Dietary administration of microalgae alone or supplemented with Lactobacillus sakei affects immune response and intestinal morphology of Pacific red snapper (Lutjanus peru).

Abstract

The aim of this study was to evaluate the effect of dietary microalgae Navicula sp single or in combination with Lactobacillus sakei on growth performance, humoral immune parameters and intestinal morphology in Pacific red snapper, Lutjanus peru. The experimental fish were grouped into four treatment diets which were a control diet (commercial diet, Control), silage microalgae Navicula sp plus L. sakei (10(6) CFU g(-1), Navicula + L. sakei), lyophilized microalgae (Navicula) and L. sakei (10(6) CFU g(-1), L. sakei). The blood and intestine samples were collected on week 4 and 8. The weight gain showed an additive effect of Navicula + L. sakei at 8 weeks of treatment compared with fish fed control diet. Overall, physiological parameters such as total protein and hemoglobin were increased in fish fed with Navicula and L. sakei diets at 4 and 8 weeks of feeding assay, respectively. There was a significant improvement in immune parameters, principally in myeloperoxidase, lysozyme, total antiproteases activities and IgM in fish fed with Navicula + L. sakei and L. sakei diets at 4 or 8 weeks of treatments. Serum antioxidant capabilities revealed significant increase in phosphatase alkaline, esterase, protease, superoxide dismutase and catalase in groups which received diet supplemented with Navicula + L. sakei and L. sakei diets. Finally, light microscopy observations revealed no effect of experimental diets on microvilli height. Curiously, the presence of vacuoles inside the enterocytes was significant higher in the intestine of L. sakei group after four or six weeks of feeding. Elevated intraepithelial leucocyte levels and melanomacrophages centers were observed in fish fed Navicula or control diets at any time of the experiment. To conclude, the results of the present study demonstrate that the fish that were fed with Navicula + L. sakei or L. sakei diets yielded significantly better immune status and antioxidant capabilities.

Keywords: Gilthead seabream; Immune system; Lactobacillus sakei; Navicula sp.