OVULATION RATE IN EWES AFTER SINGLE ORAL GLUCOGENIC DOSAGE DURING A RAM-INDUCED FOLLICULAR PHASE

A 2-factor factorial array with three replicates (N = 280) was used to simultaneously assess the effects on ovulation rate of two alternativ e doses of medroxy-progesterone acetate (MPA) (10 or 60 mg), applied d uring a 6-day priming period, and the effect of a single dosage of a g lucogenic formulation, administered immediately before ram exposure to groups of adult seasonally anovular Corriedale ewes. The glucogenic f ormulation contained 1,2,3-propanetriol (glycerol; 70% v/v), 1,2-propa nediol (propylene glycol; 20% v/v) and distilled water (10% v/v). At s ponge withdrawal, a single oral dose of 100 ml of this formulation or the same volume of distilled water was administered to treated and con trol groups, respectively, and ewes were immediately exposed to rams a nd hormonally-induced oestrous ewes. Data from an ancillary experiment (n = 10) showed significantly (P < 0.005) above normal plasma glucose levels in treated animals at 3 and 6 h after dosage. A significant in teraction (P = 0.0006) between MPA priming doses and glucogenic supple mentation was detected. Supplemented ewes, among those exposed to the lower dose of MPA, exhibited a higher (P = 0.0098) mean ovulation rate (1.56 +/- 0.076) than ewes that did not receive glucogenic treatment (1.31 +/- 0.060). In contrast, ovulation rate was significantly decrea sed (P = 0.021) from 1.30 +/- 0.058 to 1.13 +/- 0.042 after glucogenic treatment in ewes that were primed with sponges containing 60 mg of M PA. Ewes exposed to 60 mg of MPA were marked by the rams at a signific antly later (P < 0.00001) mean time (54.8 +/- 1.44 h) than ewes receiv ing 10 mg sponges (43.6 +/- 1.08 h). These results reveal the potentia l for modifying ovulation rate through short-term glucogenic manipulat ions, at least during the compressed follicular phase typical of ram-i nduced ovulations.