Murray D. Drew

Effects of Commensal Bacteria on Intestinal Morphology and Expression of Proinflammatory Cytokines in the Gnotobiotic Pig

A germ-free neonatal pig model was established to determine the effects of bacterial colonization by different species on small intestinal morphology and proinflammatory cytokine gene expression. Two experimental groups of 16 pigs were aseptically delivered by cesarian section and allocated into 4 gnotobiotic isolators. Pigs were either maintained germ-free (GF), or were orally inoculated with either a single strain of nonpathogenic Escherichia coli (EC) or Lactobacillus fermentum (LF) or conventionalized with adult porcine feces (CV). After 13 days tissue samples were collected at 5 regions corresponding to 5%, 25%, 50%, 75%, and 95% of the small intestine (SI) length. In Experiment 2, the GF isolator became contaminated with Staphylococcus epidermidis (SE). In general, intestinal responses to bacterial colonization were similar among GF, LF, and SE pigs, and intestinal responses in EC pigs were more similar to CV pigs. Responses to bacterial colonization were most pronounced in the distal SI regions (50%–95%), suggesting that nonmicrobiai factors may be more important in the proximal SI. Relative to CV pigs, the distal intestines of GF, LF, and SE pigs were characterized by long villi, shallow crypts, Increased relative intestinal mass, and decreased lamina propria cellularity, whereas SI morphology was intermediate in EC pigs. Relative expression of proinflammatory cytokines interleukin-1β (IL-1β) and IL-6 generally increased distally in the SI and was highest in EC and CV pigs. We observed regional variation in SI morphology and proinflammatory cytokine expression, which differed with bacterial species. This study demonstrates that bacterial species differentially affect intestinal morphology and expression of proinflammatory cytokines and suggests that neonatal bacterial colonization patterns may have long-term effects on intestinal health and development

Effect of the dietary supplementation of fructooligosaccharides and Bifidobacterium longum to early-weaned pigs on performance and fecal bacterial populations

Two experiments were conducted to evaluate the effect of administration of fructooligosaccharides (FOS) and Bifidobacterium longumon growth performance and fecal bacterial populations in pigs weaned at 18 d of age. In exp. 1, two groups of 20 pigs each were fed diets containing 0 or 0.5% FOS for 21 d. On days 1 and 3, pigs receiving FOS were administered an oral dose of 1010 B. longumcells. During week 1, average daily gain was higher and feed efficiency was improved (P < 0.05) in pigs fed FOS and bifidobacteria relative to the control. On day 7, supplemented pigs had reduced numbers of total anaerobes and clostridia, and increased numbers of bifidobacteria in faeces (P < 0.05). In exp. 2, 80 pigs were divided into four groups of 20 animals each in a 2 x 2 factorial design. Main effects included FOS supplementation (0 or 0.5% of diet) and B. longum supplementation (0 or 107 cells per gram feed). FOS supplementation reduced growth while B. longum supplementation increased growth (P< 0.05). On days 12 and 1...

Dietary amino acids affect intestinal Clostridium perfringens populations in broiler chickens

An experiment was performed to examine the effect of protein source and dietary amino acid profile on intestinal levels of C. perfringens in broiler chickens. Broiler chickens (age = 14 d; n = 192) were fed diets containing 400 g kg-1 crude protein with fish meal, meat/bone meal, feather meal, corn gluten meal, soy protein concentrate, pea protein concentrate, or potato protein concentrate as the primary protein source along with a control diet containing 230 g kg-1 crude protein. The birds were orally inoculated daily, with 1 mL (~1.0 × 108 CFU mL-1) of an overnight culture of C. perfringens between 14 and 21 d of age, killed at 28 d of age and C. perfringens numbers in ileum and cecum were enumerated. Birds fed fish meal, meat/bone meal, feather meal and potato protein concentrate had significantly higher intestinal C. perfringens counts than the birds fed corn gluten meal, soy or pea protein concentrates or the control diet (P < 0.05). The glycine content of the diets and ileal contents was significant...

Effects of protein level and digestibility on the growth and carcass characteristics of broiler chickens1

A study was conducted to evaluate the effects of dietary protein level and protein digestibility on the growth performance and carcass characteristics of broilers from 1 to 35 d of age. Broiler chickens (n = 320) were fed 4 different ideal protein-balanced, isocaloric diets in a 2 × 2 factorial design with 2 levels of protein [high protein (HiPro; 20 and 18% or 200 and 180 g/kg) and low protein (LoPro; 18 and 16% or 180 and 160 g/kg) on d 1 to 14 and d 15 to 35, respectively] and 2 levels of protein digestibility [high digestibility (HiDig) and low digestibility (LoDig); approximately 85% and 80% CP digestibility, respectively]. The HiDig diets were formulated using soybean meal and fishmeal, whereas the LoDig diets used wheat distillers dried grains with solubles and meat and bone meal as the primary protein sources. The standardized ileal digestibility (SID) values of the wheat distillers dried grains with solubles and meat and bone meal (56.5 and 72.0% SID for lysine, respectively) were measured before the experiment to improve the accuracy of the diet formulations. During the starter phase, the interaction was significant for ADG; birds fed the LoPro-LoDig diet grew slower than birds fed the other 3 diets (P < 0.05). During the grower phase, the interaction was significant for ADFI; birds fed the LoPro-LoDig diet had the lowest ADFI compared with those fed the other 3 diets. The interaction between protein level and digestibility was significant for the SID of most of the AA and was significantly higher for birds fed the HiPro-HiDig diet compared with those fed the other 3 diets. Total breast meat yield was significantly higher in birds fed the HiPro diets than in those fed the LoPro diets, whereas birds fed the HiDig diets had significantly more abdominal fat than those fed the LoDig diets. The results suggest that low-protein diets can support growth performance equal to high-protein diets when highly digestible ingredients are used. However, maximum breast meat yield requires a high-protein diet and is not affected by ingredient digestibility.

Effect of dietary cereal on intestinal bacterial populations in weaned pigs

Diets containing corn, barley or wheat as the main carbohydrate source were formulated to a similar nutrient content and fed for 3 wk to weaned pigs. Gut bacterial populations differed significantly between the three diets and these differences were correlated with the fibre contents of the diets. Key words: Corn, wheat, barley, intestinal bacteria, pigs

Postprandial impairment of flow-mediated dilation and elevated methylglyoxal after simple but not complex carbohydrate consumption in dogs

Hyperglycemia produces oxidative stress, which may impair endothelial function. Methylglyoxal, a reactive intermediate metabolite of glucose, is known to cause oxidative stress and is produced when excess carbohydrate is consumed in diabetic patients, but postprandial responses in healthy patients are unknown. We hypothesize that methylglyoxal levels will cause impaired endothelial function via increased oxidative stress after consuming a high glycemic index meal in healthy animals. Normal-weight laboratory beagles (n = 6) were used in a crossover study that tested postprandial responses of 4 complex carbohydrate sources (barley, corn, peas, rice) vs a simple carbohydrate (glucose). Blood samples were taken prefeeding and at timed intervals after feeding to measure serum glucose, insulin, nitrotyrosine, and methylglyoxal. Flow-mediated dilation (FMD), cardiac function (echocardiography), and blood pressure measurements were determined before and 60 minutes after feeding. The mean (±SEM) glycemic indices of the complex carbohydrate sources were 29 ± 5 for peas, 47 ± 10 for corn, 51 ± 7 for barley, and 55 ± 6 for rice. Postprandial FMD was lowest in the glucose group and significantly different from both the corn group and the FMD value for all complex carbohydrates combined. Methylglyoxal was significantly elevated at 60 minutes postprandial after glucose compared with the other carbohydrate sources. No significant effects of carbohydrate source were observed for blood pressure, nitrotyrosine, or echocardiographic variables. The novel finding of this study was that methylglyoxal levels increased after a single feeding of simple carbohydrate and may be linked to the observed postprandial decrease in endothelial function. Thus, consuming low-glycemic-index foods may protect the cardiovascular system by reducing oxidative stress.

Short-term obesity results in detrimental metabolic and cardiovascular changes that may not be reversed with weight loss in an obese dog model

The time course of metabolic and cardiovascular changes with weight gain and subsequent weight loss has not been elucidated. The goal of the present study was to determine how weight gain, weight loss and altered body fat distribution affected metabolic and cardiovascular changes in an obese dog model. Testing was performed when the dogs were lean (scores 4-5 on a nine-point scale), after ad libitum feeding for 12 and 32 weeks to promote obesity (>5 score), and after weight loss. Measurements included serum glucose and insulin, plasma leptin, adiponectin and C-reactive protein, echocardiography, flow-mediated dilation and blood pressure. Body fat distribution was assessed by computed tomography. Fasting serum glucose concentrations increased significantly with obesity (P< 0·05). Heart rate increased by 22 (SE 5) bpm after 12 weeks of obesity (P= 0·003). Systolic left ventricular free wall thickness increased after 12 weeks of obesity (P= 0·002), but decreased after weight loss compared with that observed in the lean phase (P= 0·03). Ventricular free wall thickness was more strongly correlated with visceral fat (r 0·6, P= 0·001) than with total body fat (r 0·4, P= 0·03) and was not significantly correlated with subcutaneous body fat (r 0·3, P= 0·1). The present study provides evidence that metabolic and cardiovascular alterations occur within only 12 weeks of obesity in an obese dog model and are strongly predicted by visceral fat. These results emphasise the importance of obesity prevention, as weight loss did not result in the return of all metabolic indicators to their normal levels. Moreover, systolic cardiac muscle thickness was reduced after weight loss compared with the pre-obesity levels, suggesting possible acute adverse cardiovascular effects.

Apparent absorption of methionine and 2-hydroxy-4- methylthiobutanoic acid from gastrointestinal tract of conventional and gnotobiotic pigs

The effect of commensal microbiota and feeding corn or wheat/barley-based diets on the apparent gastrointestinal absorption of dl-methionine (MET) and 2-hydroxy-4-methylthiobutanoic acid (MHA-FA) was studied in conventional (n = 32) and gnotobiotic pigs (n = 24). Conventional pigs (CON) were vaginally delivered and sow-reared until weaning at 14 days of age. Gnotobiotic pigs were derived by caesarian section and reared in HEPA (high efficiency particulate air)-filtered isolator units with ad libitum access to a milk-based formula. Corn or wheat/barley-based diets were fed to all pigs from 14 to 24 days of age. At 24 days of age, after an overnight fast, pigs were fed 20 g/kg BW of experimental diet supplemented with 107 Bq of either 3H-l-MET or 3H-l-MHA-FA per kg of feed and chromic oxide (0.5% wt/wt). Pigs were killed for sample collection 3 h after consuming the meal. Residual 3H-MET and 3H-MHA-FA were estimated in gastrointestinal contents as the ratio of 3H : chromic oxide in digesta samples to the ratio of 3H : chromic oxide in feed. In CON pigs, feeding a wheat/barley-based diet increased (P < 0.05) total aerobes, whereas supplementation with MHA-FA increased (P < 0.05) total aerobes and lactobacilli populations in proximal small intestine (SI). Among the gnotobiotic pigs, bacterial contamination occurred such that eight pigs (two isolators) were monoassociated with a Gram-negative bacteria closely related to Providencia spp. and 16 pigs (four isolators) were monoassociated with Gram positive Enterococcus faecium. Species of monoassociated bacterial contaminant and diet composition did not affect residual methionine or MHA-FA in digesta. In both CON and monoassociated (MA) pigs, methionine and MHA-FA were retained in stomach (92%) but disappeared rapidly from proximal SI. Residual methionine and MHA-FA in digesta was not different in MA pigs; however, in CON pigs, less (P < 0.01) apparent residual methionine was found in digesta recovered at 25% (from cranial to caudal) and 75% of SI length compared with MHA-FA. Apparent residual methionine was 16% and 8% compared with 34% and 15% for MHA-FA, at the 25% and 75% locations, respectively. In proximal SI tissue, significantly (P < 0.05) higher radioactivity (cpm/mg wet tissue) was associated with MET pigs (8.56 ± 0.47) as compared to MHA-FA ones (5.45 ± 0.50). This study suggests that microbial metabolism of MHA-FA increases retention in small intestinal digesta relative to methionine and contributes, in part, to the lower bioefficacy of MHA-FA compared to methionine.

Cloning of porcine proglucagon and effect of commensal bacteria on relative gene expression in the intestine of gnotobiotic pigs

Porcine proglucagon mRNA sequence was determined by designing primers based on homologous regions in bovine and human genes. The porcine sequence shared 90% nucleotide identity with human proglucagon; however, predicted Ser159Arg and Leu160Lys substitutions were observed. This newly identified sequence suggests that the intestinal trophic peptide, glucagon-like peptide 2 (GLP-2), is actually 35 amino acids in the pig rather than 33 amino acids, as previously reported. To determine the effect of different bacteria on intestinal proglucagon gene expression, 16 piglets were reared in gnotobiotic isolators maintained germ-free (GF), monoassociated with Lactobacillus fermentum (LF) or Escherichia coli (EC), or conventionalized (CV) in two separate experiments for 13 d. Cultured cecal contents confirmed microbial status with the exception of GF pigs in exp. 2, which were contaminated with Staphylococcus epidermidis (SE). Mean fold differences in ileal proglucagon expression (CV set to 1) were 1.0ab, 1.6a, 0.7b,...