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Milk production records of Ayrshire, Guernsey, Holstein, Jersey, and Brown Swiss in the Northeast were used to estimate trends in transmitting ability of sires and genetic merit of cows. Genetic trends in the transmitting ability of Artificial Insemination sires for the Ayrshire, Guernsey, Holstein, Jersey, and Brown Swiss breeds averaged 23.7, 14.6, 17.9, 18.3, and 34.7 kg per year.
Genetic trends in the AI cow populations averaged 36.1, 25.4, 26.1, 25.0 and 38.1 kg. The genetic trends of cow populations were less than twice the contribution of sires to genetic trends, indicating that estimating genetic trends in cow populations by doubling the trend in transmitting ability of sires is biased upwards.