Nutritionally Enhanced Milk

Grazing dairy cows at the WCROC

May 2018

Recently, there is an increase in global demand for grass-fed dairy products. Consumers are becoming more concerned about the origins of food, and grass-fed dairy and organic dairy has the potential to provide alternative dairy products for consumers.  Currently, organic production in the United States is dominated by cash grain crops, with the majority of organic farmers in the United States using 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. Health food stores have identified grass-fed dairy as an emerging trend based on consumer interest.  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 potential new resource for dairy production in the United States. 

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. Today, Americans consume 10 to 15 grams of omega-6 for every gram of omega-3. Previous research has shown that consuming organic dairy products lowers dietary intakes of omega-6, while increasing intakes of omega-3 and conjugated linoleic acid (CLA), a heart-healthy fatty acid. Through a recently published national study, we found that cows fed a 100% organic grass and legume-based diet produce milk with elevated levels of omega-3 and CLA, and thus provide 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 a near 1 to 1, compared to 5.7 to 1 in conventional whole milk. 

So, what is grass-fed milk?  This milk (termed "grassmilk") comes from cows fed a nearly 100% forage-based diet. During the grazing season dairy cows consume nearly all their dry matter intake 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, that may include dried or fermented forages (alfalfa, clovers, grass). Cereal crops harvested prior to the boot stage, such as oats and barley may also be fed.  Annual and perennial forage crops are managed throughout the year to provide for both grazing and stored winter feed. A lot of the 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. 

In a study over 3 years, we quantified the fatty acid profile in milk from cows fed a 100% forage-based diet and compared it to profiles from milk from cows under conventional and organic management.  The 1,163 raw milk samples came primarily from 3 regions of the United States—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: 1) "Grassmilk" cows receive an essentially 100 percent organic grass and legume forage-based diet, via pasture and stored feeds like hay and silage,  2) "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, and 3)  "Conventional" cows are fed rations in which forage-based feeds account for an estimated 53% 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 (g/100 g), compared to 0.02 g/100 g in conventional milk - a 147%increase in omega-3s. Grassmilk also had 52% less omega-6 than conventional milk, and 36% less omega-6 than organic milk. 

Omega 6 Omega 3 graph

There were some regional and seasonal variation in the fatty acid profile of grassmilk (see Figure).  The highest levels of omega-3s in grassmilk was from the Midwest and Northeast (1.60% and 1.58%), and California had the lowest (1.40%). The Midwest and Northeast had the highest concentrations of omega-6s in grassmilk.  The omega-6/omega-3 ratio was the highest in July while cows where on pasture and was lowest in December.  Seasonal variations maybe 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. 

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 would provide about 300 milligrams of CLA, which is three-fourths of the target intake for adult men and 100% of target levels for adult women.  For omega-3s, three servings of grassmilk would provide about 22% of daily needs for adult men and 32% for adult women. Conventional dairy products would supply less than half of these amounts. The three daily servings of grassmilk would supply up to 58% of total daily omega-3 intake, making dairy by far the primary source of omega-3 fatty acids across all food groups. 

Dairy supplies little omega-6s, which is less than 10% of the total in diets. Most of the omega-6 in the American diet today comes from fried foods, vegetable oils, and processed foods.  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 looking for ways to lower costs and increase profitability may look at shifting away from high-production, high-cost systems that are reliant 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, many benefits may be achieved on grassmilk farms. Understanding of the relationship between fat and health outcomes will help guide livestock and dairy farmers searching for ways to promote public health.

More information on the study can be found at Why Grass Matters.