Use of Milk Progesterone and Prostaglandin F₂ in a Scheduled Artificial Insemination Program

¹ Department of Animal Sciences and Industry, Kansas State University, Manhattan 66506-0201

We tested the efficacy of monitoring progesterone in dairy cows using a commercially available milk progesterone test as a determinant for administration of PGF₂, to induce estrus in cows before first AI. Holstein cows milked twice daily were assigned randomly for AI at their first estrus after d 42 postpartum (control) or to receive PGF₂, after a milk progesterone test. Milk progesterone was assessed in samples from the Monday morning milking in both groups of cows, but only those in the treatment received PGF₂, when milk progesterone tested high. Blood was collected before injection of PGF₂, on Monday afternoon to verify retrospectively the accuracy of the milk progesterone test. Agreement of serum concentrations of progesterone was 87% for high milk progesterone tests and 63% for low tests. Use of milk progesterone plus PGF₂, reduced days to first AI, calving intervals, rate of reproductive culling, and cost per pregnancy and increased the proportion of cows inseminated within 21 d of the beginning of breeding. As a management tool in an AI program, PGF₂ use is warranted and cost effective. However, the milk progesterone test is not justifiable unless the cost is significantly lower than the cost of a weekly injection of PGF₂.

Key Words: prostaglandin F₂ • progesterone • estrus • artificial insemination

Submitted on August 19, 1993
Accepted on January 24, 1994