Partial Replacement of Fish meal with Fish Hydrolysate and Casein in larval diet: Effect on Early Rearing of Labeo rohita

Abstract

A 35-day feeding experiment was conducted to assess the effect of partial replacement of fish meal with fish hydrolysate and casein on early rearing of Labeo rohita. The experiment was conducted in triplicates three-day post-hatch (dph) having an initial body weight of 0.40±0.07g were randomly divided into seven groups with a stocking density of 200 larvae /trough and 600 larvae /treatment. During the trial the postlarvae were fed seven different nano particulate isonitrogenous diets of Cp 50%. The groups P0 (0%), PH1 (4%) PH2(6%) and PH3(8%) having of fish hydrolysate substituted with fish meal and the other groups PC0(0%), PC1(5%), PC2(10%) and PC3 (15%) fed diet of casein substituted with fish meal respectively. Results demonstrated that PH2 group of postlarvae has a significant (p<0.05) effect on growth performance (FBW, WG, WG%, DWG, SGR% and SR%) then followed by PH1 group. The specific activity of digestive enzymes (amylase, lipase and protease) tented to increase (p<0.05) in PH2 group as compared to all other groups. Additionally, Histological examination of intestine (villi’s length, width and absorptive area) also followed the same results. Furthermore, the mRNA expression (Ghrelin and Myogenin) was observed to be highest in PH2 group then followed by PH1 group and least expression of both genes was observed in PH3 group of postlarvae. Moreover, in groups fed diet having fish meal partially substituted casein. Results showed that PC3 group of postlarvae has a significant (p<0.05) effect on growth performance (FBW, WG, WG%, DWG, SGR%) then followed by PC2 group, PC1 and control group. While SR% was significantly highest in PC2>PC1>Control and lowest in PC3 group of postlarvae. In addition to Histological examination of intestine (villi’s length, width and absorptive area) also followed the same results. Nevertheless, activity of digestive enzymes (amylase and protease) was increased (p<0.05) in PC3 group as compared to all other groups. Whereas the activity of lipase enzyme showed comparable results in PC2 and PC3 group then followed by PC1 group. Therefore, the expression of genes (Ghrelin and Myogenin) was observed to be highest in PC3 group then followed by PC2 group and least expression of both genes was observed in Control group of postlarvae. It was concluded that fish hydrolysate at moderate concentration showed a significant effect on L. rohita larvae while casein protein in combination with fish meal showed dose dependent effects on various parameters