Production and Stayability Trends in Dairy Cattle

Open Access
Publisher Website
Google Scholar
Abstract
Artificially sired cows with 1,133,804 records were used to estimate genetic and environmental trends in milk fat and stayability for 36, 48, 60, 72 and 84 mo. Sire summaries for production and stayability by the Northeast AI [artificial insemination] Sire Comparison were substituted into the original data to provide estimates of genetic and environmental trends. Ayrshire, Guernsey, Holstein, Jersey and Brown Swiss genetic trends of sires were 17, 7, 23, 11 and 23 per kg/yr for milk and .7, .3, .5, .1 and .8 kg of fat/yr. Corresponding environmental trends were 73, 57, 56, 43 and 40 kg of mild/yr and 2.3, 1.8, 2.1, 1.3 and .7 kg of fat/yr. Jerseys and Brown Swiss had positive genetic trends while Ayrshires, Guernseys and Holsteins had negative genetic trends for stayability. All environmental trends from 1965 for stayability were negative.