ALTERNATIVE PROGENY TESTING PROGRAMS FOR WEANING WEIGHT AND EASE OF CALVING IN BEEF CATTLE

Progeny test programs were characterized by numbers of young bulls, successful matings (conceptions) per young bull, herds in which each young sire was used, proven bulls used as reference sires and herd size. Matings to reference sires were calculated as a percentage of the number of young sire matings. Designs were simulated and mixed-model equations formed and added to equations obtained from the Canadian ROP program for years 1971–1978. The average standard error of prediction (SEP) of young bulls was used for comparing designs. Increasing matings per young sire decreased SEP curvilinearly. The curvilinearity was greater when either herd size or herds per young sire was low. Increasing herd size and herds per young sire improved connectedness between sires and reduced SEP. Number of young sires affected SEP only when fewer than 10 bulls were sampled. Number of young sire matings were more important in reducing SEP than percent reference sire matings. If number of young sire matings was adequate to achieve a desired level of SEP, 10% reference sire matings were sufficient. The number of reference sires used did not affect SEP. Design patterns affected SEP of weaning weight (h2 = 0.25) and calving ease (h2 = 0.10) similarly. SEP was not affected by the number of proven sires in a breed (Maine Anjou, 133 sires or Blonde d’Aquitaine, 39 sires) or by the connectedness between proven sires.