By affecting cows’ diets, climate change can affect cheese’s nutritional value and sensory traits such as taste, color and texture. This is true at least for Cantal — a firm, unpasteurized cheese from the Auvergne region in central France, researchers report February 20 in the Journal of Dairy Science.
Cows in this region typically graze on local grass. But as climate change causes more severe droughts, some dairy producers are shifting to other feedstocks for their cows, such as corn, to adapt. “Farmers are looking for feed with better yields than grass or that are more resilient to droughts,” but they also want to know how dietary changes affect their products, says animal scientist Matthieu Bouchon.
For almost five months in 2021, Bouchon and colleagues at France’s National Research Institute for Agriculture, Food and Environment tested 40 dairy cows from two different breeds — simulating a drought and supplementing grass with other fodder, largely corn, in varying amounts.
The team sampled milk from all cows at regular intervals. Milk’s fatty acid and protein profiles impact cheese formation, melting qualities and nutrition, so the researchers chemically identified distributions of those molecules with a technique called gas chromatography. They also identified beneficial microbes in the milk by making Petri dish cultures.
They found that a corn-based diet did not affect milk yield and even led to an estimated reduction in the greenhouse gas methane coming from cows’ belching. But grass-fed cows’ cheese was richer and more savory than that from cows mostly or exclusively fed corn. Grass-based diets also yielded cheese with more heart-healthy omega-3 fatty acids and higher counts of probiotic lactic acid bacteria. The authors suggest that to maintain cheese quality, producers should include fresh vegetation in cows’ fodder when it is based on corn.
Experts not involved with the study point out that warming climates impact cattle physiology as well as feed quality. “Cows produce heat to digest food — so if they are already feeling hot, they’ll eat less to lower their temperature,” says Marina Danes, a dairy scientist at the Federal University of Lavras in Brazil.
The animals also divert nutrients to their immune systems to respond to heat-caused cell stress. “This process spirals into immunosuppression, leaving the animal vulnerable to disease,” Danes adds.
Producers in warmer places like Brazil are used to heat and droughts. But “rain periods are getting shorter and more concentrated in these past few years, and hotter seasons are getting longer,” says Gustavo Abijaodi, a dairy producer in Belo Horizonte, Brazil. He’s changing his dairy system from open grazing to indoor herding to help make the cattle more comfortable.
“We were having lots of problems with milk protein and fat content due to the heat,” Abijaodi says. “If we can stabilize heat effects, the cattle will respond with better and more nutritious milk.”
The sector is also betting on different feed mixes to avoid the loss of milk quality, Bouchon’s team observed.
“The problem with the study is they increased the starch levels in the feed,” says Marcus Vinícius Couto, technical coordinator at the Central Cooperative of Rural Producers, an association of agricultural producers in Belo Horizonte. Starch is a challenge to digest for the first and largest compartment of a cow’s stomach — the rumen — where food ferments and plant fibers get broken down.
“We’re using feed with controlled starch levels,” as well as fat, hay and cottonseed fibers, to improve the milk’s composition, Couto says.
French producers will possibly need different strategies to fit their environment and cow breeds. But Bouchon is certain of one thing: “If climate change progresses the way it’s going, we’ll feel it in our cheese.”