Estimation of carcass composition using rib dissection of calf-fed Holstein steers supplemented zilpaterol hydrochloride.

A serial harvest was conducted every 28 d from 254 to 534 d on feed (DOF) to quantify changes in growth and composition of calf-fed Holstein steers (n = 115, initial body weight (BW) = 449.2 ± 19.9 kg). One-half were supplemented with the ß-2 adrenergic agonist zilpaterol hydrochloride (ZH; 8.33 mg/kg 100% dry matter (DM) basis) during the final 20 d followed by a 3-d withdrawal prior to harvest; the remainder was fed a non-ZH control (CON) ration. Five steers were randomly selected and harvested after 226 DOF which served as a reference point for modeling purposes. Fabricated carcass soft tissue was ground, mixed, and subsampled for proximate analysis. Moreover, following the traditional method of rib dissection which includes the 9th, 10th, and 11th rib contained within the IMPS 103 primal, the relationship of carcass chemical composition to 9-10-11 rib composition was evaluated. Carcasses in this investigation had more (P < 0.01) separable lean, fat, ash, and moisture concomitant with less bone and ether extract than rib dissections. However, protein levels were similar (P = 0.27) between carcasses and rib dissections. Using regression procedures, models were constructed to describe the relationship of rib dissection (RD) composition including separable lean (RDSL), separable fat (RDSF), separable bone (RDSB), ether extract (RDEE), protein (RDP), moisture (RDM), and ash (RDA) with carcass composition. Carcass lean (CL), carcass fat (CF), and carcass bone (CB) were correlated (P < 0.01) with RDSL, RDSF, and RDSB with simple r values of 0.41, 0.71, and 0.50, respectively. Chemical composition of the rib and carcass, carcass ether extract (CEE), carcass protein (CP), carcass moisture (CM), and carcass ash (CA) were correlated (P ≤ 0.01) with simple r values of 0.75, 0.31, 0.66, and 0.37, respectively. Equations to predict carcass fatness from rib dissection variables and ZH supplementation status were only able to account for 50 and 56%, of the variability of CF and CEE, respectively. Overall, the relationships quantified and equations developed in this investigation do not support use of 9/10/11 rib dissection for estimation of carcass composition of calf-fed Holstein steers.

National Beef Quality Audit - 2016: Survey of carcass characteristics through instrument grading assessments.

The instrument grading assessment portion of the National Beef Quality Audit (NBQA) - 2016 allows the unique opportunity to evaluate beef carcass traits over the course of a year. One week of instrument grading data was collected each month from 5 beef processing corporations encompassing 18 facilities from January 2016 through December 2016 ( = 4,544,635 carcasses). Mean USDA yield grade (YG) was 3.1 with 1.37 cm fat thickness (FT), 88.9 cm LM area, 393.6 kg HCW, and 2.1% KPH. Frequency distribution of USDA YG was 9.5% YG 1, 34.6% YG 2, 38.8% YG 3, 14.6% YG 4, and 2.5% YG 5. Increases in HCW and FT since the NBQA-2011 were major contributors to differences in mean YG and the (numerically) increased frequency of YG 3, 4, and 5 carcasses found in the current audit. Mean marbling score was Small, and the distribution of USDA quality grades was 4.2% Prime, 71.4% Choice, 21.7% Select, and 2.7% other. Frequency of carcasses grading Prime on Monday (6.43%) was numerically higher than the average frequency of carcasses grading Prime overall (4.2%). Monthly HCW means were 397.6 kg in January, 397.2 kg in February, 396.5 kg in March, 389.3 kg in April, 384.8 kg in May, 385.0 kg in June, 386.1 kg in July, 394.1 kg in August, 399.1 kg in September, 403.9 kg in October, 406.5 kg in November, and 401.9 kg in December. Monthly mean marbling scores were Small in January, Small in February, Small in March, Small in April, Small in May, Small in June, Small in July, Small in August, Small in September, Small in October, Small in November, and Small in December. Both mean HCW and mean marbling score declined in the months of May and June. The month with the greatest numerical frequency of dark cutters was October (0.74%). Comparison of overall data from in-plant carcass and instrument grading assessments revealed close alignment of information, especially for YG (3.1 for in-plant assessment versus 3.1 for instrument grading) and marbling (Small for in-plant assessment versus Small for instrument grading). These findings allow the beef industry access to the greatest volume of beef value-determining characteristics for the U.S. fed steer and heifer population than ever reported, resulting in potentially more precise targeting of future quality and consistency efforts.

National Beef Quality Audit-2016: In-plant survey of carcass characteristics related to quality, quantity, and value of fed steers and heifers.

The National Beef Quality Audit (NBQA)-2016 used in-plant cooler assessments to benchmark the current status of the fed steer and heifer beef industry in the United States. In-plant cooler assessments ( = 9,106 carcasses) were conducted at 30 facilities, where approximately 10% of a single day's production were evaluated for USDA quality grade (QG) and yield grade (YG) factors. Frequencies of evaluated traits were 66.5% steer and 33.4% heifer sex classes and 82.9% native, 15.9% dairy-type, and 1.2% estimated breed types. Mean USDA YG factors were 1.42 cm for adjusted fat thickness, 89.5 cm for LM area, 390.3 kg for HCW, and 1.9% for KPH. Mean USDA YG was 3.1, with a frequency distribution of 9.6% YG 1, 36.7% YG 2, 39.2% YG 3, 12.0% YG 4, and 2.5% YG 5. Mean USDA QG traits were Small for marbling score, A for overall maturity, A55 for lean maturity, and A for skeletal maturity. Mean USDA QG was Select with a frequency distribution of QG of 3.8% Prime, 67.3% Choice, 23.2% Select, and 5.6% lower score. Lower score included dark cutter (1.9%), blood splash (0.1%), and hard bone, which are USDA overall maturity scores of C or older (1.8%). Marbling score distributions were 0.85% Slightly Abundant or greater, 7.63% Moderate, 23.54% Modest, 39.63% Small, 23.62% Slight, and 0.83% Traces or less. Carcasses that were Choice or Select and USDA YG 2 or 3 accounted for 70.7% of the carcasses evaluated. Compared with the previous NBQA, we found a numerical increase in mean USDA YG, USDA QG, adjusted fat thickness, HCW, LM area, and marbling score with an increase in dairy-type carcasses and percentage of carcasses grading USDA Prime and Choice as well as frequency of USDA YG 4 and 5. The findings from this study will be used by all segments of the industry to understand and improve the quality of fed steer and heifer beef that is being produced.

Objective biometric measurements of calf-fed Holstein steers fed in confinement.

Understanding the maximum slaughter size for calf-fed Holstein steers based on hip-height has become a contemporary issue in the beef processing industry. Increased carcass size, in terms of both weight and length, has outpaced the ability of some abattoirs to handle the larger animals. Moreover, some abattoirs have begun rejecting animals that exceed 147.3 cm (58 inches) at the hip, creating a challenge for Holstein cattle feeders. The objective of this study was to quantify the skeletal growth rate of calf-fed Holstein steers fed in confinement. Hip-height of calf-fed Holstein steers ( ≤ 135) was measured every 28 d from 226 to 422 d on feed. Hip-height was a dependent variable modeled via linear regression procedures utilizing days of age and BW as independent variables. Additionally, logistic regression was used to estimate the probability of a steer exceeding a hip-height of 147.3 cm (58 inches) from independent variables of days of age and BW. The linear relationship of BW to hip-height had an adjusted value of 0.7112 (Hip-height, cm = [0.0593 × BW, kg] + 109.00) and on average the calf-fed Holstein steers grew 1.0 cm for each 16.9 kg of BW gain during the finishing phase. The 10%, 50%, and 90% probability of a steer exceeding 147.3 cm (58 inches) of hip-height was achieved at 563, 653, and 743 kg of BW, respectively. The linear relationship of days of age to hip-height had an adjusted value of 0.6687 (Hip-height, cm = [0.0937 × days of age] + 104.4) and the calf-fed Holstein steers grew 1.0 cm for each 10.7 d of age during the finishing phase. The 10%, 50%, and 90% probability of a steer exceeding 147.3 cm (58 inches) of hip-height was estimated to occur at 408, 459, and 510 d of age, respectively. Knowledge of Holstein steer growth rate in relation to BW and age may allow for more accurate sorting to prevent oversized cattle arriving at the abattoir and subsequent discounts or being rejected for slaughter.

Fabrication yields of serially harvested calf-fed Holstein steers fed zilpaterol hydrochloride.

Holstein steers ( = 110) were fed zilpaterol hydrochloride (ZH) for 0 or 20 d before slaughter during a 280-d serial harvest study. Cattle were harvested every 28 d beginning at 254 d on feed (DOF) and concluding at 534 DOF. After slaughter, carcasses were chilled for 48 h and then fabricated into boneless closely trimmed or denuded subprimals, lean trim, trimmable fat, and bone. Inclusion of ZH increased cold side weight (CSW) by 10.3 kg ( < 0.01; 212.7 vs. 202.4 kg [SEM 1.96]) and saleable yield by 10.4 kg ( < 0.01; 131.9 vs. 121.5 kg [SEM 1.16]) in calf-fed Holstein steer carcasses. Additionally, saleable yield as a percentage of CSW increased ( ≤ 0.01) by 2.19% (62.64 vs. 60.45% [SEM 0.22]) for cattle supplemented with ZH. Subprimal weights were heavier ( ≤ 0.05) from cattle that received ZH except for the bottom sirloin ball tip, back ribs, and outside skirt regardless of slaughter endpoint. Yield of top round, bottom round, and knuckle was increased ( ≤ 0.01) following ZH supplementation by 0.37, 0.24, and 0.18%, respectively. Yield of the top sirloin butt, strip loin, and tenderloin was increased ( ≤ 0.01) concurrent with ZH supplementation by 0.18, 0.11, and 0.09%, respectively. Regarding the rib primal, the rib eye roll tended ( = 0.08) to had increased yield (2.80 vs. 2.72% [SEM 0.03]) with ZH supplementation; both back ribs and blade meat exhibited increased ( ≤ 0.04) yields of 0.04%. Relative to the chuck primal, increased ( ≤ 0.03) yields of shoulder clod, pectoral meat, and mock tender were observed (0.13, 0.07, and 0.04%, respectively). Yield changes for subprimal brisket, plate, and flank were limited to increased ( < 0.01) proportion of flank steak and elephant ear (cutaneous trunci), 0.07 and 0.04%, respectively. Feeding duration notably altered ( ≤ 0.01) weights and percentages of all subprimals except the brisket. Saleable yield increased ( ≤ 0.01) by 0.192 kg/d with additional DOF. Moreover, trimmable fat and bone increased ( ≤ 0.01) by 0.146 and 0.050 kg/d, respectively. These data illustrate improved saleable meat yields for calf-fed Holstein steers supplemented with ZH and provide the beef industry knowledge of fabrication yield changes throughout a wide range of harvest endpoints.

National Beef Quality Audit-2016: Transportation, mobility, and harvest-floor assessments of targeted characteristics that affect quality and value of cattle, carcasses, and by-products.

The National Beef Quality Audit-2016 (NBQA-2016) was conducted to assess current transportation, mobility, and quality characteristics of U.S. fed steers and heifers. Data were collected at 17 beef processing facilities between March and November 2016. About 8,000 live cattle were evaluated for transportation and mobility, and about 25,000 carcasses were evaluated on the slaughter floor. Cattle were in transit to the slaughter facility for a mean duration of 2.7 h from a mean distance of 218.5 km using trailers with dimensions ranging from 17.84 m2 to 59.09 m2. Area allotted per animal averaged 1.13 m2 and ranged from 0.85 m2 to 2.28 m2. A total of 96.8% of cattle received a mobility score of 1 (walks easily, no apparent lameness). Identification types (35.1% had multiple) were lot visual tags (61.5%), individual tags (55.0%), electronic tags (16.9%), metal-clip tags (9.2%), bar-coded tags (0.05%), wattles (0.01%), and other (2.6%). Cattle were black-hided (57.8%), Holstein (20.4%), red-hided (10.5%), yellow-hided (4.8%), gray-hided (2.9%), brown-hided (1.3%), and white-hided (1.1%). Unbranded hides were observed on 74.3% of cattle; 18.6% had brands located on the butt, 6.3% on the side, and 1.3% on the shoulder (values exceed 100% due to multiple brands). For hide-on carcasses, 37.7% displayed no mud or manure; specific locations for mud or manure were legs (40.8%), belly (33.0%), tail region (15.5%), side (6.8%), and top-line (3.9%). Cattle without horns represented 83.3% of the sample, and cattle that did have horns measured: < 2.54 cm (5.5%), 2.54 to 12.7 cm (8.3%), and > 12.7 cm (2.9%). Carcasses without bruises represented 61.1% of those sampled, whereas 28.2% had 1, 8.2% had 2, 2.1% had 3, and 0.3% had 4 bruises. Of those carcasses with a bruise, the bruise was located on the loin (29.7%), round (27.8%), chuck (16.4%), rib (14.4%), and brisket/plate/flank (11.6%). Frequencies of offal condemnations were livers (30.8%), lungs (18.2%), viscera (16.3%), hearts (11.1%), heads (2.7%), and tongues (2.0%). Compared to NBQA-2011, fewer cattle were identified for traceability, fewer were black-hided, a greater number were Holstein cattle, more with no brand and no horns, fewer without bruises, more liver, lung, and viscera condemnations, and fewer heads and tongues were condemned. The NBQA remains an influential survey for the U.S. beef industry to provide benchmarks and strategic plans for continued improvement of beef quality and consistency.

National Beef Quality Audit-2016: Transportation, mobility, live cattle, and carcass assessments of targeted producer-related characteristics that affect value of market cows and bulls, their carcasses, and associated by-products.

The National Beef Quality Audit-2016 marks the fourth iteration in a series assessing the quality of live beef and dairy cows and bulls and their carcass counterparts. The objective was to determine the incidence of producer-related defects, and report cattle and carcass traits associated with producer management. Conducted from March through December of 2016, trailers (n = 154), live animals (n = 5,470), hide-on carcasses (n = 5,278), and hide-off hot carcasses (n = 5,510) were surveyed in 18 commercial packing facilities throughout the United States. Cattle were allowed 2.3 m2 of trailer space on average during transit indicating some haulers are adhering to industry handling guidelines for trailer space requirements. Of the mixed gender loads arriving at processing facilities, cows and bulls were not segregated on 64.4% of the trailers surveyed. When assessed for mobility, the greatest majority of cattle surveyed were sound. Since the inception of the quality audit series, beef cows have shown substantial improvements in muscle. Today over 90.0% of dairy cows are too light muscled. The mean body condition score for beef animals was 4.7 and for dairy cows and bulls was 2.6 and 3.3, respectively. Dairy cattle were lighter muscled, yet fatter than the dairy cattle surveyed in 2007. Of cattle surveyed, most did not have horns, nor any visible live animal defects. Unbranded hides were observed on 77.3% of cattle. Carcass bruising was seen on 64.1% of cow carcasses and 42.9% of bull carcasses. However, over half of all bruises were identified to only be minor in severity. Nearly all cattle (98.4%) were free of visible injection-site lesions. Current results suggest improvements have been made in cattle and meat quality in the cow and bull sector. Furthermore, the results provide guidance for continued educational and research efforts for improving market cow and bull beef quality.

Byproduct yields of serially harvested calf-fed Holstein steers fed zilpaterol hydrochloride.

A 2 × 11 factorial treatment structure was applied in a completely randomized experimental design to investigate differences in noncarcass tissue among serially harvested Holstein steers. Steers ( = 110) were randomly assigned to 1 of 2 dietary treatments: a ration supplemented with zilpaterol hydrochloride (ZH) fed at a rate of 8.3 mg/kg DM for 20 d followed by a 3-d withdrawal or a control ration with no ZH included in the diet. Within treatment, steers were assigned to harvest groups of 254, 282, 310, 338, 366, 394, 422, 450, 478, 506, or 534 d on feed (DOF) prior to initiation of the trial. Cattle fed ZH realized an empty BW (EBW) increase ( ≤ 0.03) of 2.8% (644.2 vs. 626.4 kg [SEM 5.4]) and a HCW increase of 5.0% (429.1 vs. 408.4 kg [SEM 4.0]) with a concomitant 12% reduction (45.1 vs. 51.2 kg [SEM 3.1]) in gastrointestinal contents and 2.1 percentage unit increase in dressed carcass yield (62.1 vs. 60.0% [SEM 0.01]). Additionally, ZH supplementation decreased (P ≤ 0.03) the absolute weight of the liver and kidneys by 0.3 and 0.1 kg, respectively. When noncarcass components were expressed on an empty body basis (g/kg EBW), reductions ( ≤ 0.01) in the limbs (18.8 vs. 19.5 g/kg EBW [SEM 0.1]), hide (81.1 vs. 78.1 g/kg EBW [SEM 0.7]), liver (14.2 vs. 13.2 g/kg EBW [SEM 0.2]), kidneys (2.6 vs. 2.3 g/kg EBW [SEM 0.04]), small and large intestines (74.9 vs. 69.6 g/kg EBW [SEM 1.2]), and gastrointestinal tract (119.8 vs. 113.4 g/kg EBW [SEM 1.3]) were observed with ZH supplementation. Additionally, there was a tendency ( = 0.07) for the proportion of total offal to be reduced (253.2 vs. 247.4 g/kg EBW [SEM 2.5]) with ZH supplementation. Empty BW and HCW linearly increased ( < 0.01) by 1.16 and 0.758 kg/d ( < 0.01), respectively, with additional DOF. The weight of the liver and intestines linearly increased ( < 0.01) by 0.007 and 0.133 kg/d ( < 0.01), respectively, with additional DOF. These data indicate the magnitude of change in noncarcass tissues that can be expected when calf-fed Holstein steers are supplemented with ZH.

The effect of days on feed and zilpaterol hydrochloride supplementation on feeding behavior and live growth performance of Holstein steers.

This experiment was designed to study the effect of days on feed (d 225-533) and zilpaterol hydrochloride (ZH) supplementation on Holstein steer ( = 110) performance and feeding behavior as part of a serial slaughter trial. Steers were randomly assigned to 1 of 11 harvest groups with 10 steers ( = 5 control and = 5 ZH; ZH at 8.33 mg/kg diet) harvested each 28 d. Steers were weighed every 28 d (d 225, 253, 281, 309, 337, 365, 393, 421, 449, 477, 505, and 533); individual daily meal consumption data for each steer were recorded using GrowSafe technology. In the pretreatment period, dry matter intake expressed a negative quadratic relationship with days on feed (DOF) {DMI = -5.7120 + (0.08370 x DOF)- (0.00011 x DOF); Adj. = 0.2574; RMSE = 0.25 75; 0.01}. A linear increase in BW ( < 0.01) occurred during the pretreatment 308 d period from 466 to 844 kg, {BWend = 137.61 + (1.4740 x DOF); Adj. = 0.8819; RMSE = 37.06; < 0.01}, whereas ADG and G:F decreased linearly. Dry matter intake per meal exhibited a quadratic relationship over days on feed and peaked ( < 0.01) during d 365 to 392 at 1.065 kg coinciding with the highest numerical daily DMI (11.19 kg). Daily consumption visit duration differed ( < 0.01) during the 308 d period, with a low of 52.29 min (d 337-364) and a high of 55.59 min (d 365-392). Consumption rate peaked at 714 g/min (d 337-364) and exhibited a quadratic relationship to DOF. The difference ( < 0.04) in DMI between control and ZH treated cattle across all 11 harvest groups averaged 0.575 kg. Moreover, ZH treatment resulted in decreased ( 0.01) DMI per meal event of 0.093 kg. Gain to feed tended to improve ( = 0.06) with ZH treatment by 0.017 kg gain per kg feed relative to the control cattle. Daily bunk, consumption, and meal visit durations were influenced by ZH during the 20 d treatment period ( = 0.01); the average difference between control and ZH supplemented cattle over the 308 d trial was 9.09, 8.71, and 11.39 min per d, respectively. The data collected in this trial indicate live growth performance and feeding behavior were impacted by both DOF and ZH supplementation.

Carcass grading characteristics of serially harvested calf-fed Holstein steers fed zilpaterol hydrochloride.

Serial harvests were conducted using Holstein steers ( = 110) fed zilpaterol hydrochloride (ZH) for 0 or 20 d prior to harvest. Steers were harvested in 28-d increments beginning at 254 d on feed (DOF) and ending at 534 DOF. After harvest and a 36-h chill period, carcasses were evaluated using grading methods standard for the United States (USDA), Canada (Canadian Beef Grading Association [CBGA]), and Japan (Japanese Meat Grading Agency [JMGA]). No ZH treatment differences ( = 0.81) were detected for 12th-rib fat thickness; however, additional DOF resulted in a daily linear increase ( < 0.01) of 12th-rib fat thickness by 0.004 cm/d. Longissimus muscle area was increased ( < 0.01) by 8.7 cm with ZH supplementation and linearly increased ( < 0.01) 0.08 cm2/d with additional DOF. Calculated USDA yield grade (YG) decreased ( < 0.01) 0.33 units due to ZH treatment and linearly increased ( < 0.01) 0.009 units/d. Steers supplemented with ZH exhibited increased ( < 0.01) CGBA LM width; however, no difference ( = 0.37) was detected in CGBA LM length. No ZH treatment differences ( = 0.64) were observed for CBGA fat class; however, CGBA fat class linearly increased ( < 0.01) by 0.01 units/d. No ZH differences ( ≥ 0.17) were detected for the CBGA estimated lean percentage or YG equations. Evaluation for JMGA occurs at the sixth and seventh rib interface; LM area was 4.6 cm2 greater ( = 0.02) for cattle supplemented with ZH and linearly increased ( < 0.01) by 0.07 cm2/d with additional DOF. Subcutaneous fat thickness was not different among ZH treatments ( = 0.10) but linearly ( < 0.04) increased ( < 0.01) by 0.005 cm/d with additional DOF using the JMGA grading method. No difference ( ≥ 0.21) was calculated between ZH treatments or DOF for JMGA estimated yield. No ZH treatment differences ( = 0.85) were detected in USDA marbling score; however, marbling linearly increased ( < 0.01) 0.07 units/d. These data illustrate the impact of ZH and increasing DOF on economically important carcass grading outcomes used in the USDA, CBGA, and JMGA grading programs.

Association of pro-melanin concentrating hormone genotype with beef carcass quality and yield.

Beef cattle from 3 independent studies conducted in the Texas Panhandle (Exp. 1: n = 3,906 and Exp. 2: n = 4,000) and southern Idaho (Exp. 3; n = 542) were used to investigate the association of pro-melanin concentrating hormone (PMCH) genotype with beef carcass quality and yield attributes. Tissue samples were collected from each animal to determine which PMCH allele they expressed (Trial 1: AA, 62.60%; AT, 32.05%; and TT, 5.35%; Trial 2: AA, 64.33%; AT, 31.07%; and TT, 4.60%; Trial 3: AA, 65.87%; AT, 29.34%; and TT, 4.80%). Twenty-four hours after harvest, carcass attributes were evaluated for all carcasses and longissimus dorsi steak samples were allocated from a subset of carcasses in Exp. 2 (n = 352; AA, 49.43%; AT, 28.98%; and TT, 21.59%) and each carcass in Exp. 3. Warner-Bratzler shear force measurements were determined for each steak after aging for 7, 14, or 21 d postmortem. Carcasses from Exp. 1 and 2 expressing the AA genotype had greater (P < 0.01) 12th rib subcutaneous (s.c.) fat depth and marbling scores, concurrent with smaller (P < 0.01) LM area than carcasses of AT and TT genotypes. Subsequently, carcasses expressing the AA genotype were represented by a greater (P < 0.02) proportion achieving Prime and Premium Choice quality grades, and a lesser (P < 0.01) proportion grading Select or Standard. In all trials, carcasses of the AA genotype had greater (P < 0.04) calculated yield grades than carcasses of the TT genotype. Carcass composition was associated with PMCH genotype evident by calculated empty body fat differences (P < 0.04) between AA and TT cattle in Exp. 1 and 3, and differences (P < 0.01) among all 3 genotypes in Trial 2. Shear force data on 7-d postmortem aging tended (P = 0.06) to favor cattle of the AA genotype in Exp. 2. However, additional aging to 14 or 21 d minimized any tenderness differences. These data illustrate the potential relationship that may exist among PMCH genotypes and indicators of carcass composition.

The effect of supplementing zilpaterol hydrochloride on feeding performance and carcass characteristics of steers sorted by leptin genotype.

The focus of this investigation was to identify interactions that may exist among alleles of the leptin gene and supplementation of zilpaterol hydrochloride (ZH). Steers (n = 4,246; initial BW = 389.8 ± 8.8 kg) were genotyped and sorted into 1 of 3 leptin genotype (LG) groups (homozygous normal [CC], heterozygous [CT], or homozygous mutant ) from a candidate pool of 7,506 steers. Steers were allocated into 48 pens of which one-half were fed the ß-adrenergic agonist ZH and the balance, a control diet. During the pretreatment period (d 1 to 102), cattle of the TT genotype exhibited increased (P = 0.02) DMI compared to other genotypes and lower G:F than the CC genotype (P = 0.03). Cattle of the CT genotype had lower (P = 0.02) ADG compared to other genotypes for the treatment period. Cattle fed ZH had improved (P < 0.01) ADG and G:F compared to cattle on the control diet for both the treatment and entire study periods (d 1 to 125). For the entire study period, cattle of the TT genotype had greater (P = 0.03) DMI than the CT allele, with CT cattle having the lowest (P < 0.01) ADG and CC cattle having greatest (P < 0.01) G:F of all alleles. Cattle of the TT genotype had greater (P = 0.03) final shrunk weight than the CT allele. Cattle of the TT genotype had lower (P = 0.04) dressed yield compared to CT cattle and greater (P = 0.01) marbling score compared to CC cattle, with a concurrent increase (P < 0.01) in calculated empty body fat (EBF) over all alleles. Cattle fed ZH had greater (P < 0.01) final shrunk weight, HCW, dressed yield, and LM area coupled with reduced (P < 0.01) marbling score, s.c. fat depth, EBF, and calculated USDA yield grade compared to control steers. Carcasses of the TT allele had a greater (P = 0.01) proportion of Choice carcasses than CT or CC alleles and lesser (P = 0.03) proportion of Select carcasses than CC alleles. Additionally, ZH supplemented cattle had fewer (P < 0.01) carcasses grading Premium Choice or better, Choice, and yield grade 3, 4, and 5 with subsequently more (P < 0.01) carcasses grading Select, Standard, and yield grade 1. Differences in live and carcass performance exist among leptin alleles, which may allow for sorting and improved timeliness of fed beef marketing.

Quantification of saleable meat yield using objective measurements captured by video image analysis technology.

Video image analysis (VIA) images from grain-finished beef carcasses [n = 211; of which 63 did not receive zilpaterol hydrochloride (ZIL) and 148 received ZIL before harvest] were analyzed for indicators of muscle and fat to illustrate the ability to improve methodology to predict saleable meat yield of cattle fed and not fed ZIL. Carcasses were processed in large commercial beef processing facilities and were fabricated into standard subprimals, fat, and bone. Images taken by VIA technology were evaluated using computer image analysis software to quantify fat and lean parameters which were subsequently used in multiple-linear regression models to predict percentage of saleable meat yield for each carcass. Prediction models included variables currently quantified by VIA technology such as LM area (LMA), subcutaneous (SC) fat thickness at 75% the length of the LM (SFT75), and intramuscular fat score (IMF). Additional distance and area measures included LM width (LW), LM depth (LD), iliocostalis muscle area (IA), SC fat thickness at 25, 50, and 100% the length of the LM (SFT25, SFT50, SFT100), SC fat area from 25 to 100% the length of the LM (SCFA), and SC fat area adjacent to the 75% length of the LM from the spinous processes (SCFA75). Multiple ratio and product variables were also created from distance and area measures. For carcasses in this investigation, a 6 variable equation (Adj. R(2) = 0.62, MSE = 0.022) was calculated which included coefficients for ZIL treatment, SCFA75, LW, SCFA, SCFA/HCW, and SFT100/HCW. Use of parameters in the U.S. (Adj. R(2) = 0.39, MSE = 0.028) and Canadian [Adj. R(2) = 0.10, root mean square error (MSE) = 0.034] yield grade equations lack the predictability of the newly adapted equations developed for ZIL-fed and non-ZIL-fed cattle. Prediction equations developed in this study indicate that the use of VIA technology to quantify measurements taken at the 12th/13th rib separation could be used to predict saleable meat yield more accurately than those currently in use by U.S. and Canadian grading systems. Improvement in saleable meat yield prediction has the potential to decrease boxed beef variability via more homogeneous classification of carcass fabrication yield.

Feeding performance, carcass characteristics, and tenderness attributes of steers sorted by the Igenity tenderness panel and fed zilpaterol hydrochloride.

Steers (n = 560; initial BW = 420 ± 26 kg) were selected from a pool of 1,040, using the IGENITY Profile DNA test for tenderness, sorted into 1 of 4 tenderness genotype (TG) groups [140 tough (TUF), 140 intermediate (INT), 140 tender (TEND), or 140 mixed (MXD)], and subsequently allocated into 56 pens at random, of which one-half (28 pens, 7 pens from each TG) were supplemented the ß-adrenergic agonist zilpaterol hydrochloride (ZH) and the balance fed a control ration. No TG × ZH interaction (P ≥ 0.15) occurred for any measured trait. Cattle from INT TG had less (P < 0.05) DMI during pretreatment (d 0 to 118) and entire trial (d 0 to 143) periods than other TG. Cattle fed ZH had greater (P < 0.01) ADG and G:F, and decreased (P < 0.01) DMI during the treatment period (d 119 to 143). Cattle from the TEND group had greater (P < 0.01) marbling scores, increased (P < 0.02) calculated USDA yield grades (YG), and more (P < 0.02) calculated empty body fat (EBF) than TUF cattle. Cattle receiving ZH during the treatment period had increased (P < 0.01) HCW, dressed yield, and LM area. Additionally, cattle fed ZH exhibited decreased (P < 0.01) EBF, marbling, KPH, and calculated USDA YG. No difference (P > 0.06) in YG distributions were detected among TG, yet TEND cattle were represented by a greater (P < 0.01) proportion of Prime and premium Choice carcasses. Cattle fed ZH exhibited increased (P < 0.01) frequencies of YG 2 carcasses and fewer (P < 0.01) YG 3, 4, and 5 carcasses concurrent with an increase (P < 0.04) in the percentage of Select carcasses. Longissimus steaks from TUF cattle had greater (P < 0.03) Warner-Bratzler Shear Force (WBSF) values at 7 and 14 d postmortem than steaks from INT or TEND cattle. Furthermore, ZH-fed cattle had increased (P < 0.01) WBSF values for all aging periods compared with control cattle. Frequency of steaks with WBSF values <3.9 kg (certified tender) were less (P < 0.05) for the TUF group. Feeding ZH resulted in fewer longissimus steaks (P < 0.01) with WBSF values <3.0 kg (guaranteed tender) across all aging periods; however, no difference in the frequency of steaks with WBSF values <3.9 kg was found after 21 d of aging. Igenity Profile tenderness scores were correlated (P < 0.05) to carcass finish attributes and WBSF values. Commercially available tenderness panels may have the potential to allow for antemortem sorting of cattle into expected tenderness groupings, which could augment feeding management strategies and ultimately lead to increased marketing value for the beef system.