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Determination of energy requirements for growth depends on measuring the composition of BW gain. Previous studies have shown that the composition of gain can be altered in young dairy calves by the composition of the milk replacer diet. Here, our objective was to determine body composition and the composition of empty body gain in young calves fed increasing amounts of a milk replacer containing adequate CP. Male Holstein calves underwent an adjustment period of 14 d after birth in which they were fed whole-waste milk at 10% of BW. Calves were then stratified by BW and randomly assigned to either an initial slaughter group (n = 11) or to groups fed 1 of 3 milk replacer amounts and slaughtered after 35 d of growth. Calves in all treatments consumed the same milk replacer containing 24.8% CP (DM basis; from all milk proteins) and 18.9% fat, reconstituted to 12.5% solids. Treatments were milk replacer fed at 1.25% of BW (DM basis; n = 6), 1.75% of BW (n = 6), or 2.25% of BW (n = 8), adjusted weekly as calves grew. Calves fed at 1.25% or 1.75% of BW were fed twice daily and those fed 2.25% of BW were fed 3 times daily. No starter was offered. Postslaughter, the bodies of calves were separated into 4 fractions: carcass; total viscera minus digesta; head, hide, feet, and tail;, and blood. The sum of those 4 fractions was empty BW (EBW), which increased linearly as the amount of milk replacer increased. Final heart girth and body length, but not withers height, increased linearly as intake increased. Gain:feed increased linearly with increasing milk replacer. Feeding more milk replacer increased the amounts of lean tissue and fat in the body. The percentages of water and protein in the final body decreased linearly, whereas fat percentage and energy content increased linearly as intake increased. As gain increased, the percentage of protein in gain decreased and the percentage of fat increased, resulting in an increase of energy content of EBW gain. Efficiency of energy use (retained energy:gross energy intake) increased linearly but retained energy:ME available for growth was not different among treatments. Efficiency of protein use increased quadratically as feeding rate increased; there was no further increase at 2.25% of BW. Plasma insulin-like growth factor 1, insulin, and glucose increased linearly, whereas urea-N decreased linearly, as milk replacer intake increased. Our data document changes in body composition that affect estimates of retained energy in the bodies of calves slaughtered at a common age. These data are important for calculations of energy requirements for young calves., (The Authors. Published by Elsevier Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).)

The study was performed to evaluate the effect of feeding ractopamine (RAC) to physically castrated barrows (PC), immunologically castrated barrows (IC), and gilts (gilts) using a randomized complete block design with a 3 × 3 factorial arrangement of treatments: 1) sex (PC, IC, and gilts) and 2) RAC inclusion level (0, 5, and 7.5 mg/kg). The IC received 2 doses of gonadotropin releasing factor analog-diphtheria toxoid conjugate (Improvest; Zoetis, Kalamazoo, MI) at the start of the study (wk 16 of age; 69.6 ± 2.96 kg BW) and 4 wk later. The study used 180 pigs housed in groups of 4 (5 groups/sex × RAC subclass) and was performed over a fixed time of 61 d with RAC being fed for the final 26 d of study. Diets were formulated to meet requirements of intact males for the first 35 d and of intact males fed 7.5 mg/kg RAC for the remainder of the study. Pigs had ad libitum access to feed and water throughout the study period. At the end of the study, pigs were harvested at a commercial facility and HCW and last rib backfat thickness were measured. There were no treatment interactions (P > 0.05) for any variables. For the overall study period, IC had greater (P ≤ 0.05) overall ADG compared to PC, which grew faster (P ≤ 0.05) than gilts (1,246, 1,083, and 1,025 g/d for IC, PC, and gilts, respectively; SEM = 20.3); ADFI was lower (P ≤ 0.05) for gilts than IC and PC, which had similar ADFI (3.36, 3.37, and 2.87 kg/d, respectively; SEM = 0.051); and G:F was greater (P ≤ 0.05) for IC than gilts and greater for gilts than PC (0.371, 0.322, and 0.358 kg/kg, respectively; SEM = 0.0039). For the period from the second dose to the end of study, IC had greater (P ≤ 0.05) ADG (28.6%), ADFI (12.3%), and G:F (14.3%) than PC. Carcass yield was lower (P ≤ 0.05) for IC compared to PC and gilts (72.8, 75.0, and 74.6%, respectively; SEM = 0.25). Feeding RAC increased (P ≤ 0.05) ADG (15.7 and 14.5% for 5 and 7.5 mg/kg, respectively), G:F (17.1 and 16.4%, respectively), carcass weight (3.7 and 3.2 kg, respectively), and carcass yield (1.0 and 1.0 percentage unit, respectively) compared to the control. These results highlight sex differences in and effects of RAC on growth and carcass characteristics and suggest that the relative response to RAC is similar in IC and PC.

The objective was to determine which tissue components contributed to the reduction in carcass yield of immunologically castrated (IC) barrows when compared to physically castrated (PC) barrows. The carcass yield of an IC barrow is less than the carcass yield of a PC barrow. This has historically been attributed to the presence of testicles, but the testes have only accounted for approximately 0.25% of live weight. This experiment included PC barrows, intact males, IC barrows, IC barrows fed ractopamine hydrochloride, and gilts. When the pigs reached 15 wk old, they were weighed, assigned to treatments (intact male or IC barrow), and penned in groups of 4 pigs per pen. Pigs designated for immunological castration were given injections at approximately 16 wk old and approximately 20 wk old. Pigs were eligible for harvest 33 d after the second injection when the average weight of the pen reached 130 kg. Immunologically castrated barrows lost on average 0.7% units more live weight during transport and lairage than PC barrows, intact males, or gilts. Physically castrated barrows had a 1.43% unit advantage over IC barrows in carcass yield. The differences in yield can be attributed to differences in testicles, reproductive tract, intestinal mass, gut fill, and some visceral organs. Testicle weight accounted for a 0.28% unit reduction in carcass yield of IC barrows when compared to PC barrows. Additional reproductive tract weights accounted for differences of 0.10% units. Intestinal mass (empty large intestine, small intestine, and stomach) was 0.2% units heavier in IC barrows when compared to PC barrows. Livers from IC barrows were 200 g heavier (P < 0.05) and kidneys were 40 g heavier than the same organs in PC barrows. These 2 organs combined for a 0.15% unit difference in carcass yield between IC and PC barrows. Gut fill, testicles, reproductive tract, intestinal mass, and the liver and kidney accounted for 0.97 of 1.43% unit differences in carcass yield between IC and PC barrows. Immunologically castrated barrows had less marbling than PC barrows, but there were no other differences in pork quality parameters. Cutability differences were less than reported in previous experiments, but IC barrows still had a 1.0% unit advantage in lean cutting yield and a 0.7% unit advantage in carcass cutting yield when compared to PC barrows.

The objective of this experiment was to test the hypothesis that the reduced carcass fat quality that is often observed in pigs fed diets containing distillers dried grains with solubles (DDGS) may be ameliorated if corn germ, beef tallow, palm kernel oil, or glycerol is added to diets fed during the finishing period. A total of 36 barrows and 36 gilts (initial BW 43.7 ± 2.0 kg) were individually housed and randomly allotted to 1 of 6 dietary treatments in a 2 × 6 factorial arrangement, with gender and diet as main factors. Each dietary treatment had 12 replicate pigs. A corn-soybean meal control diet and a diet containing corn, soybean meal, and 30% DDGS were formulated. Four additional diets were formulated by adding 15% corn germ, 3% beef tallow, 3% palm kernel oil, or 5% glycerol to the DDGS-containing diet. Growth performance, carcass characteristics, and LM quality were determined, and backfat and belly fat samples were collected for fatty acid analysis. There was no gender × diet interaction for any of the response variables measured. For the entire finisher period (d 0 to 88), diet had no effect on ADG, but pigs fed 3% palm kernel oil tended (P < 0.10) to have less ADFI and greater G:F than pigs fed the control diet. Barrows had greater (P < 0.01) ADG and ADFI, and less (P < 0.001) G:F than gilts. Pigs fed the DDGS diet had reduced (P < 0.05) loin eye area compared with pigs fed the control diet, but diet had no effect on other carcass characteristics. Barrows had greater (P < 0.001) final BW at the end of both phases, greater (P < 0.001) HCW and backfat thickness, and tended (P = 0.10) to have greater dressing percentage, but less (P < 0.001) fat-free lean percentage than gilts. Backfat of pigs fed the 5 DDGS-containing diets had less (P < 0.05) L* values than pigs fed the control diet and backfat of gilts had greater (P < 0.001) a* and b* values than barrows. Pigs fed the control diet had greater (P < 0.05) belly flop distance compared with pigs fed the 5 DDGS-containing diets, but no differences were observed among pigs fed the diets containing DDGS. Barrows had heavier (P < 0.001) bellies and greater (P < 0.001) belly flop distances than gilts. Diet had no effect on carcass fat iodine value (IV), but gilts tended (P = 0.07) to have greater backfat IV and greater (P = 0.05) belly fat IV than barrows. In conclusion, the hypothesis that carcass fat quality of pigs fed diets containing DDGS can be improved by inclusion of corn germ, beef tallow, palm kernel oil, or glycerol in finishing diets could not be confirmed.

Body weights of finishing pigs can be variable within a finishing barn near the time of slaughter; therefore, it is common to market pigs over a period of time. This allows lighter pigs more time to gain BW and approach a desired end point. Use of immunological castration late in life to control boar taint, as an alternative to physical castration early in life, increases cutting yields of finishing male pigs compared with physical castrates. Because of common marketing strategies, it is important for advantages in cutting yields to span a broad spectrum of slaughter ages and BW. The primary objectives in this study were to evaluate carcass cutting yields, pork quality, belly quality, and bacon processing characteristics of immunologically castrated (IC) male pigs fed a moderate level of distillers dried grains with solubles and slaughtered at either 4 wk (early slaughter group) or 6 wk (late slaughter group) post-second injection. A total of 156 male pigs (physical castrates or IC males) were selected from a population of 1,200 finishing pigs. Data were analyzed with the MIXED procedure of SAS as a split-split plot design. Body weights of IC males were 3.60 kg heavier (P = 0.03) than physical castrates when slaughtered at 4 wk post-second injection and 7.52 kg heavier (P < 0.0001) than physical castrates when slaughtered at 6 wk post-second injection. Because of a lack of interaction (P > 0.05) between sex and time of slaughter post-second injection, some response variables were pooled. Hot carcass weights were not different (P = 0.57) between physical castrates (91.98 kg) and IC males (92.52 kg). There was a 2.77 percentage unit decrease (P < 0.001) in dressing percentage of IC males (71.78%) compared with physical castrates (74.55%). Lean cutting yields of IC males were 2.62 percentage units greater (P < 0.0001) than physical castrates and carcass cutting yields were 2.27 percentage units greater (P < 0.0001) for IC males when compared with physical castrates. There were no differences between IC males and physical castrates for shear force (P = 0.09), ultimate pH (P = 0.57), objective color (P ≥ 0.31), subjective color score (P = 0.64), or drip loss (P = 0.30). Bellies from IC males were thinner (P = 0.01) and had narrower belly flops (P < 0.0001) than bellies from physical castrates. There were no differences (P = 0.74) in cured belly cooked yield between IC males and physical castrates. Overall, immunological castration improved cutting yields, did not affect pork quality, made fresh bellies thinner, and did not affect cured belly characteristics when pigs were fed a moderate level of distillers dried grains with solubles during the finishing phase of production.

The objective of this experiment was to determine if increasing lysine in the diets of immunologically castrated (IC) male pigs would affect further processed product characteristics when compared with physical castrates or entire males. Raw materials for this experiment were derived from a previous experiment evaluating carcass characteristics. Physical castrates, IC males, and entire males were assigned to 1 of 4 diet programs with increasing lysine in a step-down lysine inclusion program that culminated with the following concentrations in the late finishing diet: physical castrate with low lysine (0.7%), IC with low lysine (0.7%), IC with low/medium lysine (0.8%), IC with medium/high lysine (0.9%), IC with high lysine (1.0%), and entire with high lysine (1.0%). Bellies were injected with a cure solution to a target of 110% of original green weight, and weighed again to determine brine uptake. Hams were injected with same cure solution to a target of 130% of green weight. Cure solution was formulated for a finished product inclusion of 1.5% salt, 0.34% phosphate, 0.05% sodium erythorbate, 0.11% sugar, and 0.014% sodium nitrate. Physical castrates had thicker (3.77 cm) bellies (P<0.05) than all treatment groups, except IC males fed low/medium lysine (3.73 cm). Entire males (2.85 cm) had the thinnest (P<0.05) bellies of all treatment groups. There were no differences (P>0.05) in percentage brine uptake for cured bellies among IC males regardless of dietary lysine (range 9.93 to 10.67%). Cooked yield of cured bellies was not different (P>0.05) among physical castrates or IC males regardless of lysine inclusion. Cooked yield of cured bellies from entire males (95.12%) was less (P<0.05) than cooked yield for any other treatment group. Pumped weight differences of cured hams among treatment groups were similar to green weight differences, and there were no differences (P>0.05) among any treatment groups for pump uptake percentage. There were also no differences in cook loss percentages among any treatment group. Therefore, differences in cooked yield are a reflection of initial green weight. There were no differences (P>0.05) for protein fat-free values among any treatment groups. Therefore, it can be concluded, in this population of pigs, there were no differences in further processed product characteristics among physical castrates and IC males., (© 2011 American Society of Animal Science. All rights reserved.)

The objective of this experiment was to determine if increasing lysine in the diets of immunologically castrated (IC) male pigs would increase percentage fat free lean and carcass cutting yields when compared with physical castrates. The anti-gonadotropin-releasing factor (GnRF) immunological product (Improvest, Pfizer Animal Health) is used worldwide to immunologically castrate entire male pigs to control boar taint and take advantage of the inherent ability of the entire male to deposit more muscle, less fat, and grow more efficiently than physically castrated males. The immunization process essentially allows the pig to grow as an entire male pig for most of its life and then removes any boar odor (boar taint) before slaughter. Reported lean meat advantages may also provide economic benefits to the domestic meat industry. Approximately 1,200 male pigs [physical castrates, IC males, and entire males] were each assigned to 1 of 4 diet programs which differed in lysine content. In each case, lysine was fed in a conventional step-down program that culminated with the following concentrations in the late finishing diet: physical castrates fed low lysine (0.7%), IC fed low lysine (0.7%), IC fed low/medium lysine (0.8%), IC fed medium/high lysine (0.9%), IC fed high lysine (1.0%), and entire males fed high lysine (1.0%). At 25 wk of age (5 wk post-second injection), pigs were individually weighed and the 2 pigs (n=96) in each pen closest to the median pig BW were selected and slaughtered. The right side of each carcass was dissected into soft tissue, skin, and bone. Proximate composition was determined on the soft tissue to determine percentage fat-free lean. The left side of each carcass was weighed and initially fabricated into ham, loin, belly, and whole shoulder. Each primal piece was weighed again and further fabricated into respective subprimal cuts. Immunological castration did not change (P>0.05) shear force values or ultimate pH when compared with either physical castrates or entire males. Marbling appeared to decrease as dietary lysine was increased among IC males. As expected, IC males had a greater (P<0.05) percentage fat-free lean than physical castrates but less (P<0.05) than entire males. Immunologically castrated males fed diets with medium/high and high lysine had greater (P<0.05) lean cutting yields and carcass cutting yields than physical castrates. Lean cutting yield and carcass cutting yields appeared to increase as dietary lysine was increased among IC males. Overall, immunological castration improved carcass cutability, increased percentage fat free lean, and had no effect on pork quality when compared with physical castrates., (© 2011 American Society of Animal Science. All rights reserved.)

The objective of this study was to identify specific bovine genes expressed within skeletal muscle that are associated with intramuscular fat deposition. Twenty-eight Angus-Simmental cross steers and heifers were harvested at the University of Illinois Meat Science Laboratory. Four pairs of animals were identified based on similar adjusted backfat thickness but differing amounts of intramuscular fat within each pair. RNA was extracted from muscle samples devoid of visible fat and microarray analysis was performed. Based on this analysis, 9 genes were selected and expression was subsequently confirmed by qPCR. Expression levels of MYH3, HOXD10, MXRA8, and CASQ2 were increased in animals with high marbling, whereas levels of NPNT, MRC1, DNER, and CYPB4 were decreased in high marbled animals. The remaining gene, ACTN2 was determined to be a false positive and was, therefore, excluded from further study. Despite the positive results of the preliminary study, associations between gene expression and intramuscular fat content did not extend to the larger population of cattle. A significant negative association existed between expression of MRC1 and marbling level (P = 0.04). Therefore, this study was unable to identify a particular skeletal muscle gene set whose expression correlated well with marbling levels in the larger population of beef cattle.

Two studies were conducted with refined glycerin (97.7 and 97.5% glycerin for studies I and II, respectively) to determine ME content and effects on growth performance and carcass and pork quality measures of finishing pigs. An energy balance study using 24 barrows (21.5 ± 0.6 kg initial BW) determined the apparent ME content of glycerin using a generalized randomized block design with 2 dietary treatments: 1) control (99.85% corn + vitamins and minerals) and 2) glycerin (30% of corn in the control diet replaced with glycerin). A 7-d adaptation was followed by a 5-d collection period for feces and urine. The energy content of diets, feces, and urine was determined by bomb calorimetry. The DE of the glycerin diet was greater (P < 0.01) than that of the control diet (4,298 vs. 3,902 kcal/kg of DM); however, the ME content of the 2 diets was similar (3,820 vs. 3,723 kcal/kg of DM). The ME of refined glycerin (estimated by difference) was 3,584 kcal/kg of DM. A growth study was conducted with 128 gilts housed in groups of 4 and reared from 92.5 ± 0.24 kg of BW for a 28-d period, using a split-plot design with a 4 × 2 factorial arrangement of treatments: 1) dietary glycerin level (0, 5, 10, and 15%) and 2) preslaughter handling (gentle vs. intense). The handling treatment was included to simulate the range in handling intensities that are likely to be experienced in practice. At the end of the 28-d period, one-half of the pens on study were slaughtered and used for carcass and pork quality evaluation with 2 pigs from each pen being subjected to each of the preslaughter handling treatments. There were no interactions (P > 0.05) between dietary glycerin and preslaughter handling treatment. Dietary glycerin had no effect (P > 0.05) on growth performance, carcass measures, or meat quality. There were no differences (P > 0.05) between the gentle and intense handling treatments for carcass or pork quality measures. In conclusion, feeding glycerin to finishing pigs at up to 15% of the diet had no negative effect on growth performance or carcass and pork quality characteristics.

Carcass characteristics, meat quality traits, and sensory attributes were evaluated in late-finishing barrows and gilts, weighing between 100 to 130 kg of BW, fed 0, 5, or 7.4 mg/kg of ractopamine hydrochloride (RAC) for the final 21 to 28 d before slaughter. Carcass data were collected from carcasses from barrows and gilts (n = 168), and all primal cuts from the right sides of these carcasses were fabricated to calculate primal yields as a percentage of the HCW. Subjective (National Pork Producers Council and Japanese) color, firmness, and marbling scores were determined on the LM of each loin and the semimembranosus muscle (SM) of the ham, whereas the moisture, extractable lipid, Warner-Bratzler shear force (WBSF), and trained sensory evaluations (juiciness, tenderness, and pork flavor) were measured on the LM samples only. Gilts produced heavier (P < 0.05) HCW than barrows, whereas feeding RAC increased (P < 0.05) HCW over pigs fed diets devoid of RAC. Carcasses from gilts also had greater (P < 0.02) primal cut and lean cut (P < 0.01) yields than barrows, and dietary inclusion of 5 mg/kg of RAC increased (P < 0.05) total boneless cut and lean cut yields when compared with carcass from pigs fed 0 or 7.4 mg/kg of RAC. Warner-Bratzler shear forces values were greater (P < 0.05) in the LM of gilts than barrows, but only juiciness scores were greater (P < 0.03) in LM chops from barrows than gilts. The LM from barrows had greater intramuscular lipid (P < 0.001) than the LM from gilts, and even though the LM from pigs fed 5 mg/kg of RAC had greater (P < 0.04) WBSF values than the LM from pigs fed 0 or 7.4 mg/kg of RAC, including RAC in the late-finishing diets for 21 or 28 d did not affect sensory panel rating or percentages of moisture and intramuscular lipid. In summary, addition of RAC in the late-finishing diet improved carcass and primal cut yields when it was fed at 5 and 7.4 mg/kg without altering pork quality traits regardless of whether RAC was fed for 21 or 28 d.

Previous research has demonstrated that increasing the CP concentration from 16 to 26% in milk replacers fed to male preruminant dairy calves at 1.5% of BW (DM basis) daily resulted in increased ADG, G:F, and deposition of lean tissue. However, the effects of dietary CP would be expected to vary depending on ME intake. Here, male Holstein calves < 1 wk old were used to determine the effects of feeding rate and CP concentration of isocaloric, whey protein-based milk replacers on growth and body composition. After a 2-wk standardization period, calves were assigned randomly to an initial baseline group or to treatments in a 2 x 4 factorial arrangement of feeding rate (1.25 or 1.75% of BW daily, DM basis) and milk replacer CP concentration (14, 18, 22, or 26% of DM). No starter was offered, but calves had free access to water. After a 5-wk feeding period, calves were slaughtered and body composition was determined. Increasing the feeding rate increased (P < 0.05) ADG, G:F, empty-body gains of chemical components and energy, the percentage of fat in empty BW gain and in the final empty body, and concentrations of IGF-I and insulin in plasma. Increasing the feeding rate decreased (P < 0.01) percentages of water and protein in the empty body and decreased urea N in plasma. Increasing dietary CP concentration linearly increased (P < 0.05) ADG, body length, heart girth, and gains of water and protein but linearly decreased (P < 0.05) fat gain. As dietary CP increased, fat content in empty body gain decreased, and water and protein increased. Increasing CP concentration increased (quadratic, P < 0.02) G:F, with greatest efficiencies for calves fed 22% CP. Gross energetic efficiency (retained energy:intake energy) was greater (P < 0.05) for calves fed at 1.75% of BW daily. Efficiency of dietary protein use for protein gain was greater for calves fed at 1.75% of BW daily but was not affected by dietary CP. The ratio of protein gain to apparently digestible protein intake above maintenance decreased as dietary CP increased. Interactions (P < 0.05) of feeding rate and CP concentration for gains of water and protein indicated that when dietary CP was 26% the ME supply limited protein use by calves fed at 1.25% of BW daily. Body composition of preruminant calves can be markedly altered by manipulating the protein to energy ratio in milk replacers. These dietary effects on body composition and growth are not predicted by current NRC standards.

One hundred eighty barrows were evaluated to determine the effects of ractopamine hydrochloride (RAC) on lean carcass yields and pork quality. The pens were blocked by weight (six pens per block) with starting block weights of 69.0, 70.7, 73.8, 76.6, 78.4, and 84.3 kg. Pens within a block were assigned randomly to one of three RAC treatments so each treatment in a block was replicated twice. Treatments (as-fed basis) included control diet, 10 ppm of RAC added (R10), and 20 ppm of RAC added (R20) and ranged from 25 to 41 d depending on block. Pigs were slaughtered by blocks when block average live weights were 109 kg. Gain and feed efficiency were improved (P < 0.05) with increasing dietary concentrations of RAC, but feed intake did not differ (P > 0.05). Dressing percentage was higher (P < 0.05) for RAC-treated pigs. Subjective color, firmness, marbling scores, and Minolta L* reflection of the LM were not different (P > 0.05) among treatments. Carcass weights were heavier (P < 0.05) for pigs treated with RAC compared with control pigs and were higher for R20 than for R10. The RAC-fed pigs had greater (P < 0.05) yields (actual and percentage of HCW) of the following Institutional Meat Purchase Specification (IMPS) cuts than control pigs: trimmed, boneless ham (IMPS-402C and IMPS-402G), loin (IMPS-414), sirloin, and Boston butt (IMPS-406A). Pigs treated with RAC had a greater (P < 0.05) percentage of fat-free lean trimmings (IMPS-418) than did control pigs. Pigs treated with the R20 concentration had increased (P < 0.05) water-holding capacity compared with control pigs. Purge loss decreased linearly (P < 0.05) with increasing RAC compared with control for 14-d aged, non-enhanced loins. Warner-Bratzler shear (WBS) force values measured for nonenhanced chops were greater for RAC-treated pigs than for control pigs with a low dose response (P = 0.001). Enhanced chop (salt and phosphate injection) WBS values did not differ (P > 0.05) among dietary treatments. Trained sensory evaluation panel results for tenderness decreased in a low-dose plateau response fashion for nonenhanced chops (P = 0.004). Tenderness of enhanced chops decreased linearly (P = 0.04) with increasing RAC concentrations. No differences (P > 0.05) were found in juiciness or flavor of enhanced or nonenhanced chops. Feeding RAC to late-finishing swine resulted in faster growing, more efficient animals with increased boneless subprimal yields, and it had little effect on pork juiciness and flavor.

Male Holstein calves < 1 wk of age were allowed a 2-wk adaptation period after purchase, and then were blocked by BW and assigned randomly within block to either a baseline slaughter group or one of four experimental groups (n = 8 to 9 per group). Treatments were isocaloric milk replacers (12.5% solids) fed at 12% of BW that contained 16.1, 18.5, 22.9, or 25.8% CP (DM basis) from whey protein sources. After a 6-wk feeding period, all calves were slaughtered and the weights and chemical composition of the viscera-free carcasses (VFC; including head, hide, feet, and tail) were determined. Gain of BW (0.38, 0.45, 0.56, and 0.62 kg/d) and gain:feed ratio (0.51, 0.59, 0.71, and 0.78) increased linearly (P < 0.001) as dietary CP increased; rate of change in body length, wither height, and heart girth also increased linearly (P < or = 0.05). Balance measurements conducted during wk 3 and 4 of the experimental period showed that both absorbed N (16.9, 20.0, 25.8, and 30.6 g/d) and retained N (7.6, 9.0, 13.2, and 15.6 g/d) increased linearly (P < 0.001) as dietary CP increased. Retained N as a percentage of absorbed N increased linearly (P < 0.01) as dietary CP increased (44.3, 44.7, 50.7, and 50.9%), whereas biological value was unaffected (71.1, 68.7, 69.5, and 67.3%; P = 0.26). Digestible energy and ME represented 94.5 and 89.7% of intake energy, respectively, and were not affected by dietary CP content. Plasma urea N concentration increased linearly (2.9, 3.3, 4.6, and 6.0 mg/dL) as dietary CP increased. Contents of water (68.2, 69.1, 70.2, and 70.5%; P < 0.001) and protein (19.6, 20.0, 20.0, and 20.2%; P < 0.10) in VFC increased linearly, whereas contents of fat (7.2, 6.2, 5.5, and 5.2%; P < 0.001) and ash (5.1, 5.2, 4.8, and 4.7%; P < 0.02) decreased linearly as dietary CP increased. Trends in visceral tissue composition were similar to those for VFC. The content of water in VFC tissue gain increased, whereas contents of fat and energy decreased, as dietary CP increased. Final VFC energy and gain of energy in VFC were not affected by dietary CP. At similar initial ME intakes, increasing dietary CP (i.e., increasing protein: energy) linearly increased ADG, gain:feed, N retention, and deposition of lean tissue in VFC, demonstrating that diet composition can markedly affect components of body growth in preruminant dairy calves.

Crossbred gilts (n = 180) and barrows (n = 180) from the Louisiana State University (LSU) Agricultural Center and the University of Illinois (UI) were used to compare the effect of soybean meal in swine diets, relative to other protein sources, on growth performance and carcass traits of growing-finishing pigs. Four replications with five pigs each at each location were allotted to nine dietary treatments: soybean meal control (SBM), crystalline AA (corn-AA), extruded soybeans (ESB), canola meal (CAN), peanut meal (PNT), sunflower meal (SFLR), ground peas, meat and bone meal (MBM), and poultry by-product meal (PLTY). The diets were formulated to meet or exceed NRC nutrient requirements and to have equal Lys:ME according to dietary phase and sex. Corn was the grain source in all diets and the protein sources were the sole source of supplemental protein in all diets except when AA were added to meet the requirement. Pigs (three per pen at each location) were killed at an average final BW of 114 kg in the LSU or UI Meat Science Laboratories. Pigs fed SBM had greater (P < 0.05) ADG than pigs fed the corn-AA, CAN, SFLR, MBM, or PLTY and greater (P < 0.05) ADFI relative to pigs fed the corn-AA, ESB, MBM, or PLTY. Gain:feed was decreased (P < 0.05) in pigs fed corn-AA or SFLR but increased (P < 0.05) in pigs fed ESB compared with pigs fed the SBM diet. Loin muscle area was decreased (P < 0.05) in pigs fed the corn-AA or MBM diets compared with pigs fed the SBM diet. Tenth-rib backfat thickness was greater (P < 0.10) in pigs fed corn-AA, peas, or MBM than in those fed SBM. The NPPC percentage acceptable quality lean and kilograms of lean were decreased (P < 0.10) in pigs fed corn-AA, peas, or MBM compared with those fed SBM. Results from this experiment suggest that pigs fed SBM have equal or better growth performance and carcass traits than pigs fed other protein sources.

Three experiments were conducted to test the hypothesis that different starter feeding programs (High, high quality; Low, low quality) will affect growth performance and body composition of pigs from weaning to market weight and that this effect may be influenced by gender (barrows or gilts) and breed (F, Yorkshire-Duroc x Hampshire; P, PIC Camborough 15 x PIC line 405). In Exp. 1, 21 +/- 4-d-weaned F pigs (n = 90) were used in a 2 (High or Low) x 2 (barrows or gilts) factorial design. In Exp. 2, 21 +/- 3-d-weaned pigs (n = 184) were used in a 2 (F or P) x 2 (High or Low) x 2 (barrows or gilts) factorial design. In Exp. 3, 21 F pigs from each gender and feeding program treatment were killed at d 0, 3, 7, 14, 42, 82, or 152 postweaning for evaluating body composition. Two starter feeding programs (High or Low) were applied to pigs for 6 wk postweaning. Pigs from both High and Low treatments were provided the same corn-soybean meal-based diets for the growing and finishing periods. Although the ADG of all pigs receiving the High treatment during the early starter period were higher (P < .01) than those of the Low, the terminal BW of F barrows were similar between High and Low (Exp. 1 and 2) and those of gilts were similar between High and Low (Exp. 2) (P > .80). However, the BW of P pigs receiving the High treatment, regardless of gender, tended to be heavier than those receiving the Low (Exp. 2) and F barrows receiving the High treatment tended to be heavier than those receiving the Low (Exp. 1). For the first 7 d postweaning, the High-fed pigs gained more protein (P < .05) and lost less fat (P < .05) than Low-fed pigs. During the growing-finishing period, the Low-fed pigs exhibited compensatory protein gain and achieved a body protein content similar (P < .60) to High-fed pigs by termination. Protein gains from weaning to termination between High- and Low-fed pigs were not different in Exp. 2 and 3. The protein gain of gilts was higher (P < .05) than that of barrows. Similarly, fat gain within genders was not affected by starter feeding program. Fat gain of gilts, however, was lower (P < .08) than that of barrows in Exp. 3. In conclusion, the nutritional quality of the starter feeding program affected growth performance immediately after weaning but did not affect protein gain over the entire production period.

Right sides of 30 pork carcasses were fabricated into indicator cuts (Boston butt, picnic, anterior belly, posterior belly, anterior loin, posterior loin, and ham) and used to determine carcass composition by physical dissection and chemical analysis of soft tissue. Linear measures and chemical composition of whole-side grind were collected from left sides. Dissection of indicator cuts to predict dissectable composition of the side were much better indicators than linear measures (R2 = .70 to .94). Chemical analyses of soft tissue (lean + lipid) from the loin and anterior belly were better predictors of fat-free lean and extractable lipid composition of the side than linear measures; 89% of the variation in dissectable lean of the side was explained by the use of dissectable components of the anterior loin. The loin served as the best overall indicator cut across the various end points evaluated; 92% of the variation in dissectable lean of the side was explained using dissectable components of the shoulder. The anterior belly was a good indicator for percentage of dissectable lean, fat, fat-free lean, and extractable lipid.

Thirty pork carcasses were used to evaluate the interrelationships between compositional end points and the accuracy of predicting various end points from one another. Right sides were fabricated into Boston butt, picnic, anterior belly, posterior belly, anterior loin, posterior loin, and ham. Carcass composition was determined on the right side using physical dissection and chemical analyses of soft tissue. Left sides were ground (whole-side grind). Linear measures and chemical composition were made on left sides. Using dissectable components, high (r > .85) correlations occurred between percentage of fat-free lean and percentage of lipid, percentage of dissectable fat, and lipid in the whole-side grind; between weights of dissectable lean and fat-free lean; and between weights of lipid in the whole-side grind and lipid, dissectable fat, and dissectible lean. Dissectable lean percentage and fat (percentage and weight) could be predicted using weight of lipid, weight of fat-free lean, and side weight. Any physical measure could be accurately estimated from any compositional end point (r2 = .79 to .93). Regression equations using 10th-rib linear measures and hot carcass weights predicted compositional end points with R2 > or = .80, with the exception of dissectable lean (R2 = .56).

Live animal real-time ultrasound scans and carcass measures were taken on 80 pigs comprising two sexes (42 barrows; 38 gilts) and two halothane genotypes (40 carriers and 40 negatives) that were slaughtered between 108 and 148 kg live weight. Transverse scans (TRUS), at right angles to the midline, were taken on right (RS) and left (LS) sides at the last rib. Longitudinal scans (LON) were taken 6.5 cm off the midline immediately anterior (ANT) and posterior (PST) to the last rib on both the RS and LS. Longissimus muscle depth and area and backfat thickness over the longissimus muscle were measured on TRUS. Backfat thickness and longissimus muscle depth were measured at each end of the LON. Backfat thickness and longissimus muscle measurements were taken at the 10th and last rib on the RS of the carcass. Carcasses were fabricated using standard techniques to establish lean cut yields and carcass soft tissue was chemically analyzed to determine fat-free lean contents. Stepwise regression analysis was performed to develop equations to predict the weights and percentages of lean cuts and fat-free lean. Fat and muscle measures taken from ultrasound scans were generally less accurate than last rib carcass measures at predicting composition. There was little difference in R2 for equations based on either TRUS or ANT/LON; however, PST/LON, generally, were less accurate than ANT/LON. Combining measurements from more than one scan gave little improvement in R2 compared with the best single scan. Estimates of sex bias for carcass composition prediction were small. Halothane genotype and carcass lean content biases were detected; equations derived from the pooled data tended to overestimate the lean content of negative pigs and fatter carcasses and underestimate the lean content of carrier animals and leaner carcasses.

Three studies were designed using a 2 x 2 factorial arrangement of treatments within each experiment to evaluate the effects of various management techniques on growth and carcass traits of once-calved heifers. In Exp. 1, 33 yearling (16 control [C] and 17 prenatally androgenized [PA]) and 39 once-calved (20 C and 19 PA) nonpregnant heifers were used to evaluate the effects of age and PA. Once-calved heifers were approximately 31 kg heavier (P < .03) on-test, initially consumed 11% more (P < .01) DM, and gained 11% faster (P < .08), but had similar (P = .44) gain to feed ratios (.138 vs. .131) as yearlings. Growth performance was not affected by PA. The yearling and once-calved heifers were then slaughtered at approximately 707 and 1,080 d of age, respectively. Despite maturity differences (P < .01), marbling scores (P = .26) and percentage of choice carcasses (P = .27) were similar. However, on the basis of newly accepted grading changes, percentage of once-calved heifer carcasses grading choice decreased from 57.3 to 34.4%. Organoleptic properties did not differ. Experiments 2 and 3 were then conducted to evaluate effects of commercially available products (melengestrol acetate [MGA] and Synovex-H) on feedlot characteristics of heifers following weaning of their first calf. In Exp. 2, 48 once-calved Simmental-based heifers were fed during the summer to a constant compositional fat thickness of .8 cm. Experiment 3 was conducted in the late fall and early winter, during which 52 moderately sized heifers were fed for 116 d postweaning and slaughtered. Performance of heifers in Exp. 2 was not affected by MGA. However, heifers fed MGA in Exp. 3 gained 9% faster (P < .05) than controls. In Exp. 2, Synovex-H tended to improve ADG (P < .09) and feed efficiency (P < .07), but did not affect performance in Exp. 3. Most carcass traits were not affected by either treatment. Nonpregnant, once-calved heifers seem to have a large capacity for efficient weight gain as compared with yearling heifers. However, hormonal compounds, such as testosterone propionate provided pre- or postnatally (Synovex-H), and MGA do not appear to provide the consistent, positive responses often seen with younger, more typical feedlot heifers.

Growth performance, carcass characteristics, and meat quality of halothane carrier (Nn) and negative (NN) pigs grown from 40 kg live weight and slaughtered at three weights (110, 125, and 140 kg live weight) were studied. Daily gains were similar for the two genotypes (974 g for Nn and 964 g for NN), but Nn pigs had a higher gain:feed ratio than NN pigs (P < .01). Dressing percentage was higher in Nn pigs than in NN pigs (P < .001), but there were no genotype differences for carcass length, backfat thickness, or loin eye area. Percentage yield of trimmed, boneless wholesale cuts was higher for Nn pigs than for NN pigs (P < .05). This resulted from higher trimmed, boneless ham, boston, and picnic weights (P < .05) in Nn than in NN pigs (6.9, 3.2, 3.5 kg vs 6.6, 3.0, 3.4 kg, respectively). The weight of fat-free lean was higher in Nn pigs (P < .05). The longissimus thoracis muscle from carrier pigs had lower 45 min (P < .001) and 24 h (P < .01) pH. Longissimus lumborum samples from carriers had lower (P < .001) subjective' meat quality scores and a higher drip loss (P < .001); however, cooking loss, eating quality, and shear force values were similar for the two genotypes. There were no important slaughter weight x genotype interactions for the traits reported. Overall, the data from this study suggest Nn pigs had an advantage over NN pigs in terms of feed efficiency, carcass yield fat-free lean content, and commercial lean cut yields but had a higher incidence of PSE.

Pigs representing two crossbred genotypes, a breeding company hybrid (BCH) and a three breed cross (Hampshire x [Yorkshire x Duroc]) (HYD) were evaluated at five slaughter weights (SLW): 100, 115, 130, 145, and 160 kg. A total of 160 pigs were grown in like-sex (barrows [B] or gilts [G]), like-genotype groups, with four pigs/group, from 60 kg live weight. A corn-soybean meal-based diet was available on an ad libitum basis (15.8% crude protein, 3,300 kcal/kg ME). One-half of the pigs from each group (80 pigs) were slaughtered for carcass and meat quality evaluation. Genotype BCH grew faster, had lower backfat depths in the loin and lumbar regions, and a smaller loin eye area than HYD, but both groups had a similar gain:feed ratio. Few consistent genotype differences in cutting and curing yields and meat quality were observed. Differences between sexes for growth and carcass traits were generally in agreement with previous research; however, the magnitude of the differences was small. There were few nonlinear regressions involving SLW and limited differences between genotypes or sexes in the slopes of the linear regressions. Increases in SLW were associated with increases in feed intake, backfat depth and loin' eye area, and minimal changes in growth rate or gain:feed. Percentage of loin increased and ham, shoulder, and spare rib percentages decreased with slaughter weight. The weight of trimmed, boneless cuts increased with slaughter weight, but percentage trimmed, boneless cuts was reduced. Curing yields for belly increased with slaughter weight. Changes in meat quality with increasing slaughter weight were relatively small. Longissimus lumborum fat content increased and moisture content decreased with slaughter weight. These results suggest that modern genotypes can be slaughtered at live weights up to 160 kg with limited impact on growth performance, commercial meat yields, or meat quality characteristics.

At approximately 68 kg live weight, crossbred barrows and gilts (n = 144) were allocated to be fed to one of two weight end points (107 kg and 125 kg). Pigs from each weight group were treated with Ractopamine (RAC) (0, 10, or 20 ppm; n = 24/ treatment for the last 40 kg of gain. Feed consumption and weight gain were measured. Pigs were slaughtered and carcass measurements made at 24 h postmortem. Carcasses were fabricated into wholesale, trimmed wholesale, and boneless wholesale cuts for cutting yields. Hams were separated into muscle, fat, and bone. The RAC improved growth characteristics and carcass characteristics. Pigs fed RAC had increased (P < .01) average daily gain and improved (P < .01) feed:gain ratio over controls in each weight group. Carcasses from pigs treated with RAC had larger (P < .01) longissimus muscle area and reduced (P < .01) fat at the 10th rib. Cuts from 125-kg pigs were generally heavier than those from 107-kg pigs. The RAC increased (P < .05) the boneless cut weights of both weight groups. Percentage of dissected lean from the hams of RAC-treated pigs was (P < .05) higher than that of controls. Few consistent differences were observed between the 10 and 20 ppm of RAC treatments. Results from this study indicate that RAC had positive effects on the growth characteristics, carcass characteristics, and carcass cutting yields of pigs representative of the broad spectrum of market weights.

Five barrows and five gilts of each of two breeds (Meishan [Ms] and Yorkshire [Y]) were slaughtered at birth and at 41, 71, 123, and 171 d of age and five gilts of each breed were slaughtered at 260 d of age. Major organ and visceral weights were obtained immediately postmortem (PM), whereas carcass characteristics, carcass composition, femur measurements, and two individual muscle weights were obtained 24 h PM. Linear and quadratic regression coefficients on age differed between the two breeds, in favor of Y barrows and gilts, for live weight, carcass weight, longissimus muscle area (LMA), liver, heart, spleen, and kidney weights, and femur cross-sectional, medullary, and cortical areas (P < .001), leaf fat weight, and percentage of body fat and protein. In contrast to somatic tissue, Ms gilts had uteri and ovaries that grew faster than those of Y gilts from birth to 260 d of age (P < .05), although the uterus and ovary weights were similar for both breeds by 260 d of age (P < .05). Regression coefficients differed (P < .05) between the two sexes for live, carcass, liver, lung and trachea, stomach and esophagus and leaf fat weights, dressing percentage, percentage of body protein, 10th rib backfat (TRBF) thickness (P < .001), and small intestine, kidney (P < .01), heart, and spleen weights (P < .05). Breed differences in regression coefficients differed between the two sexes for percentage of body protein and leaf fat weights (P < .05). Yorkshire pigs were larger, later-maturing pigs that grew faster from birth to 171 d of age. Yorkshire pigs slaughtered at 171 d of age had heavier total wholesale cut (WC), trimmed cut (TC), and boneless cut (BC) weights than did Ms pigs of the same age (P < .001).

An experiment was conducted to evaluate the effect of feeding reduced CP, amino acid (AA)-supplemented diets to pigs from weaning to slaughter weight on growth performance and carcass characteristics. Pigs were fed a 19%-16%-14% CP starter-grower-finisher high-CP sequence of diets, respectively, or a sequence of diets reduced in CP by 4 percentage units (3 percentage units in the finisher period) with or without lysine (LYS), tryptophan (TRP), and threonine (THR) supplementation. Pigs fed the low-CP diets without AA supplementation grew more slowly, were less efficient in feed conversion, and developed carcasses that contained a smaller longissimus muscle, greater, average backfat depths, and a lower percentage of muscle compared with pigs fed the high-CP sequence of diets (P < .01). The reduction in growth performance, feed efficiency, longissimus muscle area, and percentage of muscle in pigs fed the low-CP diets was alleviated by LYS, TRP, and THR supplementation (P > .10). Although pigs fed the low-CP diets supplemented with AA had reduced average and 10th rib backfat depths compared with pigs fed the unsupplemented, low-CP diets (P < .01), these fat depth measures remained greater (P < .05) than those of pigs fed the high-CP diets. Feeding reduced dietary CP, regardless of AA supplementation, resulted in reduced heart (P < .10) and liver weights (P < .01) compared with feeding the high-CP diets.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of porcine somatotropin (pST) on growth and carcass characteristics of Meishan (Ms) and Yorkshire (Y) barrows given 3 mg of pST or saline daily were determined for two end points. First, 26 Ms and 26 Y barrows were treated from 119 d of age until the Y barrows reached 108 kg. Second, another 18 Ms barrows were treated to 108 kg BW. Age- and weight-matched treatments were analyzed. Results for both groups indicated pST effects (P < .05) for feed conversion (+) and intake (-), dressing percentage (-), percentage of carcass fat (-) and protein and water (+), leaf fat (-), backfat (BF) thickness (-), longissimus muscle area (LMA; +), skin thickness (+), muscle firmness and marbling scores (-), organ weights (+), belly (-), clear plate (-), ham (+), and total boneless cuts (BC; +). Somatotropin effects were also present for loin (-) and boneless Boston butt (BBB; +) in the age-matched group and for ADG (+), carcass weight (-), loin (-), jowl (-), and tenderloin (+) in the weight-matched group. Breed effects (P < .05), in favor of Y barrows, in both treatments existed for ADG (+) and feed intake (+), carcass weight (+), dressing percentage (+), LMA (+), skin thickness (-), muscle color and firmness scores (-), muscling score (+), all wholesale cuts (WC; +) except clear plate (age-matched), all trimmed cuts (TC; +) except picnic shoulder (weight-matched), and all BC (+). Breed effects, in favor of Y barrows, were also determined for carcass length (+), percentage of carcass ash (-), leaf fat (+), average BF thickness (+), and heart (-) and liver (-) weights in age-matched animals and percentage of carcass fat (-), protein (+), water (+), leaf fat (-), 10th rib, average, and P2 BF thicknesses (-), marbling score (-), femur length (-), and liver weights (+) in weight-matched animals. A higher response to pST (P < .05) was determined in Ms barrows than in Y barrows for percentage of carcass protein (+), liver (+), and heart (+) in the age-matched treatment and 10th rib BF thickness (-) and heart weight (+) in the weight-matched treatment. Yorkshire barrows treated with pST had more improved values for color score (+; age-matched) and BBB (+; weight-matched).

Fifty growing pigs were used in two experiments to evaluate the effects of cannulation and hyperalimentation on performance and body composition responses. Surgical implantation of a cannula into the greater curvature of the stomach and subsequent management associated with maintenance of the cannula did not result in a reduction (P > .05) of voluntary feed intake. Cannulation did not negatively affect gain (P > .05). Over the entire trial, feed efficiency was not changed by cannulation (P > .05). Cannulation itself did not affect protein or fat deposition (P > .05) in the carcass. Hyperalimentation to approximately 120% of control intake resulted in increased daily gain (P < .05) and similar feed efficiency (P > .05) compared with that of control animals. Hyperalimentation decreased protein deposition (P < .05) and tended to increase fat deposition.

Ninety-six crossbred barrows were randomly allotted to five replications of four treatments to determine the effects of diets containing 20% extruded full-fat soybeans (FFS) or 4% butter (B) on the growth, composition, and sensory characteristics of finishing pigs. Pigs were housed five per pen, except for one replication that had four pigs per pen, in environmentally regulated barns. Pigs were given ad libitum access to a corn-soybean meal diet for 11 wk (control); a corn-extruded soybeans and soft wheat midds diet for 11 wk (FFS-11); a corn-soybean meal diet for 6 wk, changed to a corn-extruded soybeans and soft wheat midds diet for 5 wk (FFS-5); or a corn-soybean meal diet for 6 wk, changed to a corn-soybean meal, soft wheat midds, and 4% butter diet for 5 wk (B). Feed intake and weight gain were measured once every 2 wk. Pigs were slaughtered and carcass data were collected. Sensory characteristics (tenderness, juiciness, pork flavor intensity, off-flavor intensity, and overall acceptability), shear force, moisture, and fat content were determined for the longissimus muscle. Sensory characteristics (pork flavor, off-flavor, rubbery, cohesiveness, and juiciness) and 2- thiobarbituric acid values were determined for ground pork (30% fat) after 1, 4, and 7 d for control, FFS-11, and B treatments. No differences (P > .05) in ADG were observed between diets. Feed efficiency of the FFS-11 group was better (P < .05) than that of the control or B groups. No consistent differences were observed for carcass, sensory, or shear-force characteristics of the longissimus muscle or ground pork.(ABSTRACT TRUNCATED AT 250 WORDS)

This study was designed to evaluate growth performance, carcass cutting yield, and processing characteristics of boneless hams and bellies from finishing pigs fed diets containing 0, 5, 10, or 20 ppm of the phenethanolamine ractopamine hydrochloride (RAC). Sixty pigs were blocked by starting weight and randomly assigned to pens (four pigs/pen) within each of three blocks. Treatments were then randomly assigned to the pens to total six pens of the 0-ppm level and three pens each at the 5-, 10-, and 20-ppm RAC levels. Weight gain and feed consumption were monitored and animals were slaughtered by weight block after approximately 48 d on trial. Slaughter weight, ADG, and feed/gain were improved (P less than .05) for RAC treatments. Dressing percentage was higher and increased linearly (P less than .05) for RAC treatments. Carcass weight, length, leaf fat weight, backfat thickness, loin eye area, and color, marbling, and firmness of the longissimus were evaluated. The RAC-treated carcasses were heavier (P less than .05) and loin eye area increased linearly (P less than .05). One side of each carcass was fabricated using National Association of Meat Purveyors specifications. Trimmed hams and loins from the RAC treatments were heavier (P less than .05) than those from control animals. No differences (P greater than .05) in carcass cutting yield (percentage of trimmed primal cuts) were observed between treatments. However, trimmed hams and loins from the 20-ppm RAC treatment represented a greater (P less than .05) percentage of carcass weight than did those from control animals. Ractopamine did not affect raw belly or bacon characteristics (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Two experiments were conducted in which pregnant crossbred cows were randomly assigned to a control group or implanted with testosterone propionate/silastic implants between d 110 and 140 of gestation in Exp. 1 and between d 80 and 110 of gestation in Exp. 2. Androgenized heifers (TH) and treated steers (TS), born to implanted dams, possessed similar birth weights compared with control heifers (CH) and steers (CS), respectively, in both experiments. In Exp. 1, yield grades were lower (P less than .05) for TH than for CH. In Exp. 2, TH possessed 9.4% greater (P less than .07) 205-d adjusted weaning weights and 9.8% heavier (P less than .05) adjusted yearling weights than CH. In Exp. 2, daily gain was 19.5% faster (P less than .05) and feed intake was 13.6% greater (P less than .05) for TH than for CH. In Exp. 2, TH possessed less (P less than .05) s.c. fat, greater (P less than .10) carcass weight gains and lower (P less than .05) yield grades than CH. Liver weight per unit of carcass weight was greater (P less than .07) for TH than for CH in Exp. 2. Androgenized heifers had lower (P less than .07) lipid content in the 9-10-11th rib section than did CH. Calving intervals were similar for implanted and nonimplanted cows in both experiments. Results from these two trials suggest that efficiency of heifers for producing carcass beef can be improved by prenatal testosterone exposure.

A 2(3) factorial arrangement of treatments was utilized to determine effects of postweaning zeranol implantation, breed (Angus vs Limousin) and castration (bull vs steer) on growth, behavior and carcass traits. An initial slaughter group was used to account for breed differences in composition and to determine fat and lean growth in the 9-10-11th rib section (NTE). The remaining cattle were fed a finishing diet to a fat end point of .76 cm, as determined by a backfat probe. Control bulls outgained (P less than .01) control steers both to the first kill date and over the entire test and did not require significantly more time to reach the fat end point. The implant did not influence gain in bulls but did increase gain in steers. Angus and Limousins were similar in growth rate for the first 126 d before the first slaughter date. Limousins required more (P less than .01) time to reach the fat end point. Bulls and Limousins produced heavier (P less than .01) carcasses and larger rib eyes (P less than .05; bulls; P less than .01; Limousins). Steers and Angus had higher (P less than .01) marbling scores and lower bone maturity. Implanting decreased (P less than .05) marbling and increased carcass maturity. Small but significant shifts in carcass wholesale cut weight distribution were found between breed and sex condition groups. Bulls and Limousins had greater lean growth in the NTE. Bulls and steers were similar in fat growth, but Angus exceeded Limousin in this trait. Zeranol reduced scrotal circumference (P less than .01) and testicle weight at slaughter (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Cull cows (N = 48) of similar age from Angus and Hereford breed types were assigned to one of four feeding periods (0, 28, 56 or 84 d) and subdivided into two groups, one implanted with Synovex-H and a non-implanted control. Cows were fed a high energy diet and slaughtered at the end of each feeding period. Average daily gain and feed efficiency were evaluated on each animal during the trial. The following carcass traits were evaluated: USDA yield and quality grade characteristics, boning yield, muscle weights, bone weights, pH and Warner-Bratzler shear force of the longissimus muscle. The left side of each carcass was boned and proximate analysis was determined. No significant implant effects were encountered for any of the traits evaluated; therefore, data were pooled and evaluated by feeding period only. Carcass weight and boneless forequarter and hindquarter tissue weights increased significantly between each feeding period; percent kidney, pelvic and heart fat (KPH) and yield grade did not differ (P greater than .05) until d 56 and 84, respectively. Quality grade and marbling scores improved (P less than .05) between 28 and 56 d of feeding. Biceps femoris weight changed during the 84-d experiment from 4.1 kg on d 0 to 5.3 kg on d 84 (P less than .05). Proximate analysis of the boneless tissue indicated an increase (P less than .05) in extractable fat of approximately 6% for each feeding period (6.3% fat on d 0 to 25.4% on d 84).(ABSTRACT TRUNCATED AT 250 WORDS)

Two experiments were conducted to evaluate the effect of implants containing zeranol on growth rate, carcass composition, palatability and reproductive organ development of intact male pigs. In Exp. 1, three treatment groups were evaluated: control barrows, intact control boars and implanted boars (implanted at either 28, 56 or 112 d of age with one 12-mg dose of zeranol). In Exp. 2, four treatment groups were evaluated: control barrows, intact control boars, boars implanted at 28 d with 24 mg of zeranol (single implant) and boars implanted at 28 d and re-implanted at 56 and 112 d of age with 24 mg of zeranol (triple implant). Differences for average daily gain and carcass traits were not consistent between treatment groups with the exception of 10th rib fat, where barrows were fatter than boars. There were no differences among treatments due to zeranol for the reproductive organ characteristics, with the exception that bulbourethal gland and teat weights were heavier for boars in Exp. 2. Penis weights and lengths were lower for barrows in both experiments. Juiciness, tenderness, Warner-Bratzler shear force, pork flavor intensity and sensory scores were not consistently affected by male condition or zeranol treatment. In two of the three comparisons, implanted boars had higher off-flavor intensity scores in Exp. 1, but no treatment difference was observed in Exp. 2. Zeranol implantation did not result in significant changes in growth rate, development of reproductive organs or carcass characteristics of young boars.

Two experiments were conducted in which pregnant crossbred ewes were randomly assigned to a control group or implanted with testosterone propionate/silastic implants between d 40 and d 60 of gestation. Implants contained approximately 2 g testosterone propionate and provided a constant delivery of 8.7 mg/d. Androgenized ewes (TE), born to implanted dams, had lower adjusted birth weights (P less than .05) than control ewes (CE) in both experiments. Treated rams (TR) also displayed lower birth weights than control rams (CR) in both experiments, but the difference was significant only in Exp. 2. Average daily gain was 16.4% more (P less than .05) for TE than for CE in Exp. 1. In Exp. 2, TE gained 9.6% faster (P less than .05) and had 14.6% (P less than .05) more weight per unit of feed consumed than CE. In both experiments, average daily gain and gain-to-feed ratio were similar for TR and CR. In Exp. 2, prenatal androgenization of ewes reduced (P less than .05) 12th rib fat thickness and decreased (P less than .05) percent kidney and pelvic fat. Yield grades of TE were lower than CE in both Exp. 1 (P less than .10) and Exp. 2 (P less than .05). From additional measurements taken in Exp. 2, liver weight per unit of carcass weight was greater (P less than .05), anogenital distance was greater (P less than .01) and test tube penetration into the vestibule was less (P less than .01) for TE than CE. The TE did not exhibit regular estrous cycles, while CE displayed recurring estrous cycles.