Superovulatory and endocrinological responses of simmental cows treated either with PMSG or hMG or in combination.

Variations in the plasma concentration of progesterone, total nonconjugated estrogens and luteinizing hormone (LH) were measured in Italian Simmental cows to compare the effects of different superovulation regimens using pregnant mare serum gonadotrophin (PMSG) and human menopausal gonadotrophin (hMG), administered either singly or in combination. The superovulatory response, expressed in terms of the number of recovered and/or transferable ova, was also examined statistically. The cows were divided into four groups, three of which (A, B, C) received different treatments intended to induce superovulation, while the fourth group (D) was used as the control to evaluate endocrinological changes induced by the treatments. Group A cows (n=17) received a single dose of 3000 IU PMSG on Days 11 to 12 of the estrous cycle. Group B cows (n=12) received 1000 IU PMSG on Days 11 to 12, followed by seven sequential injections of decreasing doses of hMG at 8-h intervals, and a total of 297.6 IU of FSH and 297.6 IU of LH. Group C cows (n=24) received nine decreasing injections of hMG and a total of 1575 IU of FSH and 1575 IU of LH, at Days 11 to 12 of estrous cycle. All the treated animals and three controls were administered 20 mg PGF2α on Days 13 to 14 of estrous cycle to induce luteolysis. The experimental results showed a) an intense steroidogenic response to treatment in Groups A and C which, particularly in Group A, could have prejudiced a normal return to reproductive activity; b) a controlled response in Group B; and c) the highest percentage of transferable ova with the combined PMSG and hMG treatment.