Effects of sixty-day milk yield on postpartum breeding performance in holstein cows.

The relationship between breeding performance and postpartum milk yield was evaluated using data collected in a prospective field project from 33 New York Holstein herds. Herds selected were enrolled in the New York Dairy Herd Improvement Cooperative program and received monthly or biweekly herd health visits from the New York State College of Veterinary Medicine. Factors other than milk yield (e.g., postpartum reproductive disorders, inseminator, housing) that influence breeding performance were controlled in multiple regression analyses. Milk yield had a slight linear antagonistic relationship with conception at first service, services per conception, and days open but not with interval from parturition to first service, interval between first and second services, or interval between second and third services. Services per conception and days open increased by .009 and .6, respectively, for each 100-kg increase in cumulative milk yield during the first 60 d of lactation. Postpartum reproductive disorders, service method (artificial vs. natural), inseminator (farmer vs. technician), and calving interval of the previous lactation had more important relationships than milk yield with measures of breeding performance.