Abstract
During the last 20 yr, the percentage of Holstein Friesian (HF) cows in the New Zealand (NZ) herd with North American Holstein genetics has increased from 2 to 38%. The use of North American Holstein genetics was increased to broaden the genetic base of the HF population in NZ and to incorporate traits for high productivity. Analysis of the national database and several comparative studies have shown that, in general, North American-derived Holstein cows were heavier, produced more milk volume and protein yield, had lower concentrations of fat and protein, and had poorer fertility and survival than NZ HF cows. Failure to get in calf and maintain a 365-d calving interval appears to be one of the key reasons for the reduced survival of North American Holstein cows within a seasonal dairying system. Analysis of the productive, reproductive, and survival characteristics of North American Holstein and NZ HF cows revealed an average advantage of $NZ 4950 per farm per year in favor of NZ HF cows, which represented approximately a 12% difference in economic farm surplus. If the population of Holstein genetics outside New Zealand is to be used in NZ pastoral dairying systems, these results suggest that fertility traits should be included in the national breeding objectives.
Published Version
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