Evolución de un programa de inseminación en la raza Assaf en la provincia de León

The Assaf breed has mostly been allocated in Castilla y León, particularly in the province of León. In 1998, a selection and genetic improvement programme was initiated for milk production in 38 flocks. Training of rams for semen collection using an artificial vagina reached a success rate of 74%, and the percentage of valid ejaculates has reached 90%. Fertility results of artificial insemination (lambing rates) have fluctuated between 35% y 40% since the programme was started. We found that fertility drops in ewes older than 4 years, and that it improved about 10% in the breeding season.