title: Activation of quiescent ovaries by administration of PMSG after LH-RH analogue treatment in heifers.
abstract: The effect of pregnant mare serum gonadotrophin (PMSG) treatment on activation of quiescent ovaries was examined in heifers. Groups of thirteen, twenty and twelve heifers which showed ovulation within 2 d and corpus luteum (CL) development after injection with a luteinizing hormone releasing hormone analogue (LH-RH-A) were supplementally injected with 500 IU of PMSG (Group I); 500 IU of PMSG and 500 mug of Prostaglandin F(2alpha) analogue (PGF(2alpha)-A; Group II); and 500 mug of PGF(2alpha)-A (Group III) on Day 6 after the injection of 200 mug of LH-RH-A (Day 0), respectively. Estrus appeared in 33.3 to 45.0% of the heifers of the respective groups after the treatment. Ovulation occurred at a significantly (P<0.01) higher rate in Groups I (100%) and II (90.0%) than in Group III (41.7%). The ovarian cyclic activity was initiated in all the heifers that ovulated. Plasma progesterone levels decreased significantly (P<0.05) to about 1 ng/ml on Day 8 and Day 7 in Group I and Groups II and III, respectively. Plasma estradiol-17beta (E(z)) levels increased significantly (P<0.05), reaching a peak on Days 7 to 7.5 in Groups I and II but not in Group III. It is concluded that PMSG treatment stimulates maturation and E(z) secretion of a follicle, thus promoting ovulation and the onset of ovarian cyclic activity.
authors.affiliation: Third Research Division National Institute of Animal Health Tsukuba, Ibaraki, 305 Japan.
authors.forename: H
authors.initials: H
authors.lastname: Kamomae
authors.forename: Y
authors.initials: Y
authors.lastname: Kaneda
authors.forename: I
authors.initials: I
authors.lastname: Domeki
authors.forename: K
authors.initials: K
authors.lastname: Nishikata
authors.forename: M
authors.initials: M
authors.lastname: Ohtake
authors.forename: T
authors.initials: T
authors.lastname: Nakahara