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Effects of Early Postpartum Breeding in Dairy Cattle^{1, 2, 3,}

University of Wisconsin, Madison, 53706

Abstract

A major objective of this study was to determine if early postpartum breeding of dairy cows is detrimental to the animals' future reproductive performance. A total of 393 calving intervals of 168 Holstein cows was used in an experiment of factorial design to compare the effects of breeding at the first postpartum estrus with the effects of breeding at the first postpartum estrus after 74 days, and how these effects might be modified by two different levels of nutrition and two genetic levels for milk production. The first postpartum ovulation occurred without observed estrous behavior in 43% of all calving intervals and high nutrition increased the percentage compared to average nutrition. The interval to first postpartum estrus was longer for cows with high genetic potential for milk production than for genetically low producers and longer for cows on high nutrition compared to average nutrition. Fertility at first insemination was lower in cows bred at the first estrus following calving compared to those bred at a later estrus. There was no indication that early breeding had a cumulative detrimental effect on fertility. The average fertility at second, third and fourth inseminations was similar for the two breeding groups. The first-estrus breeding group had fewer "open" days than the later-estrus breeding group but required more inseminations per pregnancy. Cows on high nutrition had more retained placentas than those on average nutrition and similarly had a higher incidence of metritis. Genetically high-producing cows also had more retained placentas than low producers. Significant differences were not found for the occurrence of lost pregnancies, abortions, twinning, dystocias and nonbreeders. Early breeding can be used to shorten the calving interval thereby increasing reproductive efficiency. The percent fertility at first inseminations will be lower than for later breedings.

¹ Research was supported in part by the College of Agricultural and Life Sciences, University of Wisconsin, Madison, as a collaborator under the North Central Region Cooperative Research Project entitled Improvement of Dairy Cattle Through Bleeding—NC-2, conducted in cooperation with the Animal Physiology and Genetics Institute, USDA; and by Public Health Service Training Grant No. 2-T01-HD-00104-09 from the National Institute of Child Health and Human Development.

² From the Department of Meat and Animal Science (Paper No. 627), and Department of Dairy Science and the Laboratory of Genetics (Paper No. 1635).

³ The authors wish to thank Syed Saiduddin, Vincent Sachse, Art Brieske, William Schmiling and Annabelle Allans for collecting and assembling data and also for care and management of experimental animals.