EAST LANSING, Mich. – Michigan State University researchers are studying how cattle diets influence the nutritional value of beef, aiming to understand how feed sources like grass, hay, or grains affect fatty acids and other compounds in beef.

With the focus on improving human health through better meat quality, Jenifer Fenton, an associate professor in the Department of Food Science and Human Nutrition, and Jason Rowntree, the C.S. Mott Professor of Sustainable Agriculture in the Department of Animal Science, published their findings in October 2024 issue of npj Science of Food.

Funded by the Greenacres Foundation, Fenton and Rowntree examined fatty acids and other organic compounds in grass-finished beef from cattle raised using rotational grazing methods, specifically studying whether analyzing the nutritional components in beef can lead to accurate predictions on what cattle were fed.

“How you feed the animal can change the omega-6 to omega-3 profile dramatically,” Fenton said. “Salmon is one example that gets talked about a lot. Farm-raised salmon when fed corn and soy contain higher amounts of omega-6 fatty acids, compared to wild salmon, which contain more omega-3 fatty acids because they’re feeding on small fish that eat algae.

“The same concept is true for beef,” she said. “When cattle are fed a high proportion of corn and soy, the beef has higher amounts of omega-6s relative to omega-3s.”

For some farmers and ranchers who practice rotational grazing and produce beef labeled to be grass-finished, the researchers said fresh forage isn’t always available for cattle due to snow cover and other seasonal interruptions. As a result, cattle are fed supplemental feeds such as hay, baleage (baled silage), soybean hulls and other diets.

The American Grassfed Association provides an approved list of supplemental feeds for cattle grown to produce grass-finished beef, but Fenton and Rowntree said they sought to provide evidence that could support ways to accurately authenticate grass-finished beef.

They observed differences among the fatty acids and secondary metabolites (organic compounds produced by plants, microorganisms, like bacteria and fungi, or animals, that are not directly involved in the organism’s normal growth, development or reproduction) in the beef they sampled, and then predicted which feeds were fed to cattle based on the information they recorded.

Researchers studied four groups of beef cattle at the Michigan State University Upper Peninsula Research and Extension Center, raised with different feed supplements: pasture with hay, baleage (also characterized by the high moisture content of the forage before it’s baled and wrapped), soybean hulls, and a combination of baleage and soybean hulls in confinement.

Using lab analysis, the researchers said they could accurately predict each group’s diet based on beef samples, with hay being the most traceable and showing a healthy omega-6 to omega-3 ratio.

Fenton said while a few differences among the samples confirmed certain supplemental feeds such as hay present more favorable characteristics in grass-finished beef than others, all the feeds they tested remain stable options to supplement with fresh forage.

“I think a farmer can feel assured that if they feed these byproducts at a rate similar to what was done in the study during the winter or at other points in time, the ones we’ve measured won’t greatly influence the omega-6 to omega-3 ratio,” she said.

When asked how cattle diets in the Midwest influence beef nutrition, Grant Dewell, Iowa State University beef extension veterinarian, told Farm World, “Most of the cattle finished in Iowa and the Midwest are finished on a primarily corn-based diet. From a flavor and eating satisfaction basis, this is the type of beef that most consumers prefer and expect when they purchase U.S.-finished beef.

“From a general nutritional basis, there is not much difference between grain- or grass-finished beef,” he said. “Grass-finished beef does have an increase in omega-3 fatty acids, so it is more heart healthy as omega-3s are beneficial for your heart, but otherwise, there is not much difference. Many other claims about the benefit of grass-fed beef are not substantiated.”

When asked how cattle diets in Tennessee influence beef nutrition, Andrew P. Griffith, University of Tennessee professor of agricultural and resource economics, told Farm World, “We do have people marketing grass-fed and grass-finished beef where all nutritional intake is forage-based, including supplements of things like alfalfa pellets. These animals typically sell at a premium to grain-finished animals in the freezer-beef business in Tennessee.

“This research would be a source of information to support the health benefits of grass-fed and grass-finished beef, and thus used to promote beef,” he said. “It takes longer to finish cattle on a forage diet, compared to a high starch (grain) diet, which is one reason a premium is necessary. Now this research adds credibility to why a premium is deserved for those looking for the improved health benefits.”

Rowntree said land management will continue to be an important research topic moving forward to ensure the feedstuff cattle eat and graze on is nutrient dense.

“There is a unique demand for understanding the nutrient density of the food we produce,” he said. “Our premise is that healthy soils equal healthy land, and healthy land equals healthy plants, animals and people. Understanding how management influences the nutrients in food is a growing and much-needed area.”

Fenton and Rowntree said the next step of the research is currently underway as their research team conducts similar tests to examine the nutritional profile of beef from cattle fed distillers grains.

Fenton said one area of research needing to be further explored, noting the research team may investigate it in the future, is how human health is affected when eating beef from cattle fed different diets, and how consumers choose among different beef products.

“We’d like to work toward taking the grass-finished beef with a nutrient profile favoring human health and then beef from conventionally fed cattle and feeding it to humans to see if there’s data that shows lower inflammatory markers, or a more beneficial cholesterol profile between the two,” she said.