Managing Reproduction in Dairy Cattle. II. Response of Cows to Progestogen Treated Herdmates during the Postpartum Period

Abstract

Sixty-eight lactating Holstein cows were handled as one unit but were either fed melengestrol acetate for 14 days or were contemporary controls. Cows that calved in a 21-day period were assigned to a treatment group. Those that calved during the subsequent 21 days served as controls and received no treatment. The alternating assignment was continued for 6 mo. Treated cows were between 14 to 35 days postpartum at the beginning of the feeding period. Data from all cows, combined, showed a decrease in days open (120 to 92) and services per conception (2.7 to 1.5) as compared with their previous year's record. The 34 control cows exhibited estrus over a period which coincided with that of 91% of the treated animals, with a slight delay in occurrence of first estrus. The observations suggest that control cows responded in some way to the treated cows in the early stages of the postpartum period.