Healthier Dairy Cows Produce More Milk

Ketosis affects milk supply and disease resistance

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Todd Duffield

“People need to eat,” says Ontario Veterinary College (OVC) professor Todd Duffield, “and farmers need to produce the food that will be eaten. It’s that basic. And that’s why I am passionate about agriculture.”

That passion was sparked early, when Duffield was growing up on his parents’ farm where they raised Suffolk sheep and Duffield had a chance to get to know local veterinarians Keith Douglas and Jim Harvey. It motivated him to attend OVC and earn his DVM degree. After four years in a veterinary practice near Belleville, he returned to OVC to earn a D.V.Sc. “I found I really enjoyed research and teaching, so I took a faculty position when that opened up,” Duffield says.

Fifteen years later, his research on the health of dairy cows has recently been recognized in two ways. Earlier this year, Duffield was presented with the Merck Veterinary Award 2012, which is a Canadian Veterinary Medical Association Award for a veterinarian whose work in large-animal practice, clinical research or basic sciences is judged to have contributed significantly to the advancement of large-animal medicine, surgery and theriogenology, including herd health management.

He was also notified that two of his papers – one where he was lead author, one where he was a co-author – were among the 100 most-cited papers in the field of dairy herd research, a mark of how his work is respected and valued by other researchers.

The main focus of Duffield’s work has been the problem of ketosis in dairy cows. Because today’s dairy cows have been bred to produce large volumes of milk, some of these high producers have difficulty meeting their energy demands. They then begin mobilizing their fat stores and begin producing ketone bodies. Once ketosis has started, the cow is at risk of other diseases, will produce less milk, may have trouble conceiving another calf, and is more likely to be culled.

The problem is a common one and affects 30 to 40 per cent of cows. It’s not as simple as just giving the cows more food, Duffield explains. “There are all kinds of complicated reasons why a cow may not eat the food available to her, for example. It can be the social dynamics of the herd keeping some cows away from the food. It might be the temperature in the barn – if it’s too hot, cows may not feel like eating. While the overall rate is 40 per cent, it varies dramatically from farm to farm. Some have almost none, and others have much higher percentages. That suggests that how the cows are managed is one of the key factors.”

Duffield’s work considers several different aspects of ketosis: he has studied ways to prevent it, ways to diagnose it early and ways to treat it.

Other research has looked at medications to treat the pain of calves that have been de-horned and for pain management after a cow has surgery.

The second of Duffield’s most-cited papers took a look at research itself. “In human medicine, you often see an analytical summary of current research on an issue,” he says. “It’s called a meta-analysis, but it’s not done often in veterinary medicine.” Following a study leave in Australia in 2007, Duffield worked with his co-authors to write a paper that explains how a meta-analysis is correctly done.

That affects his other research, too. “Ketosis treatments have been in veterinary textbooks forever,” he says, “but I don’t know that anyone has looked at the evidence for these treatments critically. I had one of my current students, Jessica Gordon, look at doing a meta-analysis, and she found there were not enough quality studies available to be analyzed.” Instead, Duffield was able to select the treatments that seemed most promising and will be doing clinical trials with his research team on those.

Future clinical trials may be more useful and easier to conduct than in the past thanks to new technologies. “We can already measure the ketones at every milking because they are excreted in the milk just as they are in all other body fluids,” Duffield says. In the past, a researcher might have visited a farm once a week to take milk or blood samples for ketone measurement and observed just a brief snapshot of the cow’s behaviour and interactions. Newer techniques can automatically measure ketones at each milking and record the cows’ behaviour and interactions minute by minute.

Duffield is also uncovering evidence that ketosis may begin even before the cow has given birth to a calf. Elevated ketones in the cow during the weeks before she gives birth, even if the levels are only slightly elevated, can indicate that she is at risk of ketosis once lactation begins.

Besides his ongoing research, Duffield teaches students in the DVM program and provides clinical care to ruminants, including dairy and beef cows, sheep and goats, through the OVC Ruminant Field Service Clinic. “I have a couple of herds that I care for and take students out with me,” he says. “I also take my turn at being on call. Farmers want healthy cows, too. In my work and my research, I look for the win-win-win situation where cows are healthier, they make more milk and farmers get more money. That’s what makes me feel good.”