Progesterone levels in fat-eree milk of cows during post partum period and early pregnancy diagnosis

Abstract

Progesterone concentrations were measured by radioimmunoassay in fat-free milk samples obtained weekly from 26 primiparous, suckling cows, raised in range conditions. Samples were collected in post partum period up to observation of first signs of estrus. Profiles of progesterone concentrations for early pregnancy diagnosis were also examined on milk samples taken 21 days after artificial insemination. Results showed ovarian ciclicity starting 9.89 weeks post partum in crossed Gir x Caracu cows, with 0.28 nmol/1 progesterone on the day of estrus anti 7.62 nmol/1 21 days post Al. In crossed Nelore x Caracu cows, these results were 12.08 weeks, 0.46 nmol/1 and 9.23 nmol/1, respectively. Ten pregnancies out of 12 diagnosed were confirmed by rectal palpation. There was one case of embryo mortality and three AI were practiced during luteal phase. Estrus observation efficiency was 52.94%, since out of 34 heats identified through hormonal determinations, 18 were detected visually. Variations between crossings did not significantly alter progesterone profiles on day of estrus, nor on 21^th day after AI or as for ovarian activity post partum.