Ovulatory activity, hormonal induction of ovulation and fertility of young Cashmere and Angora female goats in a temperate environment
1994
Ritar, A.J. | Robertson, J.A. (Tasmanian Dept. of Primary Industry and Fisheries, Taroona (Australia). Marine Research Lab.) | Evans, G. (Sydney Univ. (Australia). Dept. of Animal Science)
Reproductive parameters of young Cashmere and Angora goats born between 1988 and 1990 and grazed on temperate pastures in southern Australia were examined with a view to reducing the age of first breeding. Females born in August or October of 1989 and 1990 were examined each month by laparoscopy to determine natural ovulatory activity when 6-19 months old. Cashmeres commenced ovulating as young as 7 months of age or as light as 12 kg. Almost all Cashmeres were ovulating by 8-10 months of age at a liveweight of at least 18 kg, and their breeding season extended from April to October. By comparison with Cashmeres, Angoras grew more slowly, fewer ovulated, they commenced ovulation later, their ovulation rates were lower and their breeding season was shorter. Ovulation rates after injection with pregnant mare serum gonadotrophin (PMSG) and treatment with controlled internal drug release (CIDR) devices were higher for Cashmeres than for Angoras, and tended to be higher at 400 than at 200 I.U. PMSG. The kidding rates for Angoras bred at 8, 14 and 20 months of age were 8.4, 20.0 and 30.0 percent respectively. Ovulatory activity and fertility in the non-breeding period, with or without CIDR-PMSG treatment, did not improve with melatonin treatment.
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