LUTEINIZING-HORMONE AND OVARIAN RESPONSES OF EARLY POSTPARTUM DEBOUILLET EWES TREATED WITH CYPROHEPTADINE AND(OR) MELATONIN

Two trials were conducted to evaluate the effects of cyproheptadine (s erotonin receptor antagonist, Trial 1) along with administering melato nin (Trial 2) to early postpartum (PP) ewes on LH profiles and follicu lar development. In Trial 1, 12 mature ewes received either control(CO N) 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/k g 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 a nd CON ewes, respectively) with a similar trend (P < .10) of LH releas e occurring on d 9. Cyproheptadine also had a positive effect on folli cular 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, me latonin (MEL, 5 mg.ewe(-1).d(-1)), or CYP+MEL. Treatments were adminis tered 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). Fol licular development was not affected (P > .40) by CYP or MEL treatment s. Neither MEL nor CYP affected progesterone (P > .60). Cyproheptadine tended to increase LH concentration and pulse frequency in early PP e wes, but MEL had no effect on LH profiles. Both treatments failed to i nitiate ovarian cyclicity in early PP ewes.