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.”
#
Excerpts from the new study:
Dairy cow farming systems face increasing pressures due to ongoing climate change and the increasing frequency of extreme climate events (Gauly and Ammer, 2020). … Improved understanding of these strategies on dairy production and quality is necessary to support the agroecological transition in the dairy sector in a context of climate change.
#
Climate Depot note: Odd acknowledgement by the authors in this new paper:
“Supplemental material for this article is available at https://doi.org/10.57745/0VWGZX. None of the data were deposited in an official repository. The data that support the study findings are available upon reasonable request to the corresponding author. All animal-related procedures were conducted in accordance with the French guidelines for animal welfare and were approved by the local ethics committee (approval APAFIS#2015043014541577). There was no need for Institutional Review Board approval because no clinical or health data were involved in this study. Informed consent was obtained from all subjects involved in the study. The authors have not stated any conflicts of interest.”
