Effect of dietary curcumin or its nano-form on the growth, immunity, heat stress resistance and stress indicators of Nile tilapia (Oreochromis niloticus)

Abstract

This study evaluated the effects of dietary supplementation with free- or nano- curcumin on the growth performance, immune status and heat stress resistance of Nile tilapia (Oreochromis niloticus). Seven isonitrogenous (28% protein) and iso-caloric (445 Kcal/100g DM) diets were prepared. Six diets were supplemented with three levels of nano-curcumin (50 (CN50), 100 (CN100), 200 (CN200) mg kg− 1) or free curcumin (50 (C50), 100 (C100), 200 )C200) mg kg− 1), and the seventh diet was left without an additive (CON). Fish (13.54 ± 0.32 g) (mean ± SD) fed the experimental diets for 65 days. Following the feeding trial, the fish were exposed to an acute heat stress by gradually raising the water temperature from 25 to 40℃ within 3 h. Then, fish were exposed to 40℃ for 4 h. Results revealed the superiority of nano-curcumin over the free form in enhancing the growth performance (P ≤ 0.05), where the highest results were obtained at CN100 followed by CN200. Only the heat stress rather than the experimental diets increased the platelets, mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), leukocytes and neutrophils counts, while lymphocytes decreased. The CN50 and CN100 groups showed lower activity of liver enzymes (Alanine Aminotransferase (ALT) and Aspartate Aminotransferase (AST)) than the other treatments, while C200 gave the highest activity of these enzymes. The highest immunoglobulin (IgM) levels were detected in CN100, CN200, C100 and C200 followed by CN50. The C200 Group showed higher levels of complement C3 and C4 than the other treatments. The C50 and CON groups gave the lowest values of IgM, C3 and C4. Treatments of CN50 and CN100 efficiently eliminated cortisol levels compared to the other treatments. After the heat stress, ALT, AST, IgM, C3, C4, cortisol and glucose increased. Thus, nano-curcumin has a better ability than its free form to increase the resistance of Nile tilapia under the heat stress, induce innate immunity, eliminate the stress indicators and enhance growth performance with the best concentrations at 100 mg kg− 1.