Rust in oat hay

Asked July 4, 2014, 4:28 PM EDT

Is there a problem to feed horses oat hay that has rust in it? this is a new hay field, oats was planted as a cover crop for a hay mix. we did get it cut before the oat heads were mature, they are in the milky stage.
but we have had alot of moisture during the growing season, perhaps that is what caused the rust. Just wanted to know if horses will have a problem with the rust.
we will mix it with other hay as well. Hope to get a nice 2nd crop with no rust, or will it repeat?

thank you,

Dakota County Minnesota

1 Response

Dear Barb,
Crown rust is a fungus that affects the leaves of oats, and spreads from leaf to leaf when pustules release their spores.

Although rust is generally not toxic to livestock, in horses it may cause respiratory problems (spores are usually the culprit). In addition, rust will likely reduce palatability and potentially nutrient value in the affected forage.

The high moisture you mentioned likely contributed to the problem. Properly harvesting forage will help reduce rust. I can't predict whether or not the problem will recur, but drier weather will probably help. There are rust-resistant varieties of oats available, but it is often just a matter of time before rust ultimately reappears.

You might consider wetting or soaking the affected hay to help reduce spores. Ideally, I'd tell you not to feed rust-affected hay to your horses, especially if your animals have or are susceptible to respiratory problems. But if you don't have another choice, wetting or soaking the affected forage can help reduce dry spores. However, you have to feed the soaked hay right away to prevent more molds or fungus from proliferating. Remove any damp forage the horses don't eat.

Best of luck, and thanks for your question!