Candidate genes and markers for ovine aseasonality and milk production

Raluca Mateescu, Assistant Professor, Oklahoma State University
Mike Thonney, Professor

The goal of this project is to identify quantitative trait loci associated with aseasonal breeding and with milk production in sheep. The specific objectives of this research are 1) to use a candidate gene approach to determine for each gene the allele that results in the most valuable phenotype and 2) to use whole genome screening to localize genes using marker-QTL associations.

The project is based upon a unique crossbreeding experiment started in the spring of 2000 when East Friesian rams (high milk production, poor aseasonal breeding) were mated to Dorset ewes from the Cornell flock that have been selected intensely for aseasonal breeding for more than 20 years (low milk production, high aseasonal breeding). The resulting F1 ewes were purchased by a large sheep dairy to be bred to East Friesian rams to produce backcross ewes to be milked in the dairy flock. Milk production records from those ewes, along with other records in the flock, will be used in a test-day animal model to estimate breeding values for milk production. In November 2001, all 240 Cornell Dorset ewes were mated to eight of the F1 rams. Of these, 110 ewes produced 132 backcross ewe lambs in Spring 2002. Aseasonal breeding will be recorded in these ewes in spring 2003 followed by recording of actual lambing in August and September 2003. Additional backcross matings are planned to increase the number of backcrosses available for screening.

Milk production breeding values and aseasonal breeding and lambing records will be related statistically to alleles from candidate gene and marker genotypes obtained from each animal. Results of this project will speed selection for ewes that yield high amounts of milk and that breed out of season.

Increased selection intensity for aseasonal breeding and for milk production will improve the efficiency of highly productive sheep systems so that they can make better use of agricultural resources and supply excellent markets for fresh lamb and sheep cheese in the United States.