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PubMed1987

[Effect of the addition of a fiber-rich concentrate to a hay-based diet, offered at two levels of feeding in the adult rabbit. 2. Measurements of digestibility].

The effect of adding a fibre-rich concentrate (wheat bran or beet pulp) to a hay-based diet (cook's foot-lucerne: 50/50) on the apparent digestibility of diets was measured in three groups of 8 adult doe rabbits (New-Zealand White X Californian). Diet composition was as follows: 90% hay only (diet F), hay + bran (diet FS) or hay + pulp (diet FP). Two levels of feeding were tested: ad libitum and 2/3 of ad libitum intake. Addition of wheat bran and especially of beet pulp led to a significant increase in the apparent digestibility of the whole diet. Our results confirm the high digestibility of cell-wall constituents of beet pulp: the apparent digestibility coefficient of hemicellulose in diet FP reached 60% (versus 23% for diet F) and that of cellulose 45% (21% for diet F). Wheat bran supplied digestible hemicellulose (ADC = 48% for diet FS) while the apparent digestibility of bran cellulose was not higher than that of hay (ADC = 22%). This digestive interaction between raw material was accompanied by an interaction with the digestive transit. The less digestible diet (diet F) exhibited the shortest mean residence time (MRT). However, diet FS exhibited the longest residence time whereas it was less digestible than diet FP. These results suggest that, in the rabbit, wheat bran is a transit-regulator as already observed in other species. Measuring apparent digestibility between the 10th and the 16th day of the feed restriction was too early for our doe rabbits. Values measured were not significantly different from those obtained during ad libitum feeding, although the MRT of diets was longer during restricted feeding.

Animals↗
PubMed2003

Pressurized wet digestion in open vessels.

The High Pressure Asher (HPA-S) was adapted with a Teflon liner for pressurized wet digestion in open vessels. The autoclave was partly filled with water containing 5% (vol/vol) hydrogen peroxide. The digestion vessels dipped partly into the water or were arranged on top of the water by means of a special rack made of titanium or PTFE-coated stainless steel. The HPA-S was closed and pressurized with nitrogen up to 100 bars. The maximum digestion temperature was 250 degrees C for PFA vessels and 270 degrees C for quartz vessels. Digestion vessels made of quartz or PFA-Teflon with volumes between 1.5 mL (auto sampler cups) and 50 mL were tested. The maximum sample amount for quartz vessels was 0.5-1.5 g and for PFA vessels 0.2-0.5 g, depending on the material. Higher sample intake may lead to fast reactions with losses of digestion solution. The samples were digested with 5 mL HNO(3) or with 2 mL HNO(3)+6 mL H(2)O+2 mL H(2)O(2). The total digestion time was 90-120 min and 30 min for cooling down to room temperature. Auto sampler cups made of PFA were used as digestion vessels for GFAAS. Sample material (50 mg) was digested with 0.2 mL HNO(3)+0.5 mL H(2)O+0.2 mL H(2)O(2). The analytical data of nine certified reference materials are also within the confidential intervals for volatile elements like mercury, selenium and arsenic. No cross contamination between the digestion vessels could be observed. Due to the high gas pressure, the diffusion rate of volatile species is low and losses of elements by volatilisation could be observed only with diluted nitric acid and vessels with large cross section. In addition, cocoa, walnuts, nicotinic acid, pumpkin seeds, lubrication oil, straw, polyethylene and coal were digested and the TOC values measured. The residual carbon content came to 0.2-10% depending on the sample matrix and amount.

Journal Article↗
PubMed2006

Bioaugmenting anaerobic digestion of biosolids with selected strains of Bacillus, Pseudomonas, and Actinomycetes species for increased methanogenesis and odor control.

The objective of this study was to evaluate the effects of bioaugmenting anaerobic biosolids digestion with a commercial product containing selected strains of bacteria from genera Bacillus, Pseudomonas, and Actinomycetes, along with ancillary organic compounds containing various micronutrients. Specifically, the effects of the bioaugment in terms of volatile solids destruction and generation and fate of odor-causing compounds during anaerobic digestion and during storage of the digested biosolids were studied. Two bench-scale anaerobic digesters receiving primary and secondary clarifier biosolids from various full-scale biological wastewater treatment plants were operated. One of the digesters received the bioaugment developed by Organica Biotech, while the other was operated as control. The bioaugmented digester generated 29% more net CH(4) during the 8 weeks of operation. In addition, the average residual propionic acid concentration in the bioaugmented digester was 54% of that in the control. The monitoring of two organic sulfide compounds, methyl mercaptan (CH(3)SH) and dimethyl sulfide (CH(3)SCH(3)), clearly demonstrated the beneficial effects of the bioaugmentation in terms of odor control. The biosolids digested in the bioaugmented digester generated a negligible amount of CH(3)SH during 10 days of post-digestion storage, while CH(3)SH concentration in the control reached nearly 300 ppm(v) during the same period. Similarly, peak CH(3)SCH(3) generated by stored biosolids from the bioaugmented digester was only 37% of that from the control.

Actinobacteria↗
PubMed2006

Evaluation of four digestive methods for extracting diatoms.

OBJECTIVE: To compare the merit of four digestive methods (nitric acid plus hydrogen peroxide, proteinase K, nitric acid in Disorganization Can and Soluene-350) for extracting diatoms in order to choose the best digestive method for the diagnosis of drowning. METHODS: Liver, kidney and bone marrow of rabbits were minced and then digested by four digestive methods separately with the following indices compared: (1) time demanded for complete digestion; (2) degree of digestion for different tissues; (3) the reclaiming ratio of diatoms; (4) the degree of digestive destruction to diatoms. RESULTS: For sufficiently digesting the same tissue, the demanded times for the different methods ranked from the longest to the shortest were as follows: Soluene-350, proteinase K, nitric acid plus hydrogen peroxide, nitric acid in Disorganization Can. Nitric acid in Disorganization Can method and nitric acid plus hydrogen peroxide method digested the tissues more thoroughly than proteinase K, than Soluene-350 methods. For Cyclotella and Cybella, proteinase K method reclaimed most diatoms and nitric acid plus hydrogen peroxide method reclaimed less, while nitric acid in Disorganization Can and Soluene-350 methods reclaimed the least. For Navicula, the majority of diatoms could be extracted using proteinase K method, but only a few diatoms with other three methods. Under scanning electron microscopy (SEM), the structure of diatoms remained almost perfect after digestion with proteinase K, but destroyed to some extent with other three methods. CONCLUSION: This study demonstrated that different diatoms (in fresh or sea water) have different resistance to different digestive reagents. As far as the reliability and applicability of the diatom test is concerned, proteinase K method is of the best choice, nitric acid plus hydrogen peroxide can be its substitute. Soluene-350 cannot be used for extracting sea water diatoms.

Animals↗
PubMedDate not supplied

Kinetics of whole serum and prepurified IgG digestion by pepsin for F(ab')2 manufacture.

An alternative route for the production of polyclonal F(ab')(2) fragments that might be adopted for the facile preparation of antivenoms is assessed in this work. The method involves the digestion of whole serum by free pepsin, which results in reduction of the number of processing steps commonly in use, because it avoids the initial purification of IgG's prior to their proteolytic cleavage by the enzyme. Digestion kinetics of whole serum and caprylic acid prepurified IgG using free pepsin were monitored with SDS-PAGE followed by densitometric analysis and antigen binding activity assay of the digested samples. It was observed that with equal units of pepsin activity, caprylic acid prepurified IgG was digested more rapidly than whole serum but that the overall retention of antigen binding activity was significantly greater in the latter case. The estimated first-order digestion rate parameters were 11.8 and 4.42 microM min(-)(1) for pure IgG and whole serum, respectively. The K(m) value obtained for whole serum digestion was 33 microM and that for pure IgG digestion was 43.5 microM. Calibration with undigested whole serum and pure IgG samples of known concentrations was performed using SDS-PAGE followed by image analysis. A linear relationship was observed between the protein concentration and the respective band intensity within the range of concentrations investigated (0.63-31.2 microM IgG concentration). This technique proved to be relatively rapid, reproducible, and more precise than size-exclusion chromatography as a result of its F(ab')(2)/IgG resolving power. Staining and destaining protocols were reproduced in terms of staining and destaining times, volumes added, and compositions. Furthermore, all digestion experiments were performed in duplicate sets to monitor the extent of variation of the digestion kinetic parameters measured by this method. The results obtained from this technique confirm and quantify previous observations that pepsin digestion of whole serum is slower and easier to control than digestion of pure IgG and results in higher recovery of antigenic binding activity.

Animals↗
PubMed1991

Metalloproteinase digestion of cartilage proteoglycan. Pattern of cleavage by stromelysin and susceptibility to collagenase.

The action of purified rabbit bone stromelysin was investigated on proteoglycan aggregates from pig laryngeal cartilage. The enzyme caused a rapid fall in viscosity of proteoglycan aggregate solution (6 mg/ml), and the products of a partial digest (60% loss of relative viscosity) and a complete digest (95% loss of relative viscosity) were characterized. Analysis by gel chromatography on Sepharose 2B under associative conditions showed that 95% of the glycosaminoglycans in the complete digest were in small-sized fragments, whereas most of the hyaluronan-binding G1 domain and link protein remained intact and bound to hyaluronan. In contrast, there was extensive digestion of the G2 domain which resulted in 76% loss in its detection by immunoassay. Analysis of the partial digest also showed considerable loss (40%) of detection of the G2 domain, but the glycosaminoglycan-rich fragments were much larger than in the complete digest. There was also much less cleavage to create small fragments containing the G1 domain. This was evident on SDS/PAGE analysis where a 58 kDa G1 domain fragment was abundant in the complete digest, but was only present in small amounts in the partial digest. There was also only very limited conversion of link protein from a 44 kDa form to a 40 kDa form. The digestion of proteoglycan aggregate (6 mg/ml) by stromelysin was unaffected by the addition of a high concentration of extra chondroitin sulphate chains (14 mg/ml), and the digestion of proteoglycan monomer showed that the G1 domain was resistant to stromelysin digestion even when not bound to hyaluronan and link protein. The results show that stromelysin degrades the proteoglycan protein core with major cleavages close to, but not within, the G1 domain, and extensive cleavage in other regions. Experiments with purified collagenase, a metalloproteinase structurally related to stromelysin, showed that it too cleaved proteoglycan at several sites within the glycosaminoglycan-rich region of the core protein. Metalloproteinase attack on proteoglycan thus not only occurs with stromelysin but also with collagenase.

Animals↗
PubMed1989

Histochemical analysis of the chemical structure of blood group-related carbohydrate chains in serous cells of human submandibular glands using lectin staining and glycosidase digestion.

Using lectin staining methods in combination with exo- and endo-glycosidase digestion procedures, we analyzed the chemical structure of different types of blood group-related substances in serous cells of formalin-fixed, paraffin-embedded human submandibular glands. Serous cells produced only H antigen; A and B antigens were not present, and the expression of H antigen is dependent on the secretor status of the tissue donor. Although reactivity with Ulex europaeus agglutinin I (UEA-I) was not markedly reduced by alpha-L-fucosidase digestion, an affinity for peanut agglutinin (PNA) was seen after fucosidase digestion in the cells from secretors. In those from nonsecretors, no PNA reactivity appeared after enzyme digestion. On the other hand, sialidase digestion elicited PNA reactivity in serous cells irrespective of the donor's secretor status. PNA reactivity observed after fucosidase or sialidase digestion was susceptible to endo-alpha-N-acetylgalactosaminidase (endo-GalNAc-dase) digestion. SBA reactivity in UEA-I-negative cells from secretors, or in cells from fetuses and newborn infants, was markedly reduced by beta-galactosidase digestion. After galactosidase digestion, reactivity with Griffonia simplicifolia agglutinin II (GSA-II) appeared in the corresponding cells. This GSA-II reactivity was almost completely eliminated by subsequent beta-N-acetylhexosaminidase digestion. Whereas PNA reactivity in these cells was not reduced by beta-galactosidase treatment, it was significantly diminished by endo-GalNAc-dase digestion. These results suggest that at least two kinds of precursor disaccharides are produced in submandibular serous cells, i.e., SBA-reactive D-galactose-(beta 1-3,4)-N-acetyl-D-glucosamine and PNA-reactive D-galactose-(beta 1-3)-N-acetyl-D-galactosamine alpha 1-serine or threonine (O-glycosidically linked Type 3 chain or T antigen). Final fucosylation and synthesis of these two types of precursor chain appear to be under the control of the secretor gene.

ABO Blood-Group System↗
PubMed1998

Processing of defensive pigment in Aplysia californica: acquisition, modification and mobilization of the red algal pigment, r-phycoerythrin by the digestive gland.

The marine snail Aplysia californica obtains its purple defensive ink exclusively from the accessory photosynthetic pigment r-phycoerythrin, which is found in the red seaweeds of its diet. The rhodoplast digestive cell, one of three types of cell lining the tubules of the digestive gland, appears to be the site of catabolism of red algal chloroplasts (rhodoplasts) since thylakoid membranes, including phycobilisome-sized membrane-associated particles, were found within the large digestive vacuoles of this cell. Immunogold localization showed that there was a statistically significant occurrence of the red algal phycobilisome pigment r-phycoerythrin within these rhodoplast digestive vacuoles, but not in other compartments of this cell type (endoplasmic reticulum, mitochondria, nucleus) or in other tissues (abdominal ganglion). Immunogold analysis also suggested that the rhodoplast vacuole is the site for additional modification of r-phycoerythrin, which makes it non-antigenic: the chromophore is either cleaved from its biliprotein or the biliprotein is otherwise modified. The hemolymph had spectrographic absorption maxima typical of the protein-free chromophore (phycoerythrobilin) and/or r-phycoerythrin, but only when the animal had been feeding on red algae. Rhodoplast digestive cells and their vacuoles were not induced by the type of food in the diet: snails fed green seaweed and animals fed lettuce had characteristic rhodoplast cells but without the large membranous inclusions (rhodoplasts) or phycobilisome-like granules found in animals fed red seaweed. Two additional cell types lining the tubules of the digestive gland were characterized ultrastructurally: (1) a club-shaped digestive cell filled with electron-dense material, and (2) a triangular 'secretory' cell devoid of storage material and calcium carbonate. The following model is consistent with our observations: red algal rhodoplasts are freed from algal cells in the foregut and then engulfed by rhodoplast digestive cells in the tubules of the digestive diverticula, where they are digested in membrane-bound vacuoles; r-phycoerythrin is released from phycobilisomes on the rhodoplast thylakoids and chemically modified before leaving the digestive vacuole and accumulating in the hemolymph; the pigment then circulates throughout the body and is concentrated in specialized cells and vesicles of the ink gland, where it is stored until secreted in response to certain predators.

Journal Article↗
PubMed2006

The digestibility of waste activated sludges.

Laboratory digestion studies using waste activated sludges (WAS) were conducted to compare the digestion performance between anaerobic and aerobic processes. Nine samples of WAS from seven wastewater treatment plants were collected and batch-digested under both anaerobic and aerobic conditions for 30 days at 25 degrees C. The cation content of wastewater (both floc and solution phases) and solution biopolymer (protein and polysaccharide) was measured before and after digestion and compared with volatile solids destruction data. The study revealed that each digestion process was associated with a distinct biopolymer fraction, which accounted for differences in volatile solids reduction under anaerobic and aerobic conditions. The anaerobic digestion data showed strong correlations between soluble protein generation, ammonium production, percent volatile solids reduction, and floc iron (Fe). These data suggest that the amount of volatile solids destroyed by anaerobic digestion depends on the Fe content of floc. In aerobic digestion, polysaccharide accumulated in solution along with calcium and magnesium. For aerobic digestion, correlations between divalent cation release and the production of inorganic nitrogen were found. This implies that divalent cation-bound biopolymer, thought to be lectin-like protein, was the primary organic fraction degraded under aerobic conditions. The results of the study show that the cation content in wastewater is an important indicator of the material that will digest under anaerobic or aerobic conditions and that some of the volatile solids will digest only under either anaerobic or aerobic conditions.

Aerobiosis↗
PubMed2006

Increased puroindoline levels slow ruminal digestion of wheat (Triticum aestivum L.) starch by cattle.

Starch is the primary nutrient in ruminant diets used to promote high levels of performance. The site of starch digestion alters the nature of digestive end products (VFA in the rumen vs. glucose in the small intestine) and the efficiency of use. Cereal grain endosperm texture plays a major role in the rate and extent of starch degradation in ruminants. Wheat grain texture is regulated by the starch surface protein complex friabilin that consists primarily of puroindoline (PIN) A and B. Soft kernel texture in wheat is a result of both PIN genes being in the wild type active form and bound to starch. The objective of this study was to investigate the effect of varying PIN content in wheat on the rate of starch digestion in the rumen of beef cattle. In Exp. 1, 6 transgenic soft pin a/b isolines created in a hard wheat background, and 2 hard wheat controls were milled to yield a wide range of mean particle sizes across all lines. Milled samples were incubated in situ for 3 h. Increased expression of both PINA and PINB decreased DM digestibility (DMD) by 29.2% (P < 0.05) and decreased starch digestibility by 30.8% (P < 0.05). Experiment 2 separated the effects of particle size and total PIN content on digestion by milling the hardest and softest lines such that the mean particle size was nearly identical. Increased PIN decreased DMD by 21.7% (P < 0.05) and starch digestibility by 19.9% (P < 0.05) across particle sizes smaller than whole kernel. Experiment 3 addressed the time course of PIN effects in the rumen by observing ground samples of the hardest and softest lines over a 12-h in situ period. Increased PIN decreased DMD by 10.4% (P < 0.05) and starch digestibility by 11.0% (P < 0.05) across all time points. Dry matter and starch digestibility results demonstrated that increased expression of PIN was associated with a decreased rate of ruminal digestion independent of particle size. Puroindolines seem to aid in the protection of starch molecules from microbial digestion in the rumen, potentially increasing the amount of starch entering the small intestine.

Animals↗
PubMed2004

Two-stage anaerobic digestion process for complete inactivation of enteric bacterial pathogens in human night soil.

Anaerobic digestion offers a good alternative for human waste treatment. However, the fate of enteric bacterial pathogens present in human night soil (HNS) remains a major concern for hygienic safety of the process. A two-stage anaerobic digestion process, consisting of separate acidogenic and methanogenic digesters, was designed and its efficacy in the inactivation of Salmonella typhi was compared to a single-stage digestion process. In a single-stage digestion, complete pathogen inactivation was achieved only in the digesters with high levels of volatile fatty acids (VFA approximately equal to 18,000 mg/l) and acidic pH (approximately equal to 6.0). These digesters, however, showed drastic reduction in methane yield. In the two-stage digestion process, S. typhi was completely inactivated in the acidogenic digester and the methanogenic digester was free from the pathogen even after receiving a daily dose of the pathogen. The process also achieved complete inactivation of other enteric pathogens, viz., Shigella dysenteriae and Vibrio cholerae. The two-stage process was efficient in biogas generation from HNS. Thus, the two-stage process ensures complete hygienic safety in anaerobic digestion of human night soil.

Bacteria, Anaerobic↗
PubMed1995

[Agreement between animal and vegetable protein digestibility measured in vivo and in vitro and its effect on the chemical score].

Protein digestibility is a key factor in the determination of protein quality using the chemical score. Since there are several methods available for determining protein digestibility the purpose of this study was to compare three methods in vitro (pH drop, pH stat and pepsin digestibility) and two methods in vivo (true and apparent digestibility in rats) in the determination of the protein digestibility of: casein, soy protein isolate, fish meal, black beans, corn meal and wheat flour. The results showed that in the case of highly digestible proteins all methods agreed very well. However, this agreement was much less apparent in the case of protein with digestibilities below 85%. As a result, the chemical score of these proteins varied substantially depending upon the method used to determine its digestibility. Thus, when the chemical score of the proteins analyzed was corrected by the true protein digestibility measured in rats, they ranked as: casein 83.56, soy 76.11, corn-beans mixtures (1:1) 58.14, fish meal 55.25, black beans 47.93, corn meal 46.06 and wheat flour 32.77. In contrast, when the chemical score of these proteins was corrected by the pepsin digestibility method, the lowest quality was assigned to fish meal. In summary, this results pointed out that for non conventional proteins of for known proteins which have been subjected to processing, protein digestibility should be measured in vivo.

Amino Acids↗
PubMed2006

Gastrointestinal digestion of food allergens: effect on their allergenicity.

This paper reviews the in vitro digestion models developed to assess the stability digestion of food allergens, as well as the factors derived from the methodology and food structure that may affect the assay results. The adequacy of using the digestion stability of food allergens as a criterion for assessing potential allergenicity is also discussed. Data based on the traditional pepsin digestibility test in simulated gastric fluid are discussed in detail, with special attention to the influence of the pH and pepsin: allergen ratio in the pepsinolysis rate. This review points out the importance of using physiologically relevant in vitro digestion systems for evaluating digestibility of allergens. This would imply the sequential use of digestive enzymes in physiological concentrations, simulation of the stomach/small intestine environment (multi-phase models) with addition of surfactants such as phospholipids or bile salts, as well as the consideration of the gastrointestinal transit and the effect of the food matrices on the allergen digestion and subsequent absorption through the intestinal mucosa. In vitro gastrointestinal digestion protocols should be preferably combined with immunological assays in order to elucidate the role of large digestion-resistant fragments and the influence of the food matrix on the stimulation of the immune system.

Allergens↗
PubMed2006

Genetic variations of cell wall digestibility related traits in floral stems of Arabidopsis thaliana accessions as a basis for the improvement of the feeding value in maize and forage plants.

Floral stems of Arabidopsis thaliana accessions were used as a model system relative to forage plant stems in genetic variation studies of lignin content and cell wall digestibility related traits. Successive investigations were developed in a core collection of 24 Arabidopsis accessions and in a larger collection of 280 accessions. Significant genetic variation for lignin content in the cell wall, and for the two in vitro cell wall digestibility investigated traits, were found both in the core collection and in the large collection. Genotype x environment interactions, investigated in the core collection, were significant with a few genotypes contributing greatly to interactions, based on ecovalence value estimates. In the core collection, genotypes 42AV, 224AV, and 8AV had low cell wall digestibility values, whatever be the environmental conditions. Genotype 157AV, observed only in one environment, also appeared to have a low cell wall digestibility. Conversely, genotypes 236AV, 162AV, 70AV, 101AV, 83AV had high cell wall digestibility values, genotype 83AV having a slightly greater instability across differing environments than others. The well-known accession Col-0 (186AV) appeared with a medium level of cell wall digestibility and a weak to medium level of interaction between environments. The ranges of variation in cell wall digestibility traits were higher in the large collection than in the core collection of 24 accessions, these results needing confirmation due to the lower number of replicates. Accessions 295AV, 148AV, and 309AV could be models for low stem cell wall digestibility values, with variable lignin content. Similarly, accessions 83AV and 162AV, already identified from the study of the core collection, and five accessions (6AV, 20AV, 91AV, 114AV, and 223AV) could be models for high stem cell wall digestibility values. The large variations observed between Arabidopsis accessions for both lignin content and cell wall digestibility in floral stems have strengthened the use this species as a powerful tool for discovering genes involved in cell wall biosynthesis and lignification of dicotyledons forage plants. Investigations of this kind might also be applicable to monocotyledons forage plants due to the basic similarity of the genes involved in the lignin pathway of Angiosperms and the partial homology of the cell wall composition and organization of the mature vascular system in grasses and Arabidopsis.

Animal Feed↗
PubMed2004

Peanut protein allergens: gastric digestion is carried out exclusively by pepsin.

BACKGROUND: A major characteristic of many food allergens, including Ara h 1, a major peanut allergen, is their resistance to gastric digestion. One estimate of the allergenic potential of a possible protein allergen is its stability under simulated gastric conditions. OBJECTIVE: Because the rate and extent of digestion of allergenic proteins will affect the severity of any subsequent allergic response, it is important to correlate protein allergen digestion in simulated gastric fluid with that in actual gastric fluid. METHODS: A major peanut allergen, Ara h 1, was digested in vitro by using both pepsin and porcine gastric fluid. Several comparisons between the 2 sets of proteolytic conditions were assessed including pH optima and the effect of temperature, denaturants, and specific enzyme inhibitors. RESULTS: In vitro digestion of Ara h 1 with pepsin and porcine gastric fluid resulted in virtually identical hydrolysis patterns as observed on SDS-PAGE. The protease activity of both pepsin and gastric fluid were inhibited at high pH and in the presence of pepstatin. However, both remained active in 4 mol/L urea and at 60 degrees C. CONCLUSIONS: Protein digestion in the porcine stomach is carried out by pepsin. In vivo gastric digestion is modeled accurately by peptic hydrolysis. Digestion conditions in vivo are comparable to experimental conditions in vitro provided that the acidic nature of the stomach contents is optimal for characterization of the allergen under standard pepsin digestion conditions. Additional experimentation using crude food extracts, both in the presence and absence of a complete meal, is needed to elucidate the complete physiologic nature of food allergen digestion.

Allergens↗
PubMed1997

Quantitative review of ruminal and total tract digestion of mixed diet organic matter and carbohydrates.

The mean response and main factors of variation (level of concentrate, nature of carbohydrate in the concentrate and level of intake) for organic matter, cell wall material, starch digestion and microbial synthesis in the gastrointestinal tract of ruminants were quantitatively reviewed using a data base involving 157 papers. The ruminal digestion (mean +/- SE%) of organic matter, cell wall material, and starch were 45.2 +/- 11.2 (n = 553), 47.7 +/- 17.7 (n = 348), and 74.1 +/- 16.2 (n = 140), respectively and the proportion of each component digested in the rumen in relation to total tract digestibility was 64.7 +/- 12.3, 78.8 +/- 18.5 and 80.5 +/- 16.3, respectively. The efficiency of microbial synthesis (g of microbial protein/kg of organic matter truly fermented in the rumen) and the proportion of microbial nitrogen in the total amount of nitrogen leaving the stomachs (%) were, 23.6 +/- 9.3 (n = 320) and 55.1 +/- 16.5 (n = 289), respectively. The ruminal digestion of organic matter increased by 2 points for every 10 percent increase in concentrate incorporation. The ruminal digestion of cell wall material was maximal when the concentrate incorporation in the diet was 30%. When the ruminal digestion of cell wall decreased, the substitution of ruminal digestion by intestinal digestion was partial (10%). The efficiency of microbial synthesis was optimal when the level of concentrate incorporation was 40%. The nature of the carbohydrates in the concentrates had a significant effect on the efficiency of the microbial synthesis, which was higher (+6.6 g of nitrogen/kg of fermentable organic matter in the rumen) with slowly degradable starch (SS) or digestible fiber (DF) than with rapidly degradable starch (RS). Moreover, the mean depression of cellulolysis in the rumen was higher with RS (-13 points) comparatively to SS (-7 points) or DF (-5 points).

Animal Feed↗
PubMedDate not supplied

The effect of Saccharomyces cerevisiae and Aspergillus oryzae on the digestion of the cell wall fraction of a mixed diet in defaunated and refaunated sheep rumen.

The objective of this study was to determine the effect of two probiotics, Saccharomyces cerevisiae (SC) and Aspergillus oryzae (AO), without their culture medium, on the digestion of plant cell wall components in sheep that had been successively defaunated and refaunated. Six sheep fitted with large rumen cannulae were used to study 1) defaunated sheep with no probiotic, 2) defaunated sheep with SC or AO, 3) refaunated sheep with no probiotic, 4) refaunated sheep with SC or AO. The apparent digestibility of the plant cell walls was not altered (P > 0.05) by the probiotics in defaunated sheep but was increased (P < 0.05) with SC (+16%) in refaunated sheep. Simultaneously, SC stimulated the growth of the protozoal population in the rumen. As noted in most previous experiments, the positive effect of the presence of protozoa on plant cell wall digestion (P < 0.001) was confirmed here. The effect (P > 0.05) of SC or AO on in situ ADF digestion was either not significant or negative in defaunated rumens, whereas it became positive in refaunated rumen after a residence time of 12 h. The improvement of in situ ADF digestion due to the presence of protozoa was significant (P < 0.05 for NDF; P < 0.001 for ADF). However, we could not determine whether this was a direct effect of protozoa or an indirect effect operating via bacteria. The limits of the nylon bag technique for evaluating the microbial activity are discussed in relation to the ability of protozoa to enter and grow in the bags, and the pH regulation inside the bags. The pH values below 5.5 noted inside the bags can significantly alter the bacterial and protozoal populations and limit the validity of the technique. SC increased (P < 0.05) the specific activity of CMCase and xylanase of the solid-adherent bacteria (SAB) isolated from the rumen digesta of refaunated sheep. Stimulation of both the bacterial activity and protozoa numbers could explain the positive effect of SC on cell wall digestion in the rumen since the modelling of marker excretion in faeces showed that the ruminal mean retention time of hay measured from the model of Danhoa et al. was not modified (P > 0.05) by either refaunation or the presence of probiotics. AO increased (P < 0.05) the total retention time of the solid particles in the whole digestive tract and increased the ruminal liquid volume in the refaunated animals but it had no effect on the protozoa population or on the polysaccharidase activity of the SAB, which could explain the absence of effect of AO on the total digestibility of plant cell walls. Both probiotics decreased the liquid turnover in defaunated rumens (P < 0.05) but neither had any effect (P > 0.05) on this parameter after refaunation. The improvement of plant cell wall degradation in the whole digestive tract is probably due to a stimulation of digestion at the rumen level as indicated by the higher activity of the SAB in rumen digesta and the growth of protozoa.

Animal Feed↗
PubMed1975

Nutritional studies on East African herbivores. 1. Digestibilities of dry matter , crude fibre and crude protein in antelope, cattle and sheep.

1. A series of digestibility trials was done using four animals of each of the following species: Friesian cattle (Bos taurus), Boran zebu cattle (Bos indicus), Corriedale sheep, fat-tailed sheep, eland (Taurotragus oryx Pallas), Coke's hartebeest (Alcelaphus buselaphus cokei Günther), Thomson's gazelle (Gazella thomsonii Günther) and bush duiker (Sylvicapra grimmia L.). 2. Two batches of pelleted food were prepared from ground maize cobs, cassava, whs (A-E) were prepared containing 65 (A)-135 (E) g crude protein (nitrogen times 6-25)/kg dry matter. The crude-fibre contents of all the diets were similar (120-138 g/kg dry matter). 3. The animals were given the high-protein diet (E), then given diets with decreasing protein contents finishing with the low-protein (A). The antelope and half the sheep were given diets from the first batch of pelleted food, the other four sheep and all the cattle were given diets from the second batch of food. 4. In sheep, there were significant differences in digestibility between the two batches of food. 5. There were no significant differences in the over-all mean digestibilities of all diets when given to cattle (both species) and sheep. However, with diet E, dry-matter digestibility was higher in sheep than in cattle (P smaller than 0-05): the reverse was true with diet A (P smaller than 0-001). Crude-fibre and crude-protein digestibilities followed a similar pattern. The differences between Corriedale and fat-tailed sheep were not significant. The only significant difference between the two species of cattle was the higher digestibility of crude protein in Borans given diet E (P smaller than 0-05). 6. The over-all mean digestibility of the dry matter was higher (P smaller than 0-001) in hartebeest and duiker than in sheep; in Thomson's gazelle (P smaller than 0-01) and eland (P smaller than 0-001) it was lower than in sheep. The values for crude-fibre digestibilities varied in a similar way. 7. The mean apparent digestibility of crude protein was higher (P smaller than 0-001) in eland, hartebeest and duiker than in sheep and gazelle. 8. The results are discussed in relation to the feeding habits and digestive physiology of the various species.

Africa, Eastern↗