XXXIX Jornadas de Estudio. XIII Jornadas sobre Producción Animal. T. II
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.
