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Food, Health, and Eco-news
Cows' Climate-Warming Gases Cut by Grassy Diet
Cut in greenhouse gas emissions linked to higher omega-3/omega-6 ratio in grasses vs. grains; grass feeding also boosts nutritional value of milk
by Craig Weatherby

One year ago, we began offsetting the climate-warming carbon emissions associated with shipping our goods to Vital Choice customers.

The project we supported through June of this year trapped the climate-warming methane emissions from dairy cows at Pennsylvania's Brubaker Farm, and burned them to generate power.

(For the next 12 months, our carbon shipping footprint will be offset by helping the town of Greensburg, Kansas become a wind-powered community, following its near-total destruction by a tornado. To learn more, go to our Vital Green page.)

Now, the organic yogurt makers at New Hampshire's Stonyfield Farm have announced a project to reduce methane emissions from cows… greatly lessening the amount of this greenhouse gas that cows burp up in the first place!

Grass fed dairy cows proven to produce less warming gas
Stonyfield Farm, a major organic yogurt maker, is running the first program in North America to naturally decrease global warming gases caused by cows' burps (enteric emissions).

And a major side benefit of the program is that it also significantly increases the nutritional value of the milk. We reported on this back in 2007: see “Organic Produce and Milk Offer More Antioxidants and Omega-3s.” In that study, the organically raised cows were fed mostly grass.

“This is a watershed moment for the US dairy industry,” said Stonyfield President/CEO.

Gary Hirshberg. “By changing the feed we give our cows, we can simultaneously reduce greenhouse gas emissions and improve milk's nutritional content in a way that may help reduce cardiovascular disease and obesity.”

The Stonyfield Greener Cow pilot program began in late 2008 with 15 Vermont Organic Valley farms which supply the milk for Stonyfield's yogurts. The company learned about this approach from its global partner French-based Groupe Danone.

Stonyfield had been measuring its carbon footprint for over a decade, and had known milk production was the biggest part of its footprint. While it developed programs for emissions from growing feed for cows, manure, transportation, and farm energy, handling its greatest source of milk emissions, the natural digestion of the cow, was a challenge.

The pilot program works by feeding cows a diet high in natural omega-3 sources, such as alfalfa, flax and grasses. This results in an increase in the milk's omega-3 content and decrease in the levels of saturated fats. Through intensive, ongoing analysis of the feed and the cow's milk, the pilot program re-balances the cow's main stomach or “rumen”. This results in a reduction of the waste by-product methane, a greenhouse gas, which the cows emit primarily through burping.

The milk from the pilot program is tested in the lab of milk lipids expert Dr. Adam Lock at the University of Vermont using gas chromatography, an analytics technique for determining the fatty acid composition of milk fat, and from that the cow's methane emissions can be calculated.

“Stonyfield Farm has been able to reduce the enteric emissions from the cows by as much as 18%, an average of 12%. If every US dairy were to adopt this approach, in less than one year, the amount of greenhouse gas emissions we could reduce would be the equivalent of taking more than half a million cars off the road!” announced Nancy Hirshberg, Stonyfield V.P. of Natural Resources and the director of the Stonyfield Greener Cow Project.

Grassy diet improves “omega-ratio dramatically
The omega-3s in the milk increased by nearly one third (29%) and also lowered the omega-6 to omega-3 ratio… a balance that regulates key human physiological functions.

“The Stonyfield Greener Cow program is changing food in exactly the ways we need it to be changed,” said Artemis P. Simopoulos, M.D international authority on essential fatty acids and former chair of the Nutrition Coordinating Committee at the National Institutes of Health (NIH).

According to her book The Omega Diet, what we eat today contains too much omega-6 and not enough omega-3. This “hidden imbalance” makes us vulnerable to heart disease, cancer, obesity, autoimmune diseases, allergies, diabetes and depression.

Only plants can synthesize omega-6 and omega-3. By eating animals that have consumed plants high in omega-3, humans get this important nutrient. Over the past 50 years, though, our diets have changed and we now consume more omega-6 rich foods such as oils from corn, palm and soy.

We also changed what livestock eat by increasing the amount of corn and soy in their feed, and decreasing grass, which is high in omega-3. The result is that eggs, meat and dairy have less omega-3. Thus, the omega-6 to omega-3 ratio in our diets
which used to be about 1or 2 to 1is now out of balance with about 20 times more omega-6 than omega-3.

“There is an environmental cost to these changes,” stated Nancy Hirshberg. “Clearing forests for palm and soy has caused ecological devastation. For every piece of rainforest or prairie that is destroyed to grow soybean or palm, our bodies pay the price with an imbalance in the omega-6 to omega-3 ratio. Put simply, our health and nutrition are tied to what animals eat. We are what they eat!”

Stonyfield President/CEO Gary Hirshberg iterated the company's plans to make its findings available to support other interested dairy processors by late summer.

  • Stonyfield Farm. Stonyfield Farm Takes on Cow Burps with First North American Program. Londonderry, NH, June 8, 2009. Accessed at
  • Rathke L. Greener diet reduces dairy cows' methane burps. The Associated Press. Sunday, June 21, 2009. Accessed at