Peripheral plasma progesterone concentration in relation to estrus expression in Sahiwal cows

The present study investigated the changes in peripheral plasma progesterone levels in relation to expression of estrus in Sahiwal cows. Out of a total of five estrus, three were accompanied by overt signs whereas the remaining two were silent estrus. In cows with overt estrus, plasma progesterone concentrations during periestrus, early luteal, midluteal and late luteal phase were 0.40 +/- 0.02, 0.74 +/- 0.10, 1.94 +/- 0.22 and 0.63 +/- 0.16 ng/ml, respectively and the corresponding values in cows with silent estrus being 0.47 +/- 0.03, 0.94 +/- 0.08, 1.39 +/- 0.13 and 0.95 +/- 0.19 ng/ml, respectively. The overall plasma progesterone levels in cows that exhibited overt estrus was 1.23 +/- 0.99 ng/ml as against 1.08 +/- 0.09 ng/ml in silent estrus. It was concluded that progesterone levels were lower (P > 0.05) in cows that exhibited silent estrus compared to overt estrus.