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Interbreed Matings in Dairy Cattle. V. Reproductive Performance¹

Animal Husbandry Research Division, ARS, USDA, Beltsville, Maryland 20705

ABSTRACT

The reproductive performance of females of all possible two-breed combinations among Ayrshires, Brown Swiss, and Holsteins was evaluated in comparison to contemporary purebreds. Traits for Parities 1 to 4 were days from first breeding to conception and the proportion pregnant by 95, 120, and 145 days postpartum (cows) or these intervals following 380 days after birth (heifers). These measures plus time from calving to first estrus and days open in lactation were studied in Parities 2 to 4. Parity effects were significant (P < .01) for all measures, but differences among purebreds for maternal effects and general combining ability were not significant. Although the levels of heterosis for some reproductive measures were equal to or higher than yield traits, they were not statistically significant. The average percentages of heterosis for the crosses were –4.1, 9.3, 4.8, –0.7, 13.9, and 7.3 for calving to first estrus, first breeding to conception, days open, and per cent pregnant by 95, 120, and 145 days. The total percentage which conceived favored the crossbreds (90 versus 93%). Superiority in over-all reproductive performance of one-half Holstein crosses may be enough to offset lower yields and to make their net economic value higher than Holsteins.

¹ This work was part of the Southern Regional Dairy Cattle Breeding Project, S-49 (Genetic Methods of Improving Dairy Cattle for the South).

² Present address, Department of Animal Science, Cornell University, Ithaca, New York 14850.

³ Agricultural Research Service, Biometrical Services, Beltsville, Maryland.

⁴ Agricultural Research Service, Western Regional Laboratory, Albany, California.

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