Enhanced growth performance, muscle quality and liver health of largemouth bass (Micropterus salmoides) were related to dietary small peptides supplementation

Abstract

To investigate whether incorporation of small peptides into diets could change the growth performance, muscle quality and liver health of the largemouth bass, four diets were designed: SP0+ group (positive control group) was formulated according to the nutritional requirement of the largemouth bass. In SP0− group (negative control group), the crude protein level was decreased by 30 g/kg compared with SP0+ group; SP20 group was added 20 g/kg small peptides based on the SP0− group, and its crude protein level did not reach that of SP0+ group. In SP65 group, 65 g/kg small peptides were added on the basis of SP0− group to obtain same crude protein level as SP0+ group. Fish were fed with these four different diets for 9 weeks. Results showed that, compared with the negative control group, the addition of 20 g/kg small peptides had no significant effect on the weight gain rate and feed coefficient of the largemouth bass; adding 65 g/kg small peptides could significantly increase the weight gain rate and reduce the feed coefficient (p < .05), both reaching the level of the positive control group. Adding 20 g/kg or/and 65 g/kg of small peptides could significantly increase the content of cysteine and proline, the total amino acid, essential amino acid and non-essential amino acid in the muscle (p < .05), as well as fatty acids, especially ARA, EPA and DHA. Adding 20 g/kg or 65 g/kg small peptides to the feed could increase the protease activity of the digestive system and apparent protein digestibility while increasing liver and serum's antioxidant enzyme activity to control the negative effect of MDA. Because total superoxide dismutase and catalase protected fish from oxidation, muscle quality and live health were both improved, consequently enhanced transaminase in the liver and reduced transaminase in the serum were observed.