Factors in the control of feed intake of horses and ponies

Ponies are large nonruminant herbivores which are capable of utilizing the products of both enzymatic digestion in the small intestine and bacterial fermentation (volatile fatty acids, VFAs) in the cecum and large colon as sources of metabolizable energy. Recent studies have demonstrated that ponies utilize nutrient stimuli from both carbohydrate and fat digestion in the small intestine and VFAs in the cecum and large colon in the control of meal frequency. These animals, however, rely primarily upon oropharyngeal and external stimuli to control the size and duration of meals. This is perhaps an adaptation to a feeding pattern of small frequent meals and food sources which provide significant amounts of nutrients to the animal system only after microbial fermentation in the hind gut. Nutrient cues which are operant in controlling feed intake in omnivores, carnivores, and ruminants appear to be important primarily in the regulation of meal frequency and long-term energy balance in the equine animal. The emphasis on oropharyngeal stimuli in the immediate control of feed intake of ponies reflects the unusual digestive physiology of these animals relative to other species studied to date.