Effects of dietary yeast nucleotides on growth, non-specific immunity intestine growth and intestinal microbiota of juvenile hybrid tilapia Oreochromis niloticus ♀ × Oreochromis aureus ♂

This study investigated the effect of dietary supplementation of yeast nucleotides on the growth, nonspecific immunity, intestine growth and intestinal microbiota of juvenile hybrid tilapia. Tilapia(initial average weight of 8.02 g) was fed test diets supplemented with a yeast-originated nucleotide mixture(0,0.15, 0.30, 0.60, and 1.20 g/100 g diet) for 8 weeks. Fish fed the diet with 0.60% nucleotide had significantly higher weight gain than the control group(P < 0.05). Feed efficiency was improved in the fish fed 0.60 and 1.20% nucleotide compared with that in the control group. The optimal doses of nucleotides supplementation for growth and feed efficiency of fish were determined as 0.63 and 0.81%, respectively.Intestinal growth was improved in the 0.30 and 0.60% groups, as indicated by significant increase in intestine length. The fish fed 0.60 and 1.20% nucleotide showed higher super oxide dismutase(SOD)activity and lower malondialdehyde(MDA) level in the liver than the control fish, indicating enhancement of the anti-oxidant status. Serum lysozyme activity was significantly increased in the 0.15 and 0.3%nucleotide supplementation groups, suggesting an enhancement effect on the non-specific immune response. Lastly, dietary nucleotides supplementation exerted moderate influence on the intestinal microbiota of hybrid tilapia. A reduction in the cumulative abundance of putative butyrate-producing species was observed in the intestinal microbiota of fish fed diets with 0.60% nucleotide compared with the control, implying an interaction between dietary nucleotides and butyrate production. Briefly, dietary supplementation with 0.60% nucleotide improve the growth performance, immune activity and intestine growth in tilapia.