How climate change impacts dairy

If you love cheese, you might want to pay attention to what dairy cows are eating. It turns out that whether a cow grazes on fresh grass or munches mostly on corn silage can change not only how much milk she produces, but also how that milk tastes when it’s transformed into cheese. And with climate change bringing hotter, drier summers across Europe and beyond, farmers are increasingly being forced to rethink how they feed their herds.

A team of French scientists decided to address these concerns further by trying to answer the question: when summer droughts reduce the availability of pasture grass, how should farmers adapt, without sacrificing milk production or the quality of their cheese?

Their study, published in the Journal of Dairy Science, comes from a collaboration of researchers at France’s National Research Institute for Agriculture, Food and Environment, Université Clermont Auvergne, AgroParisTech, and Inserm. Led by Matthieu Bouchon and colleagues, the project integrates animal science, microbiology, and good old-fashioned cheesemaking to explore how cows and cheese respond when grass is scarce.

The relationship between grass and in cheese

To many people, cheese is just…cheese. But dairy scientists know that the story starts in the pasture. Cows that graze on grass produce milk that is often richer in certain healthy fats (like omega-3s) and more colorful, thanks to plant pigments called carotenoids. This makes for butter that’s yellower, milk that’s more flavorful, and cheese that melts differently in your mouth. Previous research has shown that cheese from grass-fed cows tends to have stronger aromas and a softer, creamier texture compared to cheese made from the milk of cows fed mainly on corn silage.

Consumers often say they prefer the taste of grass-based dairy products, which is why labels like “pasture-raised” or “grass-fed” catch attention at the supermarket. But climate change is complicating things. In semi-mountainous regions like France’s Massif Central, summer droughts are becoming more common. That means less lush green pasture for cows, and more reliance on stored feeds like hay, silage, or grain concentrates.

The researchers carried out their experiment in 2021 at a high-altitude dairy research farm in France. They worked with 40 cows, 26 Prim’Holsteins and 14 Montbéliardes, divided into four groups of ten. For the first eight weeks, two groups grazed mostly on grass (about three-quarters of their diet), while the other two groups had a corn-based mixed ration with only a little fresh grass.

Then, they introduced a variable. For the next eleven weeks, one group from each system had their grass reduced. The “grass cows” got only half as much pasture and were fed more hay and concentrates indoors. The “corn cows” had grass removed entirely from their diets, relying on silage and concentrates instead.

Throughout the trial, the team measured everything: milk yield, milk composition, feed efficiency, estimated methane emissions, and, crucially, what happened when that milk was turned into Cantal-type cheese, a traditional pressed cheese from the Auvergne region. After nine weeks of ripening, the cheeses were analyzed chemically, tested by microbiologists, and even tasted by trained sensory panels.

Basically, the experiment can be summarized as follows: the cows eat, the milk is sampled, and then cheese cheeses ripens in carefully controlled conditions. It’s rare to see a farm experiment that follows the story all the way from pasture to plate.

So, what happened to the milk?

Surprisingly, cutting grass from the corn-based diet didn’t change how much milk the cows gave. But it did make them less efficient. Without grass, they needed more feed to produce the same amount of milk.

The grass-fed cows told a different story. When their pasture was reduced but not eliminated, they actually maintained milk yield better than expected. They used their feed more efficiently and, as a bonus, produced less methane per liter of milk. That’s important because methane is a powerful greenhouse gas, and dairy cows are a major source worldwide. In short: a little bit of grass goes a long way.

And what about the cheese?

Here’s where things get really interesting. Cheeses made from milk of grass-fed cows were softer, yellower, and more flavorful. The sensory panels described them as smoother, fattier, and “meltier” in the mouth. The microbiological tests revealed why: milk from grazing cows carried more diverse communities of microbes, including certain lactobacilli that contribute to cheese flavor during ripening. These microbes often hitch a ride from the grass itself.

In contrast, cheeses made from the corn-only cows were firmer, paler, and blander. Their microbial communities were less rich, and the breakdown of milk proteins, a process that releases savory and aromatic compounds, was weaker. Removing grass didn’t hurt the volume of milk, but it clearly dulled the cheese.

Many people don’t realize how directly the cow’s diet affects the cheese on their table, but one panelist summed it up neatly: grass makes cheese taste like cheese.

This study has several implications. Farmers in regions prone to drought need strategies to keep their herds healthy and productive. This study shows that adjusting diets can work, but eliminating pasture entirely risks lowering the quality of dairy products. Moreover, it's important for sustainability. In fact, feed efficiency and methane emissions are central to making dairy farming climate-friendly. The grass-fed system, even under stress, performed better in terms of efficiency and methane intensity.

What's the lesson for all of us?

From a consumer perspective, the message is simple: when you buy cheese made from milk of cows that graze on fresh grass, you’re getting a product that’s richer, tastier, and, indirectly, better for the environment. For farmers, the decision is trickier. Grass is not always available, and relying entirely on it makes farms vulnerable to weather shocks. Corn silage and concentrates can stabilize milk supply. But this study suggests that keeping at least some fresh grass in the diet is critical to preserving cheese quality.

In other words, it’s not “all grass or no grass.” Even partial grazing seems to make a difference. Cheese may seem timeless, but as this study shows, it’s surprisingly sensitive to the shifting climate and farming choices behind it. Droughts, feed shortages, and greenhouse gases might feel like abstract global problems until you realize they’re changing the very texture and taste of your favorite wedge of Cantal or Camembert.

If you want to learn more, read the original article titled "Adaptation strategies to manage summer forage shortages improve animal performance and better maintain milk and cheese quality in grass- versus corn-based dairy systems" on Journal of Dairy Science at http://dx.doi.org/10.3168/jds.2024-25730.