Cumulative Gas Production Technique Research Articles

Cinética da fermentação ruminal de diferentes genótipos de milho e tamanho de partículas por meio da técnica de produção acumulativa de gases

The objective was to evaluate the in vitro ruminal degradation kinetics of three corn genotypes (flint, semi-flint and semi-dent) in four particle sizes (greater than 1400 µm; between 1400 and 850 µm; between 850 and 420 µm; and smaller than 420 µm), by the semi-automatic cumulative gas production technique. There was an effect of genotype and particle size on total gas production and colonization time. Flint corn in smaller particles provides better ruminal fermentation parameters, with higher total gas production, higher degradation rate of potentially degradable fraction of carbohydrates and shorter lag time.

Dietary fiber sources for gestation sows: Evaluations based on combined in vitro and in vivo methodology

An in vitro-in vivo methodology was used to evaluate the potential value of different sources of fiber for gestation sows. Soluble and insoluble dietary fiber of 9 feed ingredients were isolated and fermented in vitro with sow faecal inoculum, using the cumulative gas production technique, to examine the kinetics, end-products and microbiota of fermentation after 72 h. It was shown that all fermentation kinetics parameters of gas production varied among feed ingredients. The production of short chain fatty acids (SCFA), branched-chain fatty acids (BCFA) and ammonia (NH3) were greater for wheat grain and maize compared to other feed ingredients on insoluble dietary fiber (IDF) fermentation for 36 h, and higher for maize compared to other feedstuffs on IDF fermentation for 72 h. However, SCFA, BCFA and NH3 were the highest of sorghum grain compared to other feedstuffs on soluble dietary fiber (SDF) fermentation for 36 and 72 h. The capacity of SCFA, BCFA and NH3 produced by SDF were significantly greater than that of IDF from different ingredients. IDF and SDF of beet pulp exhibited lower pH, higher Bacteroidetes and lower Firmicutes phylum after fermentation. The observed species and Shannon index in the beet pulp IDF and SDF were significantly lower than others. In genus level, Parabacteroides and unidentified_Prevotellaceae were higher but unidentified_Lachnospiraceae was lower in SDF fermentation compared to IDF fermentation. Further, a total of 75 multiparous gestation sows (Landrace × Yorkshire) were randomly assigned three fiber-rich diets provided by beet pulp (BP), soybean hull (SH), and wheat bran (WB) after mating. The sows were fed with three different fiber diets during gestation, but all the sows were similarly fed ad libitum during lactation. Sows fed BP diets farrowed a greater number of total (+1.7 pigs, P<0.05) and alive (+1.1 pigs, P<0.1) piglets compared with sows fed SH diets. In summary, beet pulp, irrespective of fiber type maybe have a better potential to be used in sow nutrition to manipulate the fermentation activity, microbiota and a greater litter size. Moreover, IDF and SDF from different feed ingredients, as well as the same feedstuff IDF and SDF, due to differences in fiber structure and composition may affect microbiota composition and ultimately affect the level of fermentation metabolites produced.

PSXII-36 Modelling in vitro gas production kinetics of fresh alfalfa incubated with inocula from five ruminant species

Abstract The objective was to identify the non-linear model with the best fit for cumulative gas production from fermentation of fresh alfalfa, with or without tannin extract, incubated with rumen fluid from five different species of ruminants. Fifteen animals (Taurine and Zebuine cattle, water buffaloes, sheep and goats) were used as inoculum donors. During incubation, 500 mg of fresh alfalfa, with or without 150 mg of acacia tannin extract, were used as substrate in the semi-automated gas production technique. Experimental design was completely randomized in a factorial arrangement with five inoculum sources (ruminant specie) and two treatments (with or without tannin extract). We used the PROC NLMIXED to fit ten mathematical models and the best one was chosen based on the lowest AIC and MSE and highest R2. Lastly, the best model was validated using the cross validation technique. The model with the best fit was the Groot model (AIC 1255.5; MSE 174.01; R2 0.9496) comparatively to others methods and the most part of error is from random effect (97.7%). Tannin inclusion reduced parameters potential gas production (A) and time to produce half of total gas production (T1) (P &amp;gt; 0.0001); however, no difference was observed on the gas production rate (k) (P &amp;gt; 0.1181). When no tannin was added, differences between the two cattle category were observed. Comparing water buffaloes’ inoculum with Taurine inoculum, no differences were observed for “A,” however, this parameter differed among water buffaloes and Zebuine cattle. In conclusion, Groot model had the best fit on in vitro bioassay with alfalfa substrate and treated or not with tannin extract. The tannin extract reduced the potential gas production; however, it did not change the gas production rate. For evaluation of alfalfa by cumulative gas production technique, the potential gas production was changed by using different animal categories as inoculum donor.

Cinética de degradação ruminal de alimentos proteicos pela técnica in vitro de produção de gases

Chemical analysis of carbohydrates and nitrogen fractions, as well as, determination their carbohydrates digestion rates in soyben meal (SM), crambe meal (CM), radish meal (RM), wet brewery residue (WBR) and dehydrated silkworm chrysalis (SCD) were accomplished. The kinetics parameters of non-fibrous carbohydrates (NFC) and B2 fraction were estimated using cumulative gas production technique. Among the foods studied there was considerable variation in chemical composition. The crambe meal was the only food that did not present synchronism between carbohydrate and nitrogen fractions. In this food there was predominance of A+B1 carbohydrates fractions and B1+B2 nitrogen compounds fraction, and for the other predominated B2 carbohydrate fraction and B1+ B2 nitrogen compounds fraction. There were differences among the digestive kinetic parameters for all foods. The greater participation in gas production due to non-fibrous carbohydrates was found in the crambe meal and oilseed radish meal. The fermentation of fibrous carbohydrates provided higher gas volume in the wet brewery residue and in the soybean meal, however, the soybean meal was food with higher total gas volume. Non fibrous carbohydrates degradation rates of wet brewery residue and dehydrated silkworm chrysalis were far below the limits of degradation of this fraction. Due to the parameters obtained by the cumulative gas production, the soybean meal was the best food, however, all others have potential for use in animal nutrition. The cumulative gas production technique allows the estimative of degradation rates and provides further information about the ruminal fermentation kinetics of foods.

In vitro fermentation profiles of palm kernel meal (PKM)-based diet supplemented with xylanase or cellulase using caecal digesta of broiler chickens as inoculums

In vitro fermentation profiles of palm kernel meal-based diet supplemented with or without xylanase and cellulase were investigated using broiler chickens caecal digesta as inoculum. Caecal digesta from 10 six week old male Cobb 500 broilers was diluted with pre-warmed anaerobic, sterile saline (9g/L NaCl) in a ratio of 1:5, and was used as inoculum. The PKM-based diet together with semi-defined medium and caecal inoculum was incubated in 100 ml glass syringe for 72 hours at 39±5 o C. In vitro fermentation kinetics was determined through the in vitro cumulative gas production technique. End products such as ammonia, VFAs, and in vitro dry matter degradability were also quantified. The in vitro study of PKM-based diet supplemented with or without xylanase did not show any different effect on the gas production rate. However, the amount of butyrate production was increased when enzyme was supplemented. Both xylanase and cellulase supplementation in PKM diet had significantly improved (P<0.05) the in vitro dry matter degradability of the PKM compared to unsupplemented PKM diet, which more prominent result shown by xylanase supplementation.

Role of Soluble and Insoluble Polysaccharides in Omnivore and Carnivores Nutrition: A Review

Present PhD thesis was realised at the Department of Veterinary Medicine and Animal Production (University of Napoli, Federico II, Italia) in order to study the functional properties of dietary fiber fractions (soluble and insoluble) in nutrition of different mono-stomached species. With this aim more than 30 different feedstuffs were evaluated using several analytic techniques (Weende, Van Soest and Prosky) (Chapter 2). Thereafter seems interesting to underline that main of the tested substrates are by-products and could represent economical and readily available nutrient sources. Moreover, in order define the functional activities and the potential health benefits some of these feedstuffs were tested also in vitro using the cumulative gas production technique (IVGPT). Tree different trials (Chapters 3 - 4 - 5) of IVGPT were carried out using as inoculum faeces from adult dog, swine and cat, respectively. The comparison of chemical data and fermentation parameters was important to better define the potential functionality of each tested substrate in order to identify new functional ingredients. The obtained results offer a good perspectives for the possibility of using several less known materials (e.g. chestnuts, citrus by-products, legume and fruit fibers) in the formulation of diets. The study evidenced also the specific carbohydrates composition of ingredients, such as seeds of pshyllium, line and hemp, usually utilized only for their fatty acids profile. Each tested feedstuff presented specific characteristics, which allow it to be useful in specific stage of life of omnivores and carnivores species, including human.

English

Compared to a phosphate free medium containing citrate buffer, effects of phosphate concentrations (10, 20, 50 ,and 100 mmol/L) in the modified Menke and Steingass&rsquo;s medium on methanogenesis of a maize-rich substrate (Leymus chinensis&nbsp;hay:maize meal = 1:4) were determined in comparison with using an&nbsp;in vitro&nbsp;cumulative gas production technique. After the 48 h batch cultures, phosphate additions decreased total gas production (GP48, ml/g dry matter (DM)) (P &lt; 0.05) as well as the gas production rate to reach maximum digestion (RmaxG, mL/h) (P &lt; 0.01). Total volatile fatty acids (VFA) concentrations (mmol/L) were decreased by 28%, while the phosphate concentration increased up to 50 to 100 mmol/L (P &lt; 0.05). Volatile fatty acid production shifted from an initially acetate dominated production towards a propionate production as demonstrated by the ratio of non-glucogenic to glucogenic acids (NGR) (P &lt; 0.01). Although, the molar proportions of CO2, CH4, and H2&nbsp;in the fermentation gases were not altered, the net fractional CH4&nbsp;production (ml/g DM) in the phosphate levels of 10, 20, 50, and 100 mmol/L were reduced by 6.2, 11.8, 18.57, and 26.2%. The results obtained in the present study showed that a phosphate-mediated reduction in methane emissions occurred without the expense of a reduction in the digestion of the substrate, and the mechanism that phosphate inhibited acetoclastic methanogenesis on rice roots may exist in the rumen. &nbsp; Key words:&nbsp;Rumen, methanogenesis, phosphate buffer, citrate buffer,&nbsp;in vitro&nbsp;batch culture.

Metabolisable Energy, In situ Rumen Degradation and In vitro Fermentation Characteristics of Linted Cottonseed Hulls, Delinted Cottonseed Hulls and Cottonseed Linter Residue.

Dietary supplementation with conventional linted cottonseed hulls (LCSH) is a common practice in livestock production all over the world. However, supplementation with mechanically delinted cottonseed hulls (DCSH) and cottonseed linter residue (CLR) is uncommon. Cottonseed by-products, including LCSH, DCSH and CLR, were assessed by chemical analysis, an in situ nylon bag technique, an in vitro cumulative gas production technique and in vitro enzyme procedure. The crude protein (CP) content of CLR (302 g/kg dry matter (DM)) was approximately 3 times that of LCSH and 5 times that of DCSH. The crude fat content was approximately 3 times higher in CLR (269 g/kg DM) than in LCSH and 4 times higher than in DCSH. Neutral detergent fibre (311 g/kg DM) and acid detergent fibre (243 g/kg DM) contents of CLR were less than half those of DCSH or LCSH. Metabolisable energy, estimated by in vitro gas production and chemical analyses, ranked as follows: CLR (12.69 kJ/kg DM)>LCSH (7.32 kJ/kg DM)>DCSH (5.82 kJ/kg DM). The in situ degradation trial showed that the highest values of effective degradability of DM and CP were obtained for CLR (p<0.05). The in vitro disappearance of ruminal DM ranked as follows: CLR>LCSH>DCSH (p<0.05). The lowest digestibility was observed for DCSH with a two-step in vitro digestion procedure (p<0.05). The potential gas production in the batch cultures did not differ for any of the three cottonseed by-product feeds. The highest concentration of total volatile fatty acids was observed in CLR after a 72 h incubation (p<0.05). The molar portions of methane were similar between all three treatments, with an average gas production of 22% (molar). The CLR contained a higher level of CP than did LCSH and DCSH, and CLR fermentation produced more propionate. The DCSH and LCSH had more NDF and ADF, which fermented into greater amounts of acetate.

Cinética de degradação ruminal de carboidratos de volumosos secos e aquosos: técnica de produção de gases

Chemical analysis of carbohydrates fractions and determination their carbohydrates digestion rates in some foods obtained under tropical conditions and semiarid regions, were accomplished. Dry forages were studied (hays of ‘mata-pasto’, ‘sabia’, ‘juazeiro’, ‘mororo’, star grass, leucaena leaf, oat, and Tifton 85 grass), as well as, wet forages (corn, sorghum and palm silages, and also fresh forage cactus). The kinetics parameters of non-fibrous carbohydrates (NFC) and B2 fraction were estimated using cumulative gas production technique. Among the studied foods, there was considerable variation in chemical composition and in the soluble carbohydrates degradation rates. Comparing the kinetics parameters of native forages to Northeast it was verified that the high content of C fraction in of ‘juazeiro’and ‘mororo’ hay influenced in carbohydrates ruminal degradation kinetics, where the final gas volume for these hays were 6.88 and 2.58mL, respectively. The fermentation of ‘mata-pasto’ hay resulted in a higher gas production (16.38 mL) for total carbohydrates (TC) as well as the higher degradation rate (0.0276%/h) and shorter time for colonization (4.29h). For oat hay, it was observed that the values for A+B1 fraction were higher (389.6 g/kg) in relation to the Tifton 85 grass hay (300.3 g/kg) and star grass hay (344.5 g/kg), and lower for the B2fraction (441.6%). It was observed that sorghum silage had a higher gas volume (24.70 mL) compared with corn silage (16.44 mL). The cumulative gas production technique allows the estimative of degradation rates and provides further information about the ruminal fermentation kinetics of foods.

In vitro fermentation kinetics and end-products of cereal arabinoxylans and (1,3;1,4)-β-glucans by porcine faeces

Purified and semi-purified polysaccharides characteristic of cereals were fermented in vitro with a pig faecal inoculum, using the cumulative gas production technique, to examine the kinetics and end-products of fermentation after 48 h. It was shown that arabinoxylan and mixed linkage (1,3;1,4) β-glucan were rapidly fermented if soluble, while less soluble substrates (insoluble arabinoxylan, maize and wheat starch granules, and bacterial cellulose) were more slowly fermented. Relevant monosaccharides were fermented at very similar rates to soluble polymeric arabinoxylan and β-glucan, showing that depolymerisation was not a limiting step, in contrast to some previous studies. Bacterial cellulose is shown to be a useful model substrate for fermentation of plant cellulose which is difficult to obtain without harsh chemical treatments. Fermentation end-products were related to kinetics, with slow carbohydrate fermentation resulting in increased protein fermentation. Ratios of short-chain fatty acid products were similar for all arabinoxylan and β-glucan substrates.

In vitro fermentation of various carbohydrate-rich feed ingredients combined with chyme from pigs

Increased carbohydrate fermentation, compared with protein fermentation, could benefit gut health. In two in vitro experiments, the effect of carbohydrate-rich feed ingredients on fermentation characteristics of ileal chyme from pigs was assessed, using the cumulative gas production technique. Ingredients of the first experiment included gums, inulins, pectins, transgalacto-oligosaccharides, lactose and xylan. In the second experiment, a gum, pectin and transgalacto-oligosaccharides were added at different starting weights, to determine their effects on fermentation characteristics of chyme, in relation to differences in the carbohydrate concentrations. In comparison to fermentation of chyme alone, added carbohydrates led to higher total gas production (p < 0.05), faster maximum rate of gas production (except for xylan) (p < 0.05), and a decreased branched-chain fatty acids to straight chain fatty acids ratio (BCR) (p < 0.05). In the second experiment, for all carbohydrate ingredients, the BCR decreased with increasing starting weights (p < 0.05). If these supplemented dietary carbohydrates were to reach the terminal ileum of the living animal, carbohydrate fermentation in the large intestine could be stimulated, which is known to have beneficial effects on host health.

Pediocin A modulates intestinal microflora metabolism in swine in vitro intestinal fermentations

The aim of this study was to investigate in vitro the effects of pediocin A [a bacteriocin produced by lactic acid bacteria (LAB) Pediococcus pentosaceus FBB61] on microbial metabolism in the small and large intestine of pigs. Pediocin A was partially purified by ion exchange chromatography and added to an in vitro fermentation system. The intestinal inoculum was collected from pigs immediately after slaughter, diluted with a buffer, and dispensed into fermentation syringes and vessels of the 2 experimental groups: 1) Bac+ = cecal liquor + predigested diet + pediocin A (final concentration 160 activity units/mL); 2) Bac- = cecal liquor + predigested diet + partially purified supernatant of P. pentosaceus FBB61-2. Intestinal microbial growth was monitored using the cumulative gas production technique; the kinetics of fermentation, bacterial counts, VFA, ammonia, polyamines, and p-cresol production were analyzed. Pediocin A had almost no effects on small intestine fermentation parameters, whereas in the cecum pediocin A decreased gas production (-16%; P < 0.05), ammonia, and VFA production (-52 and -21%, respectively, after 24 h; P < 0.001) compared with the control group. Significant inhibition of clostridia and LAB occurred in cecal fermentations: the Bac+ group yielded a decreased number of clostridia and LAB in cecal fermentations (8.19 and 7.80 cfu/mL, respectively) compared with Bac- (9.32 and 8.95 cfu/mL, respectively; P < 0.001). The low clostridia counts in the pediocin-treated group may also explain the reduced concentration of the carcinogenic compound p-cresol (-88%; P < 0.01). Our results suggest that pediocin A could be an alternative to replace antibiotic growth promoters for the prophylaxis of enteric diseases and to improve production of farm animals.

In vitro effects of some organic acids on swine cecal microflora

The objective of this study was to evaluate the effects of different organic acids on bacterial growth and ammonia production by swine cecal microflora in an in vitro fermentation system. Formic, acetic, propionic, lactic, butyric, sorbic, fumaric, malic, citric, ±-ketoglutaric, and benzoic acids were used at different concentrations (60, 120 and 240 mmol/l) to assess if any effect on cecal microflora could be shown. Cecal microbial growth was evaluated using the cumulative gas production technique. Fermentation fluid was analyzed for ammonia concentration. Lactic acid was the only acid that enhanced bacterial fermentation at every concentration tested (+30%, 73%, and 35% gas final volume at 60, 120, and 240mmol/l, respectively; P<0.05). Citric acid strongly increased gas final volume when used at 60 and 120mmol/l (+92% and 52%, respectively; P<0.05) and almost completely inhibited bacterial activity at 240mmol/l (–85% gas final volume; P<0.05). Sorbic acid showed the strongest antibacterial activity and was the only acid that reduced final gas volume when used at 60 mmol/l (–34%; P<0.05). Only sorbic (–34%, 47%, and 67%), fumaric (–57%, 35%, and 26%), citric (–31%, 18%, and 28%), and benzoic (–33%, 29%, and 38%) acids reduced ammonia after 24h of fermentation at any given concentration (P<0.05). Other acids, such as formic, acetic, propionic, butyric, and malic acids failed to exert an effective control of ammonia levels in the fermentation liquor. After the first set of fermentations, sorbic, ±-ketoglutaric, and benzoic acids were further tested at the final concentration of 7.5, 15, and 30mmol/l. At these lower levels of inclusion, sorbic acid was the only acid that reduced final gas volume at every concentration tested (–31%, 35%, and 39% at 7.5, 15, and 30mmol/l, respectively; P<0.05). Compared with control, ammonia was reduced after 24h of fermentation by all treatments (with an average reduction of 34%, 20%, and 24% for sorbic, ±-ketoglutaric, and benzoic acids, respectively; P<0.05). In conclusion, gas production data showed that organic acids inhibit or enhance cecal bacterial activity in relation to the type and concentration of acid used. Furthermore, sorbic, ±-ketoglutaric, and benzoic acids can positively influence swine cecal microflora in vitro fermentation reducing ammonia concentrations, even when used at low concentrations.

Use of the in vitro cumulative gas production technique for pigs: An examination of alterations in fermentation products and substrate losses at various time points1

An experiment was conducted to examine changes in VFA and ammonia concentrations at different time points using 4 fermentable carbohydrate-rich feed ingredients as substrates and feces of unweaned piglets as inoculum. Fecal inoculum was collected, pooled, and mixed from 9 specially raised (no creep feed or antibiotics) crossbred piglets at 3 wk of age. Inulin, lactulose, molasses-free sugar beet pulp, and wheat starch were used as substrates and were fermented in vitro for 72 h (3 replicates per substrate). Cumulative gas production was measured as an indicator of the kinetics of fermentation. In addition, 3 bottles of substrate per time point with similar contents (amounts of substrate, inoculum, and media) were incubated but were allowed to release their gas throughout incubation. For these latter bottles, fermentation fluid was sampled at incubation time points including every hour between 1 and 24 h and at 48 h, and fermentation end products (VFA, lactate, and ammonia) and OM disappearance were measured. Dry matter and ash were analyzed from the postfermentative samples. The pH of the contents from these bottles was also recorded. The correlation in time between fermentation end products and cumulative gas produced was determined. The results showed that the prolongation of fermentation to 72 h, especially in the case of fast-fermenting inulin and lactulose, may lead to a different end product profile (P < 0.001) compared with the profile observed at the time at which most of the substrate has disappeared. Therefore, we concluded that the fermentation product profile at the end of in vitro fermentation at a specific time point cannot be used to compare fermentability of carbohydrate sources with different fermentation kinetics in terms of gas production.

Cumulative gas production: how to measure it, and what it can and cannot tell you

SummaryThe three most important factors describing the nutritive value of ruminant feeds are: feed intake, rumen fermentation, and enzymatic digestion. Animal experiments are usually expensive and time-consuming, so many in vitro techniques have been developed which are supposed to assist in the prediction of nutritive value, usually of rumen fermentation. One of these is the measurement of gas production from the substrate when incubated with a specific inoculum. The cumulative gas production technique measures gas at regular intervals in time, as an indicator of the kinetics of fermentation. The resultant cumulative gas profiles, fitted to specific equations, and in combination with other end-products (i.e. VFA and NH3) can indicate both the rate and extent of fermentability of the test substrates. This information can be used to compare substrates with each other. However, the fact that the technique has not yet been standardized, and that inoculum varies according to time and place, means that comparison both between runs and locations, can be very difficult. Also, there are a number of aspects of the technique which will always mean that its resemblance to the in vivo situation must be limited. Some of these limitations and other important considerations of the technique are described in this review.

Effect of substrate adaptation on the microbial fermentation and microbial composition of faecal microbiota of weaning piglets studied in vitro

AbstractThe in vitro cumulative gas production technique can be used to assess microbial activity of a complex community, in relation to fermentation of a particular energy source. Therefore, in combination with an in vivo study to examine the effects of two different diets for weaning piglets, microbial activities of faeces were compared from animals on the two different diets. The two diets were: CHO diet [containing added fermentable carbohydrates, including sugarbeet pulp (SBP) and wheat starch (WST)], and control diet without any added fermentable carbohydrates. Neither diet contained antibiotics or extra added copper. Twenty‐four piglets were selected from 12 litters (two per litter), weaned at 4 weeks of age (neither creep feeding nor any antibiotic treatment before and during the study), and introduced to one of the two diets. After 9 days on the diet, faecal samples were collected from selected animals, and tested for their activity in terms of gas production kinetics, and end‐products such as volatile fatty acids, ammonia and dry matter disappearance of the two test substrates SBP and WST. The bacterial diversity was also analysed before and after in vitro fermentation using denaturing gradient gel electrophoresis analysis of amplified 16S rRNA genes. There were differences both in kinetics and end‐products of the substrates. More interestingly, significant differences were detected between inocula, although mainly in terms of fermentation kinetics of the two substrates. With the CHO inoculum, SBP was fermented faster than with the control, while this effect was reversed for WST. Significantly higher diversity, as measured by DGGE fingerprint analysis, was detected in the microbial community enrichment on SBP as compared with WST at the end of fermentation. The difference between the kinetics of SBP compared with WST fermentation by faecal microbiota from the CHO diet fed piglets suggests better adaptation to SBP fermentation than to WST fermentation. The WST fermentation was more unexpected, given that a significant amount of starch is known to be fermentable by the small intestinal microbiota. It was concluded that the microbial community composition and activity in the GIT may be changed in response to diet, and that this change can be detected in vitro. Copyright © 2005 Society of Chemical Industry

Differences in microbial activity of digesta from three sections of the porcine large intestine according to in vitro fermentation of carbohydrate‐rich substrates

AbstractTo determine whether faecal microorganisms can represent the entire large intestinal population, samples from caecum, mid‐colon and rectum of three adult pigs were used for the in vitro fermentation of fructo‐oligosaccharide (FOS), potato starch, wheat bran and oat hulls. The cumulative gas production technique measured fermentation kinetics and end‐products such as total gas, NH3 and volatile fatty acids (VFA). There were significant differences in the fermentability of substrates, in terms of both kinetics and end‐products. More relevant to this study, there were also differences between pigs in respect of total gas production, the rate of gas production (RM) and VFA production. For large intestine sections, there were more VFA from mid‐colon and rectal inocula compared with that from the caecum (p &lt; 0.0001). Total gas, RM and NH3 were highest for rectal, intermediate for mid‐colon and lowest for caecal inocula (p &lt; 0.0001). It was concluded that, while faecal sampling might overestimate caecal fermentation, its use is valid for in vitro assessment of large intestinal fermentation. However, differences between pigs indicate that a mix of samples from several animals remains important. Copyright © 2004 Society of Chemical Industry

In vitro fermentation characteristics of two mushroom species, an herb, and their polysaccharide fractions, using chicken cecal contents as inoculum

In vitro fermentabilities of two mushrooms (Lentinus edodes-LenS; Tremella fuciformis-TreS), an herb (Astragalus membranaceus-AstS), and their polysaccharide fractions (LenE, TreE, and AstE) were investigated using microflora from chicken ceca. Polysaccharides were extracted using the hot water method. The mushrooms had lower polysaccharide yields (8 to 10%) than the herb (31%). Fermentation kinetics were determined using the in vitro cumulative gas production technique. End-products, such as gas, volatile fatty acids (VFA), and ammonia, were also determined. The gas profiles of intact materials were similar for AstS and LenS. The TreS had a diphasic digestion pattern. The extracts had similar profiles to the intact materials though gas production rates were faster. Intact materials tended to produce less VFA than the extracts though LenS and AstE had the highest total VFA production overall. Intact materials contained more protein than the extracts, and therefore resulted in more branched-chain fatty acids and ammonia. Fermentation kinetics and end-point products demonstrated differences in availability of substrates between the mushrooms and herb. These medicinal mushroom and herb materials, particularly their polysaccharide extracts, show promise in altering microbial activities and composition in chicken ceca. In vivo experiments are necessary for confirmation of this hypothesis.

Impact of mammalian enzyme pretreatment on the fermentability of carbohydrate‐rich feedstuffs

AbstractSeveral carbohydrate‐rich substrates (spent brewer's grains, potato peel, potato starch, wheat bran, sugarbeet pulp and a maize‐based standard diet for pigs) were pretreated with digestive enzymes, and the in vitro fermentability of these treated substrates and their untreated counterparts was assessed using the cumulative gas production technique. A comparison was also made between the enzyme‐treated (ET) and untreated (UT) standard diet for pigs, and chyme which originated from pigs fed that diet, to determine whether the enzyme treatment resulted in material with similar fermentability to that reaching the large intestine in vivo. The enzyme pretreatment was performed according to a modified in vitro method of Babinszky et al (J Sci Food Agric 50:173–178 (1990)). Generally, it was shown that the fermentabilities of the ET and UT substrates were different. There was also a significant difference between the fermentation characteristics of the ET diet and chyme. Chyme produced less gas (P &lt; 0.05), and the time at which half of the gas had been produced (C) occurred later (P &lt; 0.05). The maximum rate of fermentation (R M) was slower for chyme (P &lt; 0.05). Fermentation of chyme led to more ammonia (P &lt; 0.05) and a tendency to more volatile fatty acids at the end of fermentation. These differences in fermentability of the ET diet and chyme (from pigs fed the same diet) may be the result of differences which relate purely to the action of the enzymes chosen to work in vitro, compared with those which are actually present in vivo. However, the results also suggest that it is not only enzymatic digestion which is occurring in the small intestine. This is an important consideration when using ileal techniques to determine digestibility of feedstuffs.© 2003 Society of Chemical Industry

An organic acid blend can modulate swine intestinal fermentation and reduce microbial proteolysis

The increased use of slow-release organic acids in swine nutrition has prompted more research to assess their possible role in modulating the intestinal microflora as an alternative to antibiotics. Three diets for growing pigs containing 0 (L-NDF), 100 (M-NDF), and 200 g kg-1 (H-NDF) dried sugar beet pulp (SBP) were pre-digested to simulate ileal digestion, and used as substrate in an in vitro cecal fermentation study. The inoculum was collected from pigs immediately after slaughter. Diets tested were L-NDF, M-NDF, and H-NDF with or without the addition of an organic acid blend providing phosphoric, citric, fumaric, and malic acid at 1.53, 0.78, 2.59, and 1.12 mmol L-1, respectively. Cecal microbial growth was monitored using the cumulative gas production technique. Fermentation fluid was analyzed for ammonia and volatile fatty acids concentrations. The maximum rate of gas production was higher when H-NDF rather than L-NDF or M-NDF (+ 18%; P &lt; 0.05) was fed; such a high rate of growth (+ 14%; P &lt; 0.05) was also achieved when the acid blend was added to L-NDF. After 24 h, the acid blend reduced ammonia, isoacids, and acetic acid concentrations in fermentation fluid regardless of the type of diet (P &lt; 0.05). Organic acids stimulated bacterial fermentation when added to a low-fiber diet and were able to reduce ammonia in all diets tested. Key words: Swine, cecum, fiber, organic acids, ammonia, volatile fatty acid