Effects of dietary creatine on the muscle growth, flesh quality, lipid metabolism and antioxidant status in juvenile grass carp ( Ctenopharyngodon idellus)

To elevate the effects of creatine on muscle growth, flesh quality, lipid metabolism and antioxidant responses of aquatic animals, we set up three diets with dietary creatine levels at 0 % (Control), 1 % and 2 % for juvenile grass carp (4.33 +/- 0.02 g). Experimental fish were stocked in nine 300-L tanks (30 fish/tank) and randomly assigned with one of the three diets for 8 weeks. We found that 2 % dietary creatine improved the growth performance (SGR) and feed utilization (FCR) of the experimental grass carp. Dietary creatine supplementation further increased the diameter of muscle fibers through elevating the expression levels of muscle growth-related genes ( pax3 , mrf4, myog, myf5, mef2a, and mef2d) and proteins (Pax3, Myog and Mef2a). Furthermore, both 1 % and 2 % creatine supplementation elevated the muscle flesh quality of grass carp, indicated by the enhanced water holding capacity, improved texture properties, increased flavor compounds (flavor nucleotides and amino acids) content and decreased odorants compounds (2-MIB and GSM) content in the muscle. Dietary creatine supplementation also reduced muscle lipid deposition main forced by suppressing lipogenesis and activating fatty acids beta- oxidation. Moreover, the increased antioxidant capability and reduced oxidative stress were found in the muscle of creatine supplementation groups, as evaluated by Nrf2 nuclear-translocation, enzymatic activities, antioxidative genes and proteins expression. Therefore, our study suggested that 1 % or 2 % dietary creatine levels not only promoted the muscle growth, but also enhanced the flesh quality of juvenile grass carp.