Progesterone levels and follicular dynamic during holstein cows postpartum under low tropic conditions in Colombia

Abstract

Thirteen Holstein cows were selected at random and followed, every three days, from the 7th day postpartum until they got pregnant again or day 120 postpartum. Ovarian activity was determined through use of dynamic follicular ultrasounds and the measurement of progesterone levels (RIA). The intervals: delivery first estrus observed, first insemination, first ovulation, first rise in progesterone (>1ng/ml) and first dominant follicle were 67.3, 70.3, 27, 36 and 26 days respectively. The conception rate at first insemination was 54.4%. The patterns of follicular growth were inconsistent during the first 15 days postpartum. Some cows showed inactive ovaries and others showed follicles with diameters over 10mm. 72.6% of the cows had “silent” estrous cycles with a luteal phase shorter than those with estrus behavior (12 vs. 15 days) and lower progesterone concentration at day 15 ( 1.994 vs. 3.3873 ng/ml). Earlier luteal activity (day 3) was observed in pregnant cows than in open cows (day 6). Pregnant cows had higher progesterone levels at day 15 (over 3 ng/ml) while open cows levels went down gradually revealing early luteolysis. Results show that the beginning of postpartum ovarian activity (follicular and hormonal dynamic) is not determined by the first estrous behavior. Use of RIA is a tool to detect where in the cycle is the subject animal when there are no external signs of estrus. The delay in reproductive activity, as evaluated based the wide range of open days and the number of services per pregnancy, is not due to a lack of early ovarian activity. It is necessary to analyze together other factors, such as productive pressure and nutritional problems that could be affecting reproductive efficiency in future investigations.