Effect of dietary cottonseed meal on growth performance, physiological response, and gossypol accumulation in preadult grass carp, Ctenopharyngodon idellus

Cottonseed meal(CM) was used at up to 36.95% content in the diet(replacing 60% of dietary fish meal protein) without any negative effects on growth performance of pre-adult grass carp(initial body weight,761 g) under outdoor conditions.A culture trial was conducted in net cages installed in a large concrete pond.Seven isonitrogenous and isoenergetic diets containing a gradient of CM concentrations(0,12.2%,24.4%,36.6%,48.8%,54.8%,and 61.0%) as replacement for dietary fish meal protein(0,20%,40%,60%,80%,90%,and 100%) were formulated.Dietary non-resistant starch(from maize) was inverse to dietary CM.Growth performance and feed utilization of fish fed the diets containing CM replacing 0-40% fishmeal protein were not affected after the 6-week feeding trial.Accumulation of hepatopancreatic total gossypol in the hepatopancreas was significantly correlated with free gossypol content in the diets(HTG=88.6+1.5×DFG,R^2=0.89,P<0.05).Intestinal a-amylase and γ-glutamyl transpeptidase activities rose along with increasing dietary CM level.The structure of the mid-intestinal tissues and the ultrastructure of the enterocyte microvilli were normal when dietary CM was <36.6%(60% protein replacement).Increasing dietary CM content increased serum alanine aminotransferase levels but decreased serum alkaline phosphatase,cholesterol,high-density lipoprotein cholesterol,low-density lipoprotein cholesterol,triglycerides,and albumin(P<0.05).

Cottonseed meal （CM） was used at up to 36.95% content in the diet （replacing 60% of dietary fish meal protein） without any negative effects on growth performance of pre-adult grass carp （initial body weight, 761 g） under outdoor conditions. A culture trial was conducted in net cages installed in a large concrete pond. Seven isonitrogenous and isoenergetic diets containing a gradient of CM concentrations （0, 12.2%, 24.4%, 36.6%, 48.8%, 54.8%, and 61.0%） as replacement for dietary fish meal protein （0, 20%, 40%, 60%, 80%, 90%, and 100%） were formulated. Dietary non-resistant starch （from maize） was inverse to dietary CM. Growth performance and feed utilization of fish fed the diets containing CM replacing 0-40% fishmeal protein were not affected after the 6-week feeding trial. Accumulation of hepatopancreatic total gossypol in the hepatopancreas was significantly correlated with free gossypol content in the diets （HTG=88.6＋ 1.5 × DFG, R^2=0.89, P〈0.05 ）. Intestinal a-amylase and y-glutamyl transpeptidase activities rose along with increasing dietary CM level. The structure of the mid-intestinal tissues and the ultrastructure of the enterocyte microvilli were normal when dietary CM was 〈36.6% （60% protein replacement）. Increasing dietary CM content increased serum alanine aminotransferase levels but decreased serum alkaline phosphatase, cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triglycerides, and albumin （P〈0.05）.