Increased Ovulation Rate at the Ram-induced Ovulation and Its Commercial Application

There is evidence that the ovulation rate (number of ovulations per ewe ovulating) of successfully teased ewes was increased relative to that of their second ovulation or relative to spontaneously ovulating flock mates. The effect was observed in Merino, Prealpes and Ile-de-France breeds and may have been prevented in ewes primed with progestagen before the introduction of rams (Oldham and Cognie, unpublished). Progestagen priming ensures oestrus at the ram-induced ovulation, and ensures that the CL persist for a normal period (Hunter et al. 1971; Oldham et al. 1980). All of these factors will affect commercial application of teasing. The effects of teasing and progesterone on ovulation rate were tested in experiments on three breeds of ewe, and the possibility of commercial application of teasing to an intensive breeding system was tested in a fourth experiment. Progesterone was administered over 12 days by injections in Experiments 1 and 3 (10 mg/day) or by intravaginal sponges impregnated with fluorogestone acetate (FGA) in Experiments 2 and 4.