Effects of dietary oligosaccharides on the growth performance and faecal characteristics of young growing pigs

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Abstract

The effects of dietary fructo-oligosaccharides (FOS) and trans-galacto-oligosaccharides (TOS) were studied on growth performance and faecal characteristics of young growing pigs. FOS and TOS are non-digestible oligosaccharides (NDOs); they are not hydrolyzed by enzymes of endogenous origin, but are readily available as substrate for the gastrointestinal microflora. Dietary levels of NDO-rich products were 7.5 and 15 g kg−1 diet for FOS, and 10 and 20 g kg−1 diet for TOS. NDOs were included in an experimental corn-based control diet, which was low in NDOs (190 mg raffinose kg−1) and contained no additional copper, antibiotics or probiotics. NDO-rich products were included at the expense of glucose and purified cellulose. Resulting five experimental diets were fed ad libitum to 9-week old castrated male piglets (n=10) with an initial body weight (se) of 15.6±0.3 kg. Pigs had received the control diet for 19 days before reaching this body weight. Individual body weights and feed refusals were recorded every 3–4 days during six weeks. Fresh faeces were rectally collected at day0, day14, and day35, and analyzed for NDOs, pH, and dry matter content. Dry matter intake and body weight gain of the NDO-fed pigs were lower than the control pigs (P=0.039 and P=0.031, respectively) in week one through three. Dietary NDOs did not affect mean growth performance in week one through six. FOS and TOS could not be detected in the faeces. Dietary NDOs did not affect faecal pH. Faecal pH increased with time (P<0.01). NDO-fed pigs had a lower faecal dry matter content than control pigs (P=0.062). Pigs fed TOS-rich diets had a lower faecal dry matter content than pigs fed FOS-rich diets (P=0.061). It is concluded from this experiment that exchanging cellulose for NDOs in young growing pigs' diet results in a temporary depressed feed intake with little or no effects on faecal dry matter content and pH.

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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