A dynamic simulation model for growth of the African catfish, Clarias gariepinus (Burchell 1822) : II. Effect of feed composition on growth and energy metabolism

Abstract

A dynamic simulation model was adapted to investigate the effect of feed composition on growth of Clarias gariepinus. The effect of feed composition was restricted to that of the macronutrients, i.e. protein, fat and carbohydrates. Most parameters used in the model were derived from the literature. Parameters which were expected to have specific values for the species used, or which could not be derived from the literature, were calibrated with experimental results. Results used for calibration originate from an 84-day feeding trial with 20 different semi-moist diets. The protein content of these varied from 20 to 60% and the fat content from 0 to 38%. Data used to test the model originated from balance respiration experiments. In these experiments dietary protein content varied from 20 to 40% and fat content from 4 to 29%. A dry pelleted feed was used in these experiments. The test results of the model for fresh weight gain, protein gain, fat gain and oxygen consumption were compared with the independently obtained results of the balance respiration experiments. It is concluded that the model predicts reasonably well the effects of feed composition on growth and growth composition. The predicted values are in agreement with the observed values, except for the diets with the highest fat content. With these diets the predictions are overestimated. During the modelling procedure it became apparent that feed intake is influenced by the fat content of the fish biomass. Fat fish consume less than leaner fish of the same weight.