Determinação do período de coleta total de excretas para estimativa dos valores de energia metabolizável em frangos de corte

The effects of total excreta collection period length on estimated values of metabolizable energy [apparent (AME) and nitrogen corrected (AMEn)] were evaluated in broiler chickens from 19 to 23 days of age. Five treatments with six replicates were used in a randomized block design, in a total of 300 broiler chicks for the control and 300 broiler chicks for the reference diet. The control replaced 40% of reference diet with corn. After diet adaptation (four days), total excreta collection was performed during 1, 2, 3, 4 or 5 days, that consisted the treatments. Data were submitted to ANOVA using the GLM procedure of SAS (2001), with subsequent multiple mean comparison using Tukey test. Observed mean values of metabolizable energy for corn, as-fed basis, for the collection periods (1, 2, 3, 4 or 5 days) with the respective coefficients of variation (%), for AME (kcal/kg) were: 3,814 (7.26), 3,511 (5.32), 3,563 (2.51), 3,512 (1.31), and 3,489 (1.00) and for AMEn (kcal/kg) were: 3,709 (6.68), 3,434 (4.85), 3,482 (2.31), 3,438 (1.11), and 3,423 (1.03), respectively. It was concluded that a 4-d collection period is recommended to compose corn ME data with the same confidence as those of 5-d collection period.