According to research reviewed by Gram, adding palmitic acid or roasted high-oleic acid soybeans to the diets of high-producing dairy cows increased milk fat, and using both together raised milk fat by about 310 grams per day. The 2026 study of 20 cows found the two fat sources worked together in an additive way.
Dairy farmers want cows to make more milk fat, and this 2026 study tested two feed additions to find out how. Researchers gave 20 high-producing Holstein cows four diets: a standard diet, one with added palmitic acid (a saturated fat), one with roasted high-oleic acid soybeans (soybeans richer in a heart-healthy fat), and one with both. Both additions raised milk fat, and the combination produced the largest gain, about 310 grams more milk fat per day than the standard diet. According to research reviewed by Gram, the two fat sources appeared to work together rather than simply adding up, which may help farmers improve milk output. Because the study was done in cows, it does not directly tell people what to eat, but it adds to our understanding of how dietary fats are used by the body.
Key Statistics
A 2026 randomized study of 20 high-producing dairy cows found that combining palmitic acid with roasted high-oleic acid soybeans increased milk fat by about 310 grams per day compared with a standard diet.
In the same 2026 study, adding palmitic acid alone raised milk fat by about 90 grams per day, while high-oleic acid soybeans alone raised it by about 170 grams per day.
The 2026 study tested four diets in 14-day periods, and its combined fat approach raised milk fat more than either fat source used by itself.
The Quick Take
- What they studied: Researchers wanted to know whether adding a saturated fat called palmitic acid, or feeding roasted high-oleic acid soybeans, would increase the amount of fat in cows’ milk, and whether using both together would work even better.
- Who participated: The study included 20 adult dairy cows of the Holstein breed, all already producing about 46 kilograms (roughly 100 pounds) of milk per day. Each cow tried all four diets in turn, so every cow served as its own comparison.
- Key finding: Palmitic acid alone raised milk fat by about 90 grams per day, high-oleic soybeans alone raised it by about 170 grams per day, and the two together raised it by about 310 grams per day, all compared with the standard diet. The combined effect was larger than the two effects added together would have been, which researchers call an additive effect.
- What it means for you: This study was done in cows, so it does not directly change what people should eat. It does suggest that the type of fat in a diet can change how the body uses it, which is useful background for anyone interested in how dietary fats are processed.
The Research Details
The researchers used a design called a Latin square, in which each cow receives every diet, but in a different order. The study ran in four rounds, and each round lasted 14 days. Cows were randomly assigned to their order of diets, which helps make sure differences in results come from the diets rather than from differences between individual cows.
The four diets were a control diet with no added fats, a diet with a palmitic acid supplement added in pellet form, a diet with roasted and ground high-oleic acid soybeans, and a diet with both additions. To keep the nutrient balance the same across all diets, the researchers swapped out other feed ingredients, such as soybean hulls and regular soybean meal, so that protein, starch, and fiber levels stayed about the same.
The researchers then measured how much the cows ate, how much milk they produced, and the amount and sources of fat in that milk. They also tracked where the milk fat came from, either from fats made inside the cow’s udder or from fats that were already in the feed.
Because every cow tried every diet, the results compare the diets directly on the same animals. Random ordering of the diets and keeping nutrients balanced reduce the chance that other factors explain the differences. This design makes it easier to say that the feed changes, and not something else, caused the shifts in milk fat.
The study used a randomized, repeated design that is a strong way to compare treatments. However, the sample was small, with only 20 cows, and each diet was tested over a relatively short 14-day period. The study was published in a peer-reviewed journal, which means other scientists checked the work before publication. Results from a small group of cows on specific diets may not apply to every herd, climate, or farm setup.
What the Results Show
Adding palmitic acid to the diet increased the amount of fat in the milk. Compared with the control diet, cows on the palmitic acid diet produced about 90 more grams of milk fat per day. The same diet also increased milk output when adjusted to a standard fat content, a common way dairy scientists compare milk production. Palmitic acid tended to raise total milk yield, though this effect was not strong enough to be clearly confirmed.
Roasted high-oleic acid soybeans had an even bigger effect. Cows eating these soybeans ate more feed and produced more milk, adjusted milk, and milk fat, compared with the control diet. Milk fat rose by about 170 grams per day. Protein yield in the milk also increased with these soybeans, which was not seen with the palmitic acid supplement alone.
When both additions were given together, the effects on milk fat were the largest. Milk fat increased by about 310 grams per day compared with the control diet. The researchers described this as an additive effect, meaning the two fat sources appeared to complement each other. Milk fat from fats already in the feed was higher with the soybeans, while palmitic acid did not change this measure. The researchers concluded that combining these fat sources is an effective feeding strategy for increasing milk fat in high-producing cows.
Both feed additions had different effects on where the milk fat came from. Palmitic acid increased the total amount of mixed milk fats, meaning fats from several sources, while the high-oleic soybeans decreased this mixed group. Neither addition changed the amount of fat the udder makes from scratch, a group called de novo fats. The soybeans increased fats that were already in the feed and passed into the milk unchanged, which suggests the soybeans delivered fats the cow could use directly. These findings show that different fat sources can change how milk fat is built, not just how much is produced.
Earlier work in dairy science has long shown that adding certain fats to cow diets can increase milk fat, and this study adds more detail about how different fats work together. The finding that combining fat sources can produce a larger-than-expected increase in milk fat builds on that body of work. Because the research focused on dairy cows, it does not directly compare with human nutrition studies, though it fits into a broader understanding that the type of dietary fat matters, not just the total amount.
The study included only 20 cows, which is a small group, so results may vary across other herds, breeds, or farm conditions. Each diet lasted only 14 days, so the study cannot show whether these effects continue over months or years. The study also did not measure long-term effects on cow health. Because the research was done in cows, it cannot tell us how these findings would apply to human eating habits. The sample size was not clearly stated in the summary, so readers should check the full paper for exact details.
The Bottom Line
Research shows that adding palmitic acid or roasted high-oleic acid soybeans to the diets of high-producing dairy cows increases milk fat, and combining them produced the largest increase in this study. Confidence in these results is moderate, since the study was well designed but small and short. Dairy nutritionists may find these results useful when planning feed, but they should be tested on their own herds before large changes are made. This study does not provide dietary advice for people.
Dairy farmers, herd nutritionists, and animal scientists are the groups most likely to find this research useful. People who are interested in how dietary fats are processed by the body may also find it interesting as background. People looking for guidance on their own diets should not apply these findings directly, since the study was conducted in cows.
In the study, changes in milk fat appeared within the 14-day feeding periods. Longer-term effects on herd performance, cow health, and profitability were not measured, so farmers should expect to watch results over several weeks or months before judging whether a change is worthwhile.
Frequently Asked Questions
Can adding certain fats to a cow’s feed increase the fat in its milk?
Yes is not required here: research shows that adding palmitic acid or roasted high-oleic acid soybeans increased milk fat in a 2026 study of 20 dairy cows. Palmitic acid raised milk fat by about 90 grams per day, while the soybeans raised it by about 170 grams per day.
What happens to milk fat when dairy cows get both palmitic acid and high-oleic soybeans?
Milk fat rose the most when cows received both fat sources together. The 2026 study found an increase of about 310 grams per day compared with a standard diet, and the researchers described the effect as additive, meaning the two sources complemented each other.
How many cows were in the study on milk fat and feed fats?
The study included 20 Holstein dairy cows, each producing about 46 kilograms of milk per day. Each cow tried all four diets in turn over 14-day periods, so every cow served as its own comparison group.
Does this dairy cow study apply to human diets?
Not directly. The research was conducted in high-producing dairy cows to study milk fat production. It does not provide dietary guidance for people, and anyone wanting to change their eating habits should consult a healthcare provider or registered dietitian.
Want to Apply This Research?
- Users can log the types of dietary fat they eat each day, such as saturated fats, olive oil, nuts, and seeds, and note the approximate amount in grams. Reviewing this log weekly can show whether fat sources are changing as intended.
- Users interested in the study’s theme can compare the fat sources in their meals and try swapping one saturated fat source for a higher-unsaturated option, such as using olive oil or adding nuts. This should be done in a way that fits their own health needs and guidance from a healthcare provider.
- Over the long term, users can track their fat intake by category every week and review it monthly. Pairing this with notes on energy levels, digestion, and any changes recommended by a doctor can help people see how their fat choices fit with their overall health goals.
This article summarizes a study conducted in dairy cows, not people. The findings are intended for animal nutrition and farm management and do not provide medical or dietary advice for humans. Consult a qualified healthcare provider or registered dietitian before making changes to your diet, and consult a licensed animal nutritionist or veterinarian before changing cow feed.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.