Effects of yeast nucleotide on growth performance, serum immune index and muscle composition of Ancherythroculter nigrocauda Yih & Wu

A 50-day feeding trial was conducted to evaluate the effects of yeast nucleotide in diets on growth performance, serum immune indices and muscle composition of Ancherythroculter nigrocauda (mean initial body weight, 23.30±0.59 g). Seven isonitrogenous (approximately 42.76% crude protein) and isoenergetic (17.43 KJ g−1 gross energy) experimental diets with varying levels of yeast nucleotide (0[control], 150, 300, 450, 600, 750 and 900 mg kg−1) were fed near to satiation to triplicate groups of fish. The results showed that the highest weight gain ratio (WGR), specific growth rate (SGR), protein efficiency ratio (PER), and best feed conversion ratio (FCR) were evident in fish fed 450-600 mg kg−1 yeast nucleotide diet. The intramuscular protein and fat contents of data also supported the above level. The serum enzymes showed that activities of lysozyme (LZS) and superoxide dismutase (SOD) in fish increased first and decreased afterwards with the dietary nucleotide supplemental level increasing. The LZS activity in serum was found to be significantly (p < 0.05) greater in fish fed yeast nucleotides at 450-750 mg kg−1. The fish fed the diet with 600 mg kg−1 yeast nucleotide had higher SOD level (p < 0.05). Yeast nucleotides supplementation did not significantly influence acid phosphatase (ACP) activity of fish (p>0.05). Alkaline phosphatase (ALP) activity showed significantly (p < 0.05) greater but continuous decrease with the increase in the levels of dietary yeast nucleotide. We therefore recommend dietary yeast nucleotide administration at (450 – 600 mg kg−1) to promote growth, enhance immunity and intramuscular protein and fat content.