Prediction of carcass traits utilizing growth and feedlot performance

Abstract

An embryo transfer, crossbreeding program utilizing Angus, Brahman and F1 parents was used to create 34 families of 3/4 Angus-1/4 Brahman and 3/4 Brahman-1/4 Angus breeding. Single cross F1 matings were used to create two F2 families. Recipient Brahman x Hereford F1 females of similar age and production were used to standardize environmental and management effects. The individual sires and dams within each breeding were selected to represent a diverse range of phenotypic traits. This data base is unique due to the full-sibling families because the breeding design allows maximum genetic recombination within each family. Large differences between family were planned to distinguish growth performance and carcass characteristics. Data were collected on calves from birth to slaughter (n = 448). Measurements were used to develop prediction equations for carcass traits. Statistical analyses were performed for each carcass trait in two approaches-a prediction equation with covariate animal traits and another with covariates and class variables. This was done to compare significant predictor traits between the two methods. Ear length, gain on grass and gain on feed were the best covariates for predicting carcass traits. Bone length and circumference of the front leg measured at birth displayed a negative relationship with marbling, quality and yield grade When class variables were added to the model, family as a single predictor accounted for 20.8% of yield grade, 46.6% of marbling and 49% of quality grade variation. Family was the best single predictor for ten out of eleven carcass traits. The prediction equations of quality grade, with predictors of family, birth weight, weaning weight and gain on feed, accounted for 55.5% of the variation. Birth and weaning weight were identified with negative regressions to quality grade. Breeders with emphasis on quality grade should avoid heavy birth weight and pursue moderate weaning weight in order to enhance marbling and quality grade. Gain on grass and feed lot gain were positively associated with quality grade. Breeders who select for large frame cattle may be inadvertently selecting against marbling and quality grade. Prediction equations indicated animals which are early maturing and fast-growing ensure optimal marbling and yield grade.