A hard keeper or (British English) poor doer is a horse or other livestock animal that is naturally prone to be thin, will lose weight quickly, and has difficulty gaining weight. A horse that is too thin is not necessarily a hard keeper. The animal may be ill, elderly, or has not been provided adequate nutrition. Whenever a horse is too thin, it is well-advised to have a veterinarian give the horse a thorough examination and recommend the best course of action.