Dietary soya allergen -conglycinin induces intestinal inflammatory reactions, serum-specific antibody response and growth reduction in a carnivorous fish species, turbot Scophthalmus maximus L.

This study was conducted to investigate the effects of dietary -conglycinin on the growth performance, digestion, gut morphology and immune responses of juvenile turbot (Scophthalmus maximus L.). Four diets were formulated to contain 0%, 2%, 4% and 8% purified -conglycinin. Triplicate groups of 30 fish were fed to apparent satiation twice daily for 12weeks. Fish fed 4% and 8% dietary -conglycinin showed significantly reduced specific growth rate, feed efficiency ratio, apparent digestibility coefficient of nutrients and whole-body lipid contents, as well as a profound infiltration of mixed leucocytes in the lamina propria and a significant decrease in the absorptive surface of distal intestine. The expression of pro-inflammatory cytokines, TNF- and IL-1, in the distal intestine was significantly upregulated by 4% dietary -conglycinin, whereas a significantly lower expression level of IgM and anti-inflammatory cytokine TGF-1 was observed in fish fed 8% dietary -conglycinin. Serum lysozyme and alternative complement pathway activity were first significantly enhanced by 2% dietary -conglycinin and then rapidly declined by 4% and 8% dietary -conglycinin. Respiratory burst activity of head kidney macrophages and serum superoxide dismutase activity were significantly suppressed by 4% and 8% dietary -conglycinin. Dietary -conglycinin (2-8%) significantly increased the level of specific antibody against -conglycinin in serum. Collectively, these results suggested that higher levels of dietary -conglycinin (4-8%) induced a variety of non-specific and specific immune responses and intestinal mucosal lesions in turbot, resulting in inferior feed utilization and poor growth performance.