Combined or individual effects of dietary vitamin E and selenium nanoparticles on humoral immune status and serum parameters of rainbow trout (Oncorhynchus mykiss) under high stocking density

A 60 day feeding experiment was conducted to evaluate the effects of dietary vitamin E (vit E), selenium nanoparticles (nanoSe), and their combination on humoral immune status and serum parameters of rainbow trout under high density condition. A total of 1275 rainbow trout with an average weight of 42.6 ± 2.3 g were acclimatized, distributed into 15 tanks and divided into five experimental groups according to stocking density and diet: Normal control (20 kg m− 3; basal diet), Dense control (80 kg m− 3; basal diet), Vit E (80 kg m− 3; 500 mg kg− 1 vit E-supplemented diet), NanoSe (80 kg m− 3; 1 mg kg− 1 nanoSe-supplemented diet), and Combination (80 kg m− 3; 500 mg kg− 1 vit E and 1 mg kg− 1 nanoSe-supplemented diet). Each group consisted of three tanks. High stocking density reduced weigh gain, specific growth rate, feed intake, feed conversion ratio, serum agglutination antibody titer, total antioxidant capacity, and globulin level, but increased lysozyme, albumin, and cholesterol levels when basal diet was fed. However, vit E supplementation to diets significantly improved growth performance and health status of rainbow trout. While the combination of nanoSe with vit E promoted the performance of the fish, supplementation with nanoSe had no significant effects on performance in rainbow trout under high density conditions, suggesting that the beneficial effects observed in the performance of the Combination group may be due to vitamin E alone.