Abstract
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 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 per yr for milk and .7, .3, .5, .1, and .8 kg of fat per yr. Corresponding environmental trends were 73, 57, 56, 43, and 40 kg of milk per yr and 2.3, 1.8, 2.1, 1.3, and .7 kg of fat per 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.
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