Activated charcoal supplementation in cottonseed meal-based feed improved growth performance and antioxidant capacity through enhancing intestinal barrier function in grass carp juveniles (Ctenopharyngodon idellus)

Abstract

To evaluate the efficiency of activated charcoal (AC) in cottonseed meal-based feed (CSM; 38.46 % CSM, 1275 mg/kg free gossypol), experimental diets supplemented with 0 % AC, 1.5 % AC and 3.0 % AC were prepared and used to feed grass carp juveniles (Ctenopharyngodon idellus, initial weight of 5.0±0.5 g) for 8 weeks. The results showed that the 1.5 % AC group significantly increased final body weight (FBW), weight growth rate (WGR), specific growth rate (SGR), and activated the expressions of intestinal barrier-associated genes zonula occludens-1 (zo-1), zo-2 and claudin-c compared with 0 % AC group (P < 0.05). Additionally, the 1.5 % AC and the 3.0 % AC groups significantly promoted the expression of claudin-12 (P < 0.05). Compared with the 0 % AC group, the 1.5 % AC group had significantly higher total protein (TP) concentration and significantly lower glucose (GLU) concentration and aspartate aminotransferase (AST) activity (P < 0.05). Liver antioxidant results showed that supplementation with 1.5 % AC and 3.0 % AC groups significantly reduced malondialdehyde (MDA) content and increased glutathione reductase (GR) activity (P < 0.05). Total-superoxide dismutase (T-SOD) and glutathione-S-transferase (GST) activities were significantly higher in the 1.5 % AC group than those in the other groups (P < 0.05). The antioxidant gene results showed that gr and GST omega 1 (gsto1) levels were significantly higher in the 3.0 % AC group than in the 0 % AC group (P < 0.05). The 1.5 % AC group significantly promoted nuclear factor erythroid 2-related factor 2 (nrf2) expression, and the 1.5 % AC and 3.0 % AC groups significantly inhibited the expressions of kelch-like ECH-associated protein 1 (keap1a) and keap1b (P < 0.05). Liver apoptotic and inflammatory genes showed that the expressions of caspase 9 (casp9), BCL2 associated X a (baxa), nuclear factor-kappa B (nfκb) and inhibitor of kappa B (iκb) were significantly lower in the 1.5 % AC group than those in the other groups (P < 0.05). The expression of casp8 in the 1.5 % AC group was significantly lower than in the 0 % AC group (P < 0.05). Additionally, the expressions of p38 mitogen-activated protein kinase (p38MAPK) and iκb kinase-beta (ikkβ) were significantly suppressed in the 1.5 % AC group and 3.0 % AC group (P < 0.05). In summary, 1.5 % AC supplementation in CSM-based feed can enhance intestinal barrier function, alleviate CSM-based feed-induced apoptosis, improve liver antioxidant, and thus promote grass carp weight growth rate.

Keywords

• Herbivorous fish
• Cottonseed meal-based feed
• Activated charcoal
• Growth performance
• Intestinal barrier and liver antioxidant capacity