Effects of dietary oligosaccharides on the growth performance and faecal characteristics of young growing pigs
Introduction
Fructo-oligosaccharides (FOS) and trans-galacto-oligosaccharides (TOS) are water-soluble carbohydrates consisting of 2 to 10 monomeric units. They can be classified as non-digestible oligosaccharides (NDOs) because the β-linkages between fructose monomers (in FOS) and galactose monomers (in TOS) cannot be hydrolyzed by enzymes of endogenous origin (Burvall et al., 1979; Oku et al., 1984). As a consequence, NDOs are quantitatively available as substrates for the gastrointestinal microflora. FOS can be found in various feedstuffs like barley, wheat, and rye (Henry and Saini, 1989). FOS can also be manufactured from inulin via hydrolysis by endoglycosidases, resulting in fructose oligomers (Fm series), which may have a glucose residue (GFn series). In inulin-derived FOS, m and n, representing the number of fructosyl moieties, vary from 2 to 9 (Roberfroid, 1993). FOS may also be produced via transfructosylation of sucrose, resulting in GFn series only, with n varying from 2 to 5 (Hidaka et al., 1988). TOS are rarely found in common feedstuffs. They may be present in low concentrations in yogurts (Toba et al., 1983). They can be manufactured via transgalactosidation of lactose (Burvall et al., 1979).
Certain NDOs may improve growth performance of young pigs. Several authors reported increased growth and improved feed conversion ratio together with a reduction of diarrhoea or loose faeces as a consequence of FOS or TOS inclusion in young pigs' diets (Hidaka et al., 1985; Fukuyasu and Oshida, 1986; Hidaka et al., 1986a; Katta et al., 1993). Other authors, however, reported no or slightly negative effects of FOS on young pigs' growth performance (Kornegay et al., 1992; Farnworth et al., 1992). Control diets used in the latter studies were often based on barley and soybean products. Soybean products contain considerable amounts of NDOs like raffinose and stachyose (Saini, 1988). Therefore, a dilution or masking effect from NDOs in the control diet may have contributed to a lack of response. In addition, antibiotics or additional copper may have been part of these diets. These additives can suppress normal gastrointestinal microflora. NDOs may be fermented by beneficial members of the normal gastrointestinal microflora, including lactobacilli and bifidobacteria. Therefore, NDOs may have less or different effects in diets containing microflora-suppressing agents.
Recently, a multidisciplinary project on NDOs in food and feed has started, focusing on functional characteristics of dietary NDOs. In the present study, effects of FOS and TOS on the growth performance and faecal characteristics of young growing pigs have been investigated.
Section snippets
Diets
Table 1 gives the composition of the experimental diets. The control diet ingredients were low in NDOs. HPLC analysis of corn revealed a small amount of raffinose (300 mg kg−1); FOS or TOS were not found. Inclusion level of corn was 634.6 g kg−1. Therefore, the control diet was not completely NDO-free, and contained 0.19 g raffinose kg−1. In addition, diets did not contain additional copper, antibiotics or probiotics. Diets and water were available ad libitum. Diets met or exceeded requirements
Results
Table 3 shows the growth results from the first three weeks (n=10). Individual daily body weight gain (DWG) ranged from 552–1162 g in the first three-week period. NDO-fed pigs had a significantly lower mean DWG than the control pigs (P=0.031). This effect was the most pronounced in the first week (P=0.016). Individual daily dry matter intake (DDMI) ranged from 903–1630 g in the first three-week period. NDO-fed pigs had a significantly lower mean DDMI than the control pigs (P=0.039). Again, this
Discussion
Ingestion of certain non-digestible oligosaccharides (NDOs) may affect composition and/or activity of the normal intestinal flora. Useful functions of the normal intestinal flora include resistance against potential pathogens, vitamin production, providing energy from non-digestible components, and suppression of intestinal putrefaction, and may be enhanced through NDO-ingestion (Mitsuoka, 1990). Recently, certain NDOs have been classified as prebiotics. Prebiotics are “non-digestible food
Acknowledgements
The authors thank Ing. T. Zandstra, Ing. P.L. Van der Togt, A.A.M. Jansen, M.C.T. Verkerk, and J.W.M. Tijnagel for their technical assistance during the experimental period. Ir. K.M.J. Van Laere and Ing. M. Bosveld are thanked for the faecal NDO-analysis. This work was supported by the Netherlands Ministry of Agriculture, Nature Management and Fisheries, The Dutch Foundation on Nutrition and Health, AVEBE, Nutreco (all the Netherlands), and ORAFTI (Belgium).
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