Researchers tested whether replacing cottonseed with a flaxseed-based supplement could improve the nutritional quality of milk from dairy cows while reducing harmful methane gas emissions. Twenty-four Holstein cows were fed three different diets over several weeks. The results showed that cows eating the flaxseed supplement produced milk with better fatty acid profiles—specifically more of the healthy omega-3 fats that humans benefit from—without reducing how much milk they made. However, the supplement didn’t reduce methane emissions as hoped. This suggests flaxseed could be a useful tool for making dairy products more nutritious while maintaining farm productivity.

The Quick Take

  • What they studied: Whether feeding dairy cows a flaxseed-based supplement instead of cottonseed would change the type of fats in their milk and reduce methane gas they produce.
  • Who participated: Twenty-four Holstein dairy cows (a common dairy breed) that were about 3-4 months into their lactation cycle. The cows were divided into three groups receiving different amounts of the flaxseed supplement.
  • Key finding: Cows fed the flaxseed supplement produced milk with significantly more omega-3 fatty acids (up to 2.8 times more) and different types of healthy fats, while maintaining the same milk production levels. Methane emissions didn’t change, but hydrogen gas production increased slightly.
  • What it means for you: If you drink dairy milk, flaxseed-supplemented cow feed could make the milk you buy more nutritious with better fats. However, this approach alone won’t reduce the environmental impact of dairy farming through methane reduction. This is an early-stage finding that needs more research before widespread farm adoption.

The Research Details

This was a controlled feeding experiment using 24 dairy cows arranged in what scientists call a ‘Latin square design.’ This means each cow received all three different diets over time, with each diet lasting 28 days plus 2 weeks of adjustment. This design is powerful because each cow serves as its own comparison, reducing the effect of individual differences between animals.

The three diets tested were: a control diet (standard feed), a diet with 4.5% flaxseed supplement replacing some cottonseed, and a diet with 9% flaxseed supplement replacing more cottonseed. The researchers measured milk production daily and collected milk samples weekly to analyze the types and amounts of fats, proteins, and other components. They also measured the gases the cows produced (methane, carbon dioxide, and hydrogen) to assess environmental impact.

The study was conducted at a research facility where conditions could be carefully controlled, and all measurements were taken using standardized scientific methods.

Using a Latin square design where each cow gets all treatments is stronger than simply comparing different groups of cows, because it accounts for natural differences between individual animals. Measuring actual milk composition and gas emissions directly (rather than estimating) provides reliable data. This type of controlled study is necessary before recommending changes to how farmers feed their herds.

Strengths: The study used a rigorous experimental design, measured multiple important outcomes, and was published in a respected dairy science journal. The sample size of 24 cows is reasonable for this type of research. Limitations: The study was relatively short (28 days per diet), involved only one breed of cow, and was conducted in a controlled research setting rather than on typical farms. Results may not apply to different cow breeds, different farm conditions, or longer-term feeding.

What the Results Show

The flaxseed supplement successfully changed the fatty acid composition of the milk. Cows fed the highest level of flaxseed supplement (9%) produced milk with nearly three times more omega-3 fatty acids (1.46% versus 0.52% in control milk). The milk also had higher levels of oleic acid, a monounsaturated fat considered beneficial for human health.

Despite these changes in milk composition, the cows produced just as much milk as the control group—there was no reduction in milk yield. The milk also maintained normal levels of protein, lactose (milk sugar), and other quality indicators. This is important because it means farmers could improve milk nutrition without sacrificing productivity.

Contrary to expectations, methane emissions (the main greenhouse gas from dairy cows) did not decrease with the flaxseed supplement. Hydrogen gas production actually increased slightly in the highest flaxseed group. The researchers suggest this unexpected result occurred because the flaxseed supplement changed the fiber content of the diet in ways that offset any methane-reducing effects of the added fats.

Milk fat percentage was slightly lower in the supplemented groups (4.47-4.51%) compared to control (4.67%), though this difference was small and unlikely to be noticeable to consumers. Milk protein, lactose, and somatic cell count (an indicator of udder health) remained unchanged across all groups. Body weight changes and daily feed intake were similar among all treatment groups, suggesting the cows tolerated the supplement well without digestive problems.

Previous research has shown that adding fats to dairy cow diets can reduce methane emissions, but results vary depending on the type of fat used. This study suggests that flaxseed fats may work differently than other fat sources. The finding that milk composition can be improved without reducing methane is somewhat disappointing for environmental goals but encouraging for nutritional improvement. The increase in omega-3 fatty acids aligns with what other flaxseed studies have shown in different animal species.

The study lasted only 28 days per diet, which is relatively short for evaluating long-term effects. Only Holstein cows were tested, so results may differ in other dairy breeds. The research was conducted in a controlled facility, not on commercial farms, so real-world results might differ due to variations in farm management, other feed ingredients, and environmental conditions. The study didn’t evaluate whether consumers would notice or value the improved fatty acid profile, or whether it would affect milk taste or shelf life.

The Bottom Line

Based on this research, flaxseed supplements appear safe and effective for improving the nutritional quality of dairy milk (moderate confidence). The supplement could be considered by dairy farmers interested in producing milk with higher omega-3 content for health-conscious consumers. However, don’t expect this supplement to reduce environmental impact through methane reduction (low confidence for that goal). More research is needed on long-term effects, cost-effectiveness, and whether the improved milk nutrition translates to health benefits for consumers.

Dairy farmers interested in premium or health-focused milk products should pay attention to this research. Consumers seeking milk with better fatty acid profiles may benefit from products made with this supplement. Environmental advocates should note that this approach alone won’t solve methane emissions from dairy farming. People with flaxseed allergies should avoid products from supplemented cows. This research is most relevant to large-scale dairy operations that can implement feed changes systematically.

The changes in milk fatty acid composition happened within 28 days, suggesting relatively quick adaptation. However, consumers would need to consume this milk regularly over weeks or months to potentially experience any health benefits from the improved fatty acid profile. Long-term studies would be needed to determine if these benefits persist and whether they meaningfully improve human health.

Want to Apply This Research?

  • If using a nutrition tracking app, users could monitor their intake of omega-3 fatty acids (ALA from flaxseed-supplemented dairy) by logging dairy products and noting the source. Target: track weekly omega-3 intake from dairy sources and compare weeks when consuming flaxseed-supplemented products versus regular dairy.
  • Users could set a goal to purchase and consume dairy products specifically labeled as coming from flaxseed-supplemented cows (if available in their market). Start by replacing one regular dairy product per week with a flaxseed-supplemented version and track how consistently you maintain this swap.
  • Create a monthly check-in to assess: (1) availability of flaxseed-supplemented dairy products in your area, (2) consistency of purchasing these products, (3) any perceived differences in milk taste or quality, and (4) overall dairy intake and omega-3 consumption patterns. Use the app’s notes feature to record observations about product availability and personal preferences.

This research describes an experimental feed supplement tested on dairy cows in a controlled research setting. The findings are preliminary and should not be considered medical advice for human consumption. While the milk from supplemented cows showed improved fatty acid profiles, individual health benefits would depend on overall diet and personal health status. Consult with a healthcare provider or registered dietitian about whether flaxseed-supplemented dairy products are appropriate for your specific health needs. This study does not guarantee that commercially available flaxseed-supplemented dairy products will have the same composition or benefits. Farmers considering implementing this supplement should consult with their veterinarian and nutritionist about feasibility, cost, and long-term effects on their specific herd.