Influence of bird type, dietary fibre and particle size on apparent ileal digestibility of nutrients and energy utilisation : a thesis presented in partial fulfilment of the requirements for the degree of Masters of Science in Animal Science at School of Agriculture and Environment, Massey University, Manawatu, Palmerston North, New Zealand

Abstract

Whilst limited published data are available on the effect of bird type on the nutrients digestibility and the interaction between DF content and bird type on nutrient digestibility, no study has investigated the interaction between dietary particle size and bird type on nutrient digestibility. In the present thesis work, it was hypothesised that the interaction exists in nutrient digestibility responses of different bird types to increased dietary fibre content and particle size, with layers showing better digestion efficiency in high fibre diets and to increased dietary particle size. The objectives of the experimental research presented in this thesis are, 1. To investigate the influence of bird type (broilers, pullets and layers) and DF content (low fibre and high fibre) on apparent ileal nutrient digestibility and energy utilisation; 2. To investigate the influence of bird type (broilers and layers) and maize particle size (fine, medium and coarse) on apparent ileal digestibility of nutrients and energy utilisation. The major finding of this research was that the bird type influenced the digestibility of nutrients regardless of diet type, with higher digestibility in broilers compared to pullets and layers. Bird types showed different magnitude of digestibility responses to increased dietary fibre content. Nutrient digestibility responses to dietary fibre content were greater in layers than in broilers and pullets. Although feeding medium and coarse particles was associated with increased gizzard and proventriculus weights in both layers and broilers, only the layers benefited in terms of increase nutrient digestibility. Overall, these findings demonstrate that the digestive tract development and function in layers is more sensitive to feed structure. The implication is that feeding diets low in fibre and finely ground diets to layers should be avoided to achieve optimum digestion. The interactions observed between diet type or particle size and bird type suggest that the information available on the dietary inclusion level of fibre sources and nutrient digestibility for one type of bird may not be appropriate for use in diet formulation for the other type of birds. However, further research is required to determine the dietary fibre level and particle sizes to be considered in diets for different bird types.--From Introduction & Discussion