Starch utilisation in broiler chickens with emphases on grain sorghum, exogenous phytase and whole grain feeding

Abstract

There has been a lack of focus on starch utilisation in broiler chicken nutrition, mainly because ileal digestibility of starch in maize-based diets is of a high order. The concept of starch digestive dynamics was recently advanced and has changed nutrient utilisation assessments. The site and rate of starch digestion can influence bird performance in addition to the extent of starch digestion. Grain sorghum, exogenous phytase and whole grain feeding all have substantial significant influences on starch/energy utilisation; however, the mechanisms are not completely understood. The objective of this thesis was to investigate the relationships between grain sorghum, exogenous phytase and whole grain feeding and starch/energy utilisation in poultry. Feeding studies were completed to assess the impacts of the aforementioned factors on growth performance and nutrient utilisation. The utilisation of sorghum starch in broiler chickens is inferior to maize despite the fact that they are ostensibly similar feed grains. Concentrations of kafirin and certain ‘non-tannin’ phenolic compounds, including flavan-4-ols and ferulic acid, inherent in sorghum are almost certainly contributing factors to the inferior starch utilisation in birds offered sorghum-based diets. Starch utilisation in chicken-meat production was positively influenced by whole grain feeding and exogenous phytase. Importantly, phytase inclusion was shown to increase sodium re-absorption along the small intestine by profound margins in a series of three studies. The likelihood is that this ‘retrieval’ of sodium studies improved the co-absorption of glucose with sodium via Na+-dependent transport systems driven by ‘sodium pump’ (Na+/K+-ATPase) activity. However, considerations of starch digestive dynamics should not exclude protein; because starch and protein digestive dynamics should be considered in tandem, which is established in this thesis.