DIGESTIBILIDADE DOS NUTRIENTES E DESEMPENHO DE FRANGOS DE CORTE CONSUMINDO DIETAS FORMULADAS COM DIFERENTES NÍVEIS DE FIBRA E SUPLEMENTADAS COM ENZIMAS EXÓGENAS

The effects of fiber level and the enzymatic supplementation in diets for broilers were evaluated in two trials. The experimental treatments were diets with high and low fiber level and with enzymatic supplementation (α-galactosidase, cellulase, amylase e protease). In the first trial (14 to 19 days of birds age), 190 broilers were randomly distributed in a 2x2 factorial arrangement (fiber x enzymes), placed in metabolic cages between (9-10 birds/cage, 5 cages per treatment). It was evaluate the metabolizability (MET) of the dry matter (DM), the crude protein (CP) and the energy (E), the total apparent digestibility coefficient (TDC) for fat (F) and acid detergent fiber (ADF), the apparent metabolisable energy (AME) and the performance. Four replicates of each treatment were maintained to use in the second trial. In the 21st day age, after adaptation to the intake of the diets with indicator, the broilers were slaughtered and the ileal content was collected to evaluation of the ileal apparent digestibility coefficient (IDC) for DM, CP, E, F and the weight of the caeca. The high fiber level resulted in lower MET of DM, E, CP, and lower TDC of F and ADF (P<0.05), as well as lower IDC of DM and E (P<0.01). Enzymatic supplementation reduced the fiber effect on MET of DM, E, CP and on the TDC of ADF (P<0.05). Higher empty weight of the caeca of the birds on the high fiber diet was observed (P<0.01), as well as lower weight gain (P<0.03) and worst feed conversion ratio (P<0.01). The performance of broilers was more related with ileal apparent digestibility then with the total apparent digestibility of the nutrients and the energy. KEY WORDS: Caeca, ileal digestibility, metabolizability, performance, total digestibility.