The influence of regular and high doses of phytase on broiler growth performance and ileal nutrient utilization following the application of a phytase matrix
Three hundred and 84 Ross 308 broilers were allocated to 6 dietary treatments for 21 d. Diets were a nutritionally adequate positive control (PC) and a negative control diet (NC; deficient in aP by 0.15% and Ca by 0.16%, relative to the PC), with each of NC and PC diets supplemented with 0, 500 or 1,500 FTU/kg phytase resulting in a 3 × 2 factorial. Each treatment had 8 replicates with 8 birds per replicate. Bird and feed weights were recorded on d 0 and 21. Ileal digesta was collected on d 21 and pooled for determination of nutrient digestibility. Data were analyzed using the least squares fit model of JMP Pro 11 and means separated using orthogonal contrasts. Body weight gain (BWG) increased (quadratic, P < 0.0001) as phytase supplementation increased in the PC and NC diets. However, the response was greater in birds fed the NC, resulting in a phytase × aP interaction (P = 0.003). There was no effect of phytase, aP or the interaction on FI. Phytase supplementation, regardless of the aP level in the diet, improved (quadratic, P = 0.023) feed conversion ratio (FCR) from 1.56 to 1.40 and 1.42 in the diets with 0, 500 or 1,500 FTU/kg of phytase, respectively. There were significant phytase × aP interactions (P < 0.01) for ileal DM and N digestibility, whereas DM and N digestibility was increased (quadratic, P < 0.01) in birds fed the NC as phytase supplementation increased, but there was no effect of phytase supplementation in birds fed the PC. Ileal P digestibility was not influenced by phytase, aP or the interaction, but Ca digestibility decreased from 41 to 31% as aP (P = 0.002) increased. Ileal Ca digestibility also decreased (linear, P < 0.001) as phytase supplementation increased. Reduced dietary Ca and aP can be implemented along with the use of phytase, with these results highlighting the detrimental influence of high Ca on P digestibility.
Other Titles/Title of Conference
Poultry Science Association Meeting, Louisville, Kentucky, USA