Progesterone concentration, follicular development and induction of cyclicity in dairy cows receiving intravaginal progesterone inserts

Objectives Were to evaluate progesterone Concentrations after cows had initiated estrous cycles following calving and induction of estrous cycles in postpartum anovular high-producing Holstein dairy cows treated with controlled internal drug releasing (CIDR). In experiment 1 (EXP1). 62 cows that had initiated estrous cycles received a new CIDR (NCIDR) containing 1.38g of progesterone or a 7-d Used autoclaved CIDR (UCIDR) 48h after luteolysis for 7d. Ovaries were examined by ultrasonography. and plasma analyzed for concentrations of progesterone. In experiment 2 (EXP2). 515 cows diagnosed as anestrus were randomly assigned to untreated control, NCIDR or UCIDR for 6d. Plasma was analyzed for concentration of progesterone 12d after CIDR removal to determine ovulation. In EXP1, milk yield and body condition did not influence progesterone concentrations. Concentration of progesterone tended to increase faster (P = 0.10) in cows receiving UCIDR than NCIDR, but both treatments reached a plateau at 90 min. Cows receiving the NCIDR had greater (P = 0.04) concentrations of progesterone during the 7-d treatment. but they were mostly subluteal (<1.0 ng/mL) after d 2. After removal, concentrations of progesterone were greater for NCIDR than UCIDR for the first 45 min, and were similar thereafter. Multiparous cows had lesser (P = 0.004) concentrations than primiparous COWS throughout the study. The pattern of ovarian follicular development was not affected by treatment. In EXP2. induction of onset of estrous cycles increased (P < 0.01) with progesterone treatments, but was similar between NCIDR and UCIDR. Proportion of cows experiencing shorter than typical length estrous Cycles after first Al tended to be greater (P = 0.09) for control cows than those receiving the CIDR, and for cows remaining anestrous than those in which onset of estrous cycles was induced. Pregnancy per Al and pregnancy loss were Similar among treatments. Cows that resumed estrous cyclicity prior to first Al had greater (P = 0.01) pregnancy per Al. Treatment of high-producing Holstein cows that had previously initiated onset of estrous cycles with CIDR resulted in subluteal concentrations of progesterone, but in anestrous high-producing cows increased induction of estrous cycles with no effect on fertility at first insemination. (C) 2008 Elsevier B.V. All rights reserved.