Effects Of Guanidinoacetic Acid Supplementation Under All-plant Protein Diet On Growth,Flesh Quality And The Mechanisms For On-growing Grass Carp (Ctenopharyngodon Idella)

This study was conducted to examined the effects of al-plant protein(PP)diet supplemented with guanidinoacetic acid(GAA)on the growth and flesh quality and the potential mechanisms of on-growing grass carp.And evaluated the appropriate GAA supplementation levels based on different parameters.The healthy grass carp of mean weight169.46±0.58 g were selected to randomly and averagely distributed into six groups(30fish/group),and each group has three replicates.One of groups fed fishmeal(FM)diet and the other five groups fed PP diets,which supplemented with 0,150,300,450 and 600 mg/kg of GAA for 60 days,investigating the effects of GAA on growth and flesh quality as well as the potential mechanisms for on-growing grass carp.Results revealed that compared to the FM diet group,the PP diet for on-growing grass carp decreased PWG,FI and FE,impaired the muscle nutrition value(protein and fat),healthcare function(DHA and EPA contents),flavor(free amino acids),mouthfeel(p H,WHC and firmness)and antioxidative capacity.Whereas the GAA supplementation could reverse these adverseness,and could even exceeded the FM diet group.Further study discovered that GAA supplementation under PP diet(1)improved nutrition value by raising protein content partially correlated to activated TOR/S6K1 signaling,improved healthcare function partially correlated to increased polyunsaturated fatty acids(PUFA)(indicated by EPA and DHA)content;(2)improved flesh flavor partially by increasing the free amino acids(indicated by Gly,Ser,Ala,Asp and Glu)and flavor-related fatty acids content;(3)improved mouthfeel of fish muscle indicated by increasing postmortem p H,WHC and firmness via three ways: firstly,increased postmortem p H partly by decreasing lactate content correlated to inhibition of glycolysis and LDH activity;secondly,improved WHC partially by inhibiting apoptosis correlated to the up-regulated m RNA levels of IAP,Bcl-2and Mcl-1 and down-regulated m RNA levels of Apaf-1,Bax,Caspase-2,-3,-7,-8 and-9,which were partially by inhibiting Fas ligand(Fas L),c-Rel,c-Jun-N-terminal kinase(JNK)signaling;thirdly,improved firmness partially by increasing myofiber density,decreasing myofiber diameter and increasing collagen content which is correlated to TGFβ1/Smads signaling pathways and suppression of cathepsin B/L activities;(4)up-regulated the m RNA levels of Cu Zn SOD,Mn SOD,CAT,GPx,GST and GR,increased GSH content and decreased ROS,MDA and PC contents,which were partially by activating [Keap1/Nrf2]signaling.In summary,the PP diet for grass carp impaired the growth and flesh quality.Whereas,the appropriate GAA supplementation under PP diet for on-growing grass carp improved growth performance,muscle nutrition value,healthcare function,flavor,mouthfeel and antioxidative capacity,which were all equivalent to FM diet group.Based on PWG and DHA,p H and firmness,the appropriate levels of supplementation with GAA in PP diet for ongrowing grass carp(168.33-600.89g)were estimated as 335.35,313.75,321.72 and 314.61mg/kg,respectively.