High steam-conditioning temperature during the pelleting process impairs growth performance and nutrient utilization in broiler starters fed barley-based diets, regardless of carbohydrase supplementation

The influence of supplemental carbohy-drase (Carb) and conditioning temperature (CT) on growth performance, nutrient utilization and intestinal morphometry of broilers (d 1-21) fed barley-based diets was examined in a 2 pound 3 factorial arrangement, evaluat-ing 2 levels of Carb (0 and 150 g/tonne of feed) and three CT (60, 74, and 88 degrees C). A total of 288, 1-day-old male broilers (8 birds/cage; 6 cages/treatment) were used. The activities of endo-1,4- -glucanase, endo-1,3 (4)--glucanaseand endo-1,4--xylanasein the Carb were 800 BGU/g, 700 BGU/g and 2,700 XU/g, respectively. On d 21, ileal digesta was collected for the determination of nutrient digestibility. There was no significant inter-action between Carb and CT for any tested parameter. Supplemental Carb, regardless of CT, increased weight gain (WG; P < 0.05) and reduced feed per gain (F/G; P < 0.001) by 30 g/bird and 6.5 points, respectively. Increasing CT to 88 degrees C reduced (P < 0.05) WG, but increased (P < 0.05) F/G compared to the diets condi-tioned at 60 degrees and 74 degrees C. Regardless of CT, Carb enhanced (P < 0.05) the digestibility of starch and AMEn by 1.15% and 32 kcal/kg, respectively. Com-pared to the diets conditioned at 60 degrees and 74 degrees C, CT at 88 degrees C reduced (P < 0.05) digestibility of dry mat -ter, nitrogen, phosphorus, gross energy, and AMEn. Birds fed diets conditioned at 88 degrees C showed lower (P < 0.05) starch digestibility compared to those fed diets conditioned at 60 degrees C. Conditioning at 88 degrees C increased (P < 0.05) jejunal digesta viscosity by 10.2% compared to diets conditioned at 60 degrees and 74 degrees C. Overall, Carb supplementation improved WG, F/G, starch digestibility and AMEn in broilers fed barley-based diets, irrespective of CT applied. Conditioning barley-based diets at 88 degrees C impaired the ability of birds to utilize nitrogen, starch, phosphorus and energy, and consequently deteriorated WG and F/G. The lack of significant interactions between Carb and CT indi-cated that negative impacts caused by high CT on bird performance and nutrient utilization occurred regardless of Carb enzyme supplementation. Supple-mental Carb per se could not remedy the adverse effects of high CT.