Effects of rearing density and dietary tryptophan supplementation on intestinal immune and antioxidant responses in rainbow trout (Oncorhynchus mykiss)

Abstract

The present study was conducted to assess the effects of dietary tryptophan (Trp) supplementation on intestinal health in rainbow trout (Oncorhynchus mykiss) reared at two stocking densities. For this, the fish were kept at 15 (low density) or 25 (high density) kg m−3 initial densities and fed diets supplemented with 0 (T0), 5 (T5) and 10 (T10) g Trp. kg−1 diet. After 70 days of rearing, the fish intestinal cytokine and antioxidant-related gene expressions as well as oxidative stress were evaluated. Dietary Trp and stocking density showed significant interaction effects on intestinal tumor necrosis factor-alpha (tnfa) (P < .001), interleukin-1beta (il1b) (P = .016), interleukin 8 (il8) (P = .007), interleukin 6 (il6) (P < .001), superoxide dismutase (sod) (P = .019), catalase (cat) (P = .041), and glutathione peroxidase (gpx) (P = .001) gene expression, as well as, superoxide dismutase (SOD) (P < .001), catalase (CAT) (P = .007), glutathione peroxidase (GPx) (P < .001) activities, and malondialdehyde (MDA) (P