Post-feeding Changes of Digestion and Plasma Constituent in Young Yellowtail Fed with Raw Fish and Formulated Diets

Abstract

In order to clarify differences in the digestion and absorption processes of raw fish and formulated diets (single moist pellets) in young yellowtail Seriola quinqueradiata, the digesta contents and plasma constituent concentrations were determined with time after feeding. The digesta contents in the stomach of fish fed with a formulated diet (group F) decreased with time after feeding similarly to those of fish fed with raw fish (group R), but the contents of TCA-soluble nitrogen of the digesta in group F were less than those in group R during the test period. Though the digesta contents in the pyloric caeca and intestine were virtually constant in the two groups throughout the experimental period, both TCA-soluble and -insoluble nitrogen contents of the digesta were 2–3 times higher in group F than those in group R. Plasma concentrations of many amino acids in group R showed gentle peaks 4 h after feeding, while those in group F exhibited plateaus over 2–8 h. The results, together with data on organ size, digestive enzyme activities, and nutrient digestibility suggest that there are no marked differences in the digestion or absorption process of raw fish and formulated diet under experimental conditions. © 1993, The Japanese Society of Fisheries Science. All rights reserved.