Committee Technical Sessions:
Cow Herd Efficiency & Selection Decisions
Application of Genetic Strategies
to Utilize Reproductive Records
BOZEMAN, Mont. (June 2, 2011) —Tara McDaneld and fellow USDA-Agricultural Research Service (ARS) researchers have applied genomic tools to the evaluation of reproductive records in an attempt to identify regions of the bovine genome associated with reproductive efficiency. McDaneld, a scientist at the U.S. Meat Animal Research Center, Clay Center (USMARC), Neb., spoke during a joint technical session of the Cow Herd Efficiency and Selection Decisions committees at the 2011 Beef Improvement Federation (BIF) symposium in Bozeman, Mont.
Certain regions of the genome, she said, do appear to be associated with fertility.
However, McDaneld said researchers also discovered something rather curious. Evaluation of DNA from English-Continental females in the USMARC herd detected the presence of Y chromosomes among “exposed” females that did not conceive. But only males are supposed to possess Y chromosomes. Testing of a Bos indicus-influenced females from Florida’s Deseret Ranch resulted in detection of fragments of Y chromosomes in up to 29% of open heifers. Researchers suspect a link to low fertility in females.
McDaneld called the discovery puzzling since the Y chromosome was thought to be present only in “freemartins” (females born as twins to males), which cannot reproduce.
“But that’s not likely, because all heifers from the USMARC herd and the Deseret herd were subjected to reproductive tract examination,” said McDaneld, noting that the abnormal reproductive tracts of freemartins would be detected. “There must be something else,” she added.
McDaneld said researchers will continue searching for answers and are now looking at females from two additional populations. Among heifers from the Rex Ranch in the Nebraska Sandhills they have seen replication of regions along the genome that appear to be associated with fertility, and they have detected the Y chromosome. Studies will continue with females in a New Mexico State University research herd.
To listen to this presentation and to view the PowerPoint that accompanied it, visit the Newsroom at www.BIFconference.com.
BIF’s 43rd Annual Research Symposium and Annual Meeting was hosted June 1-4 on campus at Montana State University, Bozeman, Mont.
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