Effects of animal and plant proteins on growth, muscle composition, antioxidant abilities, mRNA expressions of genes related to TOR signaling pathway and appetite regulation in Macrobrachium nipponense

This study aimed to evaluate the effects of animal and plant proteins on growth, muscle composition, antioxidant abilities, and mRNA expressions of genes related to TOR signaling pathway and appetite regulation in juvenile oriental river prawn Macrobrachium nipponense. Three isonitrogenous and isoenergetic diets were formulated in this experiment. A basal diet containing 58 % fishmeal was used as the control (named as FM), whereas 100 % of fishmeal was replaced with a plant protein blend (soyabean meal, corn gluten meal and rapeseed meal, named as PPB) as the second diet, and lysine, threonine and methionine were added to the PPB diet to balance the amino acid content (named as PPB/Aa) as the third diet. Juvenile oriental river prawn M. nipponense with an average weight of 0.123±0.03 g was randomly divided into three groups, and each diet was fed to prawns twice daily to apparent satiation in six replicates. The experiment lasted for 8 weeks. The growth, muscle composition, antioxidant abilities, mRNA expressions related to TOR signaling pathway and appetite regulation were evaluated. The results showed that no significant difference in survival rate (SR) among three groups. The specific growth rate (SGR), weight gain (WG) and feeding rate (FR) in prawns fed PPB and PPB/Aa were significantly lower than those fed FM (P<0.05), and the feed conversion ratio (FCR) in PPB and PPB/Aa groups was significantly higher than FM group (P<0.05). The glycine content in the muscle of prawns fed FM was significantly lower than that of prawns fed PPB (P<0.05), but there were no significant differences of the other amino acids content (including lysine, threonine and methionine) among the three groups (P>0.05). The hepatopancreas content of malondialdehyde (MDA) and activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in FM were significantly lower than those in PPB and PPB/Aa (P<0.05), while there were no significant differences of activities of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) among the three groups (P>0.05). The serum activities of alkaline phosphatase (AKP), acid phosphatase (ACP) and ALT in PPB and PPB/Aa group were significantly higher than those of FM group (P<0.05), however, no significant difference of activities of AST was observed among the three groups (P>0.05). The mRNA levels of target of rapamycin (TOR), ribosomal proteins 6kinase (S6K) and neuropeptide Y (NPY) were significantly down-regulated in PPB and PPB/Aa groups compared with that in FM group (P<0.05), while no significant difference was observed about mRNA expression of leptin among all groups (P>0.05). Taken together, muscle amino acids composition, except for glycine, was not affected by dietary fishmeal and plant protein blend in M. nipponense, but the antioxidant capacity of prawns was significantly decreased by plant protein blend, and the addition of amino acids could not alleviate the growth inhibition and oxidative stress caused by plant protein blend, and the reduced mRNA levels of genes related to TOR signaling pathway and appetite regulation caused by plant protein blend. This study could provide a theoretical basis and technical support for improving the utilization rate of plant protein and optimizing the nutritional formula of M. nipponense.