The fertility of beef bulls which completed performance test in the Ontario Bull Test Program was measured by classification of success as breeders according to surveys of consignors to test, by classification of satisfaction in surveys of users of tested bulls and by measurement of calf crop percentages and birth dates of progeny relative to herdmates in the Ontario Beef Herd Improvement Program. Consignors classified 3.0% of the 2556 bulls with completed information as unsuccessful breeders. Users rated 61.5% of the 411 bulls with information from the participant survey as very satisfactory and 4.5% as very unsatisfactory. The effects of end of test weight, gain index, backfat and scrotal circumference on calf crop percentage (cows calving relative to cows exposed), percent of calves born in the first 3 wk of the calving season, percent of calves born in the first 12 wk and satisfaction score were generally small and nonsignificant as tested within breed for 122 Angus, 451 Charolais, 632 Hereford, 575 Limousin and 501 Simmental bulls. In general, gain on test and end-of-test measurements were not found to have any association with subsequent fertility of bulls tested. There was no evidence that increased scrotal circumferences were associated with increased measures of productive performance nor that increased fatness, within the range included in the Ontario Bull Test Program, decreased reproductive performance. Key words: Fertility, genetic evaluation, scrotal circumference, backfat
Evaluation and prediction of scrotal circumference in beef bulls
