Digestibility of nutrients and amino acids of different protein sources in practical diets by largemouth bass Micropterus salmoides (Lacepede, 1802)

Abstract

This study evaluated the apparent digestibility coefficients (ADCs) of dry matter, protein, lipid, energy, calcium, phosphorus, and essential and non-essential amino acid availability of animal and plant protein sources in practical diets for the carnivorous fish, largemouth bass Micropterus salmoides (8.0±0.5 g; 10.0±0.3 cm). Fish were conditioned to accept artificial feed and those stocked in plastic cages were fed pelleted test diets. Diets contained 30% of the ingredient tested mixed with 70% of a reference ration (RD) containing 40 g 100 g−1 of crude protein, 19.85 kJ g−1 crude energy, and 0.5% of chromic oxide. Cages were then transferred to cylindrical, conical-bottomed aquaria (200 L) where the faeces were collected by sedimentation in a refrigerated container. All the tested ingredients had high ADCs for protein and lipid; ADCs of amino acids of varying protein sources showed significant differences (P<0.01). Plant protein sources did not significantly influence the ADCs of diets. The results allow the inference that the availability of amino acids in plant and animal protein sources varies considerably.