Happiness is . . . less milk fat

by Amina Ali

educing milk-fat production is sure to please health-conscious consumers -- and the airy industry -- says a U of G researcher.

Animal science professor John Cant believes that feeding dairy cows different fatty acids their diets can reduce the proportion of fat in their milk.

It's known that the "trans" form of fatty acids -- with hydrogens on opposite sides of a hemical bond -- depresses milk-fat production. Cant is studying how these trans fatty acids ause milk fat to be reduced and if changing dairy feeds will alter fat production.

"Dairy farmers want to sell more milk, but their sales are limited by excess fat in their product," says Cant. "That's why we're focusing on lowering milk fats using trans fatty acids."

Cant thinks lower milk fats are possible, thanks to the bacteria that reside in a cow's rumen. These bacteria break down in cow's feed and convert it into a form the cow can absorb.

During the degradation process, the polyunsaturated fatty acids sometimes become monounsaturated. It's the monounsaturated form that contains half trans fatty acids, which depress milk fat. How this process works is a matter of blood metabolism, which Cant and Prof. Don Trout, Clinical Studies, are studying.

Feeding studies are under way using partially hydrogenated vegetable oil, which contains trans fatty acids. These results will suggest how much needs to be fed to derive an optimal fatty-acid composition in the milk. But other researchers, both at Guelph and elsewhere, have found that a diet high in trans fatty acids can be detrimental to human health. So Cant is trying to strike a balance between using trans fatty acids to decrease fat production and hoping excess levels don't appear in cows' milk.

"Trans fatty acids make up a very small percentage of a cow's diet, but we'll be sure to check what levels appear in the milk during the feeding trials," says Cant.

The data from these studies will also provide a valuable test for mathematical models of fatty acids in milk that have already been developed.

"This work will allow farmers to be more efficient, nutritionally speaking, while meeting consumer demands for greater milk proteins and less fat," says Cant.

his research is supported by the Dairy Farmers of Canada and the Natural Sciences and Engineering Research Council.