Available phosphorus and phytase interaction in the diet on performance, plasma phosphorus levels and bone parameters of commercial laying hens

Two experiments were carried out to evaluate available phosphorus (aP) x phytase interaction of the diet on performance, phosphorus plasma levels and bone parameters of laying hens. In experiment 1, 240 birds with 40 weeks old, were distributed in a 5 x 2 factorial arrangement, composed of five levels of available phosphorus (0.094; 0.194; 0.294, 0.394 and 0.494%) and two of phytase levels ( 0 and 300 Phytase Units - PU). In experiment 2, 288 birds with 44 weeks old were distributed in a 3 x 4 factorial arrangement, composed of three levels of available phosphorus ( 0.094, 0.294 and 0.494%) and four phytase levels ( 0, 300, 600 and 1,200 PU). In experiment 1, there was no available phosphorus x phytase interaction, but available phosphorus level quadraticaly influenced egg production and egg mass, phosphorus plasma levels and feed conversion by egg mass (FCEM) and, in a linear fashion, tibia ashes content and bone strength. The addition of 300 PU increased the availability of phosphorus ( from 4.034 to 4.784 mg/dL), tibia ashes content ( from 41.55 to 42.90%) and bone strength ( from 9.678 to 11.135 kgf/mm). In experiment 2, egg production increased in a linear fashion with dietary available phosphorus levels, which increased linearly with the increased phytase level. Tibia ashes content increased up to 567 PU. The increase in available phosphorus in of 600 PU level improved in a linear fashion the egg mass, FCEM or feed conversion dozen eggs. The supplementation of diet with lower of available phosphorus (0.094%) levels with 300 to 1,200 PU improved bone strength of the birds. Laying hens require on average 0.31 to 0.34% aP. Addition of 300 PU or increasing dietary available phosphorus with 600 PU improves FCEM. Supplementation of diets deficient in available phosphorus with at least 300 PU increases phosphorus plasma levels, tibia ash content and bone strength of commercial laying hens.