The potential use of daphnia meal as substitute for fishmeal in diets of hybrid red tilapia affects growth performance, activities of digestive enzymes, antioxidant, immune status and intestinal histological parameters.

ABSTRACT

The current study aimed to evaluate growth performance, digestive enzyme activities, antioxidant status, nonspecific immune response and intestinal histological status of red tilapia fed Daphnia meal (DM) as a substitute for fishmeal (FM). Hybrid red tilapia (Oreochromis mossambicus × Oreochromis aureus) fry (0.54 ± 0.05 g fish-1) was allocated in nylon haba cages (100 fry m-3) for 2 weeks as an acclimation period. The fish were divided into five groups (three replicates each). The experimental diets were prepared by replacing FM with DM at concentrations of 25%, 50%, 75% and 100% respectively. The results indicated that fish fed increasing levels of DM (50%-75%) experienced high growth performance, feed utilisation and protein content. The activities of digestive enzymes were significantly increased in all groups fed DM diets compared to the control. The antioxidant balance was improved by decreasing the level of malondialdehyde and increased the total antioxidant capacity, catalase, superoxide dismutase and glutathione reductase activities in the liver of fish fed DM. The nonspecific immune response, including lysozyme, alkaline phosphatase activities and total protein level improved significantly with increasing FM substitution levels by DM in a dose-dependent manner. Histometric analysis of the intestinal wall revealed an increase in the villus length, crypts depth and goblet cells number in groups fed DM meal up to 50% substitution level compared to other treatments. It may be concluded from results of this feeding trial that in the aquaculture of hybrid tilapia, FM may be substituted with up to 50% DM without compromising intestinal health, growth performance and immune status of the fish.