Effect of dietary fibre on ileal digestibility and endogenous nitrogen losses in the pig

Dietary fibre is defined as a heterogenous mixture of structural and non-structural polysaccharides and lignin. A large number of investigations have been carried out to study the effect of dietary fibre on digestibility and endogenous losses in pigs. Most of the authors reported that fibre content of the diet can impair apparent ileal digestibility of dietary nutrients, endogenous nitrogen and amino acid secretion and losses. Investigations during the last few years have shown that the effects of dietary fibre differ with the source and nature of fibre and relate to their chemical composition as well as to their physico-chemical properties. The effect of pure cellulose is rather low in contrast to other types of fibre (i.e. hulls, bran, endosperm fibre or pectin). In experiments, the endogenous nitrogen losses were almost twice as high after feeding barley endosperm fibre as compared to barley hulls (331 versus 180 mg N per 100 g dry matter intake (DMI)). It is difficult to ascertain which physical or chemical properties are responsible for the effects. The data presented in the review illustrate that dietary fibre solubility, viscosity and water-holding capacity seem to be the most important factors influencing ileal digestibility of nutrients and endogenous losses in pigs. The latter is also affected by protein level of the diet and protein sources.