Can horses eat peanut butter?

Yes - in small quantities. Commercial peanut butter has a lot of sugar in it as well as rich proteins and fats, so it's not good for ponies who tend to get fat. Horses are generally not allergic to peanuts.

Also, unlike dogs or cats, horses have no problem with xylitol, an artificial sweetener often found in reduced sugar peanut butter. Make sure you don't give it to dogs, though!