In order to study the effect of feeding non-starch polysaccharides (NSP) on the production and absorption of the malodorous compounds skatole and indole, eighteen male pigs, representing nine littermate groups, were used. One pig from each litter was assigned to either a low-NSP diet (87 g/kg of NSP) or a high-NSP diet (160 g/kg of NSP). Faecal samples and blood samples from vena jugularis were collected during a three-day period. The production of indolic compounds in different sections of the gastro-intestinal tract of six littermate groups was measured at slaughter (after 1 month on the diets). To investigate the absorption of indole and skatole, three catheterized pigs, acting as their own control (2 weeks on each diet) were used. Parallel determinations in portal blood, peripheral blood and in faeces of skatole and indole were conducted. Faecal, intestinal and blood samples were analysed for indolic compounds by high-performance liquid chromatography (HPLC). The production of indole and skatole in the proximal and distal part of the hind gut, respectively, was significantly reduced in pigs given the high-NSP diet. Similarly, both blood and faecal samples revealed that dietary NSP-inclusion reduced skatole concentration, whereas a dietary effect of NSP on the indole concentration was reflected in blood samples only. The absorption of skatole and indole was significantly lower in pigs given the high-NSP diet compared with those offered the low-NSP diet. The skatole concentrations in blood and faeces were highly correlated when measured within the individual animal, suggesting that a proportional amount of the skatole produced was absorbed. In contrast, only weak correlations were demonstrated when determined between animals. This emphasizes the great impact that individual hepatic clearance rate would have on the level of skatole in backfat, and consequently the importance of applying cross-over designs, when studying the absorption of indolic compounds.

Pig studies on non-starch polysaccharides (NSPs) have mainly focused on finishing and breeding animals because their digestive capacity and ability to ferment fibre are considered greater than piglets. In this study, growth and nutrient digestibility, with particular reference to NSP constituent monomers, were evaluated in piglets offered contrasting sources of NSPs. The potential for enhancing growth performance and digestibility with exogenous food enzymes (xylanase, amylase, pectinase and beta-glucanase) was investigated. A total of 240 piglets weaned at 28 days of age, in groups of six, were allocated to six treatments in a 3×2 factorial design, diet type (W, B and SBP) by enzyme supplementation (–v. +). Diet W was wheat based and formulated to supply 14 MJ digestible energy (DE) per kg. In diets B and SBP, DE was reduced to 13·25 MJ/kg by replacing wheat with barley (708 g/kg) or with 185 g/kg dried unmolassed sugar beet pulp. Growth was monitored over 4 weeks. Digestibility of diets B–, B+, SBP– and SBP+ was evaluated in 16 piglets, in groups of four, using a 4×4 Latin-square design. In the growth study, mean initial and final piglet weights were 8·1 (s.e. 0·09) and 18·0 (s.e. 0·21) kg. Piglet health remained satisfactory and food intake averaged 523 (s.e. 6·7) g/day. There were no consistent and significant effects of diet type on food intake, live-weight gain or food conversion, except in week 1 when gain on diet W was higher than on diets B and SBP, 191 v. 150 v. 125 g/day, respectively (s.e.d. 20·0, P < 0·05). Enzyme supplements enhanced the conversion of food to gain over 4 weeks (1·56 v. 1·50:1, s.e.d. 0·030, P < 0·05). Piglets given diet SBP produced faeces with a lower dry-matter content (181 v. 246 g/kg, s.e.d. 10·8, P < 0·001) but with no visual evidence of a nutritionally induced diarrhoea. There were no significant differences in apparent faecal digestibility coefficients (AFDC) for dry matter, crude protein and gross energy between diets B and SBP. AFDC for soluble, insoluble and total NSP constituent monomers were higher (P < 0·001) in diet SBP. Soluble uronic acids were the most readily digested NSP constituents in diet SBP, showing a mean AFDC of 0·96 (s.e. 0·005). Apparent faecal digestibility was not an appropriate indicator for supplementary enzyme activity in the intact digestive tract of piglets given diets rich in fermentable NSPs. Piglets given the diets supplemented with enzymes excreted increased concentrations of urinary pentoses, especially arabinose (0·113 v. 0·136 mg/ml, s.e.d. 0·0107, P < 0·05). Urinary arabinose and xylose concentrations were also increased (V < 0·001) with feeding SBP, indicating that some of the microbially released NSP sugars escaped fermentation and were directly absorbed. In conclusion, piglets were able to use simple diets, containing high and contrasting sources of NSPs to support satisfactory rates of live-weight gain. Supplementation with NSP degrading enzymes enhanced the conversion of food to live-weight gain. Urinary NSP derived sugars provided indirect evidence of NSP hydrolysis by supplementary enzymes and gut microbes.

The effect of feeding different sources of dietary fibre at varying rates of inclusion on the concentrations of skatole and indole in the backfat of finishing pigs and their subsequent carcass quality was studied. Sugar-beet pulp (SBP) and straw (S) were selected because of their assumed widely differing hind-gut fermentability characteristics. They were individually and in combination added to a diet at three rates of inclusion designed to provide concentrations of 40, 80 and 120 g non-starch polysaccharide (NSP) per kg. The digestible energy (DE) contents varied between the three levels of inclusion of NSP but were formulated to a lysine: energy ratio of 0.625 g: MJ DE with other amino acids being in the same individual proportion to lysine. The nine experimental diets were offered to 10 replicate (five entire males and five females) pigs of initial live weight 55 kg. Food intakes were adjusted between treatment to ensure that energy and nutrient intakes were common. Animals were slaughtered on reaching 85 kg live weight. Adipose tissue was analysed for skatole and indole and meat quality characteristics assessed. No significant differences in performance were detected although carcasses from animals given sugar-beet pulp were significantly fatter. There were significant correlations between the level of skatole in the backfat and the following eating quality characteristics: skatole odour intensity of the fat, abnormal odour intensity of fat, abnormal odour intensity of lean and abnormal flavour intensity of lean with correlations coefficients of 0·656 , 0·709 , 0·496 and 0·523 respectively (coefficients >0.276; P < 0·05). The range in skatole levels in the backfat were attributable substantially to very high levels found in three boars. No significant correlations were found between indole concentrations in the backfat and eating quality characteristics. However no effects of dietary NSP type or inclusion level on the eating quality characteristics of pig meat, with pigs given diets on the basis of equal energy and nutrient intakes, were detected.