Abstract
Progesterone enzyme immunoassay kit using progesterone-3-CMO-β-galacto-sidase (P-β-Gal) as a tracer and polystyrene bead coated with rabbit γ-globulin raised against 11α-OH-progesterone-hemisuccina te-BSA as a solid phase (Teikoku Hormone Mfg. Co. Ltd., Tokyo) was applied for direct measurement of progesterone in defatted milk from cows. Time required for whole procedure was 3 hours in maximum. The least detectable amount of progesterone in this kit was 11 pg./tube (0.225 ng/ml). Intra-assay coefficients of variation (CVs) were 5.9-9.2% and inter-assay CVs were 7.3-13.1%. Recovery rates of progesterone added to defatted milk were 80.0-109.4% (mean = 92.6%). There was highly significant correlation (Y=0.959X+0.054, r=0.939, P<0.01, n=40) between progesterone levels measured by P-EIA kit and by already established double antibody EIA. A progesterone level in defatted milk 1.0 ng/ml or higher indicates the presence of the functional corpus luteum. Accuracy of pregnancy diagnosis based on progesterone levels, 1.0 ng/ml or higher for pregnant cows and lower than 1.0 ng/ml for not pregnant cases, in defatted milk measured by P-EIA kit 21-24 days after AI was 86.2% (81/94) for positive cases and 100% (39/39) for negative cases. These results indicate that the P-EIA kit is the reliable and practical tool for measuring progesterone levels in defatted milk and for the assessment of presence of the corpus luteum.
