L. L. Benyshek

Biceps femoris and rump fat as additional ultrasound measurements for predicting retail product and trimmable fat in beef carcasses.

One hundred ninety-eight steers of Angus and Hereford breeding were evaluated ultrasonically for fat thickness over the 12-13th rib (UFAT), fat thickness over the rump (URUMP), 12-13th longissimus muscle area (UREA), and depth of the biceps femoris (UROUND) before slaughter. Carcass measurements associated with the USDA yield grade were also obtained. Carcasses were fabricated into closely trimmed (.32 cm fat), boneless subprimals. Regression procedures were used to predict weight and the percentages of retail product and trimmable fat. Final weight (FINALWT) accounted for most of the variation when predicting kilograms of retail product and trimmable fat, with R2 values of .836 and .435, respectively. As single predictors URUMP and UFAT accounted for most of the variation when predicting the percentages of retail product and trimmable fat with R2 values of .244 and .220, respectively. Adding URUMP to equations that included FINALWT, UREA, and UFAT increased R2 values for percentage of retail product from .175 to .318 and for weight of retail product from .847 to .865, whereas the addition of UROUND did not appreciably increase R2 values for the same models. Adding URUMP and UROUND to the model of FINALWT, UREA, and UFAT to predict kilograms and the percentage of trimmable fat increased R2 values from .530 to .610 and from .254 to .360, respectively. Models using live-animal measurements to predict weight and the percentage of retail product gave R2 values equal to models using the actual measurements found in the USDA Yield Grade equation.

Milestones in beef cattle genetic evaluation

National beef cattle genetic evaluation programs have evolved in the United States over the last 35 yr to create important tools that are part of sustainable breeding programs. The history of national beef cattle genetic evaluation programs has lessons to offer the next generation of researchers as new approaches in molecular genetics and decision support are developed. Through a series of complex and intricate pressures from technology and organizational challenges, national cattle evaluation programs continue to grow in importance and impact. Development of enabling technologies and the interface of the disciplines of computer science, numerical methods, statistics, and quantitative genetics have created an example of how academics, government, and industry can work together to create more effective solutions to technical problems. The advent of mixed model procedures was complemented by a series of breakthrough discoveries that made what was previously considered intractable a reality. The creation of modern genetic evaluation procedures has followed a path characterized by a steady and constant approach to identification and solution for each technical problem encountered. At its core, the driving force for the evolution has been the need to constantly improve the accuracy of the predictions of genetic merit for breeding stock, especially young animals. Sensible approaches, such as the principle of economically relevant traits, were developed that created the rules to be followed as the programs grew. However, the current systems are far from complete or perfect. Modern genetic evaluation programs have a long way to go, and a great deal of improvement in the accuracy of prediction is still possible. But the greatest challenge remains: the need to understand that genetic predictions are only parameters for decision support procedures and not an end in themselves.

Applications of an Animal Model in the United States Beef Cattle Industry

Abstract The theory of mixed linear models is finding widespread application in the United States beef cattle industry. At least 15 beef breeds have developed or are in the process of developing national genetic improvement programs based on best linear unbiased prediction procedures and the animal model (or reduced animal model). These 15 breeds represent over 600,000 new registrations each year. The commercial industry is moving rapidly toward acceptance of genetic values on yearling bulls from these programs. Both single trait and multiple trait analyses are conducted depending on breed and traits analyzed. All breeds have developed models for maternally influenced traits. At present, primary emphasis is on growth; however, some breeds have included such traits as calving ease and hip height. Interest is developing among breeders for genetic evaluations of carcass traits. Procedures have been developed for generating genetic values on a daily basis for young animals that are not included in the major analys is due to the time of year their records were obtained. These interim genetic values provide information between major analyses.

Correlated response in reproduction, growth and composition to selection in gilts for extremes in age at puberty and backfat

Abstract Females (n=50) were selected for extremes in early vs. late sexual maturity (12 EP, 13 LP) based on age at first detectable estrus; or, high vs. low backfat (13 HF, 12 LF) based on backfat at the tenth rib adjusted to 105 kg basis. These selected females were then heat checked daily, bred during scheduled breeding periods and allowed to farrow. Reproductive performance was then monitored. More EP than LP females demonstrated a normal cycling pattern. Also, more HF than LF females had normal cycling patterns. Early puberty (EP) female farrowed more litters per sow (P

Selection for low birth weight and high yearling weight in angus beef cattle

Abstract Angus bulls were chosen for either high birth weight (BW), high yearling weight (YW), or low BW, high YW using Expected Progeny Difference (EPD) estimates for proven sires. The high group had birth weight EPD ⩾ 3.0 kg and yearling weight EPD ⩾ 20 kg while the low group had birth weight EPD ⩽ 1.5 kg and yearling weight EPD ⩾ 20 kg. The selected sires were randomly mated to registered Angus cows over 4 years and resulting progeny data were analyzed for BW, weaning weight, post-weaning gain, YW, gestation length and yearling pelvic measurements. High group least squares means (LSM) for BW exceeded the low group by 3.8 kg ( P P > 0.10) were seen for weaning weights, post-weaning gain or yearling weights although actual LSM were in close agreement with sire EPD differences between groups. Yearling weight LSM differed by 6.6 kg compared with a 6.3 kg difference between high and low groups for sire yearling weight EPD means. Pelvic measurements were comparable between groups ( P > 0.10). Results of this study indicate that antagonistic selection for low BW and high growth rate is feasible using EPD. Therefore, the potential exists for increasing the genetic merit for growth with minimal birth problems associated with birth weight.