(906.1) Macronutrient Signals for Adaptive Modulation of Intestinal Digestive Enzymes in Two Omnivorous Galliforms

Poster Board Number: E460

Yushi Oguchi (University of Wisconsin-Madison), Momoko Rolle (University of Wisconsin-Madison), Don Mai (University of Wisconsin-Madison), Enrique Caviedes-Vidal (Universidad Nacional de San Luis, Universidad Nacional de San Luis), William Karasov (University of Wisconsin-Madison)

Most birds studied to date (15 out of 16 species) have shown the ability to adaptively modulate at least one small intestinal digestive enzyme activity to match the composition of macronutrient levels in their diet. Limited work on Galloanserae (waterfowl, quails, and chickens) suggested that this clade may have the mechanisms to modulate intestinal disaccharidase but not peptidase activity (6 out of 7 species). We tested this hypothesis in immature (70-72 d) northern bobwhites (Colinus virginianus) and juvenile (20 d) and adult (230 d) domestic chickens (Gallus gallus domesticus) by raising them on 3 semisynthetic diets varying in starch, protein, and lipid composition for 7-9 d (bobwhites) or 15 d (chickens). Birds were then euthanized, intestinal tissue harvested, and enzyme activities measured in tissue homogenates from proximal, medial and distal small intestine. We found that (1) disaccharidase (maltase and sucrase) activities were induced by dietary starch in both juvenile and adult chickens but not in northern bobwhites; (2) aminopeptidase-N activities were induced by dietary protein in both bobwhites and juvenile and adult chickens; and (3) disaccharidase activities were suppressed by dietary lipid in both bobwhites and juvenile and adult chickens. Generally, diet effects were similar all along the intestine or most pronounced in the medial intestine (chicken disaccharidases). In chickens, age did not affect the diet-driven modulation pattern except in sucrase activity – modulation was found in the distal but not in the proximal intestine in juveniles and the reverse was found in adults. We conclude that there is no general pattern with respect to which nutrient classes of digestive enzymes are adaptively modulated in the small intestine of Galloanserae, and that the modulation of each enzyme in species in this clade likely relates to its respective digestive ecology. On the other hand, the suppressive effect of lipid on the intestinal disaccharidases appears to be present in all vertebrates (birds, mammals, and fish) tested to date, although the biological significance of this effect is not yet understood. We will present a summary of adaptive intestinal digestive enzyme modulation patterns of all birds thus far studied, arranged in a cladogram.

USDA-Hatch