| dc.description.abstract | The objective of this research was to evaluate the influence of ingredient and diet nutrient differences on xylanase efficacy in broilers. Experiment one consisted of reduced nutrient diets with supplemental fat at two inclusion rates and the supplementation of xylanase at two inclusion rates, as well as a positive control as an industry reference diet. Dietary nutrient reductions led to increases in FCR at 49 d. Fat level had an effect on starter and grower FCR, but had no effect on growth performance beyond 28 d. Xylanase inclusion increased BW at 13 and 28 d and reduced FCR at 49 d in reduced energy diets regardless of supplemental fat level. These results demonstrate that variable supplemental fat inclusion does not affect xylanase efficacy or final broiler growth performance. Experiment two consisted of diets with corn from three distinct geographical locations within the US and the supplementation of xylanase at two inclusion rates. The variation in nutrient profile between corn sources influenced BW, energy digestibility, and short-chain fatty acid profile. Xylanase inclusion reduced FCR during the finisher phase and from 1 to 42 d. These results highlight the importance of understanding accurate ingredient nutrient profiles when formulating diets, as nutrient profile variability can effect broiler performance and digestibility, and demonstrate the consistency of xylanase inclusion on broiler feed efficiency improvement. Experiment three consisted of diets with three dietary AME levels and the supplementation of xylanase at two inclusion rates. Increasing AME level increased early BW and led to increases in energy and crude protein digestibility at 18 d, 33 d, and 42 d. Xylanase inclusion reduced FCR from 1 to 33 d and 1 to 42 d of age and increased energy and crude protein digestibility at 33 d and 42 d. These results demonstrate the positive effect of increased levels of dietary energy on performance and nutrient digestibility, as well as the ability of xylanase to improve digestibility resulting in increased efficacy. This research program indicates the importance of adequately understanding ingredient and diet nutrient differences and outlines the benefit of exogenous xylanase inclusion as a nutritional strategy to improve diet value or reduce production costs. | en |
