Cows raised on organic and conventional dairy farms in three regions of the United States show no significant differences in health or in the nutritional content of their milk, according to a new study by Oregon State University, Corvallis, Ore., researchers and their collaborators.

Many organic and conventional dairies in the study also did not meet standards set by three commonly used cattle welfare programs.

“While there are differences in how cows are treated on organic farms, health outcomes are similar to conventional dairies,” said Mike Gamroth, co-author of the study and professor emeritus in OSU’s College of Agricultural Sciences. “Few dairies in this study performed well in formal criteria used to measure the health and well-being of cows.”

Nearly 300 small dairy farms — 192 organic and 100 conventional — in New York, Oregon and Wisconsin participated in the study, which was funded by a $1 million grant from the National Institute of Food and Agriculture in the U.S. Department of Agriculture.

The five-year project looked at many aspects of dairy cow health, including nutrition, lameness, udder cleanliness, and other conditions. Milk samples were screened for bacteria and common diseases, and farmers were asked about their operations, including the use of veterinarians and pain relief when removing horns from cattle.

Cows on organic farms produced 43% less milk per day than conventional non-grazing cattle, the study found, and 25% less than conventional grazing herds. Milk from organic and nonorganic herds also showed few nutritional differences, researchers found. Organic milk can occasionally contain more omega-3 fatty acids, which may improve heart health. However, those increases come from seasonal grazing and are not present when cattle are fed stored forage, according to Gamroth.

(A study by Charles Benbrook of Washington State University found “large and consistent differences in the fatty acid profile of organic and conventional milk and dairy products.” See page 52 of the February 2014 issue of Dairy Foods.)

“Nearly seven in 10 organic farms previously operated conventional herds, which explains the lack of differences between them,” said Gamroth. “Many organic farmers operate in a similar fashion to when they raised conventional herds, from milking procedures, to using the same facilities, to caring for sick cattle.”

Organic farms did perform better in some areas of health: cows had fewer hock lesions, which are injuries to the legs that often form from being housed for long periods. Calves on organic farms were also fed a greater volume of milk and were weaned at an older age than on conventional farms.

 Results were based on criteria from three commonly used cattle welfare programs: the American Humane Association’s Animal Welfare Standards for Dairy Cattle, Farmers Assuring Responsible Management, and the Canadian Codes of Practice. However, the dairies surveyed for the study were not committed to these standards, said Gamroth.