Like some of their owners, many of California's domestic horses are getting a bit plump as a result of too much food and not enough exercise."One of the contributing factors to this increasing obesity among pleasure horses is simply their owners' lack of understanding of what a horse's nutritional needs are," says Jan Roser, a UC Davis associate professor of animal science and an authority on horse fertility and reproduction.Many owners also tend to buy a lot of protein-rich alfalfa hay and oat feed, and load up their animals with supplements and additives, she says.Overfed horses are at greater risk for developing colic, foot disease and chronic fatigue. Roser recommends that horse owners educate themselves on proper equine nutrition and consult their veterinarians for advice on their animal's nutrition requirements.