Carcass Traits Of Steers Research Articles

154 Antibody and Cell-Mediated Responses Associated with Bvdv and Interferon-Gamma Expression in Reciprocal Angus-Brahman First Generation Crosses

Abstract The influence of sex and reciprocal cross type were evaluated in Brahman-sired (B × A) and Angus-sired (A × B) F1 cattle following modified-live viral vaccination regarding virus neutralization titers (VNT) and cell-mediated immune (CMI) responses following in vitro exposure to Bovine Viral Diarrhea Virus (BVDV) Type 1 (BVDV1) and Type 2 (BVDV2) genotypes. VNT against BVDV were based on virus neutralization assay, and CMI responses were measured using the PrimeFlow mRNA assay for determination of the frequency of BVDV and interferon-gamma (IFN-γ) positive cells. Mixed model procedures utilized individual calf ID as a random effect with fixed effects of F1 cross type, calf sex, evaluation date, and potential 2-way interactions; models for frequency of BVDV and IFN-γ positive cells, stimulation conditions (BVDV1, BVDV2, mitogen, none) and potential two-way and three-way interactions of fixed effects. Relationships of immune responses with calf birth weight and weaning weight and steer carcass traits were also investigated. This study found several CMI traits differed due to the type of cross and calf sex; however, no differences in VNT were attributed to these effects. Cells from B × A animals consistently ranked approximately 20% greater for BVDV positive cells (BVDV+) than those from A × B animals pre-MLV vaccination; however, post-MLV vaccination, cells from A × B animals ranked 20% greater (P < 0.05) for CD2+, CD4+, and CD8+ cells. Post- MLV steers consistently had 30 to 35% greater (P < 0.05) frequencies of BVDV+ cells following viral exposure; steers had greater frequencies (P < 0.05) of CD4+ and CD335+ cells expressing IFN-γ and ranked greater for CD2+ and CD8+ cells when compared with heifers in both crosses. Only vaccination timing affected BVDV VNT. No significant correlations involving VNT and CMI responses were observed among A × B animals when stimulated with BVDV1, but among B × A animals, positive correlations were observed with IFN-γ in CD4+ (r = 0.406, P = 0.049) and CD335+ (r = 0.472, P = 0.020). When stimulated with BVDV2, positive correlations of 0.33 to 0.39 (P < 0.05) were observed between BVDV and IFN-γ frequency within cell type; these were not significant when stimulated with BVDV1, except for CD335+ cells (r = 0.41, P = 0.003). No correlations for VNT and CMI responses were observed when stimulated with BVDV2. No major correlations between immune responses and weight or carcass traits were observed, and immune response category for BVDV or IFN-γ frequency did not influence birth weight or weaning weight. Differences in CMI responses involving reciprocal cross types and sex observed in this project may relate to widely reported reciprocal cross differences in birth weight in Bos indicus - Bos taurus crossbred cattle and warrant additional study.

Associative effect of essential oils, tannins, and sodium monensin on the performance of steers finished in feedlot

The objective was to evaluate the productive performance, ingestive behavior, apparent digestibility of the diet and carcass traits of beef steers finished in feedlot under the effect of including tannins and essential oils (TAN+EO) alone or combined with sodium monensin (MO) in the feed. For this purpose, 30 ½ blood Angus steers from the same herd, with an average age of 12 months and an average initial body weight of 367.8 kg were used. The experimental design was randomized blocks, consisting of three treatments: MO - diet with sodium monensin (25 mg kg DM-1); TAN+EO - diet with tannins and essential oils (1.5 g kg DM-1); and MO+TAN+EO - diet with sodium monensin + tannins and essential oils (25 mg kg DM-1 + 1.5 g kg DM-1), with five repetitions, where each repetition was represented by a stall with two animals. Diets were formulated and consisted of a mixture of 40% corn silage and 60% concentrate, which was fed to the animals twice a day, at 06h00 am and 05h30 pm. There was no difference (P>0.05) in average daily weight gain of animals between treatments, with an average of 1.392 kg day-1. Carcass yield was higher for animals that received the compound of essential oils and tannins (55.72%), compared to animals fed the combination of tannins, essential oils and monensin (54.54%) but did not differ from those supplemented with sodium monensin alone (55.58%). Supplementation with essential oils and tannins improved the apparent digestibility of the diet, however, did not promote changes in the ingestive behavior and carcass traits of steers. The combination of essential oils and tannins with sodium monensin did not show a potentiated effect on animal performance, digestibility of DM, digestive and ingestive behavior and carcass traits of feedlot finished steers compared to the combined use of essential oils with tannins.

96. Intake, growth and carcass traits of steers offered grass silage supplemented with barley- and maize-based rations containing flaked peas, flaked beans, maize dried distillers grains or maize gluten feed

96. Intake, growth and carcass traits of steers offered grass silage supplemented with barley- and maize-based rations containing flaked peas, flaked beans, maize dried distillers grains or maize gluten feed

Combination of carbohydrases and essential oils improve dietary performance of feedlot steers on a high-energy diet

Essential oils and enzymes are alternatives to feed additives for ruminants that aim to replace the use of ionophores and improve animal performance, but their mechanisms of action are different. Therefore, the present study aimed to verify if there is a synergistic effect in the combined use of enzymes carbohydrates and essential oils on the performance, ingestive behavior and carcass traits of steers fed a high-energy diet. During the finishing period of 78 days, 40 steers were assigned to four treatments: CON- control; ENZ- enzymatic complex; EO- essential oil blend; ENZ+EO - enzymatic complex combined with essential oil blend. Regardless of the feedlot periods, the ENZ+EO treatment caused a reduction in the dry matter intake (12.48%) compared to the control. The ENZ+EO treatment resulted in the lowest mean fecal output and, consequently, the highest dry matter digestibility (DMD) and starch digestibility (SD), compared to the other treatments. Animals that received EO and ENZ+EO in the diet spent more time in feeding. As for the number of times animals visited the feeding trough, the highest values were presented by the animals in the EO, ENZ and ENZ+EO treatments. For the carcass parameters, only the subcutaneous fat thickness on the rib was significantly different between treatments, with the highest values obtained by adding EO and ENZ+EO (8.80 and 8.10 mm respectively). Thus, the combination of carbohydrate enzymes and essential oils proved to be synergistically beneficial in relation to better use of nutrients and productive performance of feedlot steers.

175 Intake, growth and carcass traits of steers offered grass silage supplemented with barley- or oats-based rations with or without peas and beans

175 Intake, growth and carcass traits of steers offered grass silage supplemented with barley- or oats-based rations with or without peas and beans

Effects of Angus or Hereford Sires Bred to Predominately Angus Cows on Steer Offspring Growth Performance and Carcass Traits

ObjectivesTo determine the effect of sire breed, Angus or Hereford, on steer offspring performance and carcass traits of predominately Angus cows.Materials and MethodsOver 6 yr, 342 fall-calving, mixed aged Angus and Angus-crossbred cows were bred to either Angus or Hereford sires. Cattle were housed with access to pasture at the University of Arkansas’ beef research unit. Calves were processed at birth and weaned early-to-middle of May. After weaning, steers grazed at the farm for 2 mo before being transported to the West Texas A&M research feedlot, located in Canyon, TX, and remained there until harvest. Steers were harvested when a minimum backfat thickness of 1.0 cm was achieved. For harvest, steers were transported to a meat processing plant in Friona, Texas. Carcass data was collected for analysis. For analysis and results, steers with Angus sires were referred to as Angus steers and steers with Hereford sires were referred to as Hereford steers.ResultsHereford steers had greater (P < 0.05) birth weight than Angus steers. The adjusted weaning weight was greater (P < 0.05) for Angus steers than Hereford steers. Angus steers had greater hot carcass weight (P < 0.05) and ribeye area (P < 0.05) compared to Hereford steers. Hereford steers had higher (P < 0.05) yield grade than Angus steers. There was no difference (P > 0.05) in backfat thickness between Angus and Hereford steers. Angus steers had higher(P < 0.05) marbling number score than Hereford steers. The number of months from birth to harvest was longer (P < 0.05) in Angus steers compared to Hereford steers.ConclusionSire breed affected various carcass traits of steers from cows that were predominately Angus.

Growth performance and carcass traits of steers finished on three different systems including legume–grass pasture and grain diets

Inclusion of legume in grass pastures optimizes protein values of the forage and promotes improved digestibility. Therefore, we hypothesized that finishing steers on a novel combination of legumes and grass pasture would produce carcasses with acceptable traits when compared to carcasses from steers finished in feedlot systems. In this study, we evaluated the effects of finishing steers on three systems including: grazing legume–grass pasture containing oats, ryegrass, white and red clover (PAST), grazing PAST plus supplementation with whole corn grain (14 g/kg BW (SUPP)), and on a feedlot-confined system with concentrate only (28 g/kg BW, consisting of 850 g/kg of whole corn grain and 150 g/kg of protein–mineral–vitamin supplement (GRAIN)) on growth performance of steers, carcass traits and digestive disorders. Eighteen steers were randomly assigned to one of three dietary treatments and finished for 91 days. Data regarding pasture and growth performance were collected during three different periods (0 to 28, 29 to 56 and 57 to 91 days). Subsequently, steers were harvested to evaluate carcass traits, presence of rumenitis, abomasitis and liver abscesses. The legume–grass pasture provided more than 19% dry matter of protein. In addition, pasture of paddocks where steers were assigned to SUPP and PAST treatments showed similar nutritional quality. When compared to PAST, finishing on SUPP increased total weight gain per hectare, stocking rate, daily and total weight gains. The increase of weight gain was high to GRAIN than SUPP and PAST. Steers finished on GRAIN had high hot carcass weight, fat thickness and marbling score when compared to PAST. However, these attributes did not differ between GRAIN and SUPP. Abomasum lesions were more prevalent in steers finished on GRAIN when compared to PAST. Results of this research showed that it is possible to produce carcasses with desirable market weight and fat thickness by finishing steers on legume–grass pasture containing oats, ryegrass, white and red clover. Moreover, supplementing steers with corn when grazing on legume–grass pasture produced similar carcass traits when compared to beef fed corn only.

Effects of nose flap devices applied to calves on cow and calf performance, carcass traits, and heifer fertility

The effects of calf nose flap (NF) presence and duration on dam performance, steer carcass traits, and subsequent heifer fertility were evaluated. Angus and Angus × Hereford primiparous cows (n = 245) and calves at 2 locations were allocated to treatments: (1) NF for 30 or 31 d, removal from dam on d 30 or 31 (LT-30R); (2) NF for 4 or 5 d, removal from dam on d 30 or 31 (ST-30R); (3) NF for 4 or 5 d, removal from dam on d 60 or 62 (ST-60R); and (4) no NF, removal from dam on d 30 or 31 (CON-30R). Among ST-60R cows, BCS was reduced (P < 0.05) on d 60 or 62 and change in cow BCS from d 0 to 60 or 62 was greater (P < 0.05) than all other treatments. At both locations, LT-30R calves gained less (P < 0.05) by d 30 or 31 than other treatments. However, there was a location × treatment interaction (P < 0.05) for calf BW where ST-30R and ST-60R calves gained less (P < 0.05) than CON-30R calves at one location, possibly due to differences in forage quality and availability. Subsequent pregnancy rate among CON-30R heifers (that had been calves in the prior year) were (P = 0.05) reduced versus other treatments. Results indicate both presence and duration of NF weaning devices can reduce preseparation calf BW gain, but use of NF in calves can improve subsequent-year heifer reproductive performance without affecting steer carcass quality.

Effects of an exogenous enzyme-containing inoculant on fermentation characteristics of barley silage and on growth performance of feedlot steers

This study investigated the effects of an inoculant on silage fermentation, aerobic stability, and the growing and finishing performance of feedlot steers. Whole-crop barley (Hordeum vulgare L.) was chopped, wilted [350–400 g kg−1 dry matter (DM)], and ensiled without (Control) or with (Treated) a bacterial inoculant containing a mixture of Pediococcus pentosaceus, Lactobacillus plantarum, and Propionibacterium freudenreicheii (1.3 × 105 CFU g−1 forage), as well as enzymes applied to fresh forage ensiled in mini or Ag-Bag® silos. Inoculation resulted in a pH decline (P &lt; 0.05) from 6.0 on the day of ensiling to &lt;4.0 after 3 d. In contrast, it required more than 20 d for the pH of the Control silage to fall below 4.0. Inoculant reduced (P &lt; 0.05) the concentration of acetic acid and aerobic stability of silage, as evidenced by a higher (P &lt; 0.05) temperature and pH in aerobically exposed silage. Although the inoculant accelerated pH decline during ensiling, it did not improve the growth performance (P &lt; 0.05) or alter the carcass traits of steers. It is possible that a reduction in the aerobic stability of the inoculated silage may have contributed to this outcome.

Impact of supplementing vitamin C for 56, 90, or 127 days on growth performance and carcass characteristics of steers fed a 0.31 or 0.59% sulfur diet.

The objective was to examine differential timing of vitamin C (VC) supplementation during the finishing period (for the first 56, 90, or 127 d) on performance, VC, and glutathione (GSH) concentrations and carcass traits of steers receiving a 0.31 or 0.59% S diet. Angus steers (n = 42) were stratified to pens by initial BW (304 ± 13 kg) and GeneMax marbling score (4.3 ± 0.12), and pens were randomly assigned to 1 of 7 treatments (6 steers/pen and 1 pen/treatment), including a high-S (HS; 0.59% S) control (HS CON), HS CON + 10 g VC∙steer(-1)∙d(-1) for the first 56 d of the finishing period, HS CON + 10 g VC∙steer(-1)∙d(-1) for the first 90 d of the finishing period, HS CON + 10 g VC∙steer(-1)∙d(-1) for the entire 127-d finishing period (HS VC127), low-S (LS; 0.31% S) diet + 10 g VC∙steer(-1)∙d(-1) for the first 56 d of the finishing period (LS VC56), LS diet + 10 g VC∙steer(-1)∙d(-1) for the first 90 d of the finishing period, or LS diet + 10 g VC∙steer(-1)∙d(-1) for the entire 127-d finishing period. Jugular blood and ultrasound measures were taken from all steers before feeding on d 0, 56, 90, and 127, and liver biopsies and ruminal hydrogen sulfide measurements were collected on d 121 or 122. Steers (n = 40) were harvested on d 127, and carcass data were collected. Data were analyzed by ANOVA as a completely randomized design with the fixed effect of treatment. Because individual intake data were collected, steer was the experimental unit. Final BW and ADG were greater (P ≤ 0.03) and DMI tended (P = 0.09) to be greater in the LS steers compared to HS steers, but G:F did not differ (P = 0.41) by treatment. A treatment × time effect (P = 0.04) for DMI was noted, likely due to lesser DMI between d 91 and 127 for all treatments except the HS VC127 and LS VC56. Plasma VC concentrations of LS steers were less (P = 0.05) than the HS steers. Total (P = 0.06) and reduced (P = 0.03) plasma GSH were greater in HS steers supplemented with VC than the HS CON, but liver GSH were not different due to S or VC (P ≥ 0.13). The ratio of oxidized to reduced liver GSH was greater (P < 0.01) in HS CON than HS steers supplemented with VC. Marbling score, LM area, KPH, and quality grade were not different (P ≥ 0.19) due to diet, but LS steers had greater (P = 0.05) back fat than HS steers. In conclusion, steers fed a HS diet had poorer live performance and unexpectedly greater plasma ascorbate concentrations than the LS-fed steers. Interestingly, increasing days of VC supplementation across the HS diets increased GSH indices, suggesting that although HS diets may negatively affect antioxidant capacity of cattle, supplementing VC may help correct this.

High-dose anabolic implants are not all the same for growth and carcass traits of feedlot steers: A Meta-Analysis (2014)

The beneficial effects of anabolic implants with respect to feedlot performance and carcass weight are nearly unequivocal. Although individual prospective studies may have concluded that there are no significant differences between implant dosages, modern production economics demand that any differences, however small, must be gleaned if they are real. The objective of this study was to conduct a meta-analysis of existing data from peer-reviewed as well as industry sources to compare the effects of different doses of anabolic implants on feedlot performance and carcass traits of steers.

Supplementation strategy during late gestation alters steer progeny health in the feedlot without affecting cow performance

Implementation of minimal supplemental strategies during late gestation has been reported to potentially increase post-weaning progeny health in the feedlot. Therefore, to investigate the effects of nutritional management strategies during late gestation on cow and subsequent steer progeny performance, 103 gestating cows grazing dormant winter range were utilized at Corona Range and Livestock Research Center, Corona, NM. Cows were supplemented with (1) a 36% crude protein (CP) supplement (CSM) fed 3×/wk at a rate of 454gcow−1d−1, (2) self-fed supplement comprised of 50% corn gluten meal and 50% mineral (SMP; 28% CP), or (3) cows fed no protein supplement during late gestation (NS). Cows were supplemented for 60 d from December until 2 wk prior to calving. Supplement consumption was 0.45, 0.17, and 0.00kg/d for CSM, SMP, and NS. After weaning, steers were preconditioned for 45 d and were received and treated as custom-fed commercial cattle at a feedlot in mid-November. Cow BW and BCS were not influenced (P≥0.55) by late gestation management strategy throughout the study. Prepartum supplementation strategies did not influence (P=0.75) subsequent pregnancy rates. Calf BW at weaning, during the feedlot phase, and HCW were not different (P≥0.52) among dam prepartum treatments. A greater percentage of steers from dams fed CSM and NS were treated for sickness than SMP steers (P=0.05). Death loss in the feedlot was greater (P=0.02) for steers from CSM dams. Steer carcass traits and quality were not different (P≥0.17) among prepartum management strategies. Net profit in the feedlot was decreased (P=0.05) in steers from CSM dams compared to steers from SMP and NS dams. In this study, the non-supplement treatment was as effective as SMP treatment for cow performance and profitability in the feedlot. This study indicates that feeding a high ruminally undegradable protein self-fed supplement during late gestation increases calf feedlot health in the feedlot compared to a traditional hand-fed, oilseed-based supplement.

Effects of Dietary Addition of Bentonite and Probiotics on Meat Characteristics and Health of Hanwoo (Bos taurus coreanae) Steers fed Rice Straw As a Sole Roughage Source (a Field Study)

A study was conducted to determine the dietary effects of Na-bentonite (NaB) and probiotics on meat characteristics and health of Hanwoo steers fed rice straw as a sole roughage source. A total of 24 growing Hanwoo steers (avg BW 232 kg) were assigned to two treatments which included a control diet (concentrate mix and rice straw) and a treatment diet (control diet + 0.5-1.0% NaB + 0.5-1.0% probiotics. The diets were fed for 22 months up to the time the animals were slaughtered. Dietary treatment increased (p<0.05) concentrations of trace minerals such as Zn, Cu, and Fe in the longissimus muscle compared to the control. The treatment diet did not affect cold carcass weight, yield traits such as backfat thickness, longissimus muscle area, yield index, yield grade and quality traits such as marbling score, meat color, fat color, texture, maturity and quality grade. Blood profiles of growing steers were within the normal ranges for healthy cattle. In conclusion, feeding a combination of clay mineral and probiotics to Hanwoo steers fed rice straw as a sole roughage source could have a desirable effect on improving trace mineral retention in longissimus muscle without any deleterious effects on carcass traits of steers.

Relationship of polymorphisms within metabolic genes and carcass traits in crossbred beef cattle1,2,3

Feed intake has been shown to alter neurological signaling related to feeding behavior and subsequent activation of adipogenic mechanisms. Fat characteristics are pivotal for carcass and meat quality, including marbling score, flavor, and tenderness. The objective of this study was to establish the association of SNP, from genes functionally related to fat metabolism and obesity, with growth, fat, and carcass traits in steers. A total of 33 informative SNP from candidate genes [cocaine- and amphetamine-regulated transcript (CART), DNA-protein kinase (DNA-PK), fatty acid synthase (FASN), and fat mass and obesity associated (FTO)] were used to genotype crossbred steers (n = 620), and associations with growth and carcass traits were assessed. Five markers within the DNA-PK gene were associated (P < 0.05) with fat thickness. One of these SNP was also associated (P < 0.05) with percent choice, yield grade, and retail product yield. Additionally, 2 unique DNA-PK SNP were associated (P < 0.05) with marbling score. Three haplotypes were observed using these SNP and were significantly (P = 0.0014) associated with marbling score. Slaughter weight, ADG, and HCW were associated (P < 0.05) with SNP from CART, FTO, and FASN. Data from this study indicate that polymorphisms within candidate genes have an indirect relationship with lipogenesis. Replication of these results within other populations will be necessary to establish if these markers will be successful as predictors of fatness components and carcass traits in cattle.

Alternative fibre sources for steers and calves fed high-grain feedlot diets

An experiment was conducted to evaluate the effect of fibre source (FS) in high-grain feedlot diets on liveweight gain (LWG) of steers and calves and carcass traits of steers at slaughter. Eighteen steers (330 ± 27.3 kg) and 18 calves (153 ± 11.9 kg) were randomly allotted within animal category to one of three high-grain diets varying in the FS, including either grass hay (H, 66% neutral detergent fibre (NDF)), rice hulls (RH, 85% NDF) or wood chips (W, 90% NDF), and a total mixed ration formulated for equal levels of digestible DM, crude protein and NDF, within category. Animals were individually fed (3 kg DM/100 kg LW, distributed in four meals) during 56 days. The LW increased linearly with time in all treatments (P &lt; 0.01). FS did not affect calves’ LWG (P &gt; 0.05), but it resulted in differences in steers LWG (H: 1.77b; RH: 1.51c; W: 2.02a kg/day, P &lt; 0.05). However, no differences were observed in hot carcass weight (P &gt; 0.05), which resulted in higher carcass yield (P &lt; 0.05) for steers fed RH (55.0%) compared with H (53.5%) and W (53.3%). There was a significant interaction (P &lt; 0.05) for feed : gain ratio, with an improvement of this value observed only for steers fed the W diet. Although varying the FS affected rumination of calves and steers (P &lt; 0.01) and the time spent eating of steers (P &lt; 0.05), it did not represent any constraint for animal production. This study suggests by-products high in fibre content, such as RH and W, could be used in substitution to H in high-grain feedlot diets when fed at equal NDF concentration in the ration, both for calves and steers. Because calves are sometimes grown on a high-concentrate diet during winter before spring grazing, further research is needed to quantify potential residual effects on LWG after they return to pasture.

Performance and carcass characteristics of steers fed a low acid-detergent lignin hull, high-oil groat oat in growing and finishing diets

Two trials were conducted to evaluate the performance and carcass traits of steers fed a low acid detergent lignin hull, high oil groat (LLH-HOG) oat in cattle diets. In trial 1, 400 steers (275.4 ± 20.8 kg) were fed one of two diets with barley or LLH-HOG oat at 37.8% of the diet (DM basis). Dry matter intake (DMI) was lower (P = 0.02) (7.49 vs. 7.72 kg d-1) and gain to feed improved (P &lt; 0.01) (0.171 vs. 0.159 kg) for steers fed the oat-based diet. Calculated NEm (1.80 and 1.71 Mcal kg-1) and NEg (1.17 and 1.09 Mcal kg-1) values were greater for the oat-based diet. In trial 2, 240 steers (341.7 ± 18.1 kg) were fed one of three diets consisting of 88.2% barley, corn or oat grain, 5.1% barley silage and 6.7% supplement (DM basis). During finishing, steers on the oat diet had lower (P &lt; 0.01) Average daily gain than barley- or corn-fed cattle (1.40, 1.69 and 1.84 kg d-1, respectively) reflecting lower (P &lt; 0.01) DMI (9.56, 10.84 and 11.56 kg d-1, respectively). Ultrasound fat and longissimus dorsi (l. dorsi) area, carcass weight and dressing percentage were lower (P &lt; 0.01) for steers fed the oat diet. Stearic acid content of the l. dorsi of oat-fed cattle was greater (P &lt; 0.01) than barley- or corn-fed cattle. The ratio of polyunsaturated to saturated fatty acids in the muscle of oat- and corn-fed cattle was greater (P = 0.01) than that of barley-fed cattle. Results indicate that the energy value of the LLH-HOG oat is equivalent or superior to that of barley for growing cattle; however, research is required to identify why feed intake of finishing cattle fed this grain source is reduced. Key words: Low lignin hull, high-oil groat oat, barley, corn, cattle performance, carcass traits

Dietary zilpaterol hydrochloride. I. Feedlot performance and carcass traits of steers and heifers

Experiments were conducted at 3 US locations (CA, ID, and TX) to determine the effects of dietary zilpaterol hydrochloride (Zilmax, Intervet Inc., Millsboro, DE) and duration of zilpaterol feeding on performance and carcass merit of finishing steers and heifers. At each site, 160 steers and 160 heifers were stratified within sex by initial BW (study d -1) and assigned randomly within BW strata to 1 of 4 treatments in a randomized complete block design (4 blocks/treatment for each sex). The 4 treatments were arranged in a 2 (no zilpaterol vs. zilpaterol) x 2 (20 or 40 d duration of zilpaterol feeding) factorial arrangement of treatments. When included in the diet, zilpaterol was supplemented at 8.3 mg/kg of DM. Each pen consisted of 10 animals. Each animal was individually weighed unshrunk on d 1, 21 or 41, and 66 of the experiment. Following d 66, cattle were slaughtered and carcass data collected. Feeding zilpaterol increased (P<0.01) final BW of steers and heifers by 11.6 and 6.7 kg, respectively. In addition, feeding zilpaterol hydrochloride increased (P <or= 0.001) ADG 36 and 18%, and increased (P<0.001) G:F 28 and 21% for steers and heifers, respectively. For heifers, DMI was decreased (P<0.001) 6.2% when zilpaterol was fed, whereas in steers DMI tended (P=0.09) to be decreased 2%. For steers and heifers, feeding zilpaterol increased (P<0.001) HCW 16.4 and 12.1 kg, dressing percentage 1.5 percentage units for each sex, and LM area 8.23 and 6.37 cm(2), respectively. Twelfth-rib fat (P >or= 0.12) and KPH (P >or= 0.70) were not affected by feeding zilpaterol to steers or heifers. Feeding zilpaterol decreased (i.e., improved; P=0.02) calculated yield grade of steer and heifer carcasses. Marbling score (P=0.002) and quality grade (P=0.002) were decreased when zilpaterol hydrochloride was fed to steers, and the decrease in marbling score and quality grade tended to be greater when zilpaterol was fed for 40 compared with 20 d (zilpaterol x duration interaction, P=0.07). For heifers, marbling score tended (P=0.07) to be decreased and quality grade was decreased (P=0.05) when zilpaterol hydrochloride was fed. In general, it appears from these data that zilpaterol hydrochloride fed for 20 to 40 d at the end of the finishing period enhances growth performance and carcass muscle deposition for steers and heifers.

National cattle evaluation system for combined analysis of carcass characteristics and indicator traits recorded by using ultrasound in Angus cattle1

The objectives were to 1) evaluate genetic relationships of sex-specific indicators of carcass merit obtained by using ultrasound with carcass traits of steers; 2) estimate genetic parameters needed to implement combined analyses of carcass and indicator traits to produce unified national cattle evaluations for LM area, subcutaneous fat depth (SQF), and marbling (MRB), with the ultimate goal of publishing only EPD for the carcass traits; and 3) compare resulting evaluations with previous ones. Four data sets were extracted from the records of the American Angus Association from 33,857 bulls, 33,737 heifers, and 1,805 steers that had measures of intramuscular fat content (IMF), LM area (uLMA), and SQF derived from interpretation of ultrasonic imagery, and BW recorded at the time of scanning. Also used were 38,296 records from steers with MRB, fat depth at the 12th to 13th rib interface (FD), carcass weight, and carcass LM area (cLMA) recorded on slaughter. (Co)variance components were estimated with ASREML by using the same models as used for national cattle evaluations by the American Angus Association. Heritability estimates for carcass measures were 0.45 +/- 0.03, 0.34 +/- 0.02, 0.40 +/- 0.02, and 0.33 +/- 0.02 for MRB, FD, carcass weight, and cLMA, respectively. Genetic correlations of carcass measures from steers with ultrasonic measures from bulls and heifers indicated sex-specific relationships for IMF (0.66 +/- 0.05 vs. 0.52 +/- 0.06) and uLMA (0.63 +/- 0.06 vs. 0.78 +/- 0.05), but not for BW at scanning (0.46 +/- 0.07 vs. 0.40 +/- 0.07) or SQF (0.53 +/- 0.06 vs. 0.55 +/- 0.06). For each trait, estimates of genetic correlations between bulls and heifers measured by using ultrasound were greater than 0.8. Prototype national cattle evaluations were conducted by using the estimated genetic parameters, resulting in some reranking of sires relative to previous analyses. Rank correlations of high-impact sires were 0.91 and 0.84 for the joint analysis of MRB and IMF with previous separate analyses of MRB and IMF, respectively. Corresponding results for FD and SQF were 0.90 and 0.90, and for cLMA and uLMA were 0.79 and 0.89. The unified national cattle evaluation for carcass traits using measurements from slaughtered animals and ultrasonic imagery of seed stock in a combined analysis appropriately weights information from these sources and provides breeders estimates of genetic merit consistent with traits in their breeding objectives on which to base selection decisions.

Genetic correlations between live yearling bull and steer carcass traits adjusted to different slaughter end points. 1. Carcass lean percentage1,2

We studied genetic relationships between age-constant live yearling beef bull growth and ultrasound traits and steer carcass traits with dissected steer carcass lean percentage adjusted to slaughter age-, HCW-, fat depth-, and marbling score-constant end points. Three measures of steer carcass lean percentage were used. Blue Tag lean percentage (BTLean) was predicted from HCW, fat depth, and LM area measurements. Ruler lean percentage (RulerLean) was predicted from carcass fat depth and LM depth and width measurements. Dissected lean percentage (DissLean) was based on dissection of the 10-11-12th rib section. Both BTLean (h2 = 0.30 to 0.44) and DissLean (h2 = 0.34 to 0.39) were more heritable than RulerLean (h2 = 0.05 to 0.14) at all end points. Genetic correlations among DissLean and RulerLean (rg = 0.61 to 0.70), DissLean and BTLean (rg = 0.56 to 0.72), and BTLean and RulerLean (rg = 0.59 to 0.90) indicated that these traits were not genetically identical. Adjusting Diss-Lean to different end points changed the magnitude, but generally not the direction, of genetic correlations with indicator traits. Ultrasound scan-age-constant live yearling bull lean percentage estimates were heritable (h2 = 0.26 to 0.42) and genetically correlated with each other (rg = 0.68 to 0.99) but had greater correlations with DissLean at slaughter age (rg = 0.24 to 0.48) and HCW (rg = 0.16 to 0.40) end points than at fat depth (rg = -0.08 to 0.13) and marbling score (rg = 0.02 to 0.11) end points. Scan-age-constant yearling bull ultrasound fat depth also had stronger correlations with DissLean at slaughter age (rg = -0.34) and HCW (rg = -0.25) than at fat depth (rg = -0.02) and marbling score (rg = -0.03) end points. Yearling bull scan-age-constant ultrasound LM area was positively correlated with DissLean at all endpoints (rg = 0.11 to 0.23). Genetic correlations between yearling bull LM method 1 width (rg = 0.38 to 0.56) and method 2 depth (rg = -0.17 to -0.38) measurements with DissLean suggested that LM shape may be a valuable addition to genetic improvement programs for carcass lean percentage at slaughter age, HCW, and fat depth constant end points. At all end points, steer carcass fat depth (rg = -0.60 to -0.64) and LM area (rg = 0.48 to 0.59) had stronger associations with DissLean than did corresponding live yearling bull measurements. Improved methods that combine live ultrasound and carcass traits would be beneficial for evaluating carcass lean percentage at fat depth or marbling score end points.

Genetic correlations between live yearling bull and steer carcass traits adjusted to different slaughter end points. 2. Carcass fat partitioning1,2

Partial carcass dissection data from 1,031 finished crossbred beef steers were used to calculate heritabilities and genetic correlations among subcutaneous, intermuscular, and body cavity fat percentage and marbling score adjusted to slaughter age-, HCW-, fat depth-, and marbling score-constant endpoints. Genetic correlations were also calculated among these fat partitions with live growth and ultrasound traits evaluated in yearling beef bulls (n = 2,172) and steer carcass measurements. Heritabilities of the different fat partitions ranged from 0.22 (marbling score-constant body cavity fat) to 0.46 (HCW-constant marbling score). Genetic correlations between subcutaneous fat and intermuscular fat (rg = 0.16 to 0.32) and between intermuscular fat and body cavity fat (rg = 0.38 to 0.50) were more highly associated than subcutaneous fat and body cavity fat (rg = -0.08 to 0.05), indicating that fat depots are not under identical genetic control. Adjusting fat depots to different end points affected the magnitude but usually not the sign of the genetic correlations. Bull postweaning gain was associated with intermuscular (-0.24 to -0.35), body cavity (-0.24 to -0.29), and marbling fat (-0.24 to -0.39) in steers. Bull hip height was associated with body cavity (-0.20 to -0.29) and marbling fat (-0.20 to -0.47) in steers. Bull ultrasound fat depth was associated with subcutaneous (0.11 to 0.29), intermuscular (0.05 to 0.36), body cavity (0.27 to 0.49), and marbling fat (0.27 to 0.73) in steers. Bull ultrasound intramuscular fat percentage was associated with subcutaneous (-0.22 to -0.44) and intermuscular fat (-0.06 to 0.31) in steers. Bull ultrasound LM area was associated with body cavity (-0.25 to -0.31) and marbling fat (-0.25 to -0.30) in steers. Ultrasound LM width measurements were negatively correlated with subcutaneous fat (rg = -0.09 to -0.18), intermuscular fat (rg = -0.53 to -0.61), body cavity fat (rg = -0.63 to -0.69), and marbling score (rg = -0.75 to -0.87) at slaughter age-, HCW-, and fat depth-constant endpoints; correlations were generally lower at a marbling score-constant end point (rg = 0.07 to -0.49). Ultrasound indicator traits measured in seedstock may be useful in altering fat partitioning in commercial beef carcasses.