Data from experiment 1 (25 piglets) and experiment 2 (40 piglets). Performance responses and environmental impacts were subjected to variance analysis using the GLM procedure (Statistical Analysis System, version 9.2). The statistical model included effects of phytase level and block. For significant dietary effect, regression analysis was performed. The degrees of freedom regarding phytase levels were deployed into polynomials, for each significative variable at variance analysis. All statistical analysis was performed using SAS (Statistical Analysis System, version 9.2).