An enzyme-linked immunoassay of milk progesterone as a diagnostic aid in embryo transfer programs

The objective of this study was to use an enzyme-linked immunosorbent assay to measure progesterone (P(4)) in donor cows as an indicator of reproductive normality and response to superovulatory treatment. Forty-eight Holstein cows were superovulated, and blood and milk samples were collected four times: 1) at initial follicle stimulating hormone treatment, 2) just prior to administration of prostaglandin F(2)-alpha, 3) at estrus and 4) at the time of embryo recovery, 6 to 7 d after estrus. Cows were inseminated twice during estrus. The P(4) profiles (ng/ml) obtained at the four collections, were, respectively, as follows: blood plasma, 2.4, 2.7, 0.2 and 11.2; defatted milk analyzed by radioimmunoassay, 3.7, 3.8, 0.5 and 14.6; preserved whole milk analyzed by ELISA, 6.3, 7.8, 0.7 and 19.1; frozen whole milk analyzed by ELISA, 9.8, 10.0, 0.8 and 21.1. All four assays resulted in the expected pattern of P(4) values for most cows at the four stages sampled. Approximately 10% of the cows had P(4) concentrations outside of the expected range of values. A majority of these cows were aberrant, based upon behavior and palpation of the reproductive organs. The rapidly available P(4) results from the ELISA were useful in making appropriate decisions regarding management of donor cows.