Hay Tested After California Horses Become Ill

Hay Tested After California Horses Become Ill

Puschner said equine photosensitivity connected to alfalfa itself is rare and its cause is elusive.

Photo: Thinkstock

Hay fed to some California horses was not tainted, according to a University of California, Davis (UC Davis), professor, but instead contained a naturally occurring, yet-to-be-identified chemical that made those animals photosensitive.

Photosensitivity is a condition that causes horses to be particularly sensitive to light. Affected horses can develop a sunburn-like skin condition, skin cracking, blistering, or peeling. Some highly sensitive horses can also experience liver damage if they ingest highly photosensitive plants.

Chuck Burt, co-owner of the Diamond C Hay and Feed Co., in Phalan, California, said area horse owners purchased alfalfa hay from the feed supplier in late July. After feeding it to their animals, however, some owners reported that their horses developed sunburn-like signs while other owners said their horses' signs of disease as chemical-like burns, Burt said. Some owners attributed their horses' conditions to tainted hay.

“It was nice hay,” Burt said. “It was raised well. It was just beautiful; it's a mystery.”

Diamond C subsequently provided samples of the hay for testing at both UC Davis and the California Department of Food and Agriculture (CDFA), Burt said.

Results of the CDFA tests remain pending. But tests conducted by UC Davis veterinary toxicologist and professor Birgit Puschner, DVM, PhD, Dipl. ABVT, indicated the hay did not contain any foreign substance that could cause photosensitivity.

“There were no weeds, noxious or otherwise, in the alfalfa,” Burt said.

However, Puschner said, equine photosensitivity can be connected to the alfalfa itself. The condition is rare and its cause is elusive, she said.

“I’ve been seeing this occur (with alfalfa) occasionally since the year 2000, but we haven't been able to isolate and identify the photo-toxic or photo-active chemical responsible for it,” Puschner said. “In my career, I've probably only seen 100 horses (with it), and only one horse that had to be euthanized.”

Owners whose horses do become photosensitive after investing alfalfa should remove the alfalfa hay from the horse's diets immediately before calling their veterinarian, Puschner recommends.

“The veterinarian can make recommendations and perhaps take a blood sample to get liver function,” Puschner said. “Sometimes, the veterinarian will prescribe an antibiotic.”

Puschner said veterinarians continue to investigate alfalfa-related photosensitivity.

About the Author

Pat Raia

Pat Raia is a veteran journalist who enjoys covering equine welfare, industry, and news. In her spare time, she enjoys riding her Tennessee Walking Horse, Sonny.

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