Fishmeal substitution with low-gossypol cottonseed meal in the diet for juvenile turbot (Scophthalmus maximus L.): Effects on growth, nutrients utilization and haematological responses

An 8-week feeding trial was carried out to explore the effects of fish meal replacement with low-gossypol cottonseed meal, a potential alternative protein source, in juvenile turbot (Scophthalmus maximus L.). Five isonitrogenous and isoenergetic diets, with different substitutional levels (0%, 15%, 25%, 35% and 45%, respectively), were formulated. The growth performance, feed utilization and haematological responses were determined. Compared with the fishmeal group, fish growth was not affected when the replacement level was no more than 35%. The feed efficiency ratio and protein efficiency ratio in LC45 group were significantly lower. The apparent digestibility coefficients (ADCs) of dry matter and crude protein, as well as the ADCs of lysine and proline, were inhibited when the replacement level reached 25%. Furthermore, the glucose and cholesterol levels in plasma in LC45 group were significantly lower than that in FM group. Significantly lower content of malondialdehyde was observed in LC25 group while the activities of alanine aminotransferase and aspartate aminotransferase in LC45 were significantly induced. The height of intestinal villi in LC45 was significantly lower than in other groups. Overall, the results indicate that low-gossypol cottonseed meal could be used as an alternative plant protein source in turbot and it could replace 35% fishmeal in the diet.