Abstract
Thirteen beef cows were superovulated using 4, 000 i.u. of pregnant mare serum gonadotrophin (PMSG) on days 9 to 14 of the estrous cycle, followed by two injections of 500 pg prostaglandin F2α analogue (PGF2<2α> 48 and 55 hrs later. Seven of them were injected intramuscularly with bovine anti-PMSG serum 12 hrs after the first signs of estrus. The remaining 6 cows were served as controls and received no antiserum. Peripheral blood concentrations of progesterone (P) and estradiol-17β (E2) were compared in relation to the superovulatory responses. The injection of anti-PMSG serum did not significantly affect the numbers of the corpora lutea (CL), the anovulatory follicles and the transferable embryos at 7 to 8 days after superovulatory estrus, but increased the ratio of embryos classified as excellent or good quality. Although the plasma P concentration showed no significant differences between the anti-PMSG-treated and control cows, the plasma E2 concentration displayed a characteristic difference, suppressing the second E2 peak in the anti-PMSG-treated cows. It is concluded that the use of bovine anti-PMSG serum for PMSG/PGF2α-treated cows at 12 hrs after the beginning of the estrus improves the quality of embryos recovered, probably due to inhibition of high estrogenic environment following ovulation.
