In fact because of them are negative horses are kept on a similiar diet - which does not contain processed foods, like many horse owners feed their horses. We breed these mares, because they are huge in muscle mass, and are producing just as huge babies some of which are positive and some which are negative. I would strongly suggest you talk to the breeders - the real professional breeders, not those people out there that have a pet horse in their backyard and breed to their neighbors stud. Yes I agree with you that as a pet horse this might be something that a layman without much experience and only wants to ride around occassionally, and feed whatever, an HYPP positive horse might not be a good choice. Canada Amy, Thanks for an amusing email.
Lets address some things.
I think your word recent is correct. I don't think the rule change was in effect yet. Third , a large percentage of the horses at the world are HYPP positive. This does not change the fact that it is a genetic mutation. I don't think the article was a soapbox just a statement of facts.