Growth, physiological and histopathological responses of red hybrid tilapia (<i>Oreochromis sp.</i>) fed dietary protein levels under saline groundwater conditions

It is important to define what is the exact protein requirement to ensure that the economic and environmental sustainability of the tilapia aquaculture, particularly in saline systems, whereby osmoregulation augments metabolic demand. This experiment used a multi-biomarker, holistic methodology in indicating the optimal dietary crude protein content of juvenile red hybrid tilapia (Oreochromis sp.) reared in saline groundwater (33 ppt) in concrete tanks. Isogenic diets with 25, 30, 34 and 38 percent crude protein were fed to fish to a 90-day period. Although the CP diet of 38% was found to give a higher growth performance and feed efficiency, it initiated a drastic physiological trade off which was represented by a drastic reduction in the survivability (51.1%). Detailed hemato-biochemical and histopathological investigations showed the price paid under the carpet by this high protein diet, systemic dysregulation with extreme cases of anemia, hypercholesterolemia, hepatic steatosis and necrosis, damage to the branchial, and activation of the intestinal immune response. The opposite extreme of this was the 34% CP diet which made the strong growth as well as retention of high survival (75.6) and homeostatic regulation among physiological and tissue wellness variables. Thus, we can deduce that the ratio of 34% crude protein in the diet is the optimum compromise afforded by having maximum zoo technical performance and a balance between physiological integrity and long-term sustainability of juvenile red hybrid tilapia under saline concrete tank culture.