Hoary Alyssum is a weed that can be toxic to horses. It is also a weed that grows on the property where I keep my horses. I was unfortunate to experience the effect of this weed on my horses for the second time in three years this week. I figured it would be good to share some knowledge of this weed with others in case your horse has similar symptoms so you know where to look.
As stated on the University of Minnesota page I’m linking here, the main symptoms of hoary alyssum ingestion are depression and stocking up (swelling in the legs). In severe cases the horse can have symptoms that resemble founder that take longer to subside. Two years ago when the horses experiences hoary alyssum poisoning, Stampede had both a fever and muscle twitches while Phoenix had a fever and almost colic-like symptoms. This time around the boys were very depressed and had huge legs. P was very foot sore as well. I presume that due to his age he has a harder time dealing with the weed.
I want to add that spotting hoary alyssum in hay is way harder than spotting it growing in a field. Two years ago I never did see it in the hay, but I could clearly see it in the field. It also has a flowering cycle, so if you catch it at certain times it’s harder to identify. The spot in the flowering cycle also seems to have an effect on the toxicity of the plant.
Once I realized what was going on this time, I removed the remaining offending hay from their stalls (they had just gotten more of it for night snack) and gave them the other kind we had (not baled on our property), but of course it still takes several days for the horses to recover. I only keep two standing wraps at the barn (I really need a second tack box with the two boys!) so I wrapped P’s hind legs since he was worse than Stampede the first night. P also got some bute the first night and banamine instead (after talking to vet) the second night. I also started them on the naquasone/dex mix I keep on hand for Stampede’s cellulitis bouts on the second day after talking to the vet. The meds worked pretty quickly thankfully.
So I’m thankful that my boys are doing okay now and I’m working with the barn to make sure that my horses are not fed any again. Sometimes I feel like no one else is as serious about horses’ care as I am, but I am totally willing to fight for what my boys deserve!