Effect Of A Non-Steroidal Aromatase Inhibitor On Ovarian Function And Synchronicity Of Estrus In Ewes At Subtropics

Effects of non-steroidal aromatase inhibitor letrozole on ovarian function in ewe were investigated through testing the hypothesis that letrozole will arrest the growth of dominant follicles, resulting in the emergence of a new follicular wave at a predictable post-treatment interval. Treatment ewes (n = 10) were treated using an intravaginal sponge (regardless of the stage of estrus) containing 7.5 mg letrozole for five days followed by prostaglandin injection. The control group (n = 10) was treated with gonadotropin prostaglandin gonadotropin (GPG) protocol for ovarian synchronization. Ovarian structures were daily monitored with trans rectal ultrasonography concomitant with blood sampling. Commercial enzyme-linked immunosorbent assay Kits assigned steroid concentration of estradiol, testosterone and progesterone. Some biochemical parameters including blood glucose, total proteins, lipid profiles were measured as a preliminary screening for the effect of applied letrozole treatment on ewes general health condition. Treatment with letrozole decreased serum concentrations of estradiol during sponge insert in the vagina while its concentration increased following removal correlated with the number of ovulatory follicles. On the other hand, the concentration of  Progesterone increased correlated with increased number and diameter of corpora lutea resulting from increased diameter and number of ovulatory follicles. The onset of estrus was about 54.00 ± 0.40 hrs. After sponge removal and continued for 25.17 ±  0.24 hrs. Ovulation was synchronous and occurred at 78.70 ±  0.21 hrs after sponge removal. There was no effect of letrozole treatment on measured metabolic parameters. We concluded that letrozole proved to have potential as a non-steroidal treatment for controlling ovarian function and onset of estrus in the ewe.