Effects of L-Malic Acid on Growth Performance,Body Composition,Digestion and Antioxidant Capacity of Triploid Cucian Carp(Carassius auratus)

This experiment was conducted to investigate the effects of L-malic acid on growth performance,body composition,digestion and antioxidant capacity of triploid cucian carp(Carassius auratus).A total of 450 triploid cucian carp with an average body weight of(16.24 ± 0.06) g were randomly divided into 6 groups with 3 replicates in each group and 25 fish in each replicate.The fish in the 6 groups were fed experimental diets supplemented with 0(control group),1,2,4,8 and 16 g / kg of L-malic acid for 90 d,respectively.The results showed as follows: L-malic acid supplementation could significantly reduce the pH and acidbinding acidity of diets(P 0.05).L-malic acid supplementation could significantly increase the feed intake(FI) and weight gain rate(WGR) as well as reduce the feed conversation rate(FCR),and the best growth performance was found in the 4 g / kg group.When the supplemental level of L-malic acid was from 0 to 8 g / kg,the moisture content in whole body was gradually reduced,while the crude protein,crude lipid and ash contents were gradually increased,and those indices in the 4 and 8 g / kg groups had significant differences compared with the control group(P 0.05).The highest dietary protein retention ratio was found in the 4 g / kg group and the highest dietary lipid retention ratio and ash retention ratio were found in the 8 g / kg group,and had significant differences compared with the control group(P 0.05).The highest amylase activity in intestine was found in the 4 g / kg group and the highest activities of lipase,trypsin and Na+/ K+-ATPase in intestine were found in the 8 g / kg group,and had significant differences compared with the control group(P 0.05).L-malic acid supplementation could significantly increase the activities of superoxide dismutase(SOD) and maltate dehydrogenase(M DH) and decrease maleic dialdehyde(M DA) content in liver;meanwhile,the best values of them were all found in the 4 g / kg group and had significant differences compared with the control group(P 0.05).In conclusion,supplementing appropriate amount of L-malic acid can promote the growth,reduce the FCR,increase the body nutrient deposition,and improve the digestion and antioxidant capacity of triploid cucian carp.The optimal supplemental level of L-malic acid in the triploid cucian carp diet is 4 to 8 g / kg.