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Grass-fed cows produce healthier milk

Quick facts

  • Dairy consumers perceive "grassmilk" as healthier. And studies have shown that it is.
  • Grass-fed dairy and organic dairy cows provide milk significantly higher in beneficial fatty acids and lower in omega-6.
  • Farmers can lower production costs by switching cows to grass and legume-based diets.
dairy cows of different colors grazing on grass in a pasture next to trees

Grass-fed dairy and organic dairy provide alternative products for consumers concerned about how and where their food is produced. The majority of organic dairy farmers in the United States use off-farm purchases to feed their organic animal herds. However, there is a high consumer preference for "grass-fed" dairy in the United States, which is perceived as healthier.

Because of the growing trend in the organic and grass-based dairy market, cattle producers may capitalize on forage for grazing and organic cattle, which may represent a new resource for dairy production in the United States.

So, what is grass-fed milk?

"Grassmilk" comes from cows fed a nearly 100 percent forage-based diet. During the grazing season dairy cows consume nearly all their dry matter  from pasture. The cows may consume certain mineral and energy supplements, such as molasses, at low levels. During the non-grazing season, grassmilk cows must consume all forage-based feeds, these may include dried or fermented forages (alfalfa, clovers, grass). Cows may also eat cereal crops harvested prior to the boot stage, such as oats and barley.

Annual and perennial forage crops are managed throughout the year to provide for both grazing and stored winter feed. Many grassmilk farmers harvest feedstuffs that are preserved to be fed as baleage. An increase in grass-based diets for cows requires careful management of pasture composition and forage production, soil fertility, and animal health.

Effect of grassmilk on human diets

Omega-6 and omega-3 fatty acids are essential human nutrients, yet consuming too much omega-6 and too little omega-3 can increase the risk of cardiovascular disease, obesity and diabetes. Research has shown that consuming organic dairy products lowers dietary intakes of omega-6, while increasing intake of omega-3 and conjugated linoleic acid (CLA), a heart-healthy fatty acid.

A recent national study found that cows fed a diet of totally organic grass and legumes produced milk with elevated levels of omega-3 and CLA, which provides a markedly healthier balance of fatty acids. The improved fatty acid profile in grass-fed organic milk and dairy products brings the omega-6/omega-3 ratio to nearly 1 to 1, compared to 5.7 to 1 in conventional whole milk.

Comparing fatty acid profiles

In a study over three years, we quantified the fatty acid profile in milk from cows fed a 100 percent forage-based diet and compared it to profiles of milk from cows under conventional and organic management. The 1,163 raw milk samples came primarily from the U.S. Midwest, Northeast and California. All samples came from farmer members of CROPP Cooperative and were tested by an independent laboratory.

We compared the fatty acid profile of milk from cows managed under three systems in the United States:

  • "Grassmilk" cows receive an essentially 100 percent organic grass and legume forage-based diet, via pasture and stored feeds like hay and silage.
  • "Organic" cows receive, on average, about 80 percent of their daily dry matter intake from forage-based feeds and 20 percent from grain and concentrates.
  • "Conventional" cows are fed rations in which forage-based feeds account for an estimated 53 percent of daily dry matter intake, with the other 47 percent coming from grains and concentrates. Conventional management accounts for over 90 percent of the milk cows on U.S. farms.

Grassmilk provided by far the highest level of omega-3s (0.05 grams per 100 grams of milk), compared to 0.02 g/100 g in conventional milk;  a 147 percent increase in omega-3s. Grassmilk also had 52 percent less omega-6 than conventional milk, and 36 percent less omega-6 than organic milk.

There were some regional and seasonal variations in the fatty acid profile of grassmilk.

  • The highest levels of omega-3 in grassmilk were from the Midwest (1.60 percent) and Northeast (1.58 percent ). California had the lowest (1.40 percent ).

  • The Midwest and Northeast had the highest concentrations of omega-6 in grassmilk.

  • The omega-6/omega-3 ratio was the highest in July while cows were on pasture and was lowest in December.

Seasonal variations may be due to climate conditions that are most extreme during drought or flooding. The duration of the grazing period also impacts forage quality, as does management attention to sustaining a good mix of grasses and legumes in pastures.

Consumer benefits of switching to grassmilk

We modeled daily fatty acid intakes for a typical 30-year old woman consuming a typical diet in the United States to assess the impact of switching to grassmilk dairy products. Shifting from conventional to grassmilk dairy products may have a positive impact on total omega-3 and CLA intake.

  • Three servings of grassmilk provide about 300 milligrams of CLA, which is 75 percent of the target intake for adult men and 100 percent of target levels for adult women.

  • For omega-3s, three servings of grassmilk would provide about 22 percent of daily needs for adult men and 32 percent  percent for adult women. Conventional dairy products would supply less than half of these amounts.

  • Three daily servings of grassmilk would supply up to 58 percent  of total daily omega-3 intake, making dairy by far the primary source of omega-3 fatty acids across all food groups.

Most of the omega-6 in the American diet today comes from fried foods, vegetable oils and processed foods, with little coming from dairy. For people striving to lower their risk of cardiovascular and other metabolic diseases, for pregnant women, and for infants and children, the greater omega-3 intake from grassmilk may help improve human health.

Dairy farmers can lower costs by switching to grassmilk

Dairy farmers looking for ways to lower costs and increase profitability may look at shifting away from high-production, high-cost systems that rely on purchased grains and concentrate feeds.

With a diverse mix of pasture and available cropland for forage production, animal genetics, a reliable milk market, and guidance, grassmilk farms may provide many benefits for both the farmer and consumer.

Understanding the relationship between fat and health outcomes will help guide livestock and dairy farmers searching for ways to promote public health. Read more about Why Grass Matters.

Brad Heins, Extension organic dairy scientist

Reviewed in 2018

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