Growth, Nutrient Utilization, and Tissue Biochemical Changes in Rohu, Labeo rohita, Fed with Natural and Prepared Diets

Abstract

A feeding trial was conducted in the laboratory (20-26°C) to evaluate the growth response, nutrient utilization and certain tissue biochemical changes in rohu, Labeo rohita, fingerling (average weight 3.0±0.47 g) fed with a natural and a prepared diet in ×feeding regimens (T1, T2, and T3) for a period of 90 days. The main objective was to investigate live and prepared diet effects on growth rate and associated biochemical parameters. Three tanks per treatment were used as replicates. The T1 group was fed exclusively with mixed plankton as natural diet; the T2 group was fed a combination of prepared diet and mixed plankton in a ratio of 1:3; the T3 group was fed the prepared diet only. The three groups were provided with the same feeding rate. The best performance in terms of fish growth, nutrient utilization, protein and lipid deposition in muscle was observed in the T2 group. RNA/DNA ratio in liver and muscle was the highest in T2, followed by T3 and T1. A positive correlation (r = 0.71) was obtained in muscle RNA concentration with respective specific growth rate of fish in different dietary treatments, and the same was indicated in the case of muscle and liver RNA:DNA ratio and total RNA and DNA content, indicating growth changes were due to the different rates of protein retention. Perusal of the amino acid composition of whole body tissue of T2 and T3 groups of fish indicated comparatively high content of individual amino acids. Total ammonia excretion after feeding was comparatively less in the T2 group, indicating less amino acid catabolism. The present study revealed that supplementation of natural diet with prepared diet led to effective nutrient utilization, thereby ensuring improved performance and minimizing discharge of aquaculture wastes through reduced nitrogen excretion.