Any discussion of the merits of grass-fed beef invites scientific comparison to grain-fed beef. One noteworthy difference between the two production systems is how long it takes to finish an animal.
“Because of the lower energy density, it typically takes longer for animals to reach slaughter weight when they’re grass-fed,” says Dr. Tim McAllister, principal research scientist in ruminant nutrition and microbiology at Agriculture and Agri-Food Canada’s Lethbridge Research and Development Centre.
The nutritional differences, though, are much more subtle. The ratio of lean to lipid within the meat likely yields the biggest differences, McAllister says. Finishing cattle in a feedlot on a high-energy diet promotes fat disposition. That means more marbling in grain-fed beef over forage-finished.
There isn’t much difference in terms of amino acid profiles or fatty acid composition, he explains, as these “all have a specific biochemical function, so they tend to be similar across cattle, regardless of what the diet is.” The chloroplast in fresh forages have more polyunsaturated fatty acids, increasing the content of this fatty acid in grass- fed beef, but its total lipid content is lower than that of grain-finished beef.
However, concentrate diets can create a type of trans fatty acid that is not found in grass-finished beef. While there isn’t much data to suggest this would have a negative impact on human health, McAllister says that some research suggests those types of trans fatty acids are less desirable than those formed in grass-based systems.
While this science is well known in the academic community, various groups and companies still use conflicting claims comparing the nutritional quality of the two. The fact that we aren’t all on the same page is what McAllister sees as the difference between science and marketing. He also notes there’s more than just the beef industry influencing these perspectives. For example, cattle can use plant cell wall material more efficiently than monogastric animals such as poultry and swine, making better use of grazing land.
“It also contributes to the preservation of our grassland ecosystems as opposed to cultivating them up and growing crops,” he says, adding that there’s a role for both production systems in Canada.
“I think you need that broader perspective to also recognize the importance of what grasslands play in beef production and other ecosystem services that they deliver to society.”