Use of Part Lactation Records in Sire Evaluation

Abstract

Estimates of sire and error components of variance of monthly records, and functions of monthly records and sire components of covariance between functions of monthly records and 10-mo. yield, obtained from the paternal half-sib analysis of monthly milk records of 1526 Holstein cows sired by 145 sires used in artificial insemination, are used to determine the number of part records required to predict the breeding value of a sire for 10-month yield with an accuracy equal to prediction on the basis of a fixed number of 10-mo. records. The estimates of variance components are presented for monthly records, cumulative monthly records, linear functions of sequential monthly records, and cumulative and sequential functions of bimonthly and trimonthly records. The estimates of sire covariance components with 10-mo. yield also are given. The required number of part records of these functions to be as accurate in predicting the breeding value of a bull for 10-mo. milk yield as 20, 30, 40, 50, 100, 150 and 200 10-mo. records are listed in tabular form. Corresponding numbers of fifth test-day records required for equal accuracy are 24, 35, 47, 58, 111, 160 and 205. Only slightly more 7- or 8-mo. records than 10-mo. records are needed for equal accuracy of prediction.