Fungous phytases in poultry nutrition

Abstract

New phytase preparations have been recently derivated from both Aspergillus ficuum and A. Niger. Most of the experiments conducted in broiler chickens have shown that vegetal P digestibility could be increased by 15 to 25 % with 500 or 1000 Units phytase/kg diet. Simultaneously the total P excretion could be reduced by 40 to 50 %. In terms of efficiency, 600 U/kg diet would correspond with 1 g mineral P/kg so that near 1000 U are probably required for optimizing growth performance (but not enough for obtaining an optimal bone mineralization). These enzymes are heat sensitive but their action seemed to be conserved when temperature was kept below 70-72°C at the end of the pelleting process. Microbial phytases have also been shown active for layer and breeder hens. Their use is probably destined to grow as a complement of a better utilization of natural phytases present in wheat or barley.