Effects Of Dietary Valine On Growth, Meat Quality, Intestinal Immune And Gene Expression For Young Grass Carp

This study was conducted to study the effects of valine on growth, meat quality, intestinal immune as well as expression of immune-and antioxidant-related gene for young grass carp (Ctenopharyngodon idelld) by feeding fish with increasing levels of valine (4.3,8.0,10.6,13.1,16.9 and 19.1 g valine/kg) for 8 weeks. Compared with the control group, valine increased content of protein, lipid and hydroxyproline as well as relative shear force in the muscle (P<0.01). Conversely, dietary valine decreased cathepsin B and L activities as well as cooking lose (P<0.01). In addition, glutathione (GSH) content, and activities of Cu/Zn superoxide dismutase (SOD1), catalase (CAT) and glutathione peroxidase (GPx) were improved with valine supplementation (P<0.01). Furthermore, SOD1, CAT and GPx mRNA levels were improved with dietary valine, which might be ascribed to the up-regulation of NF-E2-related factor 2 (Nrf2), target of rapamycin (TOR) and ribosomal protein S6 kinase 1 (S6K1) as well as down-regulation of Kelch-like-ECH-associated protein 1 (Keap1) in the muscle (P<0.01). Additional, this experiment indicated that valine enhanced lysozyme and acid phosphatase activities and complement 3 content in the intestine (P<0.01), increased mRNA levels of interleukin 10 and transforming growth factor (31 (P<0.01), and decreased tumor necrosis factor a and interleukin 8 gene expression (P<0.01), which was partly due to up-regulation of TOR and IxBa as well as down-regulated nuclear factor κB P65 (NF-κB P65) (P<0.01). Meanwhile, valine significantly increased transcript of claudin b. claudin 3. occludin and ZO-1 in the fish intestine (P<0.01), and decreased claudin 15 expression (P<0.03). However, valine did not have a significant effect on expression of claudin 12 in the intestine of grass carp (P>0.05). In addition, malondialdehyde and protein carbonyl content in the intestine were decreased by valine (P<0.01), whereas SOD1 and GPx activities and GSH increased (P<0.01). Furthermore, valine increased SOD1 and GPx expression, which might be ascribed to the up-regulation of Nrf2 and Keapl in the intestine (P<0.01). In conclusion, valine improved fish growth, fillet quality and antioxidant defense, as well as regulated gene expression of antioxidant enzymes, Nrf2, Keap1, TOR and S6K1 in the fish muscle. Meanwhile, valine improved intestinal immune status and antioxidant defense, as well as regulated gene expression of tight junction protein, antioxidant enzymes, TOR, Nrf2 and Keapl in the fish intestine. The dietary valine requirement of young grass carp based on percentage weight gain was 14.00 g kg-1 diet (4.77g kg-1 protein).