COMPARISON OF NATURAL MATING AND ARTIFICIAL INSEMINATION ON REPRODUCTIVE PERFORMANCE OF THREE STRAINS OF SHEEP HOUSED IN TOTAL CONFINEMENT

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Abstract
The reproductive performance (fertility, prolificacy and fecundity) of confined sheep was measured following natural mating or artificial insemination (AI) with 0.1 mL of unextended semen collected by artificial vagina or by electroejaculation. The estrous cycles of the ewes were synchronized in late summer using intravaginal sponges impregnated with fluorogestone acetate. Pregnant mares' serum gonadotrophin (PMSG) was administered intramuscularly to approximately half of the ewes. There was no significant difference in the reproductive performance of ewes bred by natural mating (45%) or AI (30%) or between the two methods of semen collection (30 vs. 29%). Fertility was greater (P < 0.05) in ewes treated with PMSG (33 vs. 11%) mainly because of a tendency for higher fertility in ewes bred by AI. PMSG also significantly (P < 0.01) increased prolificacy and fecundity, 1.8 vs. 1.5 and 58 vs. 16%, respectively.