Assessment of the feasibility of including high levels of oilseed meals in the diets of juvenile Chinese mitten crabs (Eriocheir sinensis): Effects on growth, non-specific immunity, hepatopancreatic function, and intestinal morphology

This study aimed to investigate the effects of including high levels of oilseed meals in the diets of Chinese mitten crabs (Eriocheir sinensis) on their growth performance, non-specific immunity, hepatopancreatic function and intestinal morphology. Eight isonitrogenous and isoenergetic diets containing soybean meal (SBM), cottonseed meal (CSM), rapeseed meal (RSM) and peanut meal (PNM) were formulated. The control diet contained 400 g/kg fish meal (FM) and 150 g/kg combined oilseed meals. The content of each oilseed meal in test diets ranged from 400 or 600 g/kg diet, with the total oilseed meals in each test diet ranging from 760 to 840 g/kg. One diet containing 651 g/kg of the combined oilseed meals and 80 g/kg FM (diet FM80) was also assessed. The experimental diets were each fed to four replicate groups of juvenile crabs (1.48 ± 0.04 g) for 14 weeks. Results showed no differences in the survival rate and feed intake among the treatments (P>0.05). The specific growth rates (SGR) of the crabs fed the test diets were lower (P<0.05) than that of the control group, with the exception of crabs fed the FM80 diet, and those fed diets containing 400 g/kg CSM or PNM. The sum of essential amino acids, protein chemical score, essential amino acid index, and total oilseed meal content in the diet were correlated (P<0.05) with the SGR, protein efficiency ratio, and feed conversion ratio (feed:gain) which suggest that the diets containing high levels of oilseed meals may be deficient in certain amino acids. The total hemocyte count decreased (P<0.05) when the crabs were fed diets containing 400 g/kg RSM and 600 g/kg of any of the oilseed meals except CSM. Alanine aminotransferase activity increased (P<0.05) when crabs were fed diets containing 600 g/kg RSM or PNM. There were no differences (P>0.05) in the activities of serum lysozyme, superoxide dismutase, phenoloxidase, and aspartate aminotransferase among the treatments. Morphological analysis revealed the presence of a peritrophic membrane in the crab intestine and no obvious changes in the intestinal morphology were induced by the high levels of oilseed meals. The results suggest that higher levels of CSM or PNM, but lower amounts of SBM or RSM, could be included in the diets of the animals crabs.