The digestion and utilisation of food fibre by growing pigs
Stebbens, Helen Rose
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A series of investigations were undertaken to provide information for compounders to consider when including fibrous foods in diets for growing pigs. The work involved measurements of nutrient digestibilities, growth trials and calorimetric studies.The digestibility of the neutral detergent fibre (NDF) fraction of a food was dependent on a number of factors including the source of fibre, the adaptation period and liveweight of the pig, and the protein and lipid contents of the diet.The level of addition of food fibre was not important in determining the digestibility of the NDF component of a fibre source, whereas an inverse relationship was found between the digestibility of nitrogen and energy, and the level of added food fibre. It was concluded that increasing the level of addition of food fibre is more important in determining the depressive effect on the digestibility of non-fibre components than its own.Rapid growth was achieved when young, weaned and growing pigs were given diets containing wheatfeed and sugar-beet pulp. A substantial part of the energy supplied was in the form of VFA produced by the fermentation of non-starch polysaccharides in the wheatfeed and sugar-beet pulp.A growth trial with diets containing sugar-beet pulp and maize revealed that fermented energy from beet pulp was used with an efficiency of 0.72 that of the energy of maize. The apparently digested energy arising from the fermentation of non-starch polysaccharides, therefore, does not correspond directly in terms of potential use to the animal with that obtained by the enzymic digestion of maize starch. A net energy value for sugar-beet pulp was also calculated.This work has shown that wheatfeed and sugar-beet pulp may be useful as dietary ingredients for growing pigs. However, growth rates may be slightly depressed due to a lower efficiency of utilisation of apparently digested energy from the fibrous fraction of the diet. This could lead to on farm problems associated with a decreased throughput eg overstocking. However, the use of a corrected digestible energy value and ileal digestibilities of amino acids for a fibrous food, when formulating rations, could lead to an improvement in the prediction in performance.As well as the nutritional aspects of feeding fibrous foods, there are also a number of non-nutritional factors which will influence the use of fibrous materials and these are discussed in the light of their practical implications for the feeding of fibrous foods to pigs.