Cows raised on organic and conventional dairy farms in three regions of the U.S. show no significant differences in health or in the nutritional content of their milk, according to a new study by Oregon State University 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, an announcement from the university said.

"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 Oregon State'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 U.S. Department of Agriculture's National Institute of Food & 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.

Researchers found the following:

* One in five herds met standards for hygiene, a measure of animal cleanliness;

* 30% of herds met criteria for body condition, which measures size and weight of cows;

* Only 26% of organic and 18% of conventional farms met recommendations for pain relief during dehorning;

* 4% of farms fed calves recommended doses of colostrum, which helps boost their limited immune systems after birth;

* 88% of farms did not have an integrated plan to control mastitis, a common disease in dairy cattle;

* 42% of conventional farms met standards for treating lameness, and

* 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 non-organic herds also showed few nutritional differences, the 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.

To become USDA-certified, organic dairy farms must allow cows access to grazing, and the grain cows consume must be grown on land free of pesticides and fertilizers. Organic farmers are not allowed the use of antibiotics, hormones or synthetic reproductive drugs.

"Nearly seven in 10 organic farms previously operated conventional herds, which explains the lack of differences between them," Gamroth said. "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."

The study also found more conventional farms (69%) used veterinarians than organic dairies (36%). Gamroth said organic dairy farmers often perform their own veterinary work because they feel vets do not always know or follow organic standards for care.

Some organic herds in the study also showed a strain of bacteria, commonly known as Strep. ag., that conventional herds eliminated long ago by using antibiotics.

Organic farms did perform better in some areas of health: cows had fewer hock lesions — 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 Assn.'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, Gamroth said.

"Our data shows there is room for improvement in dairies and sets a benchmark to measure progress in the industry," Gamroth said. "We believe adopting animal welfare standards is part of the solution, as are increases to educational efforts to improve the care of cows."

Articles from the study have been published in the Journal of Dairy Science and the Journal of the American Veterinary Medical Association.

Other project collaborators include Pamela Ruegg of the University of Wisconsin-Madison, Linda Tikofsky and Ynte Schukken of Cornell University and Charles Benbrook of the Organic Centre in Oregon.