"He's recovering from a cracked heel and I'm hoping these will make him more comfortable. Do you sell ones specifically for big animals or do I just give him a whole bag?"
Cannabis has been used in horses in the past for sedation, as topical treatments (poultices) and to treat tapeworms and colic . It is not apparent whether only hemp, with less than .3% THC was the primary medicinal. Canines can benefit from CBD, while THC can cause serious problems. Giving a whole bag sounds like a recipe for trouble. You might start with a much smaller amount, after discussing it with an equine vet.