Jaak Decuypere

Approach to the Energetic Importance of Fibre Digestion in Pigs. I. Importance of Fermentation in the Overall Energy Supply

Much research has been focussed on fibre in pig nutrition during recent years. In order to approach the energetic importance of fibre digestion as an integrated part of the overall energy supply in pigs, several aspects of fibre assimilation in pigs are examined in this paper. Firstly, the physiological influence of fibre on the enzymatic pre-caecal and microbial post-ileal digestion of nutrients is reviewed: ingestion, secretion, absorption and transit time. Secondly, the digestibility of fibre in pigs under different feeding and performance conditions is examined: source and level of fibre, feeding level, treatment, age, liveweight and physiological state of the animal, environment (climate), and the site in the gastrointestinal tract. Thirdly, the supply and utilization of energy from hindgut fermentation (volatile fatty acids, VFA) in terms of overall energy metabolism and requirements in pigs are approached through several techniques: slaughter techniques, cannulated pigs, arterio-venous differences in VFA concentration, in vitro fermentation rates in caecum and colon contents, and isotope dilution techniques. From this literature study, it appeared that VFA may make only a small, but significant, contribution to the total energy available to growing-finishing pigs under practical conditions; the mean supply of net energy (NE) from VFA to the net energy for maintenance (NEm) or basal metabolism (BM) amounts to about 15%. The importance of VFA production for energy retention may be greater, however, for non-lactating mature sows and breeding boars. Finally, measurements of energy supply from hind gut fermentation, through respiration and balance trials, are given for some fibre sources. The effect of fibre on performance and carcass traits of swine are also briefly reviewed. The conclusions emphasize that correct evaluation of the importance of VFA production to the energy supply of the animal can only be made through respiration and balance trials or carcass analysis because only these approaches take into account the depressive effect of fibre on nutrient (protein, amino acids, minerals) absorption in the small intestine, and the amount and nutritional value of the VFA formed. Fermentation should, therefore, be evaluated not as an isolated part, but as an integrated part of the overall energy-supplying system of the pig, otherwise the energetic importance of fermentation may be greatly overestimated.

Influence of the gut flora and of some growth-promoting feed additives on nitrogen metabolism in pigs. I. Studies in vitro

Abstract Nine growing pigs (10–40 kg) were cannulated either in the duodenum or ileum or caecum and fed a dry-milk powder diet. These pigs were used as donors of fresh intestinal contents for short (4 h) incubation experiments. From the incubations of duodenal contents, it appeared that the bacterial activity was not important. In consequence, the antibiotic effects of Virginiamycin and Spiramycin were also negligible. During incubations of ileal contents, eventually supplemented with free amino acids, on the other hand, 20–30% of the amino acids were degraded by the flora either by deamination, with formation of ammonia, or by decarboxylation with formation of amines: histamine, putrescine, cadaverine, tyramine, phenylethylamine. Cadaverine, the decarboxylation product of lysine, was the most important amine detected. Both processes were severely decreased when the antibacterials Virginiamycin (50 p.p.m.), Spiramycin (50 p.p.m.), Carbadox (50 p.p.m.) and copper sulphate (200 p.p.m.) were present during the incubation of the ileal contents. The fermentation of caecal contents was characterized by a pronounced production of ammonia, slightly inhibited by Virginiamycin and Spiramycin. Testing the amino acid decarboxylation activity of the dominant flora ( E. coli, S. faecalis, L. acidophilus and L. fermenti ) in the small intestine of the pig, it was found that E. coli is the main producer of amines in the small intestine of pigs. We conclude that the gut flora of pigs has a measurable negative influence on protein digestion in the small intestine and that this effect can be overcome by feeding nutritional antibacterials.

Approach to the Energetic Importance of Fibre Digestion in Pigs. II. An Experimental Approach to Hindgut Digestion

Abstract The hindgut digestibility in the pig was studied using three different methods and eight practical diets containing different fibre levels: (1) The production rates of volatile fatty acids (VFA) were measured in vitro; (2) a stoichiometric calculation of the VFA produced was made using the molar percentage distribution in vivo and the quantity of organic matter digested (OM); (3) an in vitro simulation of the hindgut digestion was made using rumen bacterial flora. The energetic importance of fibre digestion was calculated from these three methods. The results led to the conclusion that the mean quantity of VFA produced in the hindgut is about 10 g per 100 g of diet intake using each of the three experimental methods. The simulation of the hindgut digestibility in vitro, incubating the residual substrate obtained after the in vitro incubation with pepsin and pancreatin with rumen bacterial microflora, seems to be a practical method for study of the hindgut digestibility in the pig. Finally, calculation of the energy supply from the hindgut fermentation [the net energy (NE) supply from the VFA produced] to the NE diet, the net energy maintenance and the net energy production of 11.3, 41.0 and 15.6%, respectively, is discussed.

the influence of lentinus edodes (shiitake mushroom) preparations on bacteriological and morphological aspects of the small intestine in piglets

Among substances intended to replace growth promoting antibiotics in pig nutrition, non-digestible oligosaccharides or polysaccharides could be potential alternative compounds. Therefore, the influence of β-1,3-1,6 glucans on bacteriological, biochemical and morphological aspects of the small intestine in weaned piglets was investigated. As sources of β-glucans, Lentinan (extract of Lentinus edodes mycelium) or dried L. edodes mycelium were added to the diet. Four homogenous groups of 5 newly weaned piglets (4 weeks of age) received one of four diets: control diet (C), C supplemented with Avilamycin (50 mg/kg, positive control), C supplemented with 0.1% of Lentinan and C supplemented with 5% of dried L. edodes mycelium powder. A first group of 10 piglets was euthanized after 11 days and the remaining 10 on day 12 of the experiment. The gastrointestinal tract was divided in segments and samples taken from digesta (stomach, proximal and distal jejunum, caecum), mucosal scrapings (jejunum) and ring shaped tissue samples (1 cm) of proximal and distal jejunum. Bacterial counts were made with digesta and mucosal samples, and short-chain fatty acids (SCFA), lactic acid and ammonia concentrations were determined. Tissue samples of both jejunal sites were embedded in paraffin wax for morphometrical (villus length, crypt depth) and histological observations (numbers of intraepithelial lymphocytes (IEL), goblet cells, apoptotic enterocytes on villi, mitotic cells in crypts). Only the diet containing 5% of dried L. edodes consistently resulted in lower viable counts (ca. 1 – 2 log10 CFU) of total bacteria, E. coli, streptococci and lactic acid bacteria, and luminal and mucosal effects agreed very well. With this diet, acetate and butyrate concentrations in the distal jejunum were doubled, which is favourable in view of the trophic effect on enterocytes and colonocytes. Villus length (V) was increased with both diets containing β-glucans while crypt depth (C) was not altered, but V/C was higher. IEL counts were decreased by both diets although bacterial numbers, which is only one parameter of bacterial load, were only diminished with the L. edodes feed. The three supplemented feeds lowered the number of apoptotic enterocytes on the villi, but these numbers were very low (control diet : 44 cells per 100 villi), making clear interpretation difficult. The mitotic index was slightly lower with the L. edodes feed, although not statistically significant. Decreased viable counts observed with the latter diet is a favourable effect as it is accepted that a lower bacterial load causes lower turnover rates of the intestinal epithelial cells, while there is also less competition for specific substrates. A higher V/C ratio, a smaller number of IEL in the epithelium and a lower apoptotic index also indicate slower turnover rate of the mucosa when Lentinan and L. edodes diets were fed. The inconsistent effects observed with Lentinan were probably due to the low amount added to the diet. It should be taken into account that the influence of L. edodes mycelium powder was more likely due to the presence of antibacterial compounds (eg. lenthionine, lentinamycin, terpenoids, polyphenols), rather than to an immunostimulating action of β-glucans with increased release of IgA onto the mucosa surface.

Incorporation of galactomannans in the diet of newly weaned piglets: Effect on bacteriological and some morphological characteristics of the small intestine

In search of substances replacing antibiotics as growth promoters for farm animals, non-digestible oligosaccharides (NDO) or non-starch polysaccharides (NSP) have been proposed as possible alternatives. In this context, the influence of galactomannans on bacteriological and morphological aspects of the gastrointestinal tract in weanling pigs was investigated. Four groups of five newly weaned piglets received one of the following diets: control feed (C), C supplemented with guar gum (1%), C supplemented with locust bean gum (1%) and C supplemented with 10% of carob tree seeds meal as source of locust bean gum. The animals were euthanized after 11 – 12 days and digesta were sampled in stomach, jejunum (proximal and distal) and caecum, while mucosal scrapings and ring shaped tissue samples were taken of proximal and distal jejunum. On these samples bacteriological, biochemical and morphological determinations were carried out. Total count of bacteria in digesta and mucosal scrapings was not influenced by the different diets, with the exception of the proximal jejunum where a small decrease (0.5 log10 CFU) was noted with the guar gum and carob tree seeds diet. The number of E. coli increased by feeding both gums and carob tree seeds. With the latter diet, higher counts of streptococci were observed. In agreement with the lower concentration of lactic acid in jejunal contents, guar gum decreased the number of lactobacilli. Locust bean gum decreased the molar proportion of acetate in caecal contents while butyrate and valerate were augmented. Feeding the carob tree seeds resulted in shorter villi and a lower villus height/crypt depth ratio in the jejunum mucosa, which was an indication for a faster renewal rate of the epithelium. Both locust bean gum feeds significantly lowered the mitotic index in the crypts of the small intestine. Only with the carob tree seeds diet, viscosity of jejunal contents was increased. In conclusion, the effects of the addition of 1% of pure guar gum or locust bean gum were inconsistent and not very outspoken, whereas 10% of carob tree seeds meal in the diet resulted in influences on intestinal characteristics at the bacteriological and morphological level.

In vitro fermentability and physicochemical properties of fibre substrates and their effect on bacteriological and morphological characteristics of the gastrointestinal tract of newly weaned piglets

Abstract Fermentability of fibre has a great impact on the bacterial flora along the gastrointestinal tract of newly weaned piglets. Therefore, this parameter was determined by incubating in vitro different fibre substrates (chicory roots, sugar beet pulp, wheat bran and corn cobs) with contents of jejunum or caecum sampled from slaughtered pigs. Incubating with small intestinal contents, lactic acid was the only fermentation product. Fermentability was highest for chicory roots, followed by wheat bran and sugar beet pulp, while corn cobs were not fermented. Based on SCFA formed in the incubations with caecal contents, ranking of the fermentability of the fibre substrates was in the same order. The effect of adding different fibre substrates to diets of newly weaned piglets on bacteriological and morphological aspects of the gastrointestinal tract was also investigated. In Experiment 1 three groups of five piglets, weaned at four weeks of age, received a control feed (C), C supplemented with corn cobs (50 g/kg) or with chicory roots (20 g/kg). In Experiment 2, diet C was supplemented with sugar beet pulp (120 g/kg) or with wheat bran (75 g/kg). After three weeks animals were euthanized and digesta were sampled from stomach, proximal and distal jejunum, caecum and colon. Furthermore, mucosal scrapings were prepared and tissue samples were taken from jejunum, caecum and colon. Viscosity was determined for jejunal, caecal and colon contents. Corn cobs in the feed increased the number of total bacteria, lactobacilli and bifidobacteria in the stomach and proximal duodenum, while a decreased count of streptococci in distal jejunum contents was noted. Chicory roots increased the counts of Escherichia coli in the distal jejunum and on the mucosa, while sugar beet pulp decreased the number of lactobacilli on the mucosa only. Wheat bran seemed to increase the count of E. coli in jejunal digesta and on the mucosa, and also the number of lactobacilli in the stomach and jejunum. Bifidobacterial numbers were increased but only in the proximal part of the jejunum. Fibre substrates affected the concentration of lactate and SCFA in different parts of the intestinal tract. Feeding corn cobs increased villus length in the proximal jejunum by 13%. The number of intra-epithelial lymphocytes in the villous epithelium of proximal and distal jejunum was decreased by corn cobs and chicory roots supplementation while beet pulp and wheat bran had the opposite effect. In Experiment 1, apoptotic index of the mucosa of the distal jejunum was very low and decreased when corn cobs were fed. Mitotic index in the crypts was only affected by the wheat bran diet and a small decrease was noted. It was concluded that the fermentability of fibre was not an ideal criterion for predicting its effects on the flora. The effect of fibres on viscosity of digesta was negligible probably explaining the lack of clear and consistent influences on the intestinal mucosa.

Influence of Virginiamycin on the Digestive Physiology in Precaecal Re-entrant Cannulated Pigs

The present experiment was set up to study the effect of Virginiamycin, a nutritional growth promoting antibiotic, on the digestive physiology using precaecal cannulated pigs. The semipurified diet used provided 21% protein and 60% of nitrogen free extract (NFE), 2/3 as starch and 1/3 as lactose. Due the older age of the pigs, the lactose induced some degree of malabsorption as precaecal flow rate of digesta was markedly higher (3.2 kg/d) compared with published data obtained with purified diets without lactose. This was also reflected in the rather low ileal digestibility of the nutrients (%): dry matter 68.6, protein 79.6, fat 78.4 and NFE 75.0. Virginiamycin markedly lowered flow rate (2.2 kg/d) and significantly improved apparent precaecal digestibilities (%): dry matter 74.0, protein 81.4, fat 81.9 and NFE 78.7. The faecal apparent digestibility was comparable with published data. There were no treatment differences indicating that precaecal digestibilities are much more sensitive then faecal ones. In order to explain the differences obtained the mean retention time in the upper intestine was measured. Although significant differences were noted (control: 5 h, Virginiamycin: 6 h) a direct cause-effect relationship was not evident. Also the activity of selected pancreatic enzymes in ileal contents was compared. There were no consistent differences between the two treatments, except for a lower lipase activity during Virginiamycin treatment.

Chemical analysis of cell wall and energy digestibility in growing pigs

Abstract Ileal and faecal fibre digestibility was studied in pigs, with six diets containing increasing levels (1.5–9%) of beet pulp, alfalfa and wheat bran. The apparent digestibility of fibre was assessed from the crude fibre (CF), the neutral and acid detergent fibre (NDF, ADF) and the non-starch polysaccharides (NSP). The analytical methods employed gave clearly different figures for fibre content in the diets and their respective ileal and faecal residues. Crude fibre, NDF and ADF underestimated fibre degradation in the hindgut by more than 100% when compared with NSP values. Xylose and glucose polymers were the most resistant to digestion. At the ileal level, the NDF overestimated fibre digestibility. Solubilization, particularly of uronic acid residues, anterior to the caecum was apparent. Solubilized NSP glucose, on the other hand, was substantially degraded in the small intestine.

The nutritional mode of action of some feed additives in pigs

THE NUTRITIONAL MODE OF ACTION OF SOME FEED ADDITIVES IN