The effects of dietary xylooligosaccharide on mucosal parameters, intestinal microbiota and morphology and growth performance of Caspian white fish (Rutilus frisii kutum) fry.

The present study investigates the effects of different levels of dietary xylooligosaccharide (XOS) on skin mucus bactericidal activity and protein content, intestinal microbiota and morphology as well as growth performance of Caspian white fish (Rutilus frisii kutum) fry. The specimens (1.54 ± 0.03 g) were fed experimental diets supplemented with different levels of XOS [0% (control), 1%, 2% and 3%] for 8 weeks. The results revealed that feeding on XOS significantly increased skin mucus antibacterial activity and protein levels (P < 0.05) and the highest levels were observed in 3% XOS treatment. The total autochthonous intestinal heterotrophic bacteria significantly increased following XOS administration in diet (P < 0.05). Administration of 2 or 3% XOS in fry diet significantly elevated the autochthonous lactic acid bacteria (P < 0.05). However, dietary XOS had no significant effect on intestinal morphology, growth performance and diet utilisation of Caspian white fish fry (P > 0.05). These results demonstrate beneficial effects of dietary XOS on different parameters of mucosal immunity (both skin mucus and intestinal microbiota) and encourage further studies regards various aspect of XOS administration in early life stages of fish.