Development and Evaluation of a Method of Hormonal Treatment to Increase Fertility in Dairy Cows

Abstract

The objectives were: 1) to develop a practical method for improving conception rates of dairy cows by administering progesterone during the critical period of the luteal phase prior to first insemination, 2) to determine which cows respond best to such a progesterone treatment, and 3) to determine physiological changes that are associated with this treatment. Experiment 1, conducted in the US and Israel, tested three treatment protocols. Holstein cows: 1) served as controls, 2) received two injections of prostaglanding F2a (PGF) 14 days apart, or 3) received two PGF injections and were inserted with a progesterone releasing intravaginal device (PRID) for 6 days beginning 9 days after the first injection of PGF. Fertility was positively related to plasma progesterone concentations prior to the second PGF injection, but PRID treatment did not improve fertility in cows with low progesterone. Cows in synchronized estrus 2-8 days after the second injection of PGF had higher fertility and better reproductive performance than non-synchronized cows. Experiment 3, conducted in Israel, involved three studies that assessed effect of PRID treatment on: 1) progesterone concentration in ovarian tissue and uterine tissue and fluids, 2) changes in systemic LH and estradiol, and 3) development and function of dominant follicles. Treatment with PRID increased progesterone in uterine tissue and fluid exclusive of effects on systemic concentrations. Low progesterone resulted in persistent follicles that exceeded normal size and produced excessive estrogen. Experiment 4, conducted in the US, evaluated influence of endogenous progesterone on embryo development. Cows were given two injections of PGF 14 days apart and single embryos were recovered 7 days after estrus. Among cyclic cows, there was a linear relationship between progesterone concentration and percentage of cows from which an embryo was recovered. Overall these experiments show that systemic progesterone concentrations affect fertility in high-producing dairy cows through effects on follicular development and embryo survival