Relationships Between First Lactation, Later Performance, and Length of Herd Life in Holstein-Friesian Cattle

This study included 16,583 mature equivalent DHIA records of 4,819 daughters of 29 A.I. Holstein sires from 1,528 herds.First records were stratified into 11 milk and 9 milk fat groups at 1,000-and 50-1b intervals, respectively, to ascertain the correlation of first-lactation production with subsequent performance and length of herd life.Heifers in higher groups produced significantly (P < .01)more milk and fat in later life than heifers in the lower first record groups.This advantage held true for each individual lactation and for cows all of which had completed at least five records.Heifers in higher first-lactation groups remained in the herd longer than lower producers.Within sire-herd-period of first calving regressions for age at last calving and lactations completed on first-lactation production were 0.0228 nmnths/10 lb milk, 0.0670 months/lb milk fat, 0.0015 lactations/lb milk, and 0.0045 laetations/lb milk fat.Corresponding correlations were +0.254, +0.270, +0.216, and +0.234.Att values were highly significant (P < .01).Paternal half-sib heritability estinmtes for lactations completed and age at last calving were 0.13 and 0.14, respectively.Neither value was statistically significant.