Dietary modulation of intestinal hydrolytic enzymes in yellow
-rumped warblers.
Afik, Daniel, Enrique Caviedes Vidal, Carlos Martinez Del Rio, and
William H. Karasov.
Department of Wildlife Ecology, University of Wisconsin-Madison,
Madison WI 53706, Department of Ecology and Evolutionary Biology,
Princeton University, Princeton, NJ 08544
APStracts 2:0081R, 1995.
Many birds exhibit seasonal switches in diet and thus alter the
nutrients predominating their food intake. We tested for dietary
modulation of small intestine (SI) enzymes in Yellow-rumped Warblers,
a species for which such diet changes are well documented. Birds were
fed three diets formulated from either fruit, insect or seed. We
predicted that SI carbohydrases and peptidases would be modulated in
direct correlation with relative levels of dietary carbohydrate and
protein, respectively. Aminopeptidase N activity was about twice as
high in birds eating the highest protein content diet. In contrast,
there was no significant dietary effect on any of the carbohydrase
activities. There was a proximal-to-distal decrease in activities of
all the carbohydrases but not aminopeptidase N. The carbohydrase
levels of Yellow-rumps are relatively low when compared with other
species in the same family, and most similar to lower levels found in
primarily insectivorous birds rather than in primarily granivorous or
nectarivorous species. Considering this, and the fact that they do
not exhibit dietary modulation of carbohydrase levels, we conclude
that Yellow-rumps are not highly adapted for handling dietary
carbohydrates, especially starch, although they might still
efficiently break down and absorb sucrose and maltose if retention
time were sufficiently long.
Received 2 May 1994; accepted in final form 17 March 1995.
APS Manuscript Number R234-4.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 April 1995.