Live and carcass production traits for progeny of purebred sires in comparison with the clone of a USDA Prime Yield Grade One carcass
Sperber, Jessica Lynn
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A two-part study was conducted to determine the sire success of “Alpha”, a bull born in 2012 through somatic cell nuclear transfer from a carcass that graded USDA Prime Yield Grade 1 (P1). The first part of the study used a terminal sire system to compare Alpha progeny with progeny of three purebred (Angus, Charolais, Simmental) reference sires, selected for outstanding terminal sire production traits. Live production traits included: weaning weight, morbidity, mortality, and days on feed; carcass traits included: liver and lung abnormalities, individual quality and yield grade parameters, and total carcass value and value per cwt. A completely randomized experimental design structure was used. Data were analyzed using a mixed model with sire as the fixed effect and harvest date, sex, and pen as random effects. Next to Charolais-sired cattle, Alpha-sired heifers and steers had the largest (P < 0.01) longissimus muscle area and lowest yield grade, and Alpha-sired steers had the lowest (P < 0.01) measure of fat thickness. Economically, Alpha-sired steers were worth the greatest (P < 0.01) value per cwt, and Alpha-sired heifers were numerically worth the greatest value per cwt. The progeny produced from this terminal sire study were used in the second part of the study to determine the proficiency and value in sorting cattle into end-weight marketing groups upon feedyard arrival. Heifers and steers were sorted five-ways per sex (10 pens total) using a proprietary cattle classification and sorting system, combining feedlot arrival weight (kg), hip height (cm), and hip length (cm) into an equation. From there, the database projected appropriate number of days on feed by estimating incoming empty body fat, adjusted finished body weight, dry matter intake, and average daily gain. Five-way sort pens differed in targeted harvest date and days on feed. A completely randomized experimental design structure was used. Data were analyzed using a mixed model with sort pen as the fixed effect, and linear and quadratic contrasts were generated to asses trends by sort pen. In general, live traits that differed (P < 0.01) for heifers followed a curvilinear trend when sorted by pen including: feedlot arrival weight, adjusted finished body weight, incoming empty body fat(%), and average daily gain. Live traits that differed (P < 0.01) for steers followed a linear trend of significance when sorted by pen including: feedlot arrival weight, adjusted finished body weight, incoming and outgoing empty body fat(%), and estimated dry matter intake. Heifer and steer carcass traits differed by pen for hot carcass weight (P < 0.01) and total carcass value (P < 0.01), suggesting the sort system was successful in sorting cattle upon feedyard arrival to improve uniformity, ensure the likelihood of achieving target empty body fat, and maximizing dollar value of individual animals. Many differences were observed in these data for carcass traits when analyzed by sire with limited differences observed when analyzed by pen, suggesting the sorting system was effective in grouping cattle upon feedyard arrival into uniform end-market harvest groups.