Effects of non-digestible oligosaccharides in young pig diets

<p>Some carbohydrates in young pig diets escape enzymatic digestion and form substrates for the gastrointestinal microflora. These include the non-digestible oligosaccharides ( <strong>NDO</strong> ), which are found in e.g. cereals and legumes. Certain NDO may selectively stimulate the growth and/or activity of one or a limited number of favourable bacterial species, and as such beneficially affect (gut) health of the host. They are referred to as prebiotics. A series of studies was carried out to elucidate the role of dietary NDO as feedstuff components and their potential as prebiotic feed additives in young pig diets.</p><p>The two types of NDO studied, fructooligosaccharides ( <strong>FOS</strong> ) and transgalactooligosaccharides ( <strong>TOS</strong> ), were included in NDO-free diets up to 40 g/kg. The NDO were also used as substrates for <em>in vitro</em> fermentation, using young pigs' digesta and faeces as inoculum. Dietary NDO hardly affected pig performance and apparent ileal and faecal nutrient digestion. More than 90% of the FOS was degraded pre-caecally; this was 30% for TOS (estimated by others). Pre-caecal saccharolytic activity enhanced for both types of dietary NDO, resulting in prebiotic effects at the ileal level (reduced pH, reduced concentration of aerobes). However, the FOS- and TOS diets differed in terms of ileal volatile fatty acid composition and concentration of anaerobes (including lactobacilli). These may have been related to differences in rate of fermentation (FOS>TOS) and types of volatile fatty acids produced, as observed during <em>in vitro</em> fermentation. The observed prebiotic effects at the ileal level were not maintained throughout the total large intestine, due to the fast rate of fermentation of FOS and TOS. As a result, some of the stimulated microflora probably started to use proteins as a source of energy, resulting in the increased proteolytic activity observed at the faecal level (increased pH and concentration of volatile fatty acids of protein origin).</p><p>It was discussed that cereal- and legume-based diets may exert a certain level of prebiotic activity. Therefore, the use of FOS and TOS as prebiotic feed additives in such diets may be limited. However, prebiotic carbohydrates which can be fermented throughout the gastrointestinal tract, rather than only in the small intestine and/or the proximal colon, may result in prolonged prebiotic effects and prove useful as feed additive in young pig diets.</p&gt