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♀×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♀×Cyprinus carpio♂ with 4 replicates of each treatment. Isonitrogenous and isocaloric diets were formulated with the 0gkg ^-1 (control), 200gkg ^-1, 400gkg ^-1, and 560gkg ^-1 CSM. Diets with FG were made by supplementing batches of control diet with 214mgkg ^-1, 428mgkg ^-1, and 642 mgkg ^-1. Weight gain, specific growth rate, and protein efficiency ratio increased significantly up to an inclusion level of CSM of 400gkg ^-1 in the diet, with a significant decrease in food conversion ratio. Further increase in CSM to 560gkg ^-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 642mgkg ^-1 FG and that it is safe to including 400gkg ^-1 CSM in crucian carp feed.