Modification by propylene glycol of ovulation rate in ewes in response to a single injection of FSH A. Lopez-Sebastian, A. Gomez-Brunet, A. W. Lishman,

Five experiments were conducted with the objective of developing a method to induce superovulation in ewes with a single i.m. injection of FSH. This was achieved by injection of 10 mg FSH-P in propylene glycol at the same time as luteolysis was induced by cloprostenol on day 13 of the oestrous cycle (day 0 = oestrus). Experiments 1, 2, 3 and 5 were conducted in a single flock of Manchega ewes in Spain during the breeding season. Ovulation rates were determined at laparoscopy. In Expt 1, FSH-P was diluted in saline, and neither 5 mg FSH on day 1 nor 5 or 10 mg FSH-P on day 13 changed the ovulation rate after cloprostenol treat-ment on day 13. In Expt 2, FSH-P was diluted in propylene glycol and data were collected over 2 years. Ten milligrams FSH-P, on day 13 only, increased (P < 0.01) the mean number of corpora lutea to 5.5 compared with a control value of 1.5. Five milligrams FSH-P on day 13 only had no effect; however, 5 mg FSH-P on day 1 reduced the mean number of corpora lutea formed in ewes receiving 10 mg FSH-P on day 13 to 2.6 (P < 0.01). Saline and pro-pylene glycol, as vehicles for 10 mg FSH-P, were compared directly at two times of injection in Expt 3. FSH-P increased the mean number of corpora lutea when injected on day 13 in propylene glycol (4.7) but not in saline (2.5; P < 0.5). Ovulation rate did not differ betwee