Phenotypic Trends in Herdlife of Dairy Cows in the United States

Abstract

Herdlife through eighth parity of dairy cows in the United States was studied with lactation records from 87,756 Ayrshires, 108,733 Brown Swiss, 331,497 Guernseys, 294,195 Holsteins (sample of every 15th herd), and 421,911 Jerseys that first calved after 1965. Only cows not sold for dairy purposes and from herds that provided an opportunity for subsequent calving were included. Average survival rates were about 78% to second, 57% to third, 40% to fourth, 27% to fifth, 17% to sixth, 10% to seventh, and 5% to eighth parities. Survival rates were higher for registered cows than for grades for all parities and breeds. Average number of parities was 3.3 for Ayrshires, 3.4 for Brown Swiss, 3.1 for Guernseys, 3.4 for Holsteins, and 3.5 for Jerseys; average productive herdlife was 37.7, 39.4, 34.6, 38.4, and 39.4 mo. Distribution of parities within herds was similar for all breeds: 31% first lactations, 23% second, 17% third, 12% fourth, 8% fifth, 5% sixth, 3% seventh, and 1% eighth. Jerseys had upward trends for survival rate and herdlife over time; other breeds generally had downward trends. Because data from only the first eight parities