This year many of us will be dealing with hay that got wet. It may have looked OK when put in the barn, but now it’s January, and when you break open a bale, a very fine, musty smelling dust rises up. That dust is not field dirt; it’s a cloud of mold spores. As horses move the hay around with their noses, they inhale the spores. Horses exposed to mold spores are apt to develop a deep, persistent cough. This is an allergic bronchitis and is usually reversible. If there is a combination of continual exposure and poor ventilation in the barn, “heaves” may be the end result. Heaves or COPD (Chronic Obstructive Pulmonary Disease) can be helped, but not reversed. A similar process happens when a person is exposed to long term tobacco smoke. Heaves cripples horses in the same way that emphysema does people. It’s interesting that cows seem to be able to eat that same moldy hay all day long and not have a problem. It’s also worth noting that usually the mold spores don’t seem to bother the horse’s GI tract.
I usually tell clients in this situation that if the hay is fed wet, the spores don’t get into the air, aren’t inhaled, and so the problem is minimized. I have them do more than just wet the hay. I instruct them to put the hay in a clean muck bucket and cover it with water. The horses soon learn to get the hay that is under the few inches of water. Because it is soaking wet, the spores don’t rise up off the hay and get inhaled. This works well until temperatures go below freezing. Of course, you could feed complete hay pellets, cubed alfalfa, or the packaged Lucerne products that aren’t field dried. The downside is that these hay substitutes are all expensive.
Great Britain has an on going problem producing quality hay. Their climate of rainy and overcast days makes curing hay without it molding difficult. One of the ways that they have gotten around the problem is by feeding out steamed hay instead of dunked hay. There are at least two companies in England that produce commercial hay steamers. These are rugged containers somewhat bigger than a tack trunk. A bale of hay is put into the cabinet, and the lid is shut. A steamer attached to the side of the unit shoots steam up through the hay. After an hour or so the hay is “done”. The hay is wet and hot, and the companies claim that not only do the mold spores not rise into the air, but they are actually killed by the steaming. The steamers seem to be effective, but cost around $2000.
One of my clients has a mare that coughs even when fed the best quality field hay. They found out about hay steamers on the internet, but decided to build their own, which they did for under $75. They took a cast off refrigerator (you could also use an old chest freezer) and drilled a hole near its base to accommodate the tube from a wall paper steamer. They put the steamer on a timer that turns on one hour before feeding time, twice a day. When the steamer comes on, the water in its reservoir boils and steam shoots through the tube and into the old refrigerator. The refrigerator holds about a bale of hay on end. The steam works its way up through and thoroughly soaks the hay. At feed time the hay is warm, wet, and ready to be fed out. Just like water soaked hay, the steamed hay holds onto the spores which then don’t float off into the air and into their horse’s nostril. On a cold winter morning their mare tears into this nice, warm, and very safe hay without coughing. One more hay summer like we just had, and I suspect that hay steamers will become more commonplace.
–David A. Jefferson, DVM