A COMPARISON OF FRESH AND FROZEN SEMEN IN THE INSEMINATION OF CONFINED SHEEP

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Abstract
The reproductive performance of crossbred sheep maintained in total confinement was compared after artificial insemination with fresh or frozen semen. Estrus was synchronized with progestagen-impregnated vaginal sponges and pregnant mares’ serum gonadotropin. Inseminations were performed 54 and 60 h after sponge removal. The fertility of ewes inseminated with fresh semen was significantly higher than of ewes inseminated with frozen semen. Conception rates, lambing rates and litter size were 83%, 78% and 2.2 using fresh semen and 65%, 43% and 1.8 using frozen semen. In a group of similar ewes bred by natural service, the lambing performance was comparable to that obtained with fresh semen. The difference between conception and lambing rates suggests an increase in early embryonic mortality when breeding with frozen semen and confirms the need for improved frozen semen technology.