GASTROINTESTINAL MORPHOLOGY AND MOTILITY IN AMERICAN KESTRELS RECEIVING HIGH OR LOW-FAT DIETS

Fifteen yearling, male American Kestrels (Falco sparverius) were fed e ither intact day-old chicks (Gallus domesticus) (high-fat diet) or chi cks with the yolk removed plus a piece of lean turkey meat approximate ly equivalent in volume to the yolk (low-fat diet). This was done for 33-37 days to determine the influence of dietary fat on the gastrointe stinal gross anatomy and contractile activity of the kestrels. Fat con tent of the diet appeared to have little effect on either anatomy or c ontractions. Observations of contractile activity, via Image Intensifi cation Radiology, revealed a unique reflux of duodenal contents associ ated with every duodenal flux in every gastroduodenal contraction cycl e (approximately 3-4 min(-1)). This presumably improved mixing of inge sta with digestive secretions and hastened digestion of ingested nutri ents which would be advantageous to a small bird with a high mass-spec ific metabolic rate. The duodenum aias enlarged relative to the size o f this organ in other raptors, possibly to accommodate to this process . The colon also was relatively larger in this species, perhaps to per mit final processing of the diet and water absorption from the greater quantity of digesta passed from the small intestine.