BREED AVERAGES AND AGE OF DAM ADJUSTMENT FACTORS FOR BIRTH WEIGHT OF BEEF CATTLE

A subset of birth weight records consisting of 191 535 calves, from 7021 herd-years with fewer than 50% estimated weights, tested during 1971 through 1980 was selected from the data files of the Federal-Provincial Record of Performance program for beef cattle to estimate breed averages and age of dam adjustment factors. The main effects included herd-years, breed of sire, breed of dam, sex of calf and age of dam. The interaction effects for breed of sire by sex of calf on birth weight were significant (P < 0.01) and the estimated differences for 22 breeds of sire expressed as deviations from the Hereford breed ranged from − 4.05 to 6.27 kg for male calves and from − 3.70 to 6.20 kg for female calves. The effects of breed of dam, sex of calf, age of dam and all the two-way interactions were significant at P < 0.01, while the three-way interaction was significant at P < 0.05. Additive age of dam adjustment factors within sex of calf were derived for 12 breeds of dam. The general age of dam effects averaged ...