Abstract

Melengestrol acetate (MGA®) and prostaglandin F2α(PG; Lutalyse®) were used to synchronize estrus in 757 yearling, virgin, beef heifers on six commercial ranches. Heifers were inseminated artificially (AI) 12 h after first detected estrus; those not detected in estrus were time-inseminated 72 h post-PG injection. Heifers detected in estrus by 72 h had higher AI and overall pregnancy rates than their counterparts not detected in estrus. Heifers with serum progesterone>1 ng/ml at PG administration were generally more fertile than those with progesterone/ml. Of the heifers not detected in estrus and with low progesterone (/ml), 24% still conceived to the timed insemination at 72 h, but only 73% became pregnant during the entire breeding period. Overall AI conception rate, based on estrous detection and timed insemination, was 49% and varied from 24% to 69% among the six ranches. Heifers exhibiting estrus and with elevated (>1 ng/ml) serum progesterone showed acceptable pregnancy rates (63% AI and 94% overall).

Keywords: Cattlemen's Day, 1993, Kansas Agricultural Experiment Station contribution, no. 93-318-S, Report of progress (Kansas State University. Agricultural Experiment Station and Cooperative Extension Service), 678, Beef, Melengestrol acetate, Prostaglandin, Beef heifers, Fertility, Estrus, Progesterone

How to Cite:

Peters, C., Larson, R. L. & Corah, L., (1993) “Progesterone concentrations, estrous response, and fertility in beef heifers after estrous synchronization using melengestrol acetate® and prostaglandin F2α”, Kansas Agricultural Experiment Station Research Reports 1(1), 90-92. doi: https://doi.org/10.4148/2378-5977.2103