Growth performance, body lipid, brood amount, and rearing environment response to supplemental neutral phytase in zebrafish (Danio rerio) diet.

The present study was to evaluate the effects of neutral phytase supplementation on growth performance, survival ratio (SR), body lipid, brood amount, and rearing environment in zebrafish. The control diet was not supplemented phytase, and three levels of phytase (500, 1000, or 1500 U kg(-1)) was added to the three other diets (named as PP500, PP1000, and PP1500). Triplicate groups (twelve 100-L tanks) of zebrafish (initial mean weight, 0.284±0.012 g) were fed twice daily (08:00 and 16:00 h) to satiation for 12 weeks. The results showed that supplemental phytase in the diet improved weight gain (60.49%, 86.63%, 99.06%, and 111.88% in control, PP500, PP1000, and PP1500) and the specific growth ratio of zebrafish (p<0.05). Dietary phytase addition increased the whole body lipid content of zebrafish. The brood amounts (116, 123, and 124 eggs in PP500, PP1000, and PP1500) of fish fed with phytase-supplemented diets were little higher than the control (mean egg was 112). The ammonia-nitrogen concentration in water of fish fed with phytase-supplemented diet was significantly lower than the control. The nitrite concentration in water was also decreased in water of fish fed with phytase-supplemented diet. The SR was increased with the increasing of dietary phytase despite no significant difference was observed among each group. The present study first suggested that neutral phytase could be applied in the zebrafish diet. Furthermore, phytase addition increased the growth, body lipid, brood amount, and SR of zebrafish, and meanwhile decreased the ammonia-nitrogen and nitrite concentrations in rearing water.