Pigs (25-45 kg) were fed on either cereal or semi-purified basal diets supplemented with either high or low levels of sugar-beet pulp or wood cellulose (Solka-floc). The apparent digestibility and retention of N and apparent digestibility and metabolizability of energy (GE) and the apparent digestibility of nonstarch polysaccharides (NSP) and their constituent monomers were measured during weeks 2, 4 and 6 of the trial. N and GE were less well-digested, retained or metabolized from cereal basal diets than from the corresponding semi-purified diets during all three periods. N S P from sugar-beet pulp was highly digestible, unlike that from Soka-floc which was relatively poorly digested. These differences of NSP digestibility were seen more clearly when incorporated in semi-purified diets. There was no significant increase in the digestibility or retention of N, or digestibility or metabolizability of GE, or in the digestibility of sugar-beet pulp N S P with increasing time-period on the diets. In contrast, the digestibility of Solka-floc N S P tended to increase with the time-period. The digestibility of N S P from the semipurified diet with the high level of Solka-floc inclusion was much lower than that for the low level of inclusion, indicating that microbial activity had been reduced. In conclusion, adaptation to the diets in terms of N and G E balance may be complete after 1 week, but 3-5 weeks may be necessary before stability of measurements of the digestibility of resistant NSP monomers can be obtained.Non-starch polysaccharides: Digestibility : Pigs

Different sources of dietary fibre (defined here as non-starch polysaccharides, NSP) are hydrolysed to varying degrees in the GI tract of pigs. Unlike starch, NSP cannot be digested to its monomeric constituents by mammalian enzymes, but instead must be fermented by the gut microflora, to yeild volatile fatty acids (VFA). These VFA, like the glucose derived from the digestion of starch, are subsequently absorbed and metabolised to yeild ATP, but with a lower efficiency than glucose. Clearly, therefore, knowledge of the relative amounts of products of fermentation and digestion which are absorbed, will enable the nutritive value of a feed to be described more accurately. We report the time course of absorption of glucose, VFA, lactate, and α-amino N from semi-purified diets containing two contrasting sources of NSP, wheatstraw (WS) and sugar beet pulp (SBP), by growing pigs.

With the increasing interest in the use of fibrous feeds as energy sources for pigs, it is important to establish appropriate methods for determining the digestibility of such feedstuffs. In pig nutrient balance studies, a seven-day adaptation period to a new diet is frequently used. However one week may be insufficient for stability of measurements of non-starch polysaccharide (NSP) digestibility to be achieved, for Giusi-Perrier et al (1989) found that fermentation of high-cellulose diets by pigs increased up to 4 weeks after initial exposure to the diet. The aim of this experiment was to measure the development of NSP, nitrogen and energy balance in growing pigs fed contrasting types of NSP at two levels of inclusion over a period of 6 weeks. The two NSP sources chosen for study were wood cellulose (Solka floC) and plain sugar beet pulp (SBP), which are known to be poorly and highly fermentable respectively (Longland and Low 1988).

There have been a number of trials with growing pigs where the digestibility of NSP for a few feeds of varying NSP content have been measured (Graham et al 1986, Longland and Low, 1988). However, there have been few systematic studies where the digestibility of many different types of NSP have been compared at different inclusion levels so that the animals response to each type of NSP can be evaluated, and the effects of NSP source and level on energy and nitrogen (N) digestibility can be assessed. Therefore in the current study the digestibility of NSP, energy and N of semi-purified diets each containing one of eight botanically diverse sources of NSP at a range of inclusion levels was measured.

Equations based on the chemical composition of feedstuffs have traditionally been used to predict the energy value of cereal-based diets for pigs. However, the dietary fibre fraction is the greatest source of variation in predicting energy value and it is recognised that the predictive power of equations could be improved by the use of more detailed chemical analysis of the fibre fraction, as opposed to using more traditional gravimetric techniques which do not define specific chemical entities. The potentially fermentable fraction of dietary fibre is the non-starch polysaccharide (NSP) portion and there are methods available to allow the routine measurement of total NSP and its constituent monomers. In this study we investigated the effect of including total NSP and its major constituent monomers as independent variables in data sets for step-wise regression analysis in addition to more traditional measurements of fibre content on the accuracy of equations designed to predict the energy value of feedstuffs for pigs.