Genetic Testing Identifies Healthier Cows

Blood or milk sample indicates disease resistance

Mastitis costs Ontario dairy farmers millions of dollars each year. Photo by Barry Gunn

You can breed dairy cows to yield more milk, but can you use smarter breeding to make healthier herds? Yes, you can, says pathobiology professor Bonnie Mallard, who hopes an on-farm test developed at Guelph will see wider use to improve animal health, food quality and safety, and greener farming.

A new genetic profiling tool called high immune response (HIR) technology developed by Mallard and other researchers promises to help farmers and breeders select cows with better immunity to disease, especially mastitis. That ailment costs Ontario dairy farmers millions of dollars every year in lost animal and milk production and treatment costs.

The project led by the Guelph professor has yielded a test to identify and breed cattle with better immune response and disease resistance. Now Mallard is working with such companies as Semex Canada on a handy and reliable form of the test for routine breeder use on Ontario dairy farms.

“I’m really excited about it,” says Mallard, a three-time Guelph grad on the faculty of the Ontario Veterinary College (OVC) since 1990. She says this research fits with many of the goals of the University’s BetterPlanet fundraising project: “More sustainable agriculture, increased food security, it’s all about making this a better planet not only for animals but for consumers.”

For the past five years, she has led a research team within the Canadian Bovine Mastitis Research Network (CBMRN) funded by the Natural Sciences and Engineering Research Council (NSERC). Various network teams are developing tools and information to improve aspects of dairy herd health. This year, she also received an NSERC “Idea to Innovation” grant to help market the technology.

For this research, Mallard has worked with OVC professors David Kelton and Ken Leslie (now retired) from the Department of Population Medicine, and pathobiology professor emeritus Bruce Wilkie. Also involved are Prof. Niel Karrow, Department of Animal and Poultry Science, and other researchers in the Centre for Genetic Improvement of Livestock, based in that department in the Ontario Agricultural College. Many U of G grad students have also worked on the project, along with researchers in several provinces.

Their patented HIR technology uses animal genetics and immune response to breed healthier cattle naturally and safely, says Mallard. The test uses a blood or milk sample to gauge high, average or low immune response to various pathogens, including mastitis bacteria. It allows farmers to pinpoint resistant and susceptible animals in order to calculate breeding values and make decisions about breeding, management and culling.

Between 20 and 30 per cent of variation in immune response stems from inherited factors rather than things such as housing or nutrition, says Mallard. “Both genes and environmental factors are important to maximize health. The advantage of the inherited factor is that it can be identified and used to select future offspring with more robust immunity.”

The researchers tested samples from 500 cows on more than 50 farms belonging to a national cohort of 9,000 animals covering almost 100 farms in six provinces. (The cohort includes dairy cows at U of G’s Kemptville Campus.) They found that cows with low immune response have about twice the disease rate of high responders.

Mallard says until recently most farmers have based breeding strictly on milk traits rather than immune response.

In a survey of dairy producers by a Guelph agri-marketing company, nine out of 10 producers said they would be interested in a genetic test to protect cattle, improve milk quality and reduce antibiotic use. Almost 60 per cent said they would use the test on their whole herd, particularly on large herds of more than 100 animals.

Mastitis is an inflammation of the mammary gland caused by bacteria. It is the most common disease in dairy cows and the primary cause of antibiotic use in dairy herds. Losses to mastitis are estimated to cost Canadian dairy farmers more than $4 million a year, according to the CBMRN website.

Besides improving animal health and milk quality, better breeding might also help reduce the use of antibiotics on farms. Reducing drug use on farms might help improve land and water quality, says Mallard.

Along with about 40 researchers in nine institutions across Canada, the CBMRN includes numerous producer groups, government agencies and private sponsors such as the Canadian Dairy Network and the Dairy Farmers of Ontario.

After completing an agriculture undergrad at Guelph, Mallard began looking at genetic regulation of animal immune systems during her graduate degrees in quantitative genetics and immunogenetics. During her PhD with Wilkie, she studied immune response genes and proteins to develop breeding values for pigs.