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No studies have been focused on the inclusion of organic selenium in formulated feed of abalone when organic minerals are accepted by aquaculture feed industry. This experiment evaluated the effect of organic selenium on the growth, antioxidation, immunity and gene expressions of selenoproteins in abalone. Graded levels of organic selenium were included to the basal diet at 0.00, 0.15, 0.30 and 0.60 ppm providing 157.83, 322.51, 437.59 and 596.59 ug/kg of selenium in the diet. Accordingly, the diets were named as Se‐0.00, Se‐0.15, Se‐0.30 and Se‐0.60 respectively. Results had shown that survival rate, weight gain rate and shell length increase rate were lowest for Se‐0.60 group (p < 0.05). The concentration of selenium in the whole body generally increased with increasing level of dietary organic selenium (p < 0.05). The enzyme activities related to antioxidation increased initially with low levels of dietary selenium and decreased with higher levels, with the highest value in Se‐0.30 group (p < 0.05). The enzyme activities of immunity increased with the addition of dietary selenium. With the increase of dietary selenium, Myostain expression decreased initially and increased afterwards, with lowest value for Se‐0.30 group (p < 0.05). However, the expressions of other genes related to growth, antioxidation and selenoproteins firstly increased and then decreased, with the highest value recorded for Se‐0.15 group. In conclusion, the inclusion rate of 0.15 – 0.30 ppm Se in diet could promote growth, antioxidation, immunity and gene expressions of selenoproteins in abalone; however, excess selenium with 0.60 ppm inclusion lever in diet had toxic effects. [ABSTRACT FROM AUTHOR]

An 8-week feeding trial was conducted to investigate the effects of host-associated Bacillus megaterium R32 and stachyose on the intestinal mucosal defense system of turbot ( Scophthalmus maximus . L). Three isonitrogenous and isolipidic diets were formulated: control diet (C), control diet with 1.0 × 10 8  CFU/g B. megaterium R32 (RC), and 1.0 × 10 8  CFU/g B. megaterium R32 + 1.5% stachyose (RS) supplementation separately. The results showed that diets RS and RC significantly inhibited the expression of cell development and apoptosis-related genes ( β-catenin , CyclinD1 , BAX , Bid ); diets RS and RC significantly increased the expression of intestinal tight junction protein claudin-4 , while RS group significantly decreased the expression of myosin light chain kinase ; diets RS and RC significantly decreased the expression of proinflammatory factors ( IL-13 , IL-15 , IFN- γ ), diet RS also significantly decreased the expression of TNF-α and AP-1 , and increased the expression of TGF-β . 16s rRNA gene sequencing results showed that diets RS and RC significantly decreased the abundance of conditional pathogenic bacteria ( Corynebacterium , Desulfovibrio , Escherichia-Shigella ). Among them, the abundance of Bacillus in the RS group was the highest. It is concluded that the combination of stachyose and B. megaterium R32 had a more positive effect on intestinal cell development and barrier function and strengthened the intestinal mucosal defense system of turbot., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2024 Yaoyao Kong et al.)