Effects of neutral phytase on growth performance and phosphorus utilization in crucian carp (Carassius auratus)

A feeding trial was conducted for nine weeks to investigate the effects of partially replacing Ca(H 2 PO 4 ) 2 with neutral phytase on the growth performance, phosphorus utilization, nutrient digestibility, serum biochemical parameters, bone and carcass mineral composition, and digestive-enzyme-specific activity in crucian carp ( Carassius auratus ). The diets prepared with 0.8%, 0%, and 1.8% Ca(H 2 PO 4 ) 2 (1%=1 g/100 g) supplements were regarded as the P 1 E 0 , negative control (NC), and positive control (PC) groups, respectively; the other three experimental diets were prepared with the addition of 200, 300, and 500 U/kg of neutral phytase, respectively, based on the P 1 E 0 group. Three hundred and eighty-four fish ((1.50±0.01) g) were randomly distributed in the six treatments with four replicates each. The fish were initially fed with 2%–3% diets of their body weight per day, with feeding twice daily (08:00 and 16:00), under a 12-h light/12-h dark cycle at the temperature of (27.56±0.89) °C. The results showed that supplemental phytase at different levels in the diet improved the final body weight, average daily gain, feed conversion ratio, phosphorus utilization, and protein efficiency ratio of crucian carp ( P