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The present study intends to assess the effects of Na diformate oral use with citric acid on some skin mucosal immunity indices (total protein, total immunoglobulin (TIg), lysozyme, protease, esterase, and alkaline phosphatase (ALP)) of rainbow trout following experimental challenge with Yersiniosis agent (Yersinia ruckeri). Subsequent to the determination of the 7-day median lethal dose (LD50) of Yersinia ruckeri, fish were stocked in eight groups and two repetitions. The acidifiers separately with a dose of 0.2%, and combined 0.1+0.1% was added to the commercial diet. Five days after inoculation, feeding of fish with acidifiers commenced, and following 15 days, the mucus samples were gathered from the skin of anesthetized fish to measure immune indices. Results showed that the 7-day LD50 of Y. ruckeri was 8.91×105 CFU/ml. In the main experiment, findings indicated the significant effect of Na diformate on the increased levels of mucoid total protein and proteolytic activity of healthy or diseased fish. The acidifiers-contained diet because of potentially having synergistic effect caused inducing the mucus TIg. It seems that the orally use of Na difirmate in 0.2% of the diet separately or combined with citric acid, at least for 15 days, can improve the cutaneous mucus immunological indices that its result is an increase in the survival rate of farmed rainbow trout.

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Polysaccharides are one of biomacromolecules that, in addition to their peculiar physicochemical properties, possess promising biological capabilities depending on chemical structure. The objective of the present study was to evaluate the effect of molecular weight of galactofucan polysaccharides from freshwater plant Azolla filiculoides on its ability to stimulate RAW264.7 macrophage cells and inhibition of oxidation reactions. Galactofucan polysaccharide was extracted by distilled water at 65°C for 2 hours and recovered using 70% ethanol. Polysaccharide hydrolysis was performed using 0.01N HCl at 100°C for 5, 10 and 15 minutes. Crude and hydrolyzed polysaccharides were mainly composed of neutral sugars (67.46-68.02%), lower amounts of uronic acids (4.48-4.53%) and ranged in the molecular weight of 99.4-783.0 × 10³ g/ mol. Crude and hydrolyzed polysaccharides were non-toxic and hydrolysis 15 resulted in the greatest stimulation of proinflammatory response in RAW264.7 macrophage cells releasing a considerable amount of nitric oxide (55.6 μmol) into culture medium. Hydrolysis 15 led to the highest DPPH radical scavenging (65.2%) and Fe³⁺ reducing power (0.5 Abs). Overall, the present findings indicated that galactofucan polysaccharides have the ability to boost immune system and inhibit oxidation reactions and that molecular weight reduction to specific levels could improve the biological activities.