Hot Carcass Weight Research Articles

163 Effect of Enogen Feed Corn Inclusion in Conventional and Natural Finishing Cattle Diets

Abstract A finishing experiment was conducted to determine the effects of Enogen Feed Corn inclusion in comparison with a control corn hybrid within natural and conventional feeding programs on finishing performance. The experiment used 400 crossbred steers (initial BW = 384 ± 33 kg) and 200 crossbred heifers (initial BW = 330 ± 19 kg) in a 2×2 factorial arrangement of treatments with 10 replications of steers and 5 replications of heifers per treatment. Factors were Enogen Feed Corn (EFC) or control corn hybrid inclusion as dry-rolled corn and corn silage within conventional and natural feeding programs. Cattle assigned to the conventional program were fed rations that contained feed additives and received implants whereas cattle in the natural program received neither. Performance data were analyzed as a 2×2×2 factorial assessing interactions between sex, feeding program, and corn hybrid inclusion. A sex by feeding program by corn hybrid (P = 0.01) interaction was observed for dry matter intake (DMI). Interactions between sex and feeding program were observed for carcass adjusted final BW (final BW; P < 0.01), average daily gain (ADG; P < 0.01), feed efficiency (G:F; P < 0.01), and hot carcass weight (HCW; P = 0.01). No significant corn hybrid by sex interactions (P ≥ 0.12) or corn hybrid by feeding program interactions (P ≥ 0.13) were observed. Inclusion of EFC in natural heifer diets tended to increase DMI by 0.4 kg/d (P = 0.10), while hybrid inclusion had no impact on DMI of conventional heifers. Feeding EFC in conventional steer diets tended to increase DMI by 0.4 kg/d (P = 0.06) compared with steers consuming the control corn hybrid diet. Corn hybrid had no impact on DMI in natural steer diets (P = 0.15). Carcass adjusted final BW decreased by 75 kg in natural steers and 41 kg in natural heifers compared with conventional programs (P < 0.01). Natural heifers gained 0.24 kg/d less than conventional heifers (P < 0.01). Feeding steers in the natural program reduced ADG by 0.43 kg/d in comparison with conventional program steers (P < 0.01). Compared with natural cattle, G:F improved by 13.0% when heifers were fed in a conventional program (P < 0.01) and 19.4% when steers were fed in a conventional program (P < 0.01). Feeding program had no effect on marbling (P = 0.38) while conventional cattle had greater 12th rib fat than natural cattle (P < 0.01). Inclusion of EFC had no effect on ADG (P = 0.71), G:F (P = 0.22), or HCW (P = 0.57). The incorporation of implants and feed additives within the finishing period increased final BW, HCW, and ADG leading to improved G:F in steers and heifers, with the improvement being greater in steers.

250 The Impact of Increasing Levels of Dried Distillers Grains and Solubles on Finishing Pig Performance

Abstract Due to ethanol plants continuing to be more efficient extracting corn oil out of dried distillers grains and solubles (DDGS), it is necessary to understand how pigs are utilizing the energy in diets with increasing levels of current DDGS. A total of 1,120 finishing pigs (DNA 600 x 241, initially 17.5 kg) were used in a 120-day experiment to evaluate the effects of DDGS on growth performance from approximately 8 to 25 weeks of age. Dietary treatments consisted of a corn and soybean meal-based diet with either 0, 10, 20, 30, or 40% DDGS. Pigs were fed a seven-phase finishing diet program to meet their nutritional requirements. Dietary energy was allowed to fluctuate with changing levels of DDGS while maintaining a constant SID lysine to calorie ratio. Pens of pigs were randomly allotted to 1 of the 5 treatments, with 32 pigs per pen and 7 replicates per treatment. Sex was equally represented in each pen. Pigs were harvested (average final BW of 127 kg) at a commercial facility. Data were modeled in R (R Core Team, 2020) to test for both linearity and non-linear responses to DDGS levels in the diet. Models included DDGS treatment and trial start weight and pen was the experiment unit. Traits analyzed included average daily gain (ADG, kg/d), Gain to Feed (G:F), average daily feed intake (ADFI, kg/d), hot carcass weight (kg) and carcass yield (%). All traits were found to have linear trends with increasing DDGS inclusion levels (Linear: P ≤ 0.02; Quadratic: P ≥ 0.29). Overall, there was a reduction in ADG as DDGS inclusion increased from 1.00 (± 0.01) with 0% DDGS to 0.96 (± 0.01) kg/day for 40% DDGS (P = 0.04). There was a decrease in gain to feed ratio (0.39 to 0.35) with increasing DDGS inclusion (P < 0.001). Hot carcass weight decreased with increased inclusion of DDGS from 97.25 to 93.39 kg (P = 0.001), while carcass yield was not significantly different across DDGS inclusion levels ranging from 75.3% to 74.7% for 0% and 40% DDGS inclusion (P = 0.2), respectively. These data indicate that increasing levels of DDGS reduce ADG, feed efficiency, and carcass weight.

311 Evaluation of Rumen Protected B-Vitamin Blend on Finishing Steer Growth Performance, Efficiency of Dietary net Energy Utilization, Carcass Trait Responses, and Liver Abscess Prevalence and Severity

Abstract The objective of this study was to determine the influence that a rumen-protected B-vitamin (RPBV) blend (containing pantothenic acid, pyridoxine, folic acid, biotin, and cyanocobalamin; Vivalto, Trouw Nutrition, Isola Vicentina, Italy) had on growth performance, efficiency of dietary net energy utilization, carcass trait responses, and liver abscess severity and prevalence in beef steers fed a finishing diet. Steers (n = 246; initial shrunk body weight (BW) = 411 ± 25.8 kg) from two sources, were used in a 126-d randomized complete block design experiment. Within 48 h after arrival, steers were individually weighed and allotted to one of 24 pens (n = 10 to 12 steers; 8 pens/treatment) and randomly assigned to 1 of 3 treatments: 1) No RPBV; 2) RPBV1 at 1 g/hd/d; 3) RPBV2 at 2 g∙animal-1∙d-1/. During the first 14 d cattle received two transition diets. From d 15 to d 126 cattle were fed the final diet containing 53% dry-rolled corn; 23% corn silage; 20% MDGS; and 4% suspended supplement. Data were analyzed using the GLIMMIX procedure of SAS 9.4 with treatment as the fixed effect and block (Pen location) as the random effect; pen was considered the experimental unit. No differences (P ≥ 0.13) were found for dry matter intake, final live BW, average daily gain (ADG), or feed efficiency (G:F) among treatments. Carcass-adjusted final BW, ADG, and G:F were not influenced by treatment (P ≥ 0.59). Hot carcass weight, dressing percentage, marbling score, kidney-pelvic-heart fat, or BW at 28% empty body fat did not differ among treatments (P ≥ 0.11). Rib eye area (REA) was altered (quadratic effect, P = 0.02) by treatment; steers from RPBV 1g had decreased REA compared with others. Additionally, calculated yield grade (YG) and calculated retail yield (RY) were altered (quadratic effect, P ≤ 0.01) by treatment; steers from RPBV 1 g had increased YG and decreased RY compared with others. Estimated empty body fatness tended (P = 0.06) to be greater from steers fed RPBV compared with control. Overall USDA YG distribution was altered by dietary treatment (P = 0.01). The proportions of YG1 and YG5 carcasses were unaffected by treatment, but there was a shift in the proportion of carcasses that graded YG2, YG3, and YG4 among treatments. Distribution of USDA Quality Grade was not altered by treatment (P = 0.53). No differences were observed on liver abscesses among treatments. The use of RPBV altered carcass muscularity and rib fat accumulation which impacted the overall YG distribution. However, RPBV did not appreciably influence any cumulative growth performance measures liver abscess incidence or severity.

PSVI-2 Economic Evaluation of Forage-Fed vs Concentrate-Fed Beef Finishing Systems

Abstract The objective of this study was to determine the price points at which it is more economical to finish beef animals on forage-based or concentrate-based diets. To accomplish this, Hereford steers (n = 21; BW = 444 ± 10 kg) were fed out on one of three diets: a long-stemmed grass hay (HAY, 10.8% CP, 2.11 Mcal ME/kg DM), an alfalfa hay diet (ALF, 20.5% CP, 2.85 Mcal ME/kg DM) or a mixed ration consisting of 30.0% corn silage, 28.0% DDGS, 30.0% rolled corn, 10.5% soybean meal, and 1.5% mineral supplement (CON, 22.0% CP, 2.90 Mcal ME/kg DM). The data were analyzed in SAS v9.4. Animals were evaluated on intake, growth, and performance measures during a 35-day feeding trial. Average daily gain (ADG) and hot carcass weight differed significantly (P < 0.05) between treatments with CON steers gaining 1.47 kg/d with a hot carcass weight of 394.8 kg, ALF steers gaining 0.77 kg/d with a hot carcass weight of 334.7 kg, and HAY steers gaining 0.1 kg/d with a hot carcass weight of 237.4 kg. Dressing percentage was significantly different between all treatments (P < 0.05). The dressing percentage was 58.2%, 54.3%, and 50.6% for CON, ALF, and HAY, respectively. The HAY diet rendered significantly lower marbling scores than ALF or CON (P < 0.05). It was concluded based on carcass quality data that there was no difference in the high-quality forage (ALF) and the concentrate diet (CON) other than diet cost and growth rate. Price per kilogram of gain was $1.42, $1.23, and $14.80 for CON, ALF, and HAY, respectively. Results of this trial are expected to indicate at what price point it becomes more economically effective to finish animals on a high-quality forage or a concentrate-based diet.

179 Identification of Regulatory Mutations Affecting Complex Traits

Abstract Understanding genetic bases controlling complex traits of economic importance is fundamental to improve breeding programs. Recent efforts from FAANG consortium resulted in significant progress in the identification of regulatory regions in farm animals. However, most studies in cattle have focused on Bos taurus, and limited information is available for Bos indicus. Considering that Bos indicus is the predominant subspecies in tropical regions, the objective of this work was to identify regulatory variants associated with meat quality by combining information from whole genome sequence (WGS), gene expression (RNA-seq), and open chromatin regions (ATAC-seq). For genome wide association study (GWAS), an imputed panel of SNPs was obtained from WGS of 26 sires, a Bovine HD 770K panel of 374 progenies, and SNPs called from RNA-seq data of Longissimus thoracis muscle (LT) of 192 progenies. The SNPs were identified using GATK4, and the dataset included almost 4.5 million variants that were pruned to 553,581 tag-SNPs (PLINK, r2 = 0.8). ATAC-seq data was obtained from duplicated samples of LT collected from two animals. Phenotype data included back fat thickness (BFT), intramuscular fat (IMF), ribeye area (REA) and shear force (SF). Association of genotypes (553,581 SNPs) and gene expression (12,991 genes), performed in Matrix eQTL resulted in 36,916 cis-eQTL and 14,408 trans-eQTL (FDR < 0.05). For GWAS analysis of the eQTLs with phenotypic traits, we used a linear model in PLINK program (considering population stratification, contemporary group and hot carcass weight). GWAS resulted in 24 eQTLs associated with IMF, three with BFT, 12 with REA, and eight with SF (FDR < 0.10). ATAC-seq analysis (using nfcore/atacseq pipeline implemented in Nextflow) resulted in 33,734 consensus peaks with a mean size of 2.4 kb. The overlap analyses among GWAS, eQTL, and ATAC-seq positions resulted in two, four and one putative regulatory regions that control gene expression and are associated with BFT, IMF and SF, respectively. Functional studies are still necessary to establish if identified mutations are the causal mutation. In conclusion, integration of GWAS, RNAseq, and ATAC-Seq data can result in identification of regulatory mutations associated with phenotypes of economic importance.

PSV-1 Pasture Does Not Impact Pork Quality of Finishing Hogs

Abstract Sales of certified organic pork continue to increase, and an increasing number of young farmers are looking to rear hogs with organic or other niche labeling claims that require outdoor access. There is limited research available to support pastured pork operations in developing best management practices for rearing pigs in outdoor environments. The goal of this study was to evaluate the impact of housing on swine performance and pork quality and to build best management strategies for raising hogs on pasture. Pigs (n = 50) from the same sire and farrowing cohort were obtained from 10 separate litters. Pigs were grouped into separate treatments according to average body weights (BW) with equal sex rations among both groups: Indoor (n = 25), and Outdoor (n = 25), with 5 hogs per pen within each treatment. The Indoor groups were housed on 7m2 of solid concrete flooring in a ventilation-controlled barn; the Outdoor groups were housed on native grass pasture with pen size being 23m2, and a third shaded with 40% shade cloth. Outdoor pens were rotated to new grass every 14 days to manage soil destruction, while Indoor pigs remained in original pens for the duration of the project. Water access was provided via a nipple drinker system and fed a standard grow-finish ration ad libitum for both groups. All pigs were slaughtered at 26 weeks of age, with the Indoor group averaging BW of 126kg, and the Outdoor group averaging BW of 111kg (P < 0.05). Hot carcass weights were also larger (P < 0.001) of the Indoor group. All pork quality measurements were taken at the 10th rib. Color and marbling scores were not shown to vary between the treatment groups (P ≥ 0.17). Colorimeter values (L*, A*, B*) were similar across treatments as well (P ≥ 0.41). However, loin eye area exhibited a trend with the Outdoor group having a smaller average size (P = 0.07) In addition to this, pH values were also shown to vary at 0h (P = 0.03), 6h (P = 0.01), and 24h (P < 0.01) postmortem, with the Indoor group having the higher ultimate pH. Based on these data, pasture reduced final market size and loin eye area of hogs, but not overall pork quality. Although pH was reduced for the Outdoor group, no values showed a rapid decline in pH that would indicate a PSE pork product. Further, average pH between treatments were within 0.2 at all sampling times. Further research is needed to evaluate efficacy of best management practices to improve efficiency of pig growth rate on pasture and to ensure that pork quality will not be reduced.

71 Effects of Late Gestational Nutrient Restriction on Calf pre-Weaning Growth, Backgrounding and Feedlot Performance, and Carcass Composition

Abstract Fall-calving Hereford-SimAngus heifers [single-sired; BW: 451 ± 28 (SD) kg; BCS: 5.4 ± 0.7] bred to a single sire were individually fed 100% (control; CON; n = 12) or 70% (nutrient restricted; NR; n = 13) of NASEM metabolizable energy and metabolizable protein requirements for maintenance, pregnancy, and growth from day 160 of gestation to calving. Post-calving, all females were fed chopped tall-fescue hay supplemented to meet lactational nutrient requirements in Calan gates to constrain diets of calves to milk only until day 147, then pen-fed in drylots until weaning at day 242 ± 3 (SD). Post-weaning, calves were fed a tall fescue hay-based backgrounding diet in the same large drylots for 53 ± 12 d, then moved to partially covered pens with GrowSafe feeding systems in 2 groups and fed a corn-based feedlot diet (formulated to be 18.3% CP, 1.21 Mcal NEg/kg, DM basis; 89% DM) for 255 ± 3 d (similar days on feed rather than carcass endpoint). Cattle were harvested in a commercial plant, and camera carcass grading was performed. Data were analyzed with maternal treatment, calving date, and calf sex (when P < 0.25) as fixed effects; feedlot group was included for feedlot and carcass measures. We previously reported that birth weight was not affected (P = 0.72), but NR decreased (P < 0.04) milk production by 15%. Calves born to NR dams had reduced ADG from birth to day 147 (P = 0.02), day 147 to weaning (P = 0.08), and birth to weaning (P = 0.003), resulting in NR calves having 13% lighter (P = 0.004) weaning weight. Backgrounding ADG was not affected (P = 0.80) by maternal treatment; thus, feedlot entry BW was 11% less (P = 0.009) in NR calves. On day 28, 56, 84, and 112 on feed, NR calves weighed less (P ≤ 0.09) than control. Final BW was not affected (P = 0.91) by maternal treatment. Feedlot ADG was greater for NR calves from day 168 to slaughter (P = 0.02) and the overall feeding period (P = 0.03), but not before day 168 on feed (P ≥ 0.22). Calves born to NR dams had less (P = 0.02) dressing percentage, but improved (P = 0.02) yield grade and backfat thickness. Hot carcass weight, ribeye area, marbling score, and KPH were not affected (P ≥ 0.26) by maternal treatment. Percent prime, yield grade ≤ 2, and yield grade ≥ 4 were not affected (P ≥ 0.29) by maternal treatment. Overall, late gestational nutrient restriction decreased growth pre-weaning but increased late finishing growth, without affecting backgrounding or early feedlot growth. These cattle had leaner carcasses after similar days on feed, suggesting that late gestational nutrient restriction altered growth patterns or body composition.

312 Evaluation of Dietary Roughage Manipulation During the Feeding of Ractopamine Hydrochloride as a Method to Improve Ruminal Health and Control Liver Abscess Severity in Feedlot Steers

Abstract The objective of this study was to determine if additional roughage inclusion to feedlot steer finishing diets during the feeding of ractopamine hydrochloride (RH) is an effective method to improve rumen health and control liver abscess severity. Steers [n = 64; initial shrunk body weight (SBW) = 633 kg ± 35.1 kg] were sourced from an unrelated trial and remained in their previous study pens; pens (n = 8) were assigned to dietary treatment in a completely randomized design. All steers on trial were fed a common 7% [dry matter (DM) basis] roughage equivalent (RE) finishing diet composed of dry-rolled corn, dried distillers grains plus solubles, corn silage, and grass hay for the 58 d preceding study initiation. Steers were fitted with rumination tags to track daily rumination. Dietary treatments were CON: no diet change; and 12R: 5% (DM basis) RE addition to diet via grass hay during the feeding of RH. Steers were fed RH (300 mg/steer/d), finished on treatment diets for 28 d, and harvested at a commercial beef processor. Growth performance, efficiency of dietary net energy (NE) utilization, and continuous carcass data were analyzed with pen as the experimental unit (EU) and fixed effect of treatment. Minutes ruminating was analyzed as an analysis of covariance with individual animal as the EU, fixed effects of treatment, days on feed (DOF) and their interaction, and baseline minutes ruminating as a covariate in the model. Liver abscess prevalence, rumen health, and categorical carcass data were analyzed with the Fisher’s exact test to determine differences between treatments. No difference (P ≥ 0.19) was observed for final SBW, average daily gain, dry matter intake, feed conversion efficiency, dressing percentage, hot carcass weight, calculated yield grade, marbling score, 12th rib fat thickness, calculated empty body fat, observed dietary NE for maintenance and gain, observed-to-expected dietary NE for maintenance and gain, or distribution of liver abscess prevalence, ruminitis score, or USDA yield grade. Ribeye area tended (P = 0.10) to differ between treatments with 12R steers exhibiting a 3.5% larger ribeye. Distribution of USDA quality grade differed (P = 0.003) between treatments with 12R steers having 25% more carcasses grading USDA average choice or better. A treatment × DOF interaction (P = 0.045) was observed for minutes ruminating per day. Daily minutes ruminating was increased (P ≤ 0.05) for 12R on d 1, 2, and 20 and tended to be increased (P ≤ 0.10) for 12R on days 10, 13, 24, and 25. Inclusion of an additional 5% RE to finishing cattle diets during a 28 d RH feeding period can be a management strategy to decrease risk of digestive upsets without sacrificing growth performance or carcass quality.

246 Evaluation of the Complete Replacement of Soybean Meal by Rapeseed Meal on Performance and Carcass Composition of Grow-Finishing Pigs

Abstract The aim of this experiment was to evaluate the effects of replacing soybean meal (SBM) by rapeseed meal (RSM) as main protein source in diets for grow-finishing pigs. The trial included a total of 1,248 crossbred boars and gilts [Pietrain x (Landrace x Large White), with an initial body weight (BW) of 38.3 ± 5.29 kg (Mean ± SD)], distributed in 96 pens of 13 pigs. Pens were randomly distributed in 2 dietary treatments, balanced by BW, block and sex within each of the 8 slurry pits. The inclusion of SBM and RSM in the growing diets was 13.8% and 20.0%, whereas in the finishing diets (days 52-91) was 10.5% and 14.4%, respectively. Diets were formulated to have the same net energy (NE) value and crude protein differences were below 0.5%. To achieve isoenergetic diets, the inclusion of animal fat was increased by 2.4% and 1.7% in RSM diets compared with SBM for the growing and finishing phases, respectively. Standardized ileal digestible (SID) Lys was kept at 0.95% and 0.86% in the growing and finishing phases, respectively. Performance variables were analyzed by using a linear mixed model with treatment and sex as fixed effects and initial BW as covariate, while pit was included as a random effect. Individual carcass data were analyzed in a linear mixed model with treatment, sex and marketing group as fixed effects, and hot carcass weight as a covariate, and pen within a pit as random effect. During the growing phase, pigs showed lower ADFI when fed the RSM diet (1.68 vs. 1.62 kg; P = 0.002) that resulted in decreased ADG (0.842 vs. 0.803 kg; P = 0.015), but FCR was not affected (2.00 vs. 2.02; P = 0.459). Contrarily, in the finishing phase, ADFI was not significantly reduced (1.98 vs. 1.95 kg; P = 0.586) but less FCR was observed when feeding RSM (2.59 vs. 2.49; P = 0.007). Final BW was not significantly affected (112.0 vs. 110.7 kg; P = 0.404), but hot carcass weight tended to be less in RSM fed pigs (92.2 vs. 91.3 kg; P = 0.078). No significant differences were reported on carcass yield (P = 0.815), carcass leanness (P = 0.850) or backfat thickness (P = 0.850). In conclusion, feeding growing pigs diets without SBM might negatively affect their performance during the growing phase, but those effects can be partly counteracted in the finishing phase without modifying carcass composition.

205 Relationship of Resiliency to Weaning Stress with Growth, Carcass, and Meat Quality Traits in Pigs

Abstract Acute stress before slaughter has been demonstrated to have a detrimental impact on pork quality, but little is known about whether early life stress has a similar effect. Our objective was to identify if stress resiliency or vulnerability at weaning had an impact on long-term performance resulting in differences in growth, carcass, or meat quality traits. At weaning, blood samples were collected from all gilt piglets from 26 crossbred litters (n = 170) at -1 d, 0 d, and +4 d pre- and post-weaning. For each litter, serum cortisol was used to identify the gilt most capable of returning to baseline levels by +4 d as stress resilient (SR, n = 26) and the gilt least capable as stress vulnerable (SV, n = 26). The SR and SV gilts were processed at the Michigan State University Meat Laboratory and carcass and meat quality data were collected. Carcass traits included finished live weight, hot carcass weight, dressing percentage, loin muscle area, and 10th-rib backfat depth. Meat quality traits included 45-min and ultimate pH, marbling score, subjective color score, Minolta colorimeter L*, a* and b*, and drip loss. Data were analyzed using Gaussian linear models. The base model included stress group and farrowing group as fixed effects and age at slaughter as a covariate. The SR gilts showed decreased ADG at the grow-finish stage resulting in lighter finished weight (P = 0.089 and P = 0.070, respectively). The SR gilts also had a lighter hot carcass weight (P = 0.05); however, no differences were observed in dressing percentage ( P= 0.924). the SR and SV gilts did not differ in backfat depth, but SR gilts had smaller loin muscle area (P = 0.019). No differences were observed in any of the meat quality measures. In summary, we found resiliency to weaning stress to have a minimal impact on carcass merit or meat quality. Future studies will aim to determine if the observed difference in loin muscle area is associated with gene expression differences.

194 A Systems Approach to Deriving Carcass Value from Holstein x Simangus Cattle in an Accelerated Finishing Model

Abstract Crossbreeding dairy cows with beef sires has increased in the U.S. dairy industry. This beef x dairy mating results in dairy-beef which has altered the U.S. fed beef supply. The predominant mating has been Holstein x Angus, thus research was conducted to determine the effects of Holstein x SimAngus breeding on growth performance, carcass characteristics, and fresh meat quality. Starting on d 1, Holstein steers (n = 9) and Holstein x SimAngus (HolSim) steers (n = 12) were fed once daily at 0830 h, until an end weight of 635 kg was reached. Holstein steers averaged 421 d and HolSim steers averaged 432 days on feed. Daily feed offered was delivered into a semi-autonomous feed monitoring system designed to measure individual animal intake and feeding behavior (GrowSafe System Ltd). Steer body weight was recorded every 28 d. Data collected were used to calculate dry matter intake (DMI), average daily gain (ADG), and gain to feed ratio (G:F). Steers were humanely slaughtered under USDA inspection, immediately following slaughter hot carcass weight (HCW) was recorded and 48 h following slaughter, carcass length, body width, backfat thickness and area of the longissimus muscle (LM) was recorded. Strip loins were collected from each carcass and aged for 14 d. After aging, Warner-Bratzler shear force (WBSF) and slice shear force (SSF) were determined. Remaining steaks were placed under retail display for 7 d. Objective color was measured after 0, 1, 3, 5, and 7 d in retail display. No differences were observed for ADG and G:F between Holstein and HolSim steers (P > 0.05). A tendency was observed for Holstein steers to have a greater DMI compared with HolSim steers (P = 0.0646). The HolSim steers had greater HCW and dressing percentages compared with Holstein steers (P < 0.0001). The HolSim carcasses had shorter carcass lengths and body widths compared with Holstein carcasses (P = 0.0005). Holstein carcasses had less backfat compared with HolSim carcasses (P = 0.0034). The LM area was larger in HolSim carcasses (P < 0.0001). No differences were observed for WBSF or SSF (P > 0.05). Strip steaks from HolSim steers had less deoxymyoglobin and greater oxymyoglobin values on d 0 of retail (P < 0.05). Strip steaks from HolSim steers had greater a* and saturation index values on d 7 in retail (P < 0.05). Strip steaks from HolSim steers had decreased metmyoglobin values and greater oxymyoglobin values on d 7 in retail (P < 0.05). Thus, indicating strip steaks from HolSim steers had increased red color. Growth performance data in this study confirm previous literature reported when comparing dairy x dairy to beef x dairy steers. Carcass and fresh meat data suggest that Holstein x SimAngus steers had improved yield production compared with Holstein steers without a loss in quality when steers were fed to a weight constant end point.

PSV-7 Evaluation of Narasin Inclusion Level on Growth Performance and Carcass Characteristics of Growing-Finishing Pigs

Abstract Previous studies evaluating 15 mg/kg of narasin have shown improvements in BW, ADG, and G:F. However, FDA approved labeling for narasin indicates improved G:F with increased inclusion levels (20 to 30 mg/kg), which may provide greater economic return with higher feed costs. Some commercial systems have shown improvements in ADG and G:F when feeding 20 or 30 mg/kg narasin compared with 15 mg/kg. As such, two studies were conducted to evaluate 30 mg/kg of narasin on growth performance and carcass characteristics of growing-finishing pigs. Studies were carried out using a randomized complete block design with three narasin levels: 0, 15, or 30 mg/kg. Study 1 (2,545 pigs) was carried out from 42.6 ± 1.3 kg to 132.9 ± 3.6 kg. Study 2 (1,235 pigs) was carried out over a fixed time of 112 days from 39.1 ± 3.0 kg to 139.8 ± 3.5 kg. All pigs were fed diets that met or exceeded nutrient recommendations of growing-finishing pigs (NRC, 2012). Pigs were offered ad libitum access to feed and water throughout the study and weighed every 28 days and at every marketing event. Feed additions and feed remaining in the feeder at the time of pig weighing was recorded. Due to relatively low carcass recovery at the harvest facility, carcass data for Study 1 are not presented. Feeding 30 mg/kg of narasin did not improve (P > 0.05) growth or carcass performance compared with feeding 15 mg/kg narasin (Table 1). Compared with controls, feeding 15 mg/kg narasin increased final body weight (1.3 kg and 1.5 kg for Study 1 and 2, respectively), increased hot carcass weight (1.9 kg – Study 2), and improved carcass yield (0.4 percentage units), although differences were not always statistically different (P > 0.05). Overall G:F was improved 1.5% (P < 0.05) in Study 1, but not different (P > 0.05) than controls in Study 2. Results of this study confirm improvements in growth performance and carcass characteristics from feeding 15 mg/kg narasin to growing-finishing pigs. The outcomes of feeding 30 mg/kg of narasin were unexpected based on field outcomes and warrant further research.

PSV-6 Evaluation of Narasin Feeding Duration on Growth Performance and Carcass Characteristics of Growing-Finishing Pigs

Abstract Previous studies evaluating 15 mg/kg narasin have shown improvements in BW, ADG, G:F, and HCW and carcass yield when fed for an extended period of time ( >60 days). However, a detailed evaluation of feeding duration of narasin has not been completed. This study evaluated the effect of narasin feeding duration on growth performance and carcass characteristics of growing-finishing pigs. The study was carried out over a fixed time of 112 days using 1,644 pigs in a randomized complete block design. Narasin was included at 15 mg/kg in the last two, three, or four growing-finishing dietary phases, which resulted in narasin being fed for the last 68, 94, or 112 days of study and compared with a negative control diet. Pigs were fed diets that met or exceeded nutrient recommendations of growing-finishing pigs (NRC, 2012). Pigs were offered ad libitum access to feed and water throughout the study and weighed every 28 days and at every marketing event. Feed additions and feed remaining in the feeder at the time of pig weighing were recorded. Pigs were sent for harvest to a commercial slaughter facility in three marketing groups: Group 1 – 20% of pigs marketed on day 84 of study, Group 2 – 20% of pigs marketed on day 98 of study, and Group 3 – remaining 60% of pigs marketed on day 112 of study. Standard carcass grading measurements were collected for each pig and summarized by pen for data analysis. There were limited statistical differences (P > 0.05) between treatments for growth or carcass measures, likely due to the limited number of replicates (n = 16) in this research facility. Nonetheless, there were numerical improvements from feeding narasin. Final live BW (+0.3, +0.4, +1.5 kg, respectively) and ADG (+0.1, +0.4, and +1.3%, respectively; Table 1) numerically increased with increased feeding duration of narasin. Overall G:F was relatively unaffected by feeding duration. Hot carcass weight increased with increased narasin feeding duration (+0.2, +1.1, +1.9 kg, respectively), resulting in increased carcass yield with increased feeding duration (-0.2, +0.1, +0.4 percentage units, respectively). Collectively, carcass ADG and carcass G:F trended toward improvement with increased feeding duration. Results of this study confirm previously observed improvements in growth performance from extended feeding of narasin compared with controls, suggesting that a greater response to narasin is observed with longer feeding durations.

129 Effects of Standardized Ileal Digestible Lysine on Growth Performance of 12- to 136-kg PIC Line 800-Sired Pigs

Abstract The objective of this study was to evaluate growth performance and economic return of PIC 800 × Camborough pigs fed increasing SID Lys from approximately 12- to 136-kg. Pens of pigs were blocked by body weight (BW) and randomly assigned to 1 of 5 dietary treatments in a randomized complete block design with 26 pigs per pen and 16 pens per treatment. Pens were provided 1 of 5 dietary treatments with increasing SID Lys at 85, 93, 100, 107, and 115% of current (2021) PIC recommendations within 6 dietary phases as follows: phase 1 (1.09, 1.19, 1.28, 1.36, and 1.47%), phase 2 (0.97, 1.06, 1.14, 1.22, and 1.32%), phase 3 (0.87, 0.95, 1.02, 1.09, and 1.17%), phase 4 (0.75, 0.82, 0.88, 0.94, and 1.01%), phase 5 (0.66, 0.72, 0.77, 0.82, and 0.89%), and phase 6 (0.59, 0.64, 0.69, 0.74, and 0.79%). Two corn-soybean meal-based diets containing low and high Lys were blended to achieve target SID Lys levels for each treatment diet within phase. Overall (d 0 to 143), increasing SID Lys improved (linear, P ≤ 0.007) ADG and G:F, but did not impact ADFI (P > 0.10; Table). A tendency (linear, P = 0.067) for heavier hot carcass weights (HCW) was observed in pigs fed increasing SID Lys. However, there was no evidence for differences (P > 0.10) in carcass yield, backfat depth, loin depth, or carcass lean percentage across treatments. The linear (LM) model served as the best fit for both growth and economic parameters. The LM model predicted maximum ADG and G:F at levels greater than 115% of PIC’s current recommendations. However, for income over feed cost (IOFC), the LM model predicted maximum profitability at or below 85% of the current Lys recommendations of PIC. In conclusion, the optimal SID Lys level for PIC 800 × Camborough pigs from 12- to 136- kg differed upon response criteria, with growth performance maximized at levels at or above 115% of the recommendation for SID Lys by PIC; however, maximal economic returns were observed at or below 85% of PIC’s current SID Lys recommendations.

133 The Effects of Increasing Dietary Standardized Ileal Digestible Lysine Levels on Growth Performance and Carcass Characteristics of 24- to 130-kg Grow-Finish Pigs Sired by PIC 800 Boars

Abstract Our objective was to determine the effects of increasing overall standardized ileal digestible (SID) lysine (Lys) levels on growth performance and carcass characteristics of grow-finish pigs sired by PIC 800 boars. A total of 1,715 barrows and gilts (PIC800×Camborough, initially 23.7±0.58 kg) were used in a 117-d growth trial with 70 mixed sex pens in two rooms (35 pens per room), 14 pens per treatment, and 23 to 25 pigs per pen. At the beginning of the trial, pens within each room were blocked by body weight and randomly allotted to one of five treatments (overall dietary SID Lys level as 80, 88, 94, 100, or 110% of PIC SID Lys recommendations) in a randomized complete block design. Diets were corn-soybean meal (SBM)-based, and treatments were achieved through the inclusion of SBM with adjustments of corn and choice white grease inclusion rates. Diets were fed in 6 phases (24-47, 47-63, 63-75, 75-95, 95-113, and 113-130 kg) and formulated to be iso-caloric across treatment for each phase. Within each phase, only the diets of the lowest and highest SID Lys levels were manufactured, and the diets of intermediate SID Lys levels were blended by the automatic feeding system in the research facility. Growth performance data were analyzed using the GLIMMIX procedure in SAS (Version 9.4, SAS Institute, Inc., Cary, NC) and considered pen as the experimental unit. The statistical model considered fixed effects of SID Lys levels and random effects of the block. Mortality and removals were also analyzed using the GLIMMIX procedure and specified a binomial distribution. All data are reported as least square means and considered statistically significant at P < 0.05 and marginally significant at P < 0.10. Increasing overall dietary SID Lys levels marginally reduced average daily feed intake (linear, P = 0.108) and increased gain-to-feed ratio (linear, P < 0.001), but there was no evidence for difference among treatments for average daily gain (P >0.10) or removal and mortality rate (Table 1; P > 0.10). There was no evidence for increasing overall dietary SID Lys levels affect hot carcass weight, carcass yield, backfat depth, loin depth, or lean yield. In conclusion, increasing overall dietary SID Lys level over PIC recommendations through increasing SBM levels resulted in improved feed efficiency of 24 to 130 kg pigs sired with PIC 800 boars, but there was no evidence for difference in the carcass characteristics.

PSVI-4 The Influence of Diet Type on Beef Cattle Performance and Meat Quality Characteristics

Abstract The objective of this study was to determine the effect of diet type on feed intake in yearling steers. Hereford steers (n = 21; BW = 444 ± 10 kg) were assigned to one of three drylot pens based on initial BW. Each drylot pen was assigned to one of three diets: a long-stemmed grass hay (HAY, 10.8% CP, 2.11 Mcal ME/kg DM), an alfalfa hay diet (ALF, 20.5% CP, 2.85 Mcal ME/kg DM) or a mixed ration consisting of 30.0% corn silage, 28.0% DDGS, 30.0% rolled corn, 10.5% soybean meal, and 1.5% mineral supplement (CON, 22.0% CP, 2.90 Mcal ME/kg DM). Animals were fed daily at 0700 and 1700 h and weighed weekly at 0630 h. For the duration of the trial, animals were housed in drylot pens with ad libitum access to feed and water and had shade structures in each pen. Following a 14-day adaptation period, feed intake was recorded for 35 days. Body weight gain for diets HAY, ALF, and CON were 0.1, 0.77, and 1.47 kg/day, respectively. After the intake portion of the study was completed, an animal from each pen was slaughtered and evaluated for meat quality. Hot carcass weights for diets HAY, ALF, and CON were 237.4, 334.7, and 394.8 kg, respectively. Following 14 days aging, samples from the ribeye area were collected from each animal and subjected to sensory analysis and other assessments of quality. Data were analyzed as a completely random design in SAS v9.4. There was not a significant difference between the ALF diet and the CON diet based on assessment from Warner-Bratzler shear force, carcass yield, marbling score, and sensory assessment (P < 0.05). It was concluded that high-quality forage can achieve similar carcass quality without detrimental effects on meat quality when compared with a high concentrate diet.

131 Effect of Dietary Standardized Ileal Digestible Lysine Concentration Curve on Growth Performance and Carcass Characteristics of Finishing Pigs of DNA Genetics

Abstract A total of 1,125 pigs (31.4 kg BW) of DNA genetics were used in a 109-d experiment to evaluate the effect of SID Lys feeding curve of pigs from 31.4 to 133.3 kg BW. Forty-five pens of mixed sex pigs were used. Pens were blocked by location within the barn with barrow and gilt numbers in pens kept consistent within block. Pens were allotted to one of five dietary treatments in a randomized complete block design with 9 replicate pens per treatment. Dietary SID lysine concentrations were evaluated on a curve (corresponding to 90, 95, 100, 105, and 110% of the DNA Genetics SID lysine recommendations) using a 6-phase feeding program throughout the experimental period. The 100% curve concentrations used were 1.16% for phase 1 (31.4 – 47.5 kg), 1.02% for phase 2 (47.5 – 64.4 kg), 0.92% for phase 3 (64.4 – 81.8 kg), 0.79% for phase 4 (81.8 – 98.9 kg), 0.72% for phase 5 (98.9 – 117.1 kg), and 0.65% for phase 6 (117.1 – 133.3 kg). Diets were corn-soybean meal-DDGS-based and formulated for equal NE concentrations across treatment within diet phase. Data were analyzed using a general linear model. Orthogonal contrasts with coefficients for equally spaced treatments were used to analyze for linear and quadratic effects. A linear (P < 0.05) increase was observed for BW, average daily gain, and G:F as SID lysine level in the diet increased. There was a linear increase observed (P < 0.05) for lysine intake (g/d and g per lb. gain) as SID lysine level of the diet increased. While no difference (P > 0.10) was observed for NE intake, caloric efficiency improved linearly (P < 0.05) as lysine level in the diet increased. Furthermore, return over feed cost improved linearly (P < 0.05) as dietary SID lysine level increased. There was no effect of SID lysine level fed on mortality and morbidity. A linear response (P < 0.05) for hot carcass weight and loin depth was observed as SID lysine level increased. Additionally, a quadratic response was observed (P < 0.05) for fat depth and percent lean as SID lysine level increased. These data indicate the SID lysine level that optimized growth and carcass measurements for DNA pigs ranging from 31.4 to 133.3 kg to be above the 105% curve, corresponding to 1.22, 1.071, 0.966, 0.83, 0.756, and 0.683 for diet phases 1 through 6, respectively.

Effect of the inclusion of rumen-protected amino acids in the diet of growing beef cattle on animal performance and meat quality

IntroductionThis study investigated the impact of rumen-protected amino acids on beef cattle's growth, fattening performance, and meat quality.MethodsTwo groups of 40 Montbeliard steers (237.8 ± 30 kg body weight) were housed separately and fed, with mono-tunnel feeders, either a control diet (CON) or a diet containing rumen-protected lysine and methionine with 3% less crude protein (APR). Feed consumption and weight were tracked in all animals, and meat quality analysis focused on the longissimus muscle, with 10 steers randomly selected from each treatment.Results and discussionResults for overall performance revealed no significant differences in body weight, average daily gain (ADG), and concentrate conversion ratio between the CON and APR diets (p > 0.05). However, during the final 90 days of the trial, the APR group showed significantly higher ADG (p < 0.05) than the CON group, while the concentrate conversion ratio was significantly higher (p < 0.05) in the CON group compared to the APR group. The hot carcass weight, dressing percentage, and carcass conformation did not differ significantly between the CON and APR diets (p > 0.05). There was a slight tendency (p = 0.06) for higher fatness score in the CON group. Regarding meat composition, the diet did not significantly affect proximate composition, but a tendency (p = 0.059) for higher crude protein content in APR cattle's meat compared to the CON group was observed. The APR meat showed slightly lower levels of C17:1 (0.56% vs. 0.72%) and C18:1n9 (31.7% vs. 34%). There was a tendency for C14:0 to be lower (P = 0.07), and for C16:0, C18:2 and polyunsaturated fatty acids (PUFA) to be greater in meat from cattle fed APR compared to CON. However, meat quality attributes like pH, water-holding capacity, color, and texture were similar in both CON and APR groups (p > 0.05). The findings indicate that utilizing rumen-protected amino acids enables formulating diets with reduced crude protein levels while enhancing nitrogen utilization efficiency for protein synthesis in intensively reared steers. Importantly, these dietary improvements do not adversely affect meat quality.

Variation in Acetyl-CoA Carboxylase Beta Gene and Its Effect on Carcass and Meat Traits in Gannan Yaks.

Acetyl-CoA carboxylase beta (ACACB) is a functional candidate gene that impacts fat deposition. In the present study, we sequenced exon 37-intron 37, exon 46-intron 46, and intron 47 of yak ACACB using hybrid pool sequencing to search for variants and genotyped the gene in 593 Gannan yaks via Kompetitive allele-specific polymerase chain (KASP) reaction to determine the effect of ACACB variants on carcass and meat quality traits. Seven single nucleotide polymorphisms were detected in three regions. Eight effective haplotypes and ten diplotypes were constructed. Among them, a missense variation g.50421 A > G was identified in exon 37 of ACACB, resulting in an amino acid shift from serine to glycine. Correlation analysis revealed that this variation was associated with the cooking loss rate and yak carcass weight (p = 0.024 and 0.012, respectively). The presence of haplotypes H5 and H6 decreased Warner-Bratzler shear force (p = 0.049 and 0.006, respectively), whereas that of haplotypes H3 and H4 increased cooking loss rate and eye muscle area (p = 0.004 and 0.034, respectively). Moreover, the presence of haplotype H8 decreased the drip loss rate (p = 0.019). The presence of one and two copies of haplotypes H1 and H8 decreased the drip loss rate (p = 0.028 and 0.004, respectively). However, haplotype H1 did not decrease hot carcass weight (p = 0.011), whereas H3 increased the cooking loss rate (p = 0.007). The presence of one and two copies of haplotype H6 decreased Warner-Bratzler shear force (p = 0.014). The findings of the present study suggest that genetic variations in ACACB can be a preferable biomarker for improving yak meat quality.

Impact of bushfires on Australian livestock health, welfare and carcase quality

The 2019/2020 Australian bushfires were unprecedented in terms of total area burned and impact on livestock and wildlife populations. However, there is currently limited literature available relating the consequences of bushfire or smoke exposure to livestock health, welfare, and carcase quality. A retrospective cross-sectional study was conducted using historical monitoring data from a Meat Standards Australia (MSA) accredited abattoir located on the mid-north coast of New South Wales, Australia. The spatiotemporal association between exposure to bushfire smoke (specifically the duration of the bushfires, distance from closest bushfire, annual bushfire season, proportion of the property of origin burned during the bushfires and time frame since exposure to bushfires) and effects on carcase meat quality metrics and pathology were measured, by building linear, generalised linear and cumulative link mixed models. Our findings indicate that hot carcase weight increased as the distance between the property of origin and the closest bushfire became greater and decreased with exposure to bushfires of longer duration or when greater proportions of the property of origin were burnt during bushfires. Subcutaneous rib fat of carcases also increased with an increasing distance of properties from the closest recorded bushfire and decreased with exposure to bushfires during the 2019/2020 season. Higher meat colour scores (darker meat colour) were associated with exposure to bushfires during the 2019/2020 season and exposure to bushfires of longer durations. There was only a weak association between increasing distance to the closest bushfire and higher marbling scores. Evidence of pneumonia in carcases was associated with exposure to bushfires of longer duration, specifically increasing risk of pneumonia was associated with fires of longer durations. Greater periods of time since exposure (i.e., >6 months) to bushfires were also associated with a higher risk of evidence of pneumonia at the time of processing. With increasing incidence of bushfires in Australia forecasted as a result of climate change, there is an urgent need to understand the impact of bushfires on livestock, to limit the effects on livestock health and mitigate the risk of significant socioeconomic impacts to the livestock industry. By providing a greater understanding of the impact of bushfires, the findings of this study can support producers to make informed decisions to mitigate the effects of bushfires on livestock health and carcase meat quality.