Effects of an abrupt diet change from hay to concentrate on microbial numbers and physical environment in the cecum of the pony.

Microbial numbers, pH, fluid volume, and turnover rate in the pony cecum were measured during an abrupt change from an all-forage to an all-concentrate diet, both fed at maintenance energy levels. Concentrate feeding resulted in increased (P less than 0.01) numbers of total viable anaerobic bacteria. The numbers of organisms growing on selective starch medium increased (P less than 0.01) when concentrate was fed, while numbers on xylan and pectin media decreased (P less than 0.025). Seven days after the diet change to concentrate, the number of bacteria growing on lactate medium increased (P less than 0.01), followed by a gradual decline. Cellulolytic bacteria occurred in low numbers, ranging from 1.1 x 10(4) to 4.4 x 10(4) per g of cecal contents. Feeding all concentrate decreased both the number of genera (P less than 0.01) and total protozoan numbers (P less than 0.01) in the cecum. Minimum cecal pH values of 6.4 and 5.8 were obtained when forage and concentrate, respectively, were fed, with the minimum pH occurring 6 h postfeeding. Dry-matter percentage of cecal contents followed a diurnal pattern which was the inverse of the pH curve. During forage feeding, the cecum contained an average of 2.2 liters (1.6 to 3.4 liters), which turned over 3.9 times per day. When concentrate was fed, cecal volume averaged 3.9 liters (0.6 to 8.6 liters), with a mean liquid turnover of 4.2 times per day. Microbial numbers and pH changes in the pony cecum associated with an abrupt change in diet from hay to concentrate resembled those which occur in the rumen under similar feeding conditions.     

Microbiology and ration digestibility in the hindgut of the ovine

Contents of the terminal ilea, ceca-proximal colons, and terminal recta were obtained from nine sheep, three of which were fed 100% orchardgrass hay, three of which were fed 60% cracked corn-40% orchardgrass hay, and three of which were fed 80% cracked corn-20% orchardgrass hay. The digestibility of dry matter in the ceca was greatest when the all-hay diet was fed, whereas the percentage of cellulose digestion in the ceca increased with increasing levels of concentrate. For all diets, the total volatile fatty acid concentrations were higher in the ceca than in the other two sites. The cecal pH levels decreased with increased corn levels in the diet. The total microbiol numbers per gram of ileal and cecal contents increased in response to feeding of concentrate; however, across all diets, the ileal counts were 8% or less of the cecal counts. In contrast, the cellulolytic microbial numbers in the ilea were 50% or more of those in the ceca and were highest with the all-hay diet. Both bacterial and end product concentrations in the ceca were equivalent to those occurring in rumina. A total of 16 cellulolytic cultures were isolated and characterized from ileal and cecal contents of animals fed all three diets. Seven gram-negative-rod-shaped organisms were identified as Butyrivibrio fibrisolvens, whose capacity to digest cellulose exceeded that of several rumen strains. The guanine-plus-cytosine content of the DNA of one strain of B. fibrisolvens was 38.8 mol%, compared with the only previously reported value for this species of 41.2 mol%.(ABSTRACT TRUNCATED AT 250 WORDS)     

Microbiology and ration digestibility in the hindgut of the ovine.

Contents of the terminal ilea, ceca-proximal colons, and terminal recta were obtained from nine sheep, three of which were fed 100% orchardgrass hay, three of which were fed 60% cracked corn-40% orchardgrass hay, and three of which were fed 80% cracked corn-20% orchardgrass hay. The digestibility of dry matter in the ceca was greatest when the all-hay diet was fed, whereas the percentage of cellulose digestion in the ceca increased with increasing levels of concentrate. For all diets, the total volatile fatty acid concentrations were higher in the ceca than in the other two sites. The cecal pH levels decreased with increased corn levels in the diet. The total microbiol numbers per gram of ileal and cecal contents increased in response to feeding of concentrate; however, across all diets, the ileal counts were 8% or less of the cecal counts. In contrast, the cellulolytic microbial numbers in the ilea were 50% or more of those in the ceca and were highest with the all-hay diet. Both bacterial and end product concentrations in the ceca were equivalent to those occurring in rumina. A total of 16 cellulolytic cultures were isolated and characterized from ileal and cecal contents of animals fed all three diets. Seven gram-negative-rod-shaped organisms were identified as Butyrivibrio fibrisolvens, whose capacity to digest cellulose exceeded that of several rumen strains. The guanine-plus-cytosine content of the DNA of one strain of B. fibrisolvens was 38.8 mol%, compared with the only previously reported value for this species of 41.2 mol%.(ABSTRACT TRUNCATED AT 250 WORDS)     

Potential rates of fermentation in digesta from the gastrointestinal tract of pigs: effect of feeding fermented liquid feed

Microbial catabolic capacity in digesta from the gastrointestinal tract of pigs fed either dry feed or fermented liquid feed (FLF) was determined with the PhenePlate multisubstrate system. The in vitro technique was modified to analyze the kinetics of substrate catabolism mediated by the standing stock of enzymes (potential rates of fermentation), allowing a quantitative evaluation of the dietary effect on the catabolic capacity of the microbiota. In total, the potential rates of fermentation were significantly reduced in digesta from the large intestine (cecum, P < 0.1; colon, P < 0.01; and rectum, P < 0.0001) of pigs fed FLF compared to pigs fed dry feed. No effect of diet was observed in the stomach (P = 0.71) or the distal part of the small intestine (P = 0.97). The highest rates of fermentation and the most significant effect of diet were observed for readily fermentable carbohydrates like maltose, sucrose, and lactose. Feeding FLF to pigs also led to a reduction in the large intestine of the total counts of anaerobic bacteria in general and lactic acid bacteria specifically, as well as of microbial activity, as determined by the concentration of ATP and short-chain fatty acids. The low-molecular-weight carbohydrates were fermented mainly to lactic acid in the FLF before being fed to the animals. This may have limited microbial nutrient availability in the digesta reaching the large intestine of pigs fed FLF and may have caused the observed reduction in activity and density of the cecal and colonic microbial population. On the other hand, feeding FLF to pigs reduced the viable counts of coliform bacteria (indicator of Escherichia coli and Salmonella spp.) most profoundly in the stomach and the distal part of the small intestine, probably due to the bactericidal effect of lactic acid and low pH. The results presented clearly demonstrate that feeding FLF to pigs had a great impact on the indigenous microbiota, as reflected in bacterial numbers, short-chain fatty acid concentration, and substrate utilization. However, completely different mechanisms may be involved in the proximal and the distal parts of the gastrointestinal tract. The present study illustrates the utility of the PhenePlate system for quantifying the catabolic capacity of the indigenous gastrointestinal tract microbiota.     

Effects of physical properties of feed on microbial ecology and survival of Salmonella enterica serovar Typhimurium in the pig gastrointestinal tract

A two-by-two factorial experiment with pigs was conducted to study the effect of feed grinding (fine and coarse) and feed processing (pelleted and nonpelleted) on physicochemical properties, microbial populations, and survival of Salmonella enterica serovar Typhimurium DT12 in the gastrointestinal tracts of pigs. Results demonstrated a strong effect of diet on parameters measured in the stomachs of the pigs, whereas the effect was less in the other parts of the gastrointestinal tract. Pigs fed the coarse nonpelleted (C-NP) diet showed more solid gastric content with higher dry matter content than pigs fed the fine nonpelleted (F-NP), coarse pelleted (C-P), or fine pelleted (F-P) diet. Pigs fed the C-NP diet also showed significantly increased number of anaerobic bacteria (P < 0.05), increased concentrations of organic acids, and reduced pH in the stomach. In addition, pigs fed the C-NP diet showed increased in vitro death rate of S. enterica serovar Typhimurium DT12 in content from the stomach (P < 0.001). Pigs fed the C-NP diet had a significantly higher concentration of undissociated lactic acid in gastric content than pigs fed the other diets (P < 0.001). A strong correlation between the concentration of undissociated lactic acid and the death rate of S. enterica serovar Typhimurium DT12 was found. In the distal small intestine, cecum, and midcolon, significantly lower numbers of coliform bacteria were observed in pigs fed the coarse diets than in pigs fed the fine diets (P < 0.01). Pigs fed the C-NP diet showed the lowest number of coliform bacteria in these segments of the gastrointestinal tract. Pigs fed the coarse diets showed increased concentration of butyric acid in the cecum (P < 0.05) and colon (P < 0.10) compared with pigs fed the fine diets. It was concluded that feeding a coarsely ground meal feed to pigs changes the physicochemical and microbial properties of content in the stomach, which decreases the survival of Salmonella during passage through the stomach. In this way the stomach acts as a barrier preventing harmful bacteria from entering and proliferating in the lower part of the gastrointestinal tract.     

Bacterial and Fungal Numbers in Ruminal and Cecal Contents of the Blue Duiker (Cephalophus monticola)

Total and cellulolytic bacterial and fungal numbers were determined in ruminal and cecal contents of 20 blue duikers (Cephalophus monticola). The animals were equally divided by sex and fed two diets, either high roughage or high concentrate. The mean concentration for total bacterial numbers in the rumen was 26.0 × 10⁸/g of contents, with values ranging from 2 × 10⁸/g to 93 × 10⁸/g. Cellulolytic numbers averaged 6.0 × 10⁸/g with a range of 1.5 × 10⁸/g to 24.0 × 10⁸/g. No differences related to sex or diet were found. In contrast, total bacterial numbers in the cecum differed between diets (P < 0.02), i.e., 1,046 × 10⁶ bacteria per g for animals fed the high-forage diet compared with 166 × 10⁶/g for those fed the high-concentrate diet. Cellulolytic bacterial counts in the cecal contents averaged 3.1 and 7.0% of the total counts for the high-forage and high-concentrate diets, respectively. Low concentrations of fungi were found in both ruminal and cecal contents of some, but not all, animals. Unexpectedly, concentrations of bacteria and fungi in the rumen and cecum were highly correlated with their total numbers (concentration multiplied by total weight of contents).     

Moderation of ruminal fermentation by ciliated protozoa in cattle fed a high-grain diet.

The objective of this study was to assess the influence of ciliated protozoa on ruminal fermentation in cattle fed high-grain diets. Six ruminally cannulated steers fed a corn-based grain diet (85% concentrate plus 15% alfalfa hay) at 12-h intervals were assigned randomly to two groups, ciliate free and faunated, in a crossover design. Defaunation was by ruminal emptying, omasal flushing, and treatment with sodium sulfosuccinate. Two to 3 weeks after defaunation, the ruminal contents of all steers were sampled before the morning feeding (0 h) and at 1, 2, 4, 6, 8, and 12 h after feeding to measure pH, analyze fermentation products, and monitor counts of ciliated protozoa and lactic acid-producing and -fermenting bacterial groups. Total numbers of ciliated protozoa in the faunated steers averaged 4.3 x 10(5)/g, and the protozoa consisted of nine genera. Ciliate-free steers had lower (P less than 0.01) ruminal pHs (pH 5.97) than faunated cattle (pH 6.45); however, the treatment-time interaction was not significant. Ruminal lactate and ammonia concentrations were similar in both groups. The total volatile fatty acid concentration was higher (P less than 0.05) in the ciliate-free steers than in the faunated steers and exhibited a treatment-time interaction (P less than 0.05). The acetate-to-propionate ratio was higher (P less than 0.05) in the faunated group than in the ciliate-free group and showed a treatment-time interaction (P less than 0.05). Total anaerobic bacterial counts were about fourfold higher in the ciliate-free group than in the faunated group.(ABSTRACT TRUNCATED AT 250 WORDS)     

Moderation of ruminal fermentation by ciliated protozoa in cattle fed a high-grain diet.

The objective of this study was to assess the influence of ciliated protozoa on ruminal fermentation in cattle fed high-grain diets. Six ruminally cannulated steers fed a corn-based grain diet (85% concentrate plus 15% alfalfa hay) at 12-h intervals were assigned randomly to two groups, ciliate free and faunated, in a crossover design. Defaunation was by ruminal emptying, omasal flushing, and treatment with sodium sulfosuccinate. Two to 3 weeks after defaunation, the ruminal contents of all steers were sampled before the morning feeding (0 h) and at 1, 2, 4, 6, 8, and 12 h after feeding to measure pH, analyze fermentation products, and monitor counts of ciliated protozoa and lactic acid-producing and -fermenting bacterial groups. Total numbers of ciliated protozoa in the faunated steers averaged 4.3 x 10(5)/g, and the protozoa consisted of nine genera. Ciliate-free steers had lower (P less than 0.01) ruminal pHs (pH 5.97) than faunated cattle (pH 6.45); however, the treatment-time interaction was not significant. Ruminal lactate and ammonia concentrations were similar in both groups. The total volatile fatty acid concentration was higher (P less than 0.05) in the ciliate-free steers than in the faunated steers and exhibited a treatment-time interaction (P less than 0.05). The acetate-to-propionate ratio was higher (P less than 0.05) in the faunated group than in the ciliate-free group and showed a treatment-time interaction (P less than 0.05). Total anaerobic bacterial counts were about fourfold higher in the ciliate-free group than in the faunated group.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of pH on ruminal methanogenesis

Abstract: When a fistulated cow was fed an all forage diet, ruminal pH remained more or less constant (6.7 to 6.9). The ruminal pH of a concentrate-fed cow decreased dramatically in the period soon after feeding, and the pH was as low as 5.45. Mixed ruminal bacteria from the forage-fed cow converted CO₂ and H₂ to methane, but the ruminal fluid from the concentrate-fed cow did not produce methane. When the pH of the ruminal fluid from the concentrate-fed cow was adjusted to pH 7.0, methane was eventually detected, and the absolute rate constant of methane production was as high as the one observed with ruminal fluid from the forage fed cow (0.32 h⁻¹). Based on the zero-time intercepts of methane production, it appeared that the concentrate-fed cow had fewer methanogens than the forage-fed cow. When the mixed ruminal bacteria were incubated in a basal medium containing 100 mM acetate, methanogenesis was pH-dependent, and no methane was detected at pH values less than 6.0. Because the removal of acetic acid completely reversed the inhibition of methanogenesis, it appeared that volatile fatty acids were causing the pH-dependent inhibition. Based on these results, concentrate diets that lower ruminal pH may provide a practical means of decreasing ruminal methane production.     

Enumeration of selected anaerobic bacterial groups in cecal and colonic contents of growing-finishing pigs

Selected anaerobic bacterial groups in cecal and colonic contents of clinically healthy pigs fed a corn-soybean meal production diet were determined at sacrifice after 4, 8, and 11 weeks on feed, corresponding to intervals within the growing-finishing growth period. By using ruminal fluid-based media, the densities of the culturable anaerobic population; the cellulolytic, pectin-fermenting, pectin-hydrolyzing, xylan-fermenting; and the xylan-hydrolyzing, sulfate-reducing, and methanogenic bacterial populations were estimated. An analysis of variance was performed on these bacterial group variables to examine the effects of phase (weeks on feed), site (cecum or colon), or the interaction of phase with site. The population of total anaerobic bacteria was twice as dense in the colon as it was in the cecum (2 x 10(10) versus 1 x 10(10)/g [wet weight]; P = 0.001). The proportion of cellulolytic bacteria was lower at 4 weeks on feed than at 8 or 11 weeks (23 versus 32%; P = 0.026), while the proportion of pectin-fermenting bacteria depended on the interaction of phase with site (P = 0.021). The numbers of sulfate-reducing bacteria were significantly higher in the colon than in the cecum (6 x 10(7) versus 3 x 10(7); P = 0.014), as were methanogenic bacteria (19 x 10(7) versus 0.6 x 10(7); P = 0.0002). The remaining bacterial groups were stable with respect to phase and site. The results suggest that except for density differences, the microbial communities of the pig cecum and colon are similar in composition throughout the growing-finishing phase.     

Enumeration of selected anaerobic bacterial groups in cecal and colonic contents of growing-finishing pigs.

Selected anaerobic bacterial groups in cecal and colonic contents of clinically healthy pigs fed a corn-soybean meal production diet were determined at sacrifice after 4, 8, and 11 weeks on feed, corresponding to intervals within the growing-finishing growth period. By using ruminal fluid-based media, the densities of the culturable anaerobic population; the cellulolytic, pectin-fermenting, pectin-hydrolyzing, xylan-fermenting; and the xylan-hydrolyzing, sulfate-reducing, and methanogenic bacterial populations were estimated. An analysis of variance was performed on these bacterial group variables to examine the effects of phase (weeks on feed), site (cecum or colon), or the interaction of phase with site. The population of total anaerobic bacteria was twice as dense in the colon as it was in the cecum (2 x 10(10) versus 1 x 10(10)/g [wet weight]; P = 0.001). The proportion of cellulolytic bacteria was lower at 4 weeks on feed than at 8 or 11 weeks (23 versus 32%; P = 0.026), while the proportion of pectin-fermenting bacteria depended on the interaction of phase with site (P = 0.021). The numbers of sulfate-reducing bacteria were significantly higher in the colon than in the cecum (6 x 10(7) versus 3 x 10(7); P = 0.014), as were methanogenic bacteria (19 x 10(7) versus 0.6 x 10(7); P = 0.0002). The remaining bacterial groups were stable with respect to phase and site. The results suggest that except for density differences, the microbial communities of the pig cecum and colon are similar in composition throughout the growing-finishing phase.     

Effect of forage or grain diets with or without monensin on ruminal persistence and fecal Escherichia coli O157:H7 in cattle

Twelve ruminally cannulated cattle, adapted to forage or grain diet with or without monensin, were used to investigate the effects of diet and monensin on concentration and duration of ruminal persistence and fecal shedding of E. coli O157:H7. Cattle were ruminally inoculated with a strain of E. coli O157:H7 (10(10) CFU/animal) made resistant to nalidixic acid (Nal(r)). Ruminal and fecal samples were collected for 11 weeks, and then cattle were euthanized and necropsied and digesta from different gut locations were collected. Samples were cultured for detection and enumeration of Nal(r) E. coli O157:H7. Cattle fed forage diets were culture positive for E. coli O157:H7 in the feces for longer duration (P < 0.05) than cattle fed a grain diet. In forage-fed cattle, the duration they remained culture positive for E. coli O157:H7 was shorter (P < 0.05) when the diet included monensin. Generally, ruminal persistence of Nal(r) E. coli O157:H7 was not affected by diet or monensin. At necropsy, E. coli O157:H7 was detected in cecal and colonic digesta but not from the rumen. Our study showed that cattle fed a forage diet were culture positive longer and with higher numbers than cattle on a grain diet. Monensin supplementation decreased the duration of shedding with forage diet, and the cecum and colon were culture positive for E. coli O157:H7 more often than the rumen of cattle.     

Potential Rates of Fermentation in Digesta from the Gastrointestinal Tract of Pigs: Effect of Feeding Fermented Liquid Feed

Microbial catabolic capacity in digesta from the gastrointestinal tract of pigs fed either dry feed or fermented liquid feed (FLF) was determined with the PhenePlate multisubstrate system. The in vitro technique was modified to analyze the kinetics of substrate catabolism mediated by the standing stock of enzymes (potential rates of fermentation), allowing a quantitative evaluation of the dietary effect on the catabolic capacity of the microbiota. In total, the potential rates of fermentation were significantly reduced in digesta from the large intestine (cecum, P < 0.1; colon, P < 0.01; and rectum, P < 0.0001) of pigs fed FLF compared to pigs fed dry feed. No effect of diet was observed in the stomach (P = 0.71) or the distal part of the small intestine (P = 0.97). The highest rates of fermentation and the most significant effect of diet were observed for readily fermentable carbohydrates like maltose, sucrose, and lactose. Feeding FLF to pigs also led to a reduction in the large intestine of the total counts of anaerobic bacteria in general and lactic acid bacteria specifically, as well as of microbial activity, as determined by the concentration of ATP and short-chain fatty acids. The low-molecular-weight carbohydrates were fermented mainly to lactic acid in the FLF before being fed to the animals. This may have limited microbial nutrient availability in the digesta reaching the large intestine of pigs fed FLF and may have caused the observed reduction in activity and density of the cecal and colonic microbial population. On the other hand, feeding FLF to pigs reduced the viable counts of coliform bacteria (indicator of Escherichia coli and Salmonella spp.) most profoundly in the stomach and the distal part of the small intestine, probably due to the bactericidal effect of lactic acid and low pH. The results presented clearly demonstrate that feeding FLF to pigs had a great impact on the indigenous microbiota, as reflected in bacterial numbers, short-chain fatty acid concentration, and substrate utilization. However, completely different mechanisms may be involved in the proximal and the distal parts of the gastrointestinal tract. The present study illustrates the utility of the PhenePlate system for quantifying the catabolic capacity of the indigenous gastrointestinal tract microbiota.     

Effect of dietary fiber on microbial activity and microbial gas production in various regions of the gastrointestinal tract of pigs.

The microbial activity, composition of the gas phase, and gas production rates in the gastrointestinal tract of pigs fed either a low- or a high-fiber diet were investigated. Dense populations of culturable anaerobic bacteria, high ATP concentrations, and high adenylate energy charges were found for the last third of the small intestine, indicating that substantial microbial activity takes place in that portion of the gut. The highest microbial activity (highest bacterium counts, highest ATP concentration, high adenylate energy charge, and low pH) was found in the cecum and proximal colon. Greater microbial activity was found in the stomach and all segments of the hindgut in the pigs fed the high-fiber diet than in the pigs fed the low-fiber diet. Considerable amounts of O2 were found in the stomach (around 5%), while the content of O2 in gas samples taken from all other parts of the gastrointestinal tract was < 1%. The highest concentrations and highest production rates for H2 were found in the last third of the small intestine. No methane could be detected in the stomach or the small intestine. The rate of production and concentration of methane in the cecum and the proximal colon were low, followed by a steady increase in the successive segments of the hindgut. A very good correlation between in vivo and in vitro measurements of methane production was found. The amount of CH4 produced by pigs fed the low-fiber diet was 1.4 liters/day per animal. Substantially larger amounts of CH4 were produced by pigs fed the high-fiber diet (12.5 liters/day)(ABSTRACT TRUNCATED AT 250 WORDS)     

Sequestration of Holotrich Protozoa in the Reticulo-Rumen of Cattle

Studies were carried out to determine the means by which holotrich protozoa can maintain their numbers within the rumen against the washout effect associated with the flow of ingesta. When a diet composed of 2 kg of concentrate and 1.5 kg of rice straw was fed to Holstein cows, about a fourfold increase in holotrich numbers per ml of rumen fluid was observed within 1 h after the commencement of feeding, and an abrupt decrease followed. This fluctuation in numbers was not related to the time of feeding. A sole feeding of 2 kg of concentrate had almost the same effect on the holotrichs as a sole feeding of 1.5 kg of rice straw. Administration of either 2 kg of concentrate or 1.5 kg of rice straw through the rumen fistula caused similar changes, though the extent of response to the former was greater than that to the latter. The administration of either 0.7 kg of starch or 0.2 kg of glucose through the fistula had a relatively minor effect on the holotrich population. Addition of rice straw to 0.5 kg of concentrate increased the change in numbers, but its addition had little, if any, effect when 1 kg of concentrate was fed. These results suggested that the fluctuation in holotrich numbers was related not only to the nature or component of feed but also to other factors such as the quantity or volume of a diet and the act of ingesting feed. Increasing the number of feedings up to eight times per day at 3-h intervals caused a decrease in the peak heights of holotrich numbers per milliliter of rumen fluid. A thick protozoal mass which primarily consisted of holotrichs was found on the wall of the reticulum of Holstein steers slaughtered after overnight starvation. These findings suggest that holotrichs would usually sequester on the reticulum wall and migrate into the rumen only for a few hours after feeding, and that this mode of behavior would be essential for holotrichs to maintain their population within the rumen of cattle. Possible mechanisms of the migration are also discussed.     

Intestinal colonization of laboratory rats with Oxalobacter formigenes.

Six strains of Oxalobacter formigenes (anaerobic oxalate-degrading bacteria) were examined for their ability to colonize the gastrointestinal tracts of adult laboratory rats. These rats did not harbor O. formigenes. Strain OxCR6, isolated from the cecal contents of a laboratory rat that was naturally colonized by oxalate-degrading bacteria, colonized the ceca and colons of adult rats fed a diet that contained 4.5% sodium oxalate. Five days after rats were inoculated intragastrically with 10(9) viable cells of strain OxCR6, oxalate degradation rates in cecal and colonic contents increased by 19 and 40 times, respectively. Viable counts of strain OxCR6 from these rats averaged 10(8)/g (dry weight) of cecal contents. Strain OxCR6 was not detected in the cecal contents of inoculated rats fed diets that contained less than 3.0% sodium oxalate. Strains of O. formigenes isolated from the cecal contents of swine, guinea pigs, and wild rats and from human feces also colonized the ceca of laboratory rats; a ruminal strain failed to colonize the rat cecum.     

Interactive Effects of Indigestible Carbohydrates,Protein Type,and Protein Level on Biomarkers of Large Intestine Health in Rats

The effects of indigestible carbohydrates, protein type, and protein level on large intestine health were examined in rats. For 21 days, 12 groups of six 12-week-old male Wistar rats were fed diets with casein (CAS), or potato protein concentrate (PPC), providing 14% (lower protein level; LP), or 20% (higher protein level; HP) protein, and containing cellulose, resistant potato starch, or pectin. Fermentation end-products, pH, and β-glucuronidase levels in cecal digesta, and ammonia levels in colonic digesta were determined. Cecal digesta, tissue weights, cecal and colon morphology, and colonocyte DNA damage were also analyzed. Digesta pH was lower, whereas relative mass of cecal tissue and digesta were higher in rats fed pectin diets than in those fed cellulose. Cecal parameters were greater in rats fed PPC and HP diets than in those fed CAS and LP diets, respectively. Short-chain fatty acid (SCFA) concentrations were unaffected by protein or carbohydrate type. Total SCFA, acetic acid, and propionic acid concentrations were greater in rats fed LP diets than in those fed HP. Cecal pool of isobutyric and isovaleric acids was greater in rats fed PPC than in those fed CAS diets. PPC diets decreased phenol concentration and increased ammonia concentration in cecal and colonic digesta, respectively. Cecal crypt depth was greater in rats fed PPC and HP diets, and was unaffected by carbohydrates; whereas colonic crypt depth was greater in rats fed cellulose. Myenteron thickness in the cecum was unaffected by nutrition, but was greater in the colon of rats fed cellulose. Colonocyte DNA damage was greater in rats fed LP diets than in those fed HP diets, and was unaffected by carbohydrate or protein type. It was found that nutritional factors decreasing cecal digesta weight contribute to greater phenol production, increased DNA damage, and reduced ammonia concentration in the colon.     

Rumen Ciliate Protozoa of the Blue Duiker (Cephalophus monticola), with Observations on Morphological Variation Lines Within the Species Entodinium dubardi

ABSTRACT. Protozoal concentrations were determined in rumen and cecal contents of 20 blue duikers ( Cephalophus monticola ). Ten animals of each sex were fed either a high concentrate or high roughage diet. Rumen protozoa were present in 19 of the 20 animals and concentrations ranged from 4.5 to 33.7 × 10⁶ per g of rumen contents. At the higher concentrations, protozoal cells equaled between 30–40% of the total rumen contents volume. No protozoa were found in cecal contents. Weight of rumen contents was higher in females than in males ( P < 0.01), and rumen protozoa concentrations were higher in males ( P < 0.05) and in those animals fed the high concentrate diet ( P < 0.05). All the protozoa were identified as belonging to a single species, Entodinium dubardi . However, an average of about 30% of the E. dubardi cells varied from the typical morphology of this species. These cells appeared to be on variation lines leading toward 7–10 other non-caudate species of Entodinium . The present data were used to evaluate and discuss the concept of variation lines within E. dubardi .     

Effects of Physical Properties of Feed on Microbial Ecology and Survival of Salmonella enterica Serovar Typhimurium in the Pig Gastrointestinal Tract

A two-by-two factorial experiment with pigs was conducted to study the effect of feed grinding (fine and coarse) and feed processing (pelleted and nonpelleted) on physicochemical properties, microbial populations, and survival of Salmonella enterica serovar Typhimurium DT12 in the gastrointestinal tracts of pigs. Results demonstrated a strong effect of diet on parameters measured in the stomachs of the pigs, whereas the effect was less in the other parts of the gastrointestinal tract. Pigs fed the coarse nonpelleted (C-NP) diet showed more solid gastric content with higher dry matter content than pigs fed the fine nonpelleted (F-NP), coarse pelleted (C-P), or fine pelleted (F-P) diet. Pigs fed the C-NP diet also showed significantly increased number of anaerobic bacteria (P < 0.05), increased concentrations of organic acids, and reduced pH in the stomach. In addition, pigs fed the C-NP diet showed increased in vitro death rate of S. enterica serovar Typhimurium DT12 in content from the stomach (P < 0.001). Pigs fed the C-NP diet had a significantly higher concentration of undissociated lactic acid in gastric content than pigs fed the other diets (P < 0.001). A strong correlation between the concentration of undissociated lactic acid and the death rate of S. enterica serovar Typhimurium DT12 was found. In the distal small intestine, cecum, and midcolon, significantly lower numbers of coliform bacteria were observed in pigs fed the coarse diets than in pigs fed the fine diets (P < 0.01). Pigs fed the C-NP diet showed the lowest number of coliform bacteria in these segments of the gastrointestinal tract. Pigs fed the coarse diets showed increased concentration of butyric acid in the cecum (P < 0.05) and colon (P < 0.10) compared with pigs fed the fine diets. It was concluded that feeding a coarsely ground meal feed to pigs changes the physicochemical and microbial properties of content in the stomach, which decreases the survival of Salmonella during passage through the stomach. In this way the stomach acts as a barrier preventing harmful bacteria from entering and proliferating in the lower part of the gastrointestinal tract.     

ARISA analysis of ruminal bacterial community dynamics in lactating dairy cows during the feeding cycle

The bovine rumen undergoes substantial changes in environmental conditions during the animal's feeding cycle, but the effects of these changes on microbial populations have not been examined systematically. Two dairy cows fed a mixed forage/concentrate ration at 12 h intervals over 4 feeding cycles displayed substantial changes in ruminal pH and volatile fatty acid (VFA) concentrations. Automated ribosomal intergenic spacer analysis (ARISA) of solid- and liquid-associated bacterial populations in samples collected at 2, 4, 6, 9, and 12 h after feeding revealed a high degree of bacterial diversity. A total of 155 different amplicon lengths (ALs) were detected across all 83 samples, and 11–74 detected per sample. A substantial proportion (11%) of the ALs was detected in one cow but not in the other. The proportions of ALs that were detected only in the liquid phase or the solid phase were 13.5% and 1.9%, respectively. Correspondence analysis indicated that bacterial community composition differed between cows and between solid or liquid phases, but overall the solid-associated population displayed less change in composition within and across feeding cycles. The data support the notion that cows fed the same diets can have substantial differences in bacterial community composition, and that the solids-associated (biofilm) communities display greater stability than do associated planktonic communities.