USE OF LATER RECORDS IN DAIRY SIRE EVALUATION

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Abstract
First, second, and third lactation Ontario Record of Performance (ROP) 305-day milk records were analyzed separately to evaluate 246 Holstein sires. Second and third lactation records were analyzed with and without adjustment for realized selection intensity of each bull’s daughters on the basis of first lactation yield. The magnitude of adjustments for selection was small, but adjusted records gave sire proofs for second and third lactations that had a variance similar to proofs based on first lactation records. Proofs using adjusted records were more highly correlated with first lactation proofs and with percentage survival figures. One bull out of six significantly reranked on the basis of second or third lactation proofs compared to first lactation proofs. There possibly exists a sire by age of daughter interaction, but the size of the interchange does not warrant an immediate change in sire evaluation procedures or artificial insemination organization sire selection programs.

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