Plasma progesterone analysis by a time-resolved fluorescent antibody test to monitor estrous cycles in goats.

ABSTRACT

The objective of the current study was to evaluate whether blood plasma progesterone (P(4)) measurements with a time-resolved fluorescent antibody test (TR-FAT) kit designed for humans was applicable for goats. The first experiment was designed to verify whether the concentrations of P(4) measured by TR-FAT can be used to monitor the estrous and ovarian activity in goats (n = 14). Blood samples (322) were collected, and the ovaries were scanned using ultrasonography. The second experiment was carried out on 4 goats (60 samples) and designed to compare the TR-FAT with radioimmunoassay (RIA). The time interval between the lowest concentrations of P(4) assayed by TR-FAT was 21 +/- 0.3 days and did not differ significantly from the length of the interestrous interval. The highest concentrations of P(4) were confirmed by detection of corpus luteum. During estrus, the mean concentration did not differ significantly between both methods. Significant differences were present during the luteal phases; however, the profiles of P(4) assayed by both methods followed a similar pattern. Regression analysis showed a correlation between the 2 methods (r = 0.98; r(2) = 0.96; P < 0.0001). The Bland-Altman plot showed that all averages were within the 95% limits of agreement; however, the differences between both methods tend to be greater as the average increases. The results demonstrated that the TR-FAT method can be applied to monitor estrous cycles in goats through measurements of plasma P(4) concentrations. Moreover, not only does the TR-FAT meet the requirements for safety, but it is also a method of high throughput, rapidity, and simplicity.