Ovarian responses in gonadotropin-treated calves
Lineweaer, J.A.; Hafez, E.S.
American Journal of Veterinary Research 31(12): 2157-2166
1970
ISSN/ISBN: 0002-9645 PMID: 5531731 Document Number: 26202
Groups of four heifer calves (45-90 days old) were injected i/m with 2, 000 i.u. pregnant mare serum gonadotrophin (PMSG) and 120 hours later with 2, 000, 5, 000 or 10, 000 i.u. human chprionic gonadotrophin (HCG). After artificial insemination 12 hours later and at 12-hourly intervals for two days the percentages of ovulation of follicles greater than 5 mm in diameter were 30, 49 and 60, respectively. Calves injected with 5, 000 i.u. HCG 72, 120 or 168 hours after 2, 000 i.u. PMSG had similar follicle-size distributions, but the percentage ovulations were 0.5, 49 and 52, respectively. Animals injected once, or on five successive days, with 50 mg progesterone, followed 72 hours later by 2, 000 i.u. PMSG and then 5, 000 i.u. HCG 120 hours later, or injected with 2, 000 i.u. PMSG and 24 hours later with 100 micro g oestradiol cypionate showed an increased number of follicles, with fewer smaller than 5 mm in diameter, and a decreased ovulation rate. Calves with experimentally induced corpora lutea had lower ovulation rates than calves with no previous corpora lutea. Ovulation began 24 hours after HCG administration in calves given gonadotrophins and continued for at least 48 hours. Ovulation rates were 12, 54 and 68% 24, 48 and 72 hours after HCG injection. Egg recovery was highest (20%) in calves with ovarian volumes between 25 and 74 ml.