Dietary alanyl-glutamine and vitamin E supplements could considerably promote the expression of GPx and PPARα genes, antioxidation, feed utilization, growth, and improve composition of juvenile cobia

Abstract

This experiment was conducted to study the effect of various dietary alanyl-glutamine dipeptide (AGD) and/or vitamin E (VE) supplement(s) on the expression of glutathione peroxidase (GPx) and peroxisome proliferator-activated receptor α (PPARα) genes, antioxidation, feed utilization, growth, and composition of juvenile cobia (Rachycentron canadum). Six groups of the juveniles in triplicate were fed for 12weeks using 6 diets: Control diet (D0) contained only basic ingredients; Diet 1 (D1) contained single added AGD 10gkg−1 dried feed; Diet 2 (D2) contained single added VE 100IUkg−1 dried feed; Diet 3 (D3) contained added AGD 10gkg−1 dried feed and VE 100IUkg−1 dried feed; Diet 4 (D4) contained added AGD 5gkg−1 dried feed and VE 50IUkg−1 dried feed; Diet 5 (D5) contained added AGD 2.5gkg−1 dried feed and VE 25IUkg−1 dried feed. The juveniles were sampled randomly for analysis in week 0 and week 12. The main results were as follows: the diets with combined AGD and VE supplements could considerably promote feed utilization, growth, and improve composition of the juveniles; the combined AGD and VE supplements could significantly promote (P<0.05) glutathione peroxidase (GPx), catalase (CAT), glutathione S-transferase (GST), total antioxidant capacity (T-AOC), the expression of PPARα and GPx genes, and significantly decrease (P<0.05) malondialdehyde (MDA) in the liver and muscle of the juveniles; the effect of AGD supplement alone on the expression of GPx gene was significantly greater (P<0.05) than that of VE supplement alone in the liver; whereas the effect of VE supplement alone on the expression of PPARα gene was significantly greater (P<0.05) than that of AGD supplement alone in the liver and muscle. We concluded that the combined AGD and VE supplements could cooperate and considerably promote the expression of GPx and PPARα) genes, antioxidation, feed utilization, growth, and improve composition of juvenile cobia; the optimum was D4, with 5g of AGD and 50IU of VE added per kg of dried feed. Statement of relevanceThere is a need to assess light effect on lice settlement in controlled conditions due to conflicting results. We analyzed lice settlement while taking into account preexisting fin erosion and fish size. Findings confirm that light is not requirement for lice infestation. Fin erosion influenced the number of lice on paired fins suggesting the importance of considering fin erosion as a potential biophysical parameter