Please excuse any typos - my computer died yesterday and I had to resort to my laptop, with it's itty bitty key board.
Daughter took her two year old colt to the vet's today. He literally looked like a walking skeleton and was covered with icky scabs. We had no idea what was wrong with him - the farrier thought the scabs may be from a fungus, and the snotty nose may be the start of pneumonia.
We had been feeding him alfalfa pellets and a mare and foal formula because he had lost so much weight. He was eating his fool head off, but kept losing weight. Our other horses had lost a lot of weight recently - but that was more due to the neglect from their caretaker while we were on vacation than anything else. They are gaining weight, but not Junior.
Junior is a paint, and it turns out the scabs and sores were due to an allergy to the sun. The sores are only on his white areas. His biggest problem, though, is an inability to process alfalfa. Apparently something in his liver is unable to metabolize it properly, causing a build-up of toxins resulting in extreme anemia and weight loss.
It's really sad - the more alfalfa we fed him to help him gain weight, the more weight he lost - we very nearly killed him with kindness! We may well have killed his mother - she died New Year's Eve. Vet said he never thought about the alfalfa causing her problems. He's been seeing more and more of it - probably because more and more people are feeding alfalfa in the form of pellets, just as we are.
This does NOT change the value of alfalfa as a feed for horses, and we will continue to feed it to our horses as ususal - just not to Junior. I don't want to discourage anyone from using alfalfa - just be aware that it can cause problems in some horses - and that problem also seems to have a genetic link.