Journal of Animal Science, Vol 75, Issue 9 2535-2540, Copyright © 1997 by American Society of Animal Science

JOURNAL ARTICLE

Luteinizing hormone and ovarian response of early postpartum Debouillet ewes treated with cyproheptadine and(or) melatonin

R. T. Kridli and D. M. Hallford
Department of Animal and Range Sciences, New Mexico State University, Las Cruces 88003, USA.

Two trials were conducted to evaluate the effects of cyproheptadine (serotonin receptor antagonist, Trial 1) along with administering melatonin (Trial 2) to early postpartum (PP) ewes on LH profiles and follicular development. In Trial 1, 12 mature ewes received either control (CON) or cyproheptadine (CYP) treatments (six ewes/treatment). Beginning on d 5 PP, each ewe received i.v. either 0 (vehicle) or .1 mg of CYP/kg BW twice daily for 5 d. Cyproheptadine tended to stimulate (P < .10) release of LH on d 5 PP (1.3 and .8 +/- .2 ng LH/mL for CYP-treated and CON ewes, respectively) with a similar trend (P < .10) of LH release occurring on d 9. Cyproheptadine also had a positive effect on follicular development, but no luteal activity was detected. In Trial 2, 16 mature ewes received CON, i.v. CYP (.1 mg/kg BW twice daily), i.m. melatonin (MEL, 5 mg x ewe(-1) x d(-1)), or CYP+MEL. Treatments were administered from d 5 through 14 PP. Cyproheptadine tended to increase (P < .10) LH pulsatility on d 5 and 14, but MEL had no effect (P > .20). Follicular development was not affected (P > .40) by CYP or MEL treatments. Neither MEL nor CYP affected progesterone (P > .60). Cyproheptadine tended to increase LH concentration and pulse frequency in early PP ewes, but MEL had no effect on LH profiles. Both treatments failed to initiate ovarian cyclicity in early PP ewes.