On-Farm Milk Progesterone Tests

Results from milk progesterone assays can provide ovarian information, making it possible to monitor the reproductive status of the cow. Rapid, simple, and accurate on-farm milk progesterone tests are commercially available. Procedures for performing milk progesterone tests are specific for each test; however, principles of testing are similar. On-farm tests are designed to determine the relative progesterone concentration ("high" or "low") rather than obtaining a precise concentration. Evaluation of results is based on either a color or agglutination reaction with comparison to known standards. Potential uses of progesterone testing in a reproductive management program are: 1) identifying errors in detection of estrus, 2) predicting time of estrus, 3) assisting in pregnancy diagnosis, 4) differentiating types of ovarian cysts, and 5) evaluating response to endocrine therapy.