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Fall 2009
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Short Reports

Mary Had a Lot of Lambs: Researchers Speed Up Sheep Breeding

By Chris Bently ’10

Mary had a little lamb, but only once a year. Cornell Sheep Program researchers have discovered an unusual form of a gene that prompts ewes to breed out of

Raluca Mateescu

Former Cornell postdoc Raluca Mateescu co-authored a study with Professor Mike Thonney that identifies a way to prompt ewes to breed more frequently and at younger ages.

They identified the presence of the unusual form of the so-called M allele in their test flock and then validated the gene’s relationship with aseasonal breeding by observing that trait.

The finding, published in the August issue of the Journal of Animal Science (Vol. 87, No. 8), may be a boon for the sheep industry worldwide.

“The primary biological limit for sheep production worldwide is the seasonality of breeding, but the market for high-quality lamb is a 52-week thing,” says Doug Hogue, CALS professor emeritus of animal science. His colleague Mike Thonney and former CALS postdoctoral researcher Raluca Mateescu, MS ’01, PhD ‘04, now at Oklahoma State University, co-authored the paper with Andrea Lunsford, a grad student at OSU.

Although the presence of the M allele has been definitively correlated with the breeding out of season, the researchers caution that it may only be a marker for the gene actually responsible for the trait.

“Breeding out of season is complex, so there are a lot of genes controlling it,” Mateescu says.

“In this case, we’re talking about a receptor gene for melatonin [a naturally produced hormone],” Thonney explains. The change in the DNA sequence of the M allele does not change the amino acid sequence of the protein, so it may be an accurate indicator for breeding out of season, though it’s uncertain whether the gene actually affects how the sheep’s body reacts to melatonin. And there may be a risk of losing the association over generations, as recombination could occur between the marker and the functional gene.

The researchers stress that it will be important to validate the gene’s ability to indicate for aseasonal breeding each time the allele is bred into a new sheep population.

Mateescu is now focusing on placing markers across the sheep’s entire genome to more accurately determine which gene or genes directly affect the trait of aseasonal reproduction.