The Influence of beta-Mannan and Xylose on Energy Metabolism in the Pig

摘要

Feed ingredient economics are pushing pork producers to increase the use of higher-fiber coproducts while maintaining high production and efficiency goals. To do this, nutritionists utilize beta-mannanase and xylanase enzymes. It is important to evaluate the metabolic impacts of beta-mannan and xylose to accurately estimate enzyme effects on dietary energy availability. Therefore, the overall objective of the work presented in this dissertation was to evaluate the influence of beta-mannan and xylose on energy metabolism in the pig. Beta-mannanase is added to swine diets with the objective of inhibiting an energetically-expensive beta-mannan-induced immune response; however, this rationale was not supported by the experiments presented in Chapters 2 and 3. Research presented in Chapter 2 showed that beta-mannanase did not affect immune status, nutrient digestibility, growth performance, energy balance, or maintenance energy requirements (MEm) of young pigs. These conclusions were further supported by a nursery growth trial that tested the interactions of dietary beta-mannan concentration and beta-mannanase inclusion, presented in Chapter 3. In Chapter 2 it was also found that a lipopolysaccharide-induced innate immune challenge elevated pigs' MEm by 23.3% which lipid deposition by 30.2% and lead to an 18.3% decrease in ADG during the immune challenge. These novel data directly related decreased ADG to increased MEm independent of changes in feed intake in immune-challenged pigs. Xylose metabolism in the pig was also evaluated and presented in Chapter 4. An improved understanding of xylose metabolism in the pig and its energetic value is essential for effective xylanase utilization. Our data showed that the pig can utilize xylose but does so less efficiently as more xylose is consumed; and only 40--60% of xylose was retained. Furthermore, pigs can adapt over time to improve xylose utilization. By applying metabolomic approaches, urinary metabolites of xylose were identified and quantified. This information facilitated construction of a comprehensive pathway for xylose metabolism in the pig. Overall, research presented in this dissertation improved our understanding of how beta-mannanase and xylanase impact pig energy metabolism. This research also furthered the understanding of how immune activation repartitions energy and increases maintenance energy requirements.