Lifetime Productivity of Straightbred and F Cows of a Five-Breed Diallel

Abstract

Weaning records of 2,010 calves born to straightbred and F1 cows of a diallel of Angus, Brahman, Hereford, Holstein and Jersey were used to characterize these breeds and crosses (reciprocals pooled) for lifetime productivity. Cows were culled only when they remained non-pregnant for 18 consecutive months. Females were mated by artificial insemination to contemporary males. Upon completion of three inter se parturitions, cows were mated randomly by natural service to Charolais or Red Poll bulls. Calves were weaned at approximately 7 mo of age. Male calves were not castrated. Weaning weights were adjusted for sire breed, season, year, age of calf and sex of calf using least squares constants from a preliminary analysis of the data. Cumulative number of calves and calf weaning weight per cow were analyzed for each age of dam (4 to 12 yr) using a one-way analysis of variance with breed-type of cow as the independent variable. In addition, cumulative adjusted calf weaning weight per year of herd life of each cow was analyzed using the breed-type of cow model. Specific and average heterotic effects were estimated using linear functions of appropriate straightbred and crossbred means. Among straightbreds, Angus weaned the most calves (6.65) with the heaviest total weight (1,237 kg) by 12 yr of age; Brahman produced the fewest calves (3.13), and Jersey produced the lightest cumulative weight (556 kg). Angus produced the most calf weaning weight per year of herd life and Brahman produced the least. Crossbred cows produced 1.63 more (P < .01) calves and 397 kg more (P < .01) calf weaning weight than straightbred cows by 12 yr of age. Average heterosis for cumulative weaning weight per year of calf was 30.7 kg (P < .01).