CLAY CENTER, Neb. – A heifer that fails to get pregnant becomes a rancher’s liability.
However, genetic researchers may have discovered what goes wrong with some of these animals.
A DNA mapping study to evaluate breeding females found that a small but significant percentage of open heifers carried the Y chromosome, researcher Tara McDaneld said during a recent genetics seminar at the United States Meat Animal Research Center near Clay Centre.
The researchers were looking at the heritability of reproductivity, a difficult trait to find because it is influenced by multiple genes.
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They used a 770K SNPs panel and found the male chromosome was showing up in various places along the genome. This test can look at 770,000 locations on the bovine genome.
“We wanted to look deeper into this Y chromosome and why we were seeing it in females,” she said.
The discovery needs further study to see if it has a direct correlation to fertility problems.
“On those ranches that have a high emphasis on fertility, we were not seeing the Y chromosome,” she said.
DNA was tested from 1,000 continental and 1,000 British cattle on commercial operations.
They do not know if the tests found only fragments of the Y chromosome, but it seems to prevent pregnancy.
“Can we determine which females possess this SNP and what would it mean to the industry if we could identify females right away before breeding that are not going to get pregnant so you can automatically put them in the feedlot instead of spending time on them trying to get pregnant?” McDaneld said.
Researchers checked their work by running a test that is used to sex embryos.
Some of same females tested Y positive when only a male embryo should carry it.
Researchers also checked to see if the females were undetected freemartins, which are sterile female fraternal twins. This did not seem to be the case, but they plan to check further.
“We took a pool of freemartins and ran them on the chip and saw the same thing, where you will see a Y chromosome in these females,” she said.
Freemartins that tested positive in the sexing test also tested positive in the DNA test.
Researchers also checked sires and found one was responsible for two heifers with the male chromosome.
