Genetic Means and Trends of Dairy Sires in the United States

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Abstract
Nearly 2 million 1st-lactation records with predicted differences for sires were used to compare subpopulations of regions, stages, progeny from artificial insemination and natural service and registered and grade cows. Annual breed trends in sire predicted differences for milk for 1st-lactation cows calving 1973-1978 ranged from 15 kg for Milking Shorthorn to 32 kg for Holstein. Range in merit of sires of cows among the 4 regions was 69 kg of milk for Holsteins and higher in 4 of 5 other breeds in 1978. State differences were large; the range in predicted difference milk for Holsteins was 137 kg among 10 states having the most data. States where Holstein sires of higher merit have been used employed artificial insemination more and have a larger proportion of grade cows. Artificial-insemination sires in all breeds were at least $45 higher than natural-service sires in expected gross income from milk sales/lactation. Predicted differences for sires of grade cows were higher than for sires of registered cows, which suggests that breeders of registered cows are sacrificing production to select for other traits. Coefficients of regression of lactation yield on sire predicted difference within herds were 1.02 and higher, providing evidence of the value of selecting sires on predicted difference.

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