Strategies to Manipulate Progesterone for Improved Ovarian and Fertility Responses in Bovines - A Review

Progesterone (P4) is a steroid hormone primarily secreted by the Corpus luteum (CL). Adequate circulating P4 concentration is essential for establishment and maintenance of pregnancy. Exposure to insufficient circulating level of P4 during the growth of the ovulatory follicle is one of the important factors that affect fertility in high producing animals. P4 has a negative feedback effect on LH secretion and it is believed that sub-luteal phase plasma P4 concentrations result in elevated LH pulse-frequency. There is a linear trend for the number of LH pulses to decrease concurrently with the increase in P4 concentrations as the estrous cycle progresses. These changes in LH pulse frequency are supposed to be associated with alterations in the process of follicular maturation and subsequent embryo survival. Beneficial effects of increased progesterone level during growth of dominant follicle or following AI can be documented from the current literature. P4 concentration during the development of dominant follicle (DF) influences the fertility since the DF of first and second wave use to grow under different P4 environment. Further a slight increase in circulating level of progesterone near the time of artificial insemination (AI) is highly detrimental for fertility. So, a control of follicle and CL development through utilization of various hormonal regimens is routinely done now days to further enhance the reproductive performance of dairy animals. Taking into account above all facts, the present review highlights the progesterone manipulation strategies to improve bovine fertility.