Over the past decade, in vitro methods have been developed to study intestinal fermentation in pigs and its influence on the digestive physiology and health. In these methods, ingredients are fermented by a bacterial inoculum diluted in a mineral buffer solution. Generally, a reducing agent such as Na2S or cysteine-HCl generates the required anaerobic environment by releasing metabolites similar to those produced when protein is fermented, possibly inducing a dysbiosis. An experiment was conducted to study the impact of two reducing agents on results yielded by such in vitro fermentation models. Protein (soybean proteins, casein) and carbohydrate (potato starch, cellulose) ingredients were fermented in vitro by bacteria isolated from fresh feces obtained from three sows in three carbonate-based incubation media differing in reducing agent: (i) Na2S, (ii) cysteine-HCl and (iii) control with a mere saturation with CO2 and devoid of reducing agent. The gas production during fermentation was recorded over 72 h. Short-chain fatty acids (SCFA) production after 24 and 72 h and microbial composition of the fermentation broth after 24 h were compared between ingredients and between reducing agents. The fermentation residues after 24 h were also evaluated in terms of cytotoxicity using Caco-2 cell monolayers. Results showed that the effect of the ingredient induced higher differences than the reducing agent. Among the latter, cysteine-HCl induced the strongest differences compared with the control, whereas Na2S was similar to the control for most parameters. For all ingredients, final gas produced per g of substrate was similar (P>0.10) for the three reducing agents whereas the maximum rate of gas production (R-max) was reduced (P<0.05) when carbohydrate ingredients were fermented with cysteine-HCl in comparison to Na2S and the control. For all ingredients, total SCFA production was similar (P>0.10) after 24 h of fermentation with Na2S and in the control without reducing agent. Molar ratios of branched chain-fatty acids were higher (P<0.05) for protein (36.5% and 9.7% for casein and soybean proteins, respectively) than for carbohydrate (<4%) ingredients. Only fermentation residues of casein showed a possible cytotoxic effect regardless of the reducing agent (P<0.05). Concerning the microbial composition of the fermentation broth, most significant differences in phyla and in genera ascribable to the reducing agent were found with potato starch and casein. In conclusion, saturating the incubation media with CO2 seems sufficient to generate a suitable anaerobic environment for intestinal microbes and the use of a reducing agent can be omitted.

The effects of tropical forage legumes on feed intake, growth performance and carcass traits were investigated in 16 groups of two Large White × Duroc pigs. The diets consisted of a commercial corn–soybean meal diet as the basal diet and three forage-supplemented diets. Four groups of control pigs received daily 4 % of body weight of the basal diet, and 12 groups of experimental pigs were fed the basal diet at 3.2 % of body weight completed with fresh leaves of one of the three forage legumes (Psophocarpus scandens, Stylosanthes guianensis and Vigna unguiculata) ad libitum. The study lasted 90 days. The in vitro digestion and fermentation of the forage legumes were also determined. The in vitro digestible energy content of the legumes was between 0.72 and 0.77 that of the basal diet (14.4 MJ/kg dry matter (DM)). V . unguiculata was the most digestible forage legume expected for crude protein digestibility. Feeding forage legumes lowered the dry matter intake by 4.5 to 9.6 % (P < 0.05), final body weight (P = 0.013), slaughter weight, average daily gain and hot carcass weight (P < 0.05) without affecting the feed conversion ratio (FCR), dressing percentage and back fat thickness. In conclusion, using forage to feed pig could be interesting in pig smallholder production with limited access to concentrate, as FCR was not significantly affected.

Innovative plant biomass fractionation methods produce new feed additives that could modulate pig intestinal microbial communities. Such novel indigestible carbohydrates (CHO) were investigated for their prebiotic potential and their influence on Salmonella Typhimurium in a co-inoculation in vitro fermentation model of pig intestines. Inulin, cellobiose, pectic oligosaccharides (POS), isomalto-oligosaccharides (IMO), xylooligosaccharides (XOS), and gluconic acid (GLU) were fermented for 72 h by a bacterial fecal inoculum from pigs in an in vitro model in the presence of Salmonella. Gluconic acid was the fastest fermenting CHO followed by inulin and IMO (P = 0.01). After 6 h, cellobiose yielded the highest lactate molar ratio (0.484). Pectic oligosaccharides fermented more slowly. Xylooligosaccharides and GLU were little fermented (150 and 175 mg short-chain fatty acids/g after 24 h). Nonetheless, GLU yielded the highest butyrate molar ratio of all CHO (0.290 at 12 h; P < 0.01). Although Salmonella counts did not differ, inulin and IMO displayed prebiotical properties, because they supported the highest Lactobacillus and Bifidobacterium populations after 12 and 24 h of fermentation (7.38 to 8.86 log cfu/mL; P < 0.01). Cellobiose and GLU scored well for Lactobacillus too but poorly supported Bifidobacterium (6.41 to 6.92 log cfu/mL; P < 0.01). It is concluded that IMO seems the most promising prebiotic, but owing to their specific fermentation patterns, cellobiose and GLU deserve further consideration.

The chemical characteristics of co-products recovered during a laboratory-scale wet milling procedure as well as that of whole corn flour were characterised and their digestibility and fermentability value determined using a 2 steps in vitro digestibility and fermentation model of the pig digestive tract. Five co-products differing in their chemical composition were collected and analysed. These co-products differed in their in vitro dry matter Digestibility and in their kinetic of fermentation. High coefficients of digestibility were observed for starchy samples, while low coefficients of digestibility were observed for samples rich in lignocellulosic components. Fermentation patterns of samples analysed were different as well as the profile of volatile fatty acids produced during the fermentation. The production of straight-chain fatty acids produced was significantly correlated with the proportion of starch in the sample, while branched-chain fatty acids were correlated to proteins concentration of samples.

Adding mucus to in vitro fermentation models of the large intestine shows that some genera, namely lactobacilli, are dependent on host-microbiota interactions and that they rely on mucosal layers to increase their activity. This study investigated whether this dependence on mucus is substrate dependent and to what extent other genera are impacted by the presence of mucus. Inulin and cellulose were fermented in vitro by a fecal inoculum from pig in the presence or not of mucin beads in order to compare fermentation patterns and bacterial communities. Mucins increased final gas production with inulin and shifted short-chain fatty acid molar ratios (P < 0.001). Quantitative real-time PCR analyses revealed that Lactobacillus spp. and Bifidobacterium spp. decreased with mucins, but Bacteroides spp. increased when inulin was fermented. A more in-depth community analysis indicated that the mucins increased Proteobacteria (0.55 vs 0.25%, P = 0.013), Verrucomicrobia (5.25 vs 0.03%, P = 0.032), Ruminococcaceae, Bacteroidaceae and Akkermansia spp. Proteobacteria (5.67 vs 0.55%, P < 0.001) and Lachnospiraceae (33 vs 10.4%) were promoted in the mucus compared with the broth, while Ruminococcaceae decreased. The introduction of mucins affected many microbial genera and fermentation patterns, but from PCA results, the impact of mucus was independent of the fermentation substrate.

The present study investigated the influence of bacterial metabolites on monocarboxylate transporter 1 (MCT1) expression in pigs using in vivo, ex vivo and in vitro approaches. Piglets (n 24) were fed high-protein (26 %) or low-protein (18 %) diets with or without fermentable carbohydrates. Colonic digesta samples were analysed for a broad range of bacterial metabolites. The expression of MCT1, TNF-α, interferon γ (IFN-γ) and IL-8 was determined in colonic tissue. The expression of MCT1 was lower and of TNF-α and IL-8 was higher with high-protein diets (P< 0·05). MCT1 expression was positively correlated with l-lactate, whereas negatively correlated with NH3 and putrescine (P< 0·05). The expression of IL-8 and TNF-α was negatively correlated with l-lactate and positively correlated with NH3 and putrescine, whereas the expression of IFN-γ was positively correlated with histamine and 4-ethylphenol (P< 0·05). Subsequently, porcine colonic tissue and Caco-2 cells were incubated with Na-butyrate, NH4Cl or TNF-α as selected bacterial metabolites or mediators of inflammation. Colonic MCT1 expression was higher after incubation with Na-butyrate (P< 0·05) and lower after incubation with NH4Cl or TNF-α (P< 0·05). Incubation of Caco-2 cells with increasing concentrations of these metabolites confirmed the up-regulation of MCT1 expression by Na-butyrate (linear, P< 0·05) and down-regulation by TNF-α and NH4Cl (linear, P< 0·05). The high-protein diet decreased the expression of MCT1 in the colon of pigs, which appears to be linked to NH3- and TNF-α-mediated signalling.

1 : Laboratoire de Génie Microbiologique et Applications, Campus Chaâberssas, Faculté des Sciences de la Nature et de la Vie, Université Constantine 1, Constantine, Algérie. 2 : Unité de Zootechnie, Faculté Gembloux Agro-Bio Tech, Université de Liège, Passage des Déportés 2-5030, Gembloux, Belgique. 3 : Laboratoire des Molécules Végétales et Amélioration des Plantes, Faculté des Sciences Exactes et des Sciences de la Nature et de la Vie, Université Larbi Ben Mhidi, Oum El Bouaghi, Algérie.

To assess modifications induced in starch granules during high temperature drying of corn grain and their effect on the nutritive value of corn-starch, physicochemical and structural characteristics of starch granules from corn grains dried at different temperatures have been determined. Additionally, their in vitro digestibility and fermentation patterns were investigated, using a two steps in vitro model of the pig digestive tract. High drying temperatures induced a partial gelatinization of starch granules and produced a very favorable substrate for porcine pancreatic amylase and led to an altered physical structure which affected the rate and extent of starch granules digestion by gastric and pancreatic enzymes. Starch micrographs showed that granules extracted from corn dried at 130 degrees C were less angular, bigger, and had smoother surface than granules extracted from corn dried at lower temperature. High-temperature drying increased the digestibility of wet-milled starch granules, while the residues of starch from corn dried at lower temperature produced higher volume of gas during their in vitro fermentation, despite their more pronounced crystalline characteristic. The residues from pepsin-pancreatic digestion of overall samples analyzed showed highly degraded and pitted granules or fragmented external shells, starch from corn dried at 130 degrees C being the most degraded. Aforementioned changes of nutritional attributes of starch granules are discussed according to the restructuration occurring within both their amorphous and crystalline phase, as well as to the changes of the granules size and purity.

Globally, pressure on concentrate feed resources is increasing, especially in the tropics where many countries are net importers of food. Forage plants are a possible alternative, but their use as feed ingredients for pigs raises several issues related to their higher fibre and plant secondary metabolites contents as well as their lower nutritive value. In this paper, the nutritive value of several forage species and the parameters that influence this nutritive value in relationship to the plant family, the physiological stage, the plant part and the preservation method (fresh, hay and silage) are reviewed. The influence of the breed and the physiological status of the animal on animal voluntary intake of fibre-rich ingredients, digestibility as related to gastrointestinal volume and transit time and growth performances are also discussed. The final section highlights the advantages and drawbacks of forage plants in pig diets and stresses the need for proper economic evaluation to conclude on the benefits of the use of forage plants in pig feed.

Manuscript History: This study aimed to determine the nutritive value of seaweed Ulva lactuca collected from the Algerian coast by estimation of its chemical composition and fermentation characteristics, comparatively to vetch-oat hay (control), using in vitro gas production technique. Seaweed and control were incubated with rumen liquor taken from fistulated and non lactating cows. Gas production was recorded at: 2, 4, 6, 8, 12, 24, 48 and 72h. The in vitro rumen fermentation parameters were measured after 24h and 72h of fermentation. Proteins degradability was investigated by the enzymatic technique using a protease extracted from Streptomyces griseus. The results showed a wide variation between the chemical components of seaweed and conventional fodder used as control. The main constituents in Ulva lactuca were ashes (39.1% DM), fibers (22.8 % DM) and proteins (15.3% DM). The gas production profile of seaweed during 72h of incubation showed a slow and low gas production. Cumulative gas production obtained after 24h for seaweed (42 ml/g OM) was significantly lower than control (128.4 ml/g OM) (P<0.001). pH, ammonia, volatile fatty acids (VFAs), apparent digestibility of dry matter (DDM), organic matter digestibility (OMD) and metabolizable energy (ME) were significantly different between seaweed and vetch-oat hay (6.86, 290.1 mg/ml, 1.25 mmol/g DM, 38.3%, 29.2%, 3.81MJ/Kg DM respectively for seaweed). Protein degradability measurement indicates the weak hydrolysis of seaweed crude protein which is beneficial for ruminants. This study showed that the use of Ulva lactuca as non conventional feed in ruminant nutrition can be considered under certain conditions.

The effects of four tropical forage legume hays (Vigna unguiculata, Psophocarpus scandens, Pueraria phaseoloides and Stylosanthes guianensis) on voluntary feed intake (VFI) and their nutritive value were studied in growing pigs using a corn-soybean meal-based diet containing varying proportions of forage legume hays (0, 10, 20 and 40 % or 0, 12.5 and 25 % for VFI and nutritive value determination, respectively). There was no difference in VFI between species (P > 0.20), but a linear response to forage inclusion level (P < 0.05) was observed decreasing from 126 for 0 % to approximately 84 g/kg of body weight for the 40 % forage diets, except for V. unguiculata, where the response was quadratic (P = 0.01). All four forage species linearly decreased the total tract apparent digestibility (TTAD) from 0.76 to 0.61, 0.80 to 0.68, 0.54 to 0.40 and 0.58 to 0.31 except for S. guianensis (0.44) for DM, N, NDF and N retention, respectively. Differences in digestibility (P < 0.05) between species were also observed. Due to their negative influence on the overall digestibility, the contribution of hays should not exceed 12.5 %, except for S. guianensis, in which N retention remained quite high (0.44) at the highest inclusion level (25 %). P. phaseoloides hay should be avoided in pigs as it combines the lowest VFI with the lowest nutrient digestibility.

Although fermentable carbohydrates (CHO) can reduce metabolites derived from dietary protein fermentation in the intestine of pigs, the interaction between site of fermentation and substrate availability along the gut is still unclear. The current study aimed at determining the impact of two different sources of carbohydrates in diets with low or very high protein content on microbial metabolite profiles along the gastrointestinal tract of piglets. Thirty-six piglets (n = 6 per group) were fed diets high (26%, HP) or low (18%, LP) in dietary protein and with or without two different sources of carbohydrates (12% sugar beet pulp, SBP, or 8% lignocellulose, LNC) in a 2 × 3 factorial design. After 3 weeks, contents from stomach, jejunum, ileum, caecum, proximal and distal colon were taken and analysed for major bacterial metabolites (D-lactate, L-lactate, short chain fatty acids, ammonia, amines, phenols and indols). Results indicate considerable fermentation of CHO and protein already in the stomach. HP diets increased the formation of ammonia, amines, phenolic and indolic compounds throughout the different parts of the intestine with most pronounced effects in the distal colon. Dietary SBP inclusion in LP diets favoured the formation of cadaverine in the proximal parts of the intestine. SBP mainly increased CHO-derived metabolites such as SCFA and lactate and decreased protein-derived metabolites in the large intestine. Based on metabolite profiles, LNC was partly fermented in the distal large intestine and reduced mainly phenols, indols and cadaverine, but not ammonia. Multivariate analysis confirmed more diet-specific metabolite patterns in the stomach, whereas the CHO addition was the main determinant in the caecum and proximal colon. The protein level mainly influenced the metabolite patterns in the distal colon. The results confirm the importance of CHO source to influence the formation of metabolites derived from protein fermentation along the intestinal tract of the pig.

In the DemocraticRepublic of the Congo(DRC), pigs are raised almost exclusivelyby smallholderseither in periurban areas of major cities such as Kinshasa or in rural villages. Unfortunately, little information is available regarding pig production in the Western part of the DRC, wherefore a survey was carried out to characterize and compare 319 pig productionsystems in their managementand feedingstrategies, along a periurban- rural gradientin Western provinces of the DRC. Pig breeding was the main source of income (43%) and half of respondents were active in mixed pig and crop production, mainly vegetable garden. Depending on the location, smallholders owned on average 18 pigs, including four sows. Piglet mortality rate varied from 9.5 to 21.8% while average weaned age ranged between 2.2 and 2.8 months. The major causes of mortality reported by the farmers were African swine fever 98%, swine erysipelas (60%), erysipelas trypanosomiasis (31%), swine worm infection (17%), and diarrhoea (12%). The majority of the pigs were reared in pens without free roaming and fed essentially with locally available by-products and forage plants whose nature varied according with the location of the farm. The pig production systems depended on the local environment; particularly in terms of workforces, herd structure and characteristics, production parameters, pig building materials, selling price and in feed resources. It can be concluded that an improvement of Congolese pig production systems should consider (1) a reduction of inbreeding, (2) an improvement in biosafety to reduce the incidence of African swine fever and the spread of other diseases, and (3) an improvement in feeding practices.

The nutritive value of 20 forage plants commonly used for feeding pigs in the Democratic Republic of the Congo was studied to determine chemical composition, protein amino acid profiles, mineral content, and in vitro digestibility using a two-step method combining an enzymatic pepsin and pancreatin hydrolysis followed by a 72h gas-test fermentation. The highest protein contents (270–320g/kg DM) were obtained for Vigna unguiculata, Psophocarpus scandens, Leucaena leucocephala, Manihot esculenta, and Moringa oleifera. Grasses, Acacia mangium, and Eichhornia crassipes, showed the lowest crude protein (CP) and highest NDF contents. Cajanus cajan and Trypsacum andersonii had the most balanced amino acid profile, being deficient in lysine and slightly deficient in histidine, while Megathyrsus maximus displayed the highest number of essential amino acids deficiencies. High mineral contents were obtained from, in ascending order, with M. oleifera, V. unguiculata, E. crassipes, Ipomea batatas and Amaranthus hybridus. In vitro dry matter digestibility ranged from 0.25 to 0.52, in vitro CP digestibility from 0.23 to 0.80, in vitro energy digestibility from 0.23 to 0.52. M. esculenta, M. oleifera, I. batatas, Mucuna pruriens, V. unguiculata, P. scandens and A. hybridus showed high digestibilities for all nutrients. Gas production during fermentation of the pepsin and pancreatin-indigestible fraction of the plants varied from 42ml/g DM for A. mangium to 202ml/g DM for I. batatas (P<0.001). Short-chain fatty acid production during fermentation varied from 157 to 405mg/g of the pepsin and pancreatin indigestible fraction. It is concluded that some of these species are interesting sources of proteins and minerals with a good digestibility that might be used more economically than concentrate, especially in smallholder production systems, to improve pig feeding, mineral intake and intestinal health in pigs reared in the tropics.

Management of livestock grazing in highly-productive mountain meadows is an important aspect for the economic viability and the environmental impact of a grassland-based farm. The main aim of this study was to build near infrared models to determine the chemical composition and in vitro organic matter digestibility of Romanian meadow forages. The treatments were organic and mineral fertilizer combinations, and forage samples were obtained from three fertilization experiments conducted in the Apuseni Mountains; these samples were analysed using classical and NIR methods. The samples were scanned in the NIR wavelength band. The CRA-W Gembloux ‘local’ calibration models were validated with Romanian meadow forages and then used in order to predict the forage quality of samples. A second objective of the study was to determine the effects of fertilization on forage quality. The results showed a decrease in crude protein content from the NPK treatment (150:75:75), which can be explained by a reduction of Fabaceae plants with this treatment from 17.25% of the populations in the control (semi-natural meadow not fertilized) to 6.25% in the fertilized plots. The decrease in protein content and in vitro organic matter digestibility was related to a reduced Fabaceae presence. Our recommendation is to use mineral fertilization with NPK doses less than 100:50:50 to improve meadow productivity; meanwhile organic fertilization can also be used to complement and maintain biodiversity and forage quality.

In this review, various applications of near-infrared hyperspectral imaging (NIR-HSI) in agriculture and in the quality control of agro-food products are presented. NIR-HSI is an emerging technique that combines classical NIR spectroscopy and imaging techniques in order to simultaneously obtain spectral and spatial information from a field or a sample. The technique is nondestructive, nonpolluting, fast, and relatively inexpensive per analysis. Currently, its applications in agriculture include vegetation mapping, crop disease, stress and yield detection, component identification in plants, and detection of impurities. There is growing interest in HSI for safety and quality assessments of agro-food products. The applications have been classified from the level of satellite images to the macroscopic or molecular level.