Evaluation of protein requirement of Labeo rohita during early life stage

Abstract

The present study aimed to determine the dietary protein requirements of Labeo rohita during early life stage. Six different nano-particulate diets with three levels of protein, 40% (PR 40), 45% (PR45) and 50% (PR50) and PH40, PH45 and PH50 where 10% fish meal was replaced with fish hydrolysate were prepared. A 35-day completely randomized feeding trial in triplicate was designed and postlarvae of L. rohita were evenly distributed (200 postlarvae/trough) in eighteen troughs and fed their respective diets. At the end of the feeding trial, dietary protein level showed a significant effect on growth performance, intestinal enzyme activity and histological indices of the intestine. One-way ANOVA followed by LSD pair-wise comparison showed significantly higher weight gain, SGR and survival (%) in a group of larvae reared on PH45 diet. The gene expression activity of myogen in muscles and IGF-1 in liver, also showed a similar trend, i.e., higher in the PH45 fed group. The intestinal enzymes, protease, amylase, and trypsin also followed a similar trend, i.e., higher in the PH45 fed group, while lipase in PH45 and PH45 showed statistically comparable but significantly higher activity as compared to other groups of fries. Microscopic anatomy of the intestine also showed significantly increased villi length and width and villi absorptive area in a group of larvae reared on the PH45 diet. Based on the results, it seems that nano-particulate feed having 45% CP with 10% fish meal replacement with fish hydrolysate is best for the rearing of L. rohita during early life stages.