Below are some additional resources regarding not only horses, but all animals.
If you see the neglect or abuse of an animal the first place to contact is your county animal control.
For information about how to determine if a horse is starved go to this site that lists and explains the official scoring method for a horse’s weight. The site includes other relevant material about horse rescue : Henneke Body Condition Scoring System at Habitat for Horses
Information on Federal Laws pertaining to Equine, notably the controversial Horse Protection Act – USDA Animal Welfare
HealthCare Horse Advice for a wide variety of information from hoofs to health care to nutrition.
Southern States Cooperative devoted to equine offers information on nutrition, training and a variety of other topics.