After a long winter, most of us Pennsylvania and New Jersey horse people can’t wait to get back in the saddle. The beauty of springtime may also bring out a bit of gardener in us. As a horse owner, no doubt you have ready access to horse manure. It has probably crossed your mind to “go organic” and use those horse droppings to fertilize your flower and vegetable gardens. Using manure in a garden, however, requires taking certain precautions so it pays to do a little research on food safety so that you don’t put your health — and your family’s health — at risk.
Michele Jay-Russell, a veterinarian and research microbiologist and program manager of the Western Center for Food Safety has taken horse manure research to a new level. He is co-author of a soon-to-be-released study that highlights the hazards associated with using raw animal manure in the garden. The study will be published in the journal Zoonoses and Public Health.
The basis of the study according to the UC Davis School of Veterinary Medicine,
all began back in July of 2010 when a shire mare from a rural Northern California farm was brought to the William R. Pritchard Veterinary Medical Teaching Hospital for treatment of colic. Following protocol, the veterinarians screened the horse for Salmonella to avoid infecting other horses during hospitalization and the horse tested positive. After successful treatment for colic, the horse was released and went home. Her owners then notified the veterinarians that some of their other draft horses were sick as well—all eight were tested and six came back positive for the same Salmonella Oranienburg strain including the mare that still had the infection.
Jay-Russell heard about the case from her colleague John Madigan, professor of medicine and epidemiology at the school. The farm’s owners invited Jay-Russell and Madigan to the farm to see if they could uncover the source of the Salmonella infection. They sampled water from horse troughs, manure storage piles, wild turkey feces and soil from the family’s edible home garden where raw horse manure had been used as fertilizer. Each of those locations had a percentage of positive samples over the sampling period from August 2010 to March 2011.
“We showed the owners how to continue collecting samples and provided them with a Fed Ex number to ship them to UC Davis,” Jay-Russell said. “During that whole time, the garden soil kept coming back positive, which showed that this strain of Salmonella could persist for months.”
While the researchers couldn’t be completely certain about the original source of Salmonella on the farm, they suspect that a recent surge in the wild turkey population on the property introduced the bacteria to the horses by pooping in the horse corrals and in the water troughs. They speculated that the wild turkeys brought the Salmonella onto the property, although they couldn’t rule out the possibility that the birds were exposed on the farm or to other potential sources of Salmonella.
“What is clearer is that the raw horse manure applied as fertilizer was the most likely source of garden soil contamination,” Jay-Russell explained. “We suspect that the damp climate in Mendocino County may have contributed to the longevity of this bacterium in the soil long after the owners stopped applying the horse manure to the garden. Fortunately, the owners didn’t get sick, but our investigation showed the potential for widespread dissemination of Salmonella in a farm environment following equine infection.”
To promote safe gardening practices, Jay-Russell has teamed with Trevor Suslow, a Cooperative Extension food safety specialist in the Department of Plant Sciences, to speak to groups of small farmers around the state about best practices. They also use a brochure in English and Spanish, “Food Safety Tips for Your Edible Home Garden,” that includes information about safe uses of animal manure and ways to minimize animal fecal contamination.
“It’s good to let people know about the risks and to correct misinformation about ways to treat the compost pile before using it in the garden,” Jay-Russell said. “The biggest take home message from this experience is to be very careful about using manure from sick horses—and to be cautious about offers of free manure—you don’t know what’s in there. Commercial compost should be bought from a reputable source.”
She urges gardeners to take a class and learn how to compost correctly and safely. Each county has a farm advisor and many have University of California Extension specialists on hand as well.
(Click here to continue reading this article and learn a few quick and basic guidelines for composting and food safety.)
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