Horse Illustrated Magazine

The Georgia agriculture commissioner is alerting horse owners to a problem that has occurred with some alfalfa hay coming out of Michigan and the upper Midwest.

The hay may contain hoary alyssum (Berteroa incana), a weed that is toxic to horses.

“We have a report of 25 horses sickened from eating alfalfa hay from Michigan that contained this plant. The horses had swollen legs, fever and some were even foundering,” said Commissioner Tommy Irvin. “What is especially troubling is that the alfalfa hay looked perfect. The weed was practically invisible in the hay. It was only after close investigation after the horses got sick that the presence of this plant was found.”

Hoary alyssum has round stems and an alternate leaf pattern. (The leaves are not directly opposite each other but appear alternately up the stem.) Because the dried leaves are fragile, most of them will have fractured and become part of the alfalfa “dust” in the bale. The older stems may have a purple blush. Stems may have a slight fuzz or “hoary” appearance.

“I urge all horse owners in Georgia to check their alfalfa hay and to contact their veterinarian if they see any problems with their horses,” Irvin says.

Irvin is concerned about his state’s horses, but any horse owner who feeds hay grown in the upper Midwest should check their alfalfa hay.

Hoary alyssum is native to Europe and naturalized throughout much of the northern United States. For more information, horse owners can refer to “Hoary Alyssum: Toxicity to Horses, Forage Quality and Control” from the University of Minnesota at: www.extension.umn.edu/distribution/livestocksystems/DI5567.html .