Utilization of frozen-thawed epididymal ram semen to preserve genetic diversity in Scrapie susceptible sheep breeds.

The European Union has introduced transmissible spongiform encephalopathy (TSE) resistance breeding programmes for several sheep breeds to cope with the genetic susceptibility to Scrapie infections. Due to the different allele frequencies among breeds, strong selection for ARR alleles is associated with a loss of genetic diversity in small populations and in larger populations with unfavourable ARR allele frequencies. To ensure maintenance of genetic diversity, an adhoc cryopreservation programme was initiated employing epididymal sperm from 109 rams representing 16 different breeds within one breeding season. Epididymal semen was chosen for this adhoc programme because time consuming training of rams for ejaculated semen collection via an artificial vagina was not possible. Prior to freezing, average sperm motility was 79.7% and acrosome integrity was 93.7%. After freezing, these levels were decreased to 60.5 and 72.8%, respectively. An insemination trial using frozen-thawed epididymal semen resulted in a lambing rate of 87.5%. Results show that this semen preservation method is robust and efficient and associated with high fertility. It may also be useful for other animal species.