Seven horses belonging to a Spring Hill, Tenn., riding academy are recovering after ingesting hay contaminated with botulism. Four other animals were euthanized at the scene as a result of botulism poisoning. The surviving horses were transported to the Tennessee Equine Hospital in Thompson's Station for treatment.

Botulism is an anaerobic bacteria that produces a toxin that when ingested can cause illness or death in animals and humans. The bacteria can infiltrate hay bales when organic matter decays due to excessive moisture, or when an animal caught up in the hay during harvest decomposes. Botulism poisoning symptoms can include excessive sweating, unsteadiness while standing, and difficulty swallowing.

Safe Haven Riding Academy owner Jay Schwartz said a round bale of hay in the horses' pasture probably became contaminated during recent rainstorms in Tennessee.

"Either the hay wicked up some of the moisture from recent rains, or the storms washed up a dead animal that came in contact with the hay," he said