V. A.B. progeny in A.B. herds

Abstract

Results from a questionnaire sent to users of the A.B. service provided by Livestock Improvement Associations in 1973 showed that only 84% of the heifer calves reared as potential replacements were A.B. progeny, another 10% of the calves were progeny of a herd sire, and the remaining 6% were the progeny of a sire used with maiden heifers. Only 47% of herd owners reared only A.B. progeny and another 34% reared at least one heifer calf produced by a 2-year-old heifer; the latter was more common in large herds. Among herd owners rearing at least one A.B. heifer calf, 69% endeavoured to obtain and rear only A.B. progeny. The difference between the 69% of herd owners wanting and the 47% of herd owners rearing only A.B. progeny may be the result of patterns of A.B. usage. One reason could be the practice of rearing only heifer calves born during the first 5 weeks of the calving programme. Although the mean range in the age of heifer calves was 6.9 weeks, 33% of herd owners using A.B. had calves with age ranges of 5 weeks or less. The reduced rate of genetic improvement resulting from rearing other than A.B. progeny is discussed.