Effect of dietary graded levels of cottonseed meal and gossypol on growth performance, body composition and health aspects of allogynogenetic silver crucian carp, Carassius auratus gibelio♀ x Cyprinus carpio♂

A 6-month trial was conducted to evaluate the effects of dietary cottonseed meal (CSM) and free gossypol (FG) on allogynogenetic silver crucian carp, Carassius auratus gibelio female x Cyprinus carpio male with 4 replicates of each treatment. Isonitrogenous and isocaloric diets were formulated with the 0 g kg(-1) (control), 200 g kg(-1), 400 g kg(-1), and 560 g kg(-1) CSM. Diets with FG were made by supplementing batches of control diet with 214 mg kg(-1), 428 mg kg(-1), and 642 mg kg(-1). Weight gain, specific growth rate, and protein efficiency ratio increased significantly up to an inclusion level of CSM of 400 g kg(-1) in the diet, with a significant decrease in food conversion ratio. Further increase in CSM to 560 g kg(-1) did not cause further changes in fish performance. Free gossypol did not affect fish performance significantly at any inclusion level. Neither CSM nor FG caused significant effects in any of the other evaluated parameters such as whole body composition, haemoglobin concentration, activities of serum lysozyme, superoxide dismutase, alanine aminotransferase and aspartate aminotransferase, and histology of hepatic tissues and midgut. Our results suggested that crucian carp can tolerate at least 642 mg kg(-1) FG and that it is safe to including 400 g kg(-1) CSM in crucian carp feed.