Effects of neutralization of pregnant mares' serum gonadotrophin (PMSG) shortly before or at the preovulatory LH surge in PMSG-superovulated heifers on follicular function and development.
Normally cyclic heifers (n = 34) received 2500 iu pregnant mares' serum gonadotrophin (PMSG) i.m. at day 10 of oestrus, and 15 mg prostaglandin (PG) i.m. at day 12. Thereafter, a monoclonal antibody against PMSG was administered i.v. before (n = 24), at (n = 6) or shortly after (n = 4) the preovulatory LH surge. Peripheral blood concentrations of LH and oestradiol were compared; follicular development was monitored by daily ultrasound scanning; and the numbers of preovulatory-sized follicles and ovulations were counted 96 h after injection of PG following death. Anti-PMSG treatment before the LH surge inhibited the LH surge in 16 heifers (67%). In these heifers, the initial increase in oestradiol concentration upon PMSG stimulation to 167.5 +/- 35.0 pmol l-1 was terminated immediately after anti-PMSG treatment and decreased rapidly to basal values, while the number of preovulatory-sized follicles remained constant until 68 h after PG injection; on average 0.4 +/- 0.1 ovulations were counted. In the remaining eight heifers, five animals showed an immediate, but temporary, 20-60% drop in oestradiol concentration after anti-PMSG treatment. In all eight heifers 25% of the preovulatory-sized follicles ovulated. Treatment with anti-PMSG at or shortly after the LH surge did not affect the pattern of oestradiol concentration, but a significantly higher ovulation rate was observed in the animals treated shortly after the LH surge: 20.3 +/- 2.6 versus 6.3 +/- 2.3 in animals treated at the LH surge, which corresponded to 76% and 24% of the preovulatory-sized follicles monitored shortly before the period of multiple ovulation.(ABSTRACT TRUNCATED AT 250 WORDS)
Department of Herd Health and Reproduction, Faculty of Veterinary Medicine, University of Utrecht, The Netherlands.
P L
PL
Vos
A
A
van der Schans
A A
AA
de Wit
M M
MM
Bevers
A H
AH
Willemse
S J
SJ
Dieleman
D000818:Animals; D000911:Antibodies, Monoclonal / Q000008:administration & dosage; D002417:Cattle; D004958:Estradiol / Q000097:blood; D005260:Female; D006064:Gonadotropins, Equine / Q000276:immunology / Q000494:pharmacology*; D007986:Luteinizing Hormone / Q000097:blood / Q000378:metabolism*; D006080:Ovarian Follicle / Q000502:physiology*; D011863:Radioimmunoassay; D013480:Superovulation / Q000502:physiology*
D000911:Antibodies, Monoclonal; D006064:Gonadotropins, Equine; D004958:Estradiol; D007986:Luteinizing Hormone