A feeding trial was conducted for nine weeks to investigate the effects of partially replacing Ca(H2PO4)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(H2PO4)2 (1%=1 g/100 g) supplements were regarded as the P1E0, 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 P1E0 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<0.05).
Phytase supplementation increased the
mineral content in serum (P), bone (P, Ca), and carcass (P, Ca, Zn, Na, and Mg) (P<0.05); the
trypsin and
chymotrypsin activity soared when fed with the
phytase-supplemented diets (P<0.05). We may conclude that supplemental dietary neutral
phytase improved the growth performance,
phosphorus utilization as well as nutrient utilization in crucian carp, and it can be considered an important nutritional replacement for Ca(H2PO4)2.