Replacement of dietary fish meal by soybean meal on growth performance, immunity, anti-oxidative capacity and mTOR pathways in juvenile abalone Haliotis discus hannai Ino

Abstract

This study aimed to evaluate the effects of replacing fish meal with soybean meal (SBM) on growth performance, immunity, anti-oxidative capacity and mTOR pathway in juvenile abalone Haliotis discus hannai Ino. Five isonitrogenous (about 29% of crude protein) and isolipidic (about 4% of crude lipid) experimental diets with graded levels of fish meal replaced by SBM (0, 25, 50, 75 and 100%, respectively) were fed to abalone (initial body weight: 21.87 ± 0.07 g, initial shell length: 53.18 ± 0.18 mm) for 16 weeks. These experimental diets were named as SBM0, SBM25, SBM50, SBM75 and SBM100, respectively. The results showed that: 1) There was no significant difference in survival of abalone among all the treatments. The highest weight gain rate was found in the SBM50 group, and the group did not significantly differ from those in the SBM75 and SBM100 groups. 2) Replacement of fish meal by SBM linearly and quadratically increased the crude lipid content in muscle of abalone, which reached its highest level in the SBM50 group. 3) Trypsin activity in the digestive gland of abalone fed SBM25 diet was significantly higher than that of other groups. 4) The highest total anti-oxidative capacity and superoxidase activity in digestive gland were found in the SBM50 group. 5) The highest mRNA levels of pi3k and eif-4e, and the lowest level of 4e-bp in muscle were found in the SBM50 group. There was no significant difference in the mRNA level of mtor in the muscle among all the groups. 6). The lowest expression level of nf-κb and the highest expression level of mytimacin 6 in digestive gland of abalone were observed fed SBM50 diet. A significant quadratic trend was found in the mRNA levels of il-16 with increasing levels of dietary SBM. Meanwhile, the mRNA level of β-defensin was linearly decreased after total replacement of fish meal by SBM. Take the growth, antioxidation, immune and mTOR pathway into account, 50% replacement of dietary fish meal by SBM was recommended for abalone.