Trends in Breeding Value and Production

Abstract

Over 3.6 million first lactation records by cows on official test were studied. About 15.5 yr of data for six dairy breeds were represented. Sire breeding value was twice the sire's Modified Contemporary Deviation from the USDA Sire Summary. Sire breeding values for milk and fat of cows calving in the later years increased for all breeds but Ayrshires, which were essentially static. Annual trends in sire breeding values for kg milk in the breeds over 1968 to 1975 were Ayrshire 7, Guernsey 26, Holstein 38, Jersey 65, Brown Swiss 80, and Milking Shorthorn 58. The corresponding trends of estimated breeding values of first-lactation cows were 16, 20, 21, 34, 45, and 38 kg.