Genetic Screen

The Y Behind Infertility

Victoria G Myers
By  Victoria G. Myers , Progressive Farmer Senior Editor
Geneticist Tara McDaneld (left) and technician Tammy Sorensen, with USMARC, are part of a team focused on finding genetic markers that can predict fertility in cattle. (Photo by Janice Watts)

Ever wonder why that nice replacement heifer didn't conceive the first or second time around? Maybe her body condition was a little low. Maybe she was delayed in her maturity. Maybe, maybe, maybe.

When things go wrong, the tendency is to think that given enough time or improved management, the little bovine ship will right herself. But a breakthrough in genetics research has found some open heifers may not have the ability to conceive at all -- no matter how long they stay in the herd. These females carry a portion of a Y, or male, chromosome. Scientists refer to it as a "Y single nucleotide polymorphism" (Y-SNP).

A team of researchers, led by geneticist Tara McDaneld of the USDA's Meat Animal Research Center (USMARC) in Clay Center, Neb., examined records of 6,400 cows and heifers from herds across Colorado, Florida and Nebraska. They separated data based on whether or not the animal became pregnant in its first spring breeding.

GENE POOLS

Using a genetic screening method called "DNA pooling," groups of about 100 animals each were created and genotyped -- meaning their genetic makeup was examined. Of those animals that had not conceived, researchers found 20% to 25% tested positive for a portion of the Y chromosome on their DNA.

"Basically we found that the animals that tested positive for the Y anomaly do not get pregnant," said McDaneld. She added that given this is part of the animal's DNA, it is present from birth and will not change over time.

"We used a SNP chip," she explained. "This has over 700,000 variations in an animal's DNA". Using this technology she said it is possible to find portions of the Y chromosome where they don't belong -- on female DNA. This allowed researchers to identify females with the anomaly.

If this information were available to a producer, it would allow him to eliminate any female calf carrying the Y-SNP as a potential breeding animal early in its life, saving development costs and increasing herd fertility on the whole.

COMMERCIAL USE

"Once we identified those SNPs, we developed PCR [polymerase chain reaction] tests, which are a way of amplifying the section of the Y, so you can more quickly find this anomaly," explains McDaneld. "We've shared that with the genetics companies and they are using the information to develop DNA tests for use within the industry."

This finding is a significant step in being able to pinpoint genetic anomalies that impact fertility. The team's work has already found its way to genetic tests for both commercial and seedstock producers.

Stewart Bauck, general manager of Neogen's GeneSeek, said the company is using a low-density (LD) Illumina chip on its Igenity Silver and Igenity Gold tests -- which are for commercial and crossbred producers -- that can identify the Y-SNP. In addition, GeneSeek Genomic Profilers (GGP) for seedstock producers, both in the LD and the HD (high-density) 150k versions, can note the anomaly. Cost to add the Y-SNP screen to a profile is $5.

McDaneld added this is just the first fruit to come from research aimed at uncovering genetic answers to fertility questions within the cattle industry.

"I really hope we get better at predicting the genetic merit of these animals," she said. "It is a big deal to be able to look at an animal and predict its productivity in your herd. What that can do for the industry would be huge."

(VM/CZ)

Victoria Myers