Carbohydrates comprise between 60 and 80% of the digestible dry matter in majority of feedstuffs for weaner pigs, and may be divided into the starch and the dietary fibre (DF) fraction. The major constituent of DF in the diets of piglets influencing production, gut function and possibly enteric susceptibility is derived from non-starch polysaccharides (NSPs). The following chapter presents recommended levels of fibre for weaner pig diets, and discusses the physicochemical properties of NSP and the effects of processing on its structure, as well as the influence of NSP on weaner performance, particularly its effects on gut physiology, nutrient digestion and absorption. Ways to improve the utilization of NSP in weaner diets are presented. The chapter also relates the use of NSP with gut health of weaners, elaborating on postweaning colibacillosis and porcine intestinal spirochaetosis.

Summary This paper discusses the general hypothesis that certain enteric diseases in pigs can be controlled, or at least ameliorated, by nutritional management of the gastrointestinal (GI) tract. The impetus for such an approach is the mounting concerns amongst retailers, the public, feed manufacturers, producers and regulatory bodies regarding the ‘safety’ of the production chain supplying pig meat. The prime concern is the use of antibiotics, recent events in Europe sending a clear signal that alternatives to the use of viable and cost– effective growth–promoting antibiotics will be required sooner rather than later. Results of research summarized in this paper suggest that associations, currently largely undefined, exist between bacterial pathogens, the host, and dietary substrates to cause diseases in the GI tract. Available data implicate the non–starch polysaccharide (NSP) and amylase–resistant starch in the clinical expression of a number of economically important bacterial diseases. The use of highly–digestible cereal sources such as cooked white rice limits the severity of enteric diseases such as post–weaning diarrhoea, swine dysentery and porcine intestinal spirochaetosis. Interactions with other dietary components in the aetiology of enteric diseases also are possible, including the level and type of protein fed to pigs.

Sources of viscous soluble fibre, such as barley and oats, have often been included in the weaning diet of the pig to accelerate development of the large intestine. Inclusion of a non-fermentable, viscous compound, sodium carboxymethylcellulose (CMC), in a low-fibre weaning diet was tested to assess the influence of digesta viscosity on the gut in the absence of increased fermentation. Two CMC sources, of low and high viscosity, were added to cooked rice-based diet at 40 g/kg total diet. A third control rice diet did not contain any CMC. Diets were fed for 13 d following weaning at 3 weeks of age. Addition of CMC to the diet significantly increased the intestinal viscosity of digesta within the small (P<0·001) and large (P<0·05) intestine. No simple association was found between increases in intestinal viscosity and effects on intestinal morphology and whole-body growth. The average empty-body-weight gain and the small intestinal villus height increased with low-viscosity CMC, but decreased with the high-viscosity CMC group. The full large intestinal weight increased in all pigs fed CMC. Dietary CMC (both low- and high-viscosity) increased the percentage moisture of digesta and faeces, and was associated with increased faecal shedding of enterotoxigenic haemolytic Escherichia coli. Feed ingredients in weaning diets that excessively increase the viscosity of the intestinal digesta may be detrimental to pig health and production.

Interactions between diet and enteric bacterial infections are complex and multifactorial. In production situations, more than one pathogen or disease may occur simultaneously. The intestinal environment in which pathogens proliferate can be altered by dietary manipulation and thereby can affect the outcome of disease (1). Post-weaning colibacillosis (PWC) affects newly-weaned pigs and is associated with excessive multiplication of enterotoxigenic Escherichia coli in the small intestine (2). Intestinal spirochaetosis (IS) is characterised by a mild typhylocolitis resulting from colonisation of the large intestine with the intestinal spirochaete Brachyspira pilosicoli (3). A previous study in weaner pigs found increased intestinal viscosity resulting from addition of carboxymethylcellulose to the diet may encourage intestinal proliferation of E. coli (4). There is also anecdotal evidence that pigs with PWC are then more commonly affected by IS. This study aimed to confirm the influence of viscosity on intestinal proliferation of E. coli, to investigate the influence of viscosity on proliferation of S. pilosicoli in the large intestine, and examine possible interactions between the two pathogens after weaning.

Although it is recognised that high levels of dietary insoluble non-starch polysaccharides (NSP) depress growth in pigs (1), trials investigating the effect of dietary soluble NSPs (sNSP) on performance have produced inconsistent results, depending on the type of grain fed, age of pig and other interacting factors. Diets with high levels of sNSP depress growth and have anti-nutritive properties when fed to poultry, and part of this effect is attributed to the ability of sNSP to increase the viscosity of intestinal digesta (2). A previous study into the effects of guar gum, a viscous water-soluble NSP, on the performance and health of weaner pigs showed a detrimental effect on growth and an exacerbation of experimental post-weaning colibacillosis caused by enterotoxigenic Escherichia coli when this ingredient was fed (3). The aim of this study was to further investigate the potential detrimental effects of increased intestinal viscosity in weaner pigs by feeding them an experimental diet supplemented with carboxymethycellulose (CMC), a water-soluble preparation resistant to fermentation. The effect of increased viscosity on gastrointestinal development, growth performance and incidence of diarrhoea caused by haemolytic E. coli was monitored.

This study evaluated the effects of adding soluble fibre to the diet of healthy weaner pigs and weaner pigs experimentally infected with enterotoxigenic Escherichia coli (ETEC) in a model of post-weaning colibacillosis. Bodyweight gain, intestinal changes and proliferation of ETEC were measured 7 days following weaning. The basal diet consisted of pregelatinised rice fortified with animal protein. Addition of guar gum to this diet elevated the soluble fibre content from 1 to 6 per cent, and was associated with reduced bodyweight gains, increased large intestinal weights and fermentation, and increased proliferation of ETEC in the small intestine. The optimal levels and type of dietary fibre used for weaner pig diets require further evaluation.

The significance to health and intestinal development of non-starch polysaccharides (NSP) and resistant starch (RS) in the diet of the weaner pig is presently unclear, although there have been suggestions that certain levels of dietary NSP would be beneficial (1). This study investigated the influence of NSP derived from lupin (L. angustifolius) and RS on the performance and digestive physiology of piglets in the first 10 days after weaning.

Postweaning colibacillosis remains an important production-limiting condition in many piggeries. Its occurrence can be influenced by many factors, including the composition of the weaner diet (1). There is some evidence that feeding diets high in non-starch polysaccharides (NSP) may alleviate postweaning colibacillosis (2,3). In this study we examined the effect of dietary NSP in the weaner pig on body growth and the interaction with experimentally reproduced post-weaning colibacillosis.

Postweaning colibacillosis in piglets is associated with proliferation and colonisation of β-haemolytic entertoxigenic Escherichia coli in the small intestine. The pathogenesis of this disease is complex, with dietary composition being an important contributing factor. In this experiment the interaction between dietary fibre and intestinal β-haemolytic E. coli populations was studied in 33 experimentally infected newly-weaned piglets. A source of soluble fibre (guar gum) was added to the base diet (cooked rice/ animal protein) to increase the dietary soluble fibre content from 1 to 6% on a dry matter basis. The base diet and the guar gum diet were fed to a separate group of piglets for a week from weaning. Experimental inoculation with haemolytic E. coli took place 48 hours after weaning, and all intestinal samples were taken 6-7 days postweaning. Pigs fed the guar gum diet had significantly higher (p<0.05) number of colony-forming units (CFU) of β-haemolytic E. coli per gram of mucosal scraping at 50% along the length of the small intestine (8.0 x 10 9 compared to 1.3 x 10 4 CFU/gram mucosal scraping). No significant differences in haemolytic E. coli numbers were found in the large intestine between diets. Addition of guar gum to the base diet also resulted in reduced weight gain after weaning (p<0.0001). Soluble fibre in the diet appears to be detrimental to growth and health of pigs in the first week postweaning.

Growth setbacks and the occurrence of post-weaning colibacillosis in piglets in the first week post-weaning can have a major influence on the overall time taken to reach market weight. The inclusion of non-starch polysaccharides (NSP) in the diet has been advocated as a means of reducing the severity and incidence of post-weaning colibacillosis by accelerating large intestinal development (Bolduan et al., 1988). The aim of this experiment was to study the effects of differences in post-weaning dietary NSP on pig growth, gut development, and intestinal proliferation of haemolytic Escherichia coli.

This study reports the effects of feeding a source of soluble nonstarch polysaccharide (NSP) on (a) animal performance and aspects of gut development, and (b) haemolytic E.coli populations in the small intestine.