Sire-Sex Interactions of Economic Traits in Beef Cattle

The objective of this study was to evaluate the genetic-environment interactions for certain live and carcass traits in beef cattle by determining if sires rank the same in growth and carcass traits with respect to their bull and steer progeny. The differences between bulls and steers represent a different physiological environment in which genotypes develop. An analysis of sire and sex differences and their interaction provides an estimate of one type of genetic-environment interaction for beef performance traits. The data used in this study were collected during 1963, 1964, and 1965.One hundred fifty-two male calves from the University of Nebraska Angus beef breeding herd were used in this experiment.One or two bull calves from each sire were designated as herd sire prospects and were fed as bulls. At weaning time all other calves were allotted at random to two slaughter-sex groups. The calves to be fed as steers were castrated within a few days after weaning. The two slaughter dates used were approximately forty-two days apart and were designated as early and late slaughter groups. Two slaughter dates were used to evaluate the effect of the length of the feeding period on the traits studied.Final selection of herd sires was made from the group of herd sire prospects near the end of the feeding period.The non-selected bulls among the herd sire prospects were randomly allotted to one of the bull slaughter groups.The progeny of 15 sires were represented in the study.Four of the 15 sires were represented in two of the three years (1964 and 1965) but all are treated as different sires each year in the analysis of variance. Each sire had both steer and bull progeny groups. Advisors: Robert M. Koch and Vincent H. Arthau