth or mortality to 21 d of age. These data do not support the concept that biotin supplementation of sow diets is needed.

We investigated the effects of weaning or fasting of 21- or 35-d-old swine by monitoring serum mitogenic activity, circulating insulin-like growth factor I (IGF-I) and its binding proteins using L6 myoblast bioassays, RIA and ligand blotting techniques. Serum samples were collected from 21- or 35-d-old animals just before and 36 h after weaning or fasting. Sera from 21- and 35-d-old weaned animals were not significantly altered in their ability to promote myoblast proliferation, whereas sera from 21- and 35-d-old fasted animals caused 29 and 21% decreases (P less than .05) compared with preweaning. The mitogenic activity of control serum was inhibited by serum from fasted animals but not by preweaned or weaned sera. Serum IGF-I levels were decreased 65 to 70% (P less than .05) with weaning or fasting at both ages. Unoccupied binding sites on circulating IGF binding proteins in the 155 kDa range decreased 18 to 19% with weaning at both ages and decreased 40% (P less than .05) with fasting at 21 d but only 17% at 35 d. Ligand blotting revealed that the 43 and 39 kDa IGF binding protein bands decreased with weaning and fasting at both ages, whereas the 29-kDa band increased with weaning and fasting. These data indicate that serum IGF-I and specific IGF binding protein bands decrease during weaning or fasting at 21 and 35 d of age. However, serum mitogenic activity did not always follow serum IGF-I levels.

Five ruminally and abomasally cannulated heifers (average weight 365 kg) were fed 6 kg/d of early (EOG) or late (LOG) maturity orchardgrass (OG) hay with or without replacement of EOG or LOG by 1.5 kg/d red clover hay (RC) in a 5 x 5 Latin square design. A fifth treatment, of LOG supplemented with 100 g/d casein (LOG + C), was used to evaluate the effect of supplemental protein. In situ fiber digestion, in vivo nutrient digestion and rate of passage from the rumen of large (retained on a 1.68-mm screen; labeled with La) and small (passed a 1.68-mm screen; labeled with Sm) EOG and LOG particles were determined in heifers fed these diets. Early maturity OG hay had 20% and 62%, respectively, greater (P less than .05) rates, and 61% and 73%, respectively, greater (P less than .05) extents of in situ NDF and ADF disappearance than LOG. Red clover substitution for OG increased (P less than .05) in situ extent of NDF disappearance by 6%. Early maturity OG large and small particles had 40% and 36%, respectively, greater (P less than .05) rates of passage than LOG. Large and small particle ruminal pool sizes were increased (P less than .05) by 115% and 33%, respectively, with LOG. Red clover substitution for OG increased (P less than .10) large and small particle output (kg/d) from the rumen by 15% and large particle rate of passage by 20%. Grass maturity may be affecting intake through rate of large particle size reduction and passage and small particle passage, although legume supplementation of OG may influence intake by increasing rate of large particle size reduction and passage.

Postmortem aging of carcasses obtained from Angus-Hereford (n = 8) and 5/8 Brahman crossbred (n = 8) heifers was investigated to determine the cause of variation in meat tenderness. Raw longissimus muscle (LM) myofibril fragmentation index was lower and cooked LM Warner-Bratzler shear force was greater for the 5/8 Brahman crossbreds (P less than .05). The activities of calcium-dependent protease (CDP) -I and -II were not affected (P greater than .05) by breed; however, CDP inhibitor activity was higher (P less than .05) in the 5/8 Brahman carcasses. The activities of cathepsins B and B + L were not affected by breed or postmortem storage time (0, 1, 3, 7 or 14 d). Hereford-Angus carcasses were fatter opposite the 12th rib and had higher USDA yield grades and marbling scores (P less than .05). Hereford-Angus crossbreds had less dark, coarse band formation around the exterior of the LM and lighter, finer-textured lean (P less than .05). Cooking loss (%) and cooking rate (g/min) were not affected by breed or postmortem aging (P greater than .05). The increased toughness in the 5/8 Brahman carcasses may be due to increased CDP inhibitor activity.

Growth, feed conversion, serum chemistry and gross slaughter characteristics were determined in 20 steers (initially 9 mo of age, 231 +/- 18 kg) receiving daily injections of either saline (S) or recombinantly derived bovine somatotropin (rBST, 20.6 mg/d) for 112 d. Live weight gains were 15% greater for steers treated with rBST than for those treated with S. Feed intake was not different between S- and rBST-treated steers; thus, feed conversion was 12% more efficient in rBST steers. Scanogram backfat measurements were not affected by treatments. Serum electrolytes, protein, glucose and most enzyme activities were similar in S and rBST steers. Serum urea, creatinine and cholesterol (toward the end of treatment) concentrations, however, were lower (P less than .05) in rBST steers, suggesting that nitrogen retention was increased and lipid turnover was decreased by rBST. Total (P less than .1) and conjugated (P less than .05) bilirubin concentrations and glutamate-pyruvate transaminase activity (P less than .05) were lower in rBST steers. Carcass weights were not altered, but dressing percentages were lower (P less than .05) in rBST steers. This indicated that weight gain response to rBST was primarily in noncarcass components; further examination showed that this gain was predominantly in gut fill (approximately 2/3 of the greater live weight gain in rBST steers). Alternative protocols, such as administering the hormone to younger animals and (or) for a longer duration, may be necessary in order to achieve desirable responses in carcass growth.

The ability of neuropeptide Y (NPY) to stimulate feed intake was tested in combination with two treatments known to depress feed intake in sheep. Six ewe and three wether lambs (mean BW = 40 kg) fitted with lateral cerebral ventricular guide cannulas and ruminal cannulas had free access to a nutritionally complete, pelleted diet. Balloons placed into the rumen were filled with either 0, 30 or 60 ml of water/kg BW and left in place for 6 h; intake was measured. Based on the decline in feed intake observed with increasing balloon volume in the rumen, Exp. 2 was designed to test effects of NPY injection (0 or 3.0 nmol) into the lateral cerebral ventricle and ruminal distension (0 or 35 ml/kg BW) for 6 h. During the 6-h test period, feed intake was depressed (P less than .05) by intraruminal balloon distension, but feed intake was increased by NPY injection (P less than .05); no interaction between NPY and distension was detected. Ruminal evacuation revealed that digesta occupied only 43% of the rumen's total volume capacity. Balloons occupied 14% of capacity, whereas meal size in control sheep following a 1.5-h fast equaled 7% of capacity. In Exp. 3, intraruminal infusion of 8 mmol/min of propionate depressed (P = .11) feed intake, whereas NPY injection enhanced (P less than .05) intake. There was no interaction between NPY and propionate infusion. In none of these experiments was cumulative feed consumption at 24 h influenced. We conclude that NPY is a versatile feeding stimulant. It promotes feed intake in feed-satiated, ruminally distended and propionate-infused sheep.

Administration of growth promotants with estrogenic activity via hastening closure of the growth plate could have an economic impact on lambs because closure results in ovine carcasses being classified as yearlings. Twelve wether lambs approximately 12 mo old were given silastic implants filled with estradiol-17 beta and allotted randomly to be slaughtered 30, 60, 90, or 220 d after implantation to determine time of growth plate closure in relation to date of implanting. Seven comparable wethers not implanted served as controls. Four wethers implanted at 2 mo of age and slaughtered 220 d later also were included. Implanted wethers had serum concentrations of estradiol averaging 13.9 pg/ml over the 220-d implant period; controls averaged 2.7 pg/ml. Estradiol implants increased carcass maturity scores but fat deposition was not altered. Growth plate widths decreased (P less than .05) as wethers grew older and implants were in place for longer periods of time. Metacarpal growth plates in 12-mo-old lambs were completely ossified 220 d after implanting, but control wethers and wethers implanted at 2 mo maintained growth plate widths. Neither metacarpal nor metatarsal bone lengths differed (P less than .05) between control and implanted wethers. Growth plate ossification was not complete until 570 d of age in implanted lambs, even though bone length had stopped increasing by 408 d. Therefore, even though estradiol and other growth stimulants with estrogenic activity increase rate of ossification of the metacarpal growth plate, bone length or mature size is not limited.(ABSTRACT TRUNCATED AT 250 WORDS)

A digestion and ruminal fermentation trial involving five ruminally cannulated steers assigned to a 5 x 5 Latin square with a 2 x 2 + 1 arrangement of dietary treatments was conducted to evaluate the effects of variety of rapeseed silage (RS) containing either a high (HG) or a low (LG) glucosinolate concentration when fed at 100 or 50% of diet DM. A bromegrass hay-corn-soybean meal mixture, which was expected to be isocaloric and isonitrogenous with the RS, was used as the control (C) treatment and replaced RS in the 50% diets. In situ disappearance of substrate from both RS varieties was measured in ruminal environments created by each diet. No dietary treatment x RS substrate interactions were observed for any in situ variable. Total tract digestibility and extent of in situ disappearance of both DM and NDF were greater (P less than .01) for HG than for LG. In situ DM and NDF disappearance at 8, 16 and 24 h was greater (P less than .01) for RS than for the C diet. Similarly, total tract DM digestibility was greater (P less than .01) for RS (61.0%) vs C (56.0%) diets. Diets with 50% RS had greater (P less than .01) NDF digestibility (50.4%) than 100% RS (43.6%) diets. Variety of RS had no effect on particulate passage rate. In a 77-d growth trial with 60 beef steers, ADG was greater (P less than .01) for HG vs LG (.46 vs .36 kg), 50 vs 100% (.52 vs .31) and C vs RS (.64 vs .41) diets.(ABSTRACT TRUNCATED AT 250 WORDS)

Ultrasonic measurements of fat thickness (FAT) and ribeye area (REA) were analyzed together with weight (WT), scrotal circumference (SC) and age data from 385 yearling Hereford bulls representing 45 sires. Additional variables created were 100*REA/WT (REACWT) and 365-d adjusted REA (AREA). Multiplicative age adjustment for AREA was calculated from linear regression of REA on age. Heritabilities were .45 +/- .17 for REACWT, .36 +/- .16 for WT, .12 +/- .13 for REA, .11 +/- .13 for AREA, .04 +/- .13 for FAT and .18 +/- .14 for SC. Phenotypic and genetic correlations were strongly negative for WT with REACWT. Neither AREA nor REACWT alone were considered suitable muscling variables due to their association with age, WT and FAT. Ultrasound REA measurements should be adjusted for the linear effects of age and WT and quadratic effects of FAT before being used for selection. Measurement of SC indicated a strong association with WT (r = .55) and a moderate positive genetic correlation with REA (.49 +/- .58).

The effects on anabolic steroid implantation on feedlot performance and carcass composition and quality were examined in control (CNTRL), ovariectomized (OVX) or melengestrol acetate-fed (MGA) beef heifers or heifers actively immunized against GnRH (Anti-GnRH). Heifers (n = 112) were assigned randomly to a 2 x 4 factorial experiment. The two classes were made up of heifers not implanted and those implanted with Synovex-H. The four treatments were 1) CNTRL, 2) MGA, 3) OVX and 4) Anti-GnRH. Heifers were housed in individual pens and fed a high-energy diet for the 4-mo study. Synovex-H increased final live weight (P less than .005), carcass weight (P less than .005), ADG (P less than .0001) and feed efficiency (P less than .005) but did not alter carcass quality and yield grade (P greater than .05). Synovex-H increased deposition of protein (P less than .0001) and reduced deposition of fat (P less than .0001). Oral administration of MGA had no significant effect on feedlot performance or carcass quality. For heifers not implanted, active immunization against GnRH, but not ovariectomy, depressed ADG (P less than .05) and increased fat deposition (P less than .05) while reducing protein deposition (P less than .05). These effects of active immunization were reversed by concurrent administration of Synovex-H. Feedlot performance and carcass composition of heifers were improved by administration of anabolic steroids. When heifers were housed singly, neither ovariectomy, active immunization against GnRH nor oral administration of MGA improved feedlot performance of heifers implanted with Synovex-H.

In an experiment to determine the effects of mastication and microbial contamination on in situ forage disappearance, samples of masticated (M) or nonmasticated alfalfa hay (AH), orchardgrass hay (OGH) and bermudagrass hay (BGH) were incubated in the rumen of two steers for 6, 12, 24, 48 and 96 h. Using diaminopimelic acid as a marker, microbial DM and CP contamination ranged from 10.3 to 22.3% and 46.3 to 95.3% of residual DM and CP, respectively. Percentage contamination was influenced by both time of incubation and forage treatment (P less than .001). Corrected DM and CP disappearances (DMD and CPD) were higher than apparent disappearances (P less than .001). Maximal NDF and ADF disappearances (NDFD and ADFD) obtained at 96 h were 58.2, 52.4; 62.7, 62.3 and 56.7, 52.6% for AH, OGH and BGH, respectively. Lag times (h) for corrected DMD and CPD were shorter (at least P less than .05) than for apparent disappearances, except for corrected CPD of AH. There were no differences (P greater than .10) in lag time of NDFD or ADFD among forages. Rates of disappearance (%/h) of corrected DMD and CPD were faster (at least P less than .01) than for apparent disappearances. The total quantity of microbial CP (mg CP/g DM) associated with residues varied with time depending on forage type (P less than .001). There was a significant relationship between the quantity of microbial CP contamination and the extent of disappearance. Masticated forages followed trends similar to those of nonmasticated forages, but the effect of mastication was not consistent. Results support the need for microbial correction of in situ forage residues.

A total of 180 crossbred, weanling pigs were assigned to five dietary treatment groups: 1) a basal corn-soybean meal diet formulated to current NRC recommendations, 2) basal + monosodium phosphate (2 x NRC P recommendations; P), 3) basal + alpha-tocopheryl acetate (220 IU/kg; E), 4) basal + sorbitol (1% of the diet; S) and 5) basal + PES. Dietary treatments were continued until market weight (104 kg). Blood samples were obtained at 3-wk intervals for analysis of serum alpha-tocopherol, P and total cholesterol. Liver and muscle (semimembranosus) samples were obtained at the end of the starter, grower and finisher phases for determination of total cholesterol concentration. The Ca:P imbalance produced by the high-phosphorus diets (P and PES) increased feed intake during the finisher phase. Dietary treatment did not consistently affect total serum cholesterol at any phase of growth. A transient 21.5% (P less than .05) depression of liver cholesterol concentration was observed in the PES-fed pigs at the end of the starter phase but was not apparent at market weight. A similar trend (nonsignificant) was noted for muscle cholesterol concentration. The present study suggests that the PES diet can decrease tissue cholesterol concentration during the nursery phase, but it remains uncertain whether this transient response is a function of age and(or) diet transition at weaning. Further research is necessary to determine whether this response can be translated to the finishing phase, and thereby reduce carcass cholesterol.

Growth and carcass traits of finishing swine fed amino acid-supplemented raw soybean (RSB) diets were examined. Experiments 1 and 2 were identical and included the following treatments: 1) corn-soybean meal (SBM), 2) corn-RSB (lysine equal to Diet 1), 3) Diet 2 + .15% L-lysine (LYS), 4) Diet 3 + .1% L-threonine (THR), 5) Diet 3 + .05% L-tryptophan (TRP), 6) Diet 3 + .15% DL-methionine (MET) and 7) Diet 3 + THR + TRP + MET equivalent to Diets 4 to 6. The unsupplemented corn-RSB diet reduced (P less than .05) gain, gain:feed, plasma urea N, loin eye area, and percentage of muscling compared with the corn-SBM diet. The addition of LYS or LYS + TRP generally improved these response variables, whereas the addition of LYS + THR or LYS + MET tended to reduce gain and gain:feed compared with the LYS addition alone. The LYS + THR + TRP + MET addition resulted in growth and carcass traits that were intermediate between those of pigs fed the corn-RSB and the corn-SBM diets but not different (P greater than .05) from either. Experiment 3 included Diets 1, 2 and 7 from Exp. 1 and 2, in addition to the following treatment: corn-RSB + LYS + THR + TRP. The LYS + THR + TRP addition improved (P less than .05) growth and carcass traits compared with the LYS + THR + TRP + MET addition.(ABSTRACT TRUNCATED AT 250 WORDS)

Steers (n = 165) of known percentage Brahman (B) and Angus (A) breeding were used to study effects of breed group (A, 3/4A:1/4B, 1/2A:1/2B, 1/4A:3/4B), age-season of feeding (calves fed during the cool season vs yearlings fed during the warm season) and slaughter end point (less than .90, 1.0 to 1.15, 1.27 to 1.40, greater than or equal to 1.5 cm of adjusted fat over the ribeye) on feedlot performance and carcass characteristics. The 1/2B and 3/4B steers had heavier (P less than .05) initial and final feedlot weights than the A and 1/4B steers and higher (P less than .05) unshrunk ADG than the A steers did. Breed types did not differ for feed efficiency. Yearling steers fed in the warm season had higher (P less than .05) unshrunk ADG than calves fed in the cool season, but ADG calculated on an empty-rumen basis did not differ between the two age-seasons of feeding. Calves fed in the cool season were more efficient (P less than .05) than yearlings fed in the warm season when efficiency was expressed on an empty-rumen basis; however, on a live weight basis there was no difference in feed efficiency. No breed group by age-season of feeding interactions on performance were detected. Slaughter end point did not significantly affect feed efficiency on an empty-rumen basis. The 1/2B and 3/4B steers had smaller ribeye areas (REA) per 100 kg hot carcass and lower marbling scores than the 1/4B and A steers. Yearlings fed in the warm season produced heavier carcasses (P less than .05) than calves fed in the cool season. As s.c. fat thickness at slaughter increased, hot carcass weight and numerical yield grade increased, whereas REA per 100 kg of hot carcass decreased. Marbling also increased as fatness increased up to about 1.5 cm subcutaneous fat.

Market data on 1,315 rabbits from 201 litters from Californian (CAL), New Zealand White (NZW), CAL X NZW and NZW X CAL dams bred to CAL, NZW and Flemish Giant sires were subjected to multiple regression and path analyses. Market traits observed in litters at 56 d included average kit weight (A56W), litter size (LS56), total litter weight (L56W) and within-litter uniformity in individual weights (LCV). Preweaning variables as covariates included in the model were dam metabolic body weight (DMW), litter born (LSB), litter birth weight (LBW), milk yield from 1 to 21 d (MY) and feed intake from 1 to 28 d of the dam and litter (FI). Results from multiple regression analyses indicated linear and quadratic effects (P less than .20) due to LSB and MY for all four market characters. The LBW influenced (P less than .05) LS56 and L56W, and FI affected (P less than .05) LS56, L56W and LCV. Separate analyses were conducted involving 28-d weaning and feed intake variables as covariates: litter size weaned (LSW), litter weaning weight (LWW) and litter feed intake from 28 to 56 d (LFI). The three weaning covariates were important (P less than .05) for all market traits except LS56 (LWW was not significant). The most accurate regression equations were obtained from the weaning model for prediction of L56W and LS56 (R2 = .68 and .78). Path analyses revealed that preweaning covariates generally had direct rather than indirect effects on market traits. Both direct and indirect effects of weaning covariates were important for market traits. Results suggest that litter market traits of size and weight can be predicted with a reasonable degree of accuracy.

Relationships of gain, intake, feed efficiency and severity of liver abscesses were evaluated in 12 experiments involving 566 head of individually fed cattle. Concentrate level in the diets ranged from 64 to 95%. In all experiments, livers were scored as unabscessed (0), one or two small abscesses (A-), two to four small active abscesses (A) or one or more large, active abscesses (A+). Based on homogeneity of variances, nine of the experiments were divided into two groups. In one group (four experiments) the incidence of liver abscesses was 32.1% and no significant (P greater than .25) effects of liver abscess severity score on feedlot performance variables were found. In the second group (five experiments), the incidence of liver abscesses was 77.7%. In the second group, liver abscess severity score affected final live weight (P less than .10), hot carcass weight (P less than .0001), dry matter intake (P less than .10), daily gain based on live weight recorded 24 h prior to slaughter (P less than .10), daily gain based on live weight estimated from hot carcass weight with a 62% dressing percentage (P less than .0001), feed efficiency using final live weight estimated from hot carcass weight (P less than .0001) and dressing percentage (P less than .01). In all cases, performance means for cattle with A+ liver scores were the only ones that differed significantly from those of non-abscessed cattle.

Two trials were conducted in which Angus x Hereford first-calf cows were assigned randomly at calving to one of two treatments: exposure to mature penile-blocked bulls (BE) or isolation from bulls (NE). In Trial 1 (BE, n = 38; NE, n = 37), cow to bull ratio increased from 12:1 to 19:1 over a 14-d period; in Trial 2 (BE, n = 25; NE, n = 24), this ratio was maintained at 13:1. In both trials, blood samples were collected weekly for progesterone and ovaries and uteri of cows were examined rectally. Cows were observed for estrus twice daily (am:pm) beginning 10 d after calving. In Trial 2, intensive blood sampling for LH began 10 d after calving (eight cows per treatment) and continued at weekly intervals until estrus or the end of the trial. Postpartum weight change, condition score change and time to uterine involution did not differ (P greater than .10) between treatments in either trial. Interval to estrus was shorter (P less than .05) for BE cows than for NE cows in both trials. A greater proportion (P less than .05) of BE cows exhibited estrus by 60 and 90 d after calving and showed an increase in progesterone before first estrus. Mean and baseline LH concentrations and amplitude, frequency and duration of LH pulses were not altered (P greater than .10) by bull exposure. In conclusion, exposing first-calf suckled beef cows to bulls after calving hastened resumption of estrous cycles. Bull exposure did not alter patterns of LH concentrations but did increase proportions of cows that showed increased progesterone before first estrus.

Pregnancy rate, calf survival rate to weaning and calf age at weaning of several types of crossbred cows (2/3 or more Brahman) were compared to those of straightbred Brahman and Angus cows over a 12-yr period at Subtropical Agricultural Research Station near Brooksville, FL. The purpose of this study was to determine the relative importance of additive vs nonadditive genetic effects on reproductive and calf survival traits in a population of cattle whose foundation was selected on the basis of superior reproductive performance under harsh environmental conditions. Best linear unbiased estimates (BLUE) of direct additive effect (measured as the deviation of Brahman additive breed effect from Angus) for pregnancy rate and calf age, measured as traits of the dam, were 6 +/- 3% and -7.2 +/- 2.1 d, respectively. Thus, Bos taurus germ plasm did not increase pregnancy rate but resulted in an earlier calving date. The BLUE of nonadditive (intralocus) direct genetic effects measured as deviations from intralocus group genetic effects in the parental breeds on pregnancy rate and calf age at weaning were 25 +/- 4% and -6.4 +/- 2.5 d. Nonadditive effects on pregnancy rate were the primary cause of the superior reproductive rates observed in Brahman crossbred cows. Calf survival was considered to be a trait of the calf, and BLUE of direct additive, direct nonadditive, maternal additive and maternal nonadditive genetic effects was obtained. Only maternal nonadditive genetic effects were found to have a significant effect on survival rate (9 +/- 4%).