Supplementation of Saccharomycopsis fibuligera nucleotides in soybean-based diets enhanced growth, intestinal health, and reduced inflammatory responses of turbot juveniles (Scophthalmus maximus L.)

In this study, Saccharomycopsis fibuligera nucleotides (SFN) were extracted for exploring the influence on growth, inflammatory response and intestinal health level in turbot juveniles (initial weight 7.16 ± 0.01 g) for 10 weeks. Five isonitrogenous and isolipidic experimental feeds were formulated to include fishmeal-based diet (FM) that contained no SFN, while the other four soybean meal-based diet (SBM), that replaced 30 % FM, contained 0.25, 0.5 or 0.75 % SFN hereafter referred to as SBM0.25, SBM0.5 and SBM0.75, respectively. The feed efficiency exhibited a significantly quadratic or linear increase with the increase of SFN intake and the values reached the peak in the SBM0.5 treatment (P < 0.05). With the increase of SFN supplementation, the specific growth rate presented a significantly linear increase tendency (P < 0.05), and reached a peak in the SBM0.5 treatment. The hepatic antioxidant ability of turbot juveniles was significantly linear or quadratic promoted with dietary SFN supplementation in SBM-based diets (P < 0.05). Moreover, activities of plasma transaminases and γ-glutamyl transpeptidase of turbots showed significantly linear and quadratic decreasing trends with the SFN supplementation increasing (P < 0.05). The hepatic pro-inflammatory factor mRNA expressions were significantly linear or quadratic down-regulated and the anti-inflammatory factor mRNA expression was significantly linear and quadratic up-regulated with the SFN supplementation increasing (P < 0.05). Moreover, the height of villi and microvilli, the thickness of the muscularis and the tight junction proteins mRNA expression level exhibited significantly linear or quadratic increasing trends with the increasing dietary SFN supplementation (P < 0.05). The relative abundance of Lactobacillus plantarum of hindgut was significantly higher of fish fed the SBM0.75 diet compared with the SBM treatment. In conclusion, SFN supplementation was beneficial to the growth and health level of turbot juveniles, the appropriate amount of SFN supplemented was above 0.5 % in this study.