In recent years, American milk has undergone a quiet transformation. The milk produced by our dairy cows has become creamier and more luscious as breakthroughs in cow genetics and nutrition have pushed the fat component of milk—also known as butterfat—to all-time highs. In 2000, the average dairy cow made 670 pounds of fat in her milk a year; today, she’s making 1,025 pounds. No single trait in dairy cows has improved as rapidly with genomic selection as fat, according to Chad Dechow, a dairy-cattle geneticist at Penn State. It’s a triumph of dairy science.
Lately, though, all is not well in the world of butterfat. Dairy science has arguably made our cows too good too fast at fatmaxxing.
This past fall, butter prices collapsed as a “tsunami” of butterfat inundated the market. “We really have an oversupply right now,” Corey Geiger, the lead economist for dairy at CoBank, told me. The reason is twofold, he explained: U.S. farmers are keeping a near-record number of dairy cows, which are in turn producing milk with a record level of fat. For customers, this oversupply means cheaper butter. For farmers, “it’s going to be a tough year,” Dechow told me. “The farmers take it on the chin.”
Until last autumn’s crash, farmers had every economic incentive to keep pushing the limit on fat. Butter and cheese consumption have been growing steadily since the 1990s, and butterfat prices were sky-high for several years running. When dairy farmers sell milk, they are generally paid not by volume—milk is mostly water, after all—but by the weight of its solid components, primarily fat and protein. More fat plus more protein adds up to a bigger milk check. Although protein, too, has ticked up in milk, fat has proved more responsive to changes in genetics and diet. After hovering for decades around 3.65 percent, milk fat began rising first slowly and then quickly, reaching 4.24 percent in 2024.
“Genetics sets the ceiling, and nutrition determines the floor,” Dechow said. After the first dairy cow’s genome was sequenced in 2009, the industry started raising the genetic ceiling. By marrying DNA markers to the milk-production records of millions of cows, farmers are able to choose bulls for breeding based on the predicted traits—including milk-fat yield—of their future daughters. And when those daughters are born, some farmers once again DNA-test the young cows, keeping only the ones with the most potential. This precise level of selection has allowed the high-butterfat versions of milk genes to spread far and wide in the American dairy herd over just a few generations. Genetics explains about half to two-thirds of the rise in butterfat levels, experts told me.
For a cow to meet her genetic butterfat potential, though, she needs the right diet. “Cows do not make milk fat from thin air,” Kevin Harvatine, a dairy nutritionist at Penn State, told me. A modern cow’s dietary intake is precisely managed, down to the length of plant fibers optimal for digestion. Even the crops they eat—low-lignin alfalfa, high-oleic soybeans—have been genetically modified or bred to stimulate high milk and milk-fat production in a cow’s body. Farmers can also add specific supplements, such as palmitic acid, a by-product of palm-oil production, to further boost butterfat. (This practice came to widespread attention during Buttergate, in 2021, when Canadians began noticing that their butter had become firmer and less spreadable at room temperature. Palmitic acid does indeed increase the melting temperature of butter.)
You can’t actually buy this extra-rich cow’s milk at grocery stores. Despite its name, the whole milk sold in plastic jugs is not the whole milk, but a standardized fiction: For decades, the U.S. has defined whole milk to meet a minimum of 3.25 percent fat—the low end of what was once a cow’s natural range. That number has remained unchanged even as the actual average fat content of milk has risen a full percentage point above it. Any excess of fat from “whole milk” is instead transformed into high-fat dairy products: the various creams (heavy, whipping, sour, ice), butter, triple-crème Bries, ultra-lush yogurts, and so on.
Today’s 4-percent-plus milk has created problems for certain cheese makers. It is simply too rich for varieties such as cheddar, Colby, and Monterey Jack, which require a lower fat-protein ratio. Cheese makers have had to reconfigure their manufacturing lines, either to receive extra dairy protein in the form of skim milk or to install a million-dollar separator to remove excess fat. “It’s extra cost, extra steps, extra bother,” Dean Sommer, a cheese and food technologist at the Center for Dairy Research at the University of Wisconsin at Madison, told me. “They’re transitioning from the world they knew, when it comes to the fat content of milk, to the world we’re dealing with.”
The unwanted fat from cheesemaking ends up at processors such as Grassland Dairy, a large butter maker based in Wisconsin. Lately, says its president, Trevor Wuethrich, Grassland has had to keep its facility running more often to keep up with all of the leftover fat coming from cheese makers. Cheese makers that used to send a truckload of cream a week, he told me, are now sending “a load a day.” Some days, he has to turn loads away.
Where else can the extra butterfat go? A few years ago, back when butterfat prices were high, Geiger said, some ice-cream makers swapped out dairy cream for cheap gums and air, making “frozen dairy desserts” that contained too little dairy cream to be legally labeled “ice cream.” “I think there’s an opportunity to get more cream back into ice cream,” he told me. Ice-cream makers, naturally, may want to see sustained low prices before jumping back on the butterfat train.
Meanwhile, dairy farmers are already looking to hedge their bets: If not fat, then protein? (And Americans sure love their protein these days.) But breeding cows for milk protein would be more challenging, Dechow said. Milk-protein yield varies less from cow to cow, making it more difficult to make changes through genetic selection. The fat and protein levels of milk are also linked, so enhancing protein would likely enhance fat too.
The high-milk-fat dairy cow won’t be going anywhere, though. At current prices, Harvatine said, “it still makes sense for us to convert feed into butter. It’s just not nearly as profitable as it was a year ago.” If a dairy farmer is doing 10 different things to maximize butterfat, the first nine things might still make sense, he said—only “now I’m questioning the last thing that I’m doing.” And genetically, the American cow is locked in. Breeding decisions made as recently as a few months ago—when butterfat prices were at a peak—will come to fruition only over the next three or four years, as those calves are born, mature into cows, and start producing the super-rich milk of their genetic destiny. The butterfat boom is far from over.
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