It was midafternoon on an early spring day. I was scheduled for spring shots at Charlotte’s barn. I gave her a call when I was 30 minutes out, so that she would have time to get the horses in. As my technician Erin backed our truck up to the barn door, we saw Charlotte bringing up the last of her four horses from the lower pasture. We hadn’t seen Charlotte for a full year, so we spent a few minutes catching up, and then began the annual exams and vaccinations. First on the list was Zip, a 6 year old Quarter horse gelding. I began my usual physical. As the last part of my exam I always look in a horse’s mouth to see what the oral membranes look like and to check the teeth. A glance at the first few molars told me that he needed floating to reduce the sharp edges. As I was checking him over, Erin was busy getting his vaccines ready.
After Zip was vaccinated, Erin and I approached him with a mouth speculum so that I could see way, way back in his mouth and begin filing down his sharp points. We fitted the speculum plates over his upper and lower incisors and snugged up the leather strap around his poll. Erin and I worked as a team and pulled steadily down on the arms of the speculum. It went through a series of clicks on the ratchets as his jaw opened wide. In equine dentistry feeling the edges of the teeth is just as important as looking, and I have learned to trust the speculum to protect my fingers. I ran my hand back to the last molars. As I suspected there were sharp edges all the way back. What caught me by surprise was the volume of saliva that started pouring out of his mouth and running down my arm. As I pulled my hand out the saliva started to pool at my feet. Charlotte, Erin, and I stood there dumbfounded as over 3 cups of saliva gathered in front of Zip, with more coming in a steady stream. I glanced up at the roof of his mouth thinking that perhaps a stick was jammed across the roof of his mouth between the molars on each side. That will sometimes cause a horse to hyper salivate. There was no stick, and our bright LED light revealed no other abnormalities, but that saliva just kept coming! I was still scratching my head over this when Charlotte exclaimed, “Hey, look, Pablo’s doing the same thing!” Charlotte’s stalls are built so that each horse can see all the others. Erin and I glanced next door, and sure enough, Pablo was drooling just like Zip. We released the speculum, removed it from Zip’s mouth, and walked down the barn floor checking each stall. Every one of those four horses had his head slightly lowered, and saliva was pouring out of their mouths as if a faucet inside their heads had been left running. No horse was in distress, but in front of each horse a slippery puddle of saliva was gathering.
The fact that every horse was affected woke me up as to what was going on. I said, “I think we need to take a walk around your pasture.” The day pasture is a 2 acre field, and down in the lower corner was a large patch of white clover, about 100 feet by 100 feet. Instead of the usual bright green color of the leaves, the clover looked a little dull. On closer inspection we could see small dark dots on the leaves indicative of a fungus. Its official name is Rhizoctonia leguminicola. The common name is black patch, and it produces a toxin called slaframine. The toxin irritates the tongue and gums and causes copious salivation. The text book name of the problem is slaframine poisoning. Most everyone calls it “the slobbers.” It had been a very wet and cool spring, and Charlotte had not opened that lower pasture until that very morning because it had been so boggy. When let out of the barn, her horses must have immediately headed for that tasty clover that they hadn’t seen since last fall. By the time we arrived, the effects of the toxin were just being felt. Not every horse likes clover, so it was a little surprising that all four horses were affected. Incidentally, we put off floating the horses for another day when we wouldn’t get our shoes slimy.
We expect calls about slobbers in cool wet weather when the fungus is active. This was the first time that I had been on the scene to watch it develop, and I was as surprised as Charlotte. It is truly amazing how much saliva a horse can produce. The books will tell you that a normal adult horse will put out 10 gallons of saliva a day. Horses with slobbers produce even more. Since it is spilling out, it doesn’t get recycled, so it has the potential of causing dehydration. Slobbers isn’t strictly a pasture problem. If hay is baled with the fungus on the leaves, the same thing can happen when it is eaten. I am told that the longer it is stored, the less effect it has. I understand that buttercup can also irritate the mouth and cause salivation, but it has been my experience that horses avoid it, and I personally have never seen it cause a problem. Alfalfa in hay or pasture can also be affected, but I haven’t seen that either, probably because we don’t grow much of it in northern New England.
I remember one case, right in my town when a mare with a funny appetite chowed down on a rhubarb plant growing in the paddock. I’m not sure if it was the leaves (known to be poisonous) or the stalks that that caused the problem, but she came down with slobbers that just wouldn’t quit. The owner was pretty panicky, but after she learned that the mare wasn’t going to die, she got curious and put a pail under the mare’s head, and collected a five gallon bucket before she got bored and turned the mare out to drain. To this day I wonder if it was a fungus toxin, or just the puckery taste of the rhubarb that caused her slobbers.
The good news is that usually within 4-8 hours the salivation slows down and finally stops. There is no medical treatment other than keeping plenty of water available to replace all that has been lost. Electrolyte supplementation is wise as minerals are lost in saliva that drools out. One article suggests taking the affected animals outside and flushing their mouths out with a hose. I’ve never tried that, but if you had a well broke horse that would permit it, it would be something to try, and makes sense to me. Another source recommends giving a horse atropine, but I don’t agree. This powerful drug will dry up the saliva, but too much of it will shut down the gut, potentially causing the far worse problem of colic. I’d much rather see them salivate and flush out the toxin.
I called Charlotte after we got home that evening and she said that the problem was just about over. Charlotte mowed that pasture close and fenced it off for a while, and there has been no recurrence to date. The bottom line in Slobbers is that there is no need to panic but a call to your vet, who may have further thoughts, would probably be in order.
Slobbers is always from the mouth. A horse that is choked will have saliva, but not as much, and usually mixed with feed, coming out of the nostrils. Choke is described in a previous article, and as noted there, it is much more serious.
-David A. Jefferson, DVM