Effect of dietary phosphorus reduction and phytase supplementation on growth of rabbits.

New Zealand White rabbits were used to study the influence of exogenous phytase enzyme additions at the expense of supplemental inorganic phytate on growth performance. A total of 300 rabbits aged 35 d were weaned and with respect to body weight half were housed individually or in pairs up to 77 d of age. Within each housing system, rabbits were assigned randomly to three dietary groups in a balanced manner according to body weight at weaning. A basal diet with 0.24% added inorganic monocalcium phosphate (MCP) was used in the control group (C). This feed was supplemented with 1000 FTU/kg of Aspergillus niger phytase (Natuphos®5000) at the expense of MCP that was reduced by 50% of the control level (i.e. from 0.24 to 0.10%) in the Phytase group (P) or not used (0% MCP) in the Phytase-MCP group (P-MCP). Total phosphorus contents of the diets were 0.58, 0.45 and 0.35%, respectively. The 35-77 d feed intake was 136, 138 and 131 g/d in the C, P and P-MCP groups, respectively (P=0.112). Feed conversion was not affected (3.30, 3.32, 3.27; P=0.592). Differences in 35-77 d weight gain (40.3, 40.2, 39.6 g/d; P=0.556) and 77-d body weight (2706, 2699, 2677 g; P=0.651) were not significant. Health risk was comparable during the fattening period (30, 26, 28%; P>0.05). Supposing lower faecal phosphorus excretions with Phytase or Phytase-MCP feeds than with the control diet (under evaluation), both enzyme supplemented diets can be promising since using them resulted in production similar to that of conventional rabbit feed.