CATTLEMEN LOOK FOR LINK BETWEEN GENETICS AND HEALTH

Seasoned cattlemen have long suspected a link between calf genetics and health, and a mounting body of research is proving them right. Uncovering that connection might lead to new tools for managing disease resistance.

A 2006 USDA Meat Animal Research Center (MARC) study looked at genetics and bovine respiratory disease (BRD). More than 18,000 records, encompassing 12 breed types across 15 years, showed varying levels of disease occurrence among breeds.

The average for Angus cattle was the most favorable at 10.2 percent. Crossbreeds were in the middle and the highest rates, 32 percent to 35 percent illness, were seen in four other pure breeds.

Researchers estimate the heritability at 0.18 out of a theoretical 1.00. That makes it just “lowly heritable,” compared to the moderate heritability of carcass traits.

“These would be more along the lines of fertility traits,” says Larry Kuehn, MARC research geneticist.

But given the economic impact, “BRD resistance should be considered for incorporation into beef cattle breeding programs,” says a recent Iowa State University study.

That research points to a .10 to .11 heritability for BRD resistance in Angus cattle, compared to .02 to .06 for Simmentals, indicating selection within the Angus breed could yield more progress. The ISU work also indicates several helpful correlations between BRD resistance and other traits, such as a negative relationship with birth weight and a positive association with marbling.

“It could be included in a performance index where traits are weighted by their economic effect,” says J.R. Tait, ISU animal scientist. “It has a large enough impact that it would get some selection pressure.”

MARC researchers and private companies are looking at DNA markers to help with the development of breeding tools.

“Most bull producers aren't going to expose cattle to respiratory diseases and then report it on their registration forms,” Kuehn says. “Understandably, they're trying to keep calves from getting sick. DNA is probably going to be the most efficient way to study this.”

“We're trying to identify which genes would tell us that they're more likely to be resistant or susceptible to respiratory disease,” he says.

“We're hopeful in a couple of years or so we'll have something that producers can apply,” says Kent Andersen, associate director of technical services with Pfizer Animal Genetics. He says every segment of the industry will be able to use the technology.

“Even though progress would be slow, avoiding bulls that are the biggest potential troublemakers at least moves us in the right direction and minimizes the propagation of animals that are particularly susceptible,” he says. “For cow-calf producers, there's probably an opportunity for value differentiation when you're selling calves if you can demonstrate that they have a lower disease risk.”

DNA tools could also help producers with limited access to feedlot health information right now.

“It may be the first opportunity for many cattlemen to select for improved health, and the effects would impact the entire supply chain,” says Jason Osterstock, genetic epidemiologist with Pfizer Animal Genetics. “Unless the producers are retaining ownership and collecting information from the feedlot, they may have limited disease data with which to make health-based breeding decisions.”

He says feedlots might become more strategic in how they use animal health products.

“Judicious use of antimicrobials is an important part of what the entire livestock industry is striving for,” Osterstock says. “There's potential to move towards what in the human side they've referred to as ‘individualized medicine.' The decisions regarding how we prevent or treat disease in a specific animal will be made differently for different animals that have unique genotypes.”

All of this is good news for an industry that loses an estimated at $750 million a year to respiratory disease alone.

“We can hopefully breed for feeder cattle that have more bulletproof immune systems from the get-go,” Andersen says, “and then pair them with the right animal health programs to really maximize production and minimize losses associated with either death or lower performance and grade because of these pathogens.”







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