The effects of several oligosaccharides on true amino acid digestibility and true metabolizable energy in cecectomized and conventional roosters.

Prebiotics, such as indigestible oligosaccharides, are considered to be possible dietary alternatives to antibiotic growth promoters in poultry. The effects of indigestible oligosaccharides on nutrient digestibility in poultry are largely unknown. Therefore, an experiment was conducted to evaluate the effects of several oligosaccharides on amino acid digestibility and TMEn in roosters. The dietary treatments consisted of a corn-isolated soy protein control diet or that diet supplemented with 4 or 8 g/kg of inulin, oligofructose, mannanoligosaccharide (MOS), short-chain fructooligosaccharide, or transgalactooligosaccharide (TOS). Each of the 11 diets was tube-fed (30 g) to 4 cecectomized and 4 intact Single Comb White Leghorn roosters that had been fasted for 24 h. Excreta were then collected for the following 48 h, freeze-dried, and analyzed for amino acid content. The true digestibility of lysine and valine was increased (P<0.05) in cecectomized roosters fed 8 g/kg of MOS or TOS when compared with roosters fed the control diet. In addition, methionine digestibility was improved (P<0.05) in cecectomized roosters fed 4 g/kg of MOS or short-chain fructooligosaccharide and by 8 g/kg of oligofructose or TOS. The true digestibility of isoleucine was increased (P<0.05) in cecectomized roosters fed 8 g/kg of MOS or 4 or 8 g/kg of TOS. The magnitude of the increases in amino acid digestibility coefficients for cecectomized roosters ranged from 3 to 9 percentage units. Feeding either 4 or 8 g/kg of inulin to intact roosters decreased (P<0.05) the true digestibility of methionine. The oligosaccharides generally had no significant effect on TMEn. The results of this study indicated that the indigestible oligosaccharides had no significant effect on the digestibility of most amino acids in a corn-isolated soy protein diet. The digestibility of a few amino acids, however, was increased by some oligosaccharides in cecectomized roosters but not in intact roosters.