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.