The gut microflora and the uptake of glucose from the small intestine of the chick

Comparative biology of germ-free and conventional poultry

Interaction between the host and the enteric microbiome is highly complex. Microbial involvement in certain pathologies is moderately well established, but the contribution of the microbiome to animal welfare, behavior, sustainability, immune development, nutritional status, physiology, and maturation is less clear. A valuable experimental model to enable scientists to explore the role of the microbiome in various domains is to compare various phenotypes of a conventionally reared (CV) cohort with those in a germ-free (GF) state. A GF animal is one that is devoid of any detectable microbial life including bacteria, viruses, protozoa and parasites. The GF state is different from gnotobiotic animals where the microbiome is fully described, or ‘specific pathogen free’ (SPF) animals where a moderately normal microbiome is present but devoid of pathogenic microorganisms. Pioneering GF research in poultry in the late 1940s and 1950s has its origin in a need understand the mode of action of antibiotics. Early researchers quickly established that GF chicks responded differently to antibiotics than CV counterparts. The GF experimental model has since been exploited in many divergent fields including pathology, immunology, metabolism, anatomy, physiology, and others. The absence of a microbiome presents the host with a range of advantages and disadvantages. For example, GF chicks often grow more quickly and have lower feed conversion ratio (FCR) than their CV counterparts but may be less resilient to external stress and have a compromised immunological maturation rate. This review will summarize the literature on GF animal research with a special emphasis on poultry. The objective of the review is to establish a frame of reference to understand the extent of the role of the microbiome in animal health, welfare, nutrition, and growth, to provide opportunities for targeted modulation of the microbiome to achieve desired phenotypic responses whilst simultaneously minimizing unintended collateral effects.

A time-lagged association between the gut microbiome, nestling weight and nestling survival in wild great tits

Natal body mass is a key predictor of viability and fitness in many animals. While variation in body mass and therefore juvenile viability may be explained by genetic and environmental factors, emerging evidence points to the gut microbiota as an important factor influencing host health. The gut microbiota is known to change during development, but it remains unclear whether the microbiome predicts fitness, and if it does, at which developmental stage it affects fitness traits. We collected data on two traits associated with fitness in wild nestling great tits Parus major: weight and survival to fledging. We characterised the gut microbiome using 16S rRNA sequencing from nestling faeces and investigated temporal associations between the gut microbiome and fitness traits across development at Day-8 (D8) and Day-15 (D15) post-hatching. We also explored whether particular microbial taxa were 'indicator species' that reflected whether nestlings survived or not. There was no link between mass and microbial diversity on D8 or D15. However, we detected a time-lagged relationship where weight at D15 was negatively associated with the microbial diversity at D8, controlling for weight at D8, therefore reflecting relative weight gain over the intervening period. Indicator species analysis revealed that specificity values were high and fidelity values were low, suggesting that indicator taxa were primarily detected within either the survived or not survived groups, but not always detected in birds that either survived or died. Therefore these indicator taxa may be sufficient, but not necessary for determining either survival or mortality, perhaps owing to functional overlap in microbiota. We highlight that measuring microbiome-fitness relationships at just one time point may be misleading, especially early in life. Instead, microbial-host fitness effects may be best investigated longitudinally to detect critical development windows for key microbiota and host traits associated with neonatal weight. Our findings should inform future hypothesis testing to pinpoint which features of the gut microbial community impact on host fitness, and when during development this occurs. Such confirmatory research will shed light on population level processes and could have the potential to support conservation.

Delivery routes for probiotics: Effects on broiler performance, intestinal morphology and gut microflora

Four delivery routes, via, feed, water, litter and oral gavage, were examined for their efficacy in delivering a novel probiotic of poultry origin, Lactobacillus johnsonii, to broilers. Seven treatments of 6 replicates each were allocated using 336 one-day-old Cobb broiler chicks. The treatments consisted of a basal diet with the probiotic candidate, L. johnsonii, added to the feed, and three treatments with L. johnsonii added to the drinking water, sprayed on the litter, or gavaged orally. In addition, a positive control treatment received the basal diet supplemented with zinc-bacitracin (ZnB, 50 mg/kg). The probiotic strain of L. johnsonii was detected in the ileum of the chicks for all four delivery routes. However, the addition of L. johnsonii as a probiotic candidate did not improve body weight gain, feed intake and feed conversion ratio of broiler chickens raised on litter during the 5-week experimental period regardless of the route of administration. The probiotic treatments, regardless of the routes of delivery, affected (P < 0.05) the pH of the caecal digesta and tended (P = 0.06) to affect the pH of the ileal digesta on d 7, but the effect disappeared as the birds grew older. All probiotic treatments reduced the number of Enterobacteria in the caeca on d 21, and tended (P < 0.054) to reduce it in the ileum and caeca on d 7 and in the ileum on d 21 compared with the controls. The probiotic also tended to increase the number of lactic acid bacteria and lactobacilli in the ileum and caeca on d 7, but this trend was not evident on d 21. The trend appeared most pronounced when the probiotic was delivered orally or via litter. The probiotic also decreased (P < 0.05) the population of Clostridium perfringens rapidly from an early age to d 21 in the caeca, leading to a 3-fold decrease in the number of C. perfringens between d 7 and 21. It also showed that the probiotic treatment presented the lowest number of C. perfringens in the caeca. Delivery of the probiotic through feed, water and litter increased (P < 0.01) the weight of the pancreas on d 21, but the probiotic did not affect other morphometric parameters of the gut. Furthermore, the probiotic did not affect the pH and the concentrations of short chain fatty acids and lactic acid in either the ileum or caeca.

Early intestinal growth and development in poultry

While there are many accepted "facts" within the field of poultry science that are in truth still open for discussion, there is little debate with respect to the tremendous genetic progress that has been made with commercial broilers and turkeys (Havenstein et al., 2003, 2007). When one considers the changes in carcass development in poultry meat strains, these genetic "improvements" have not always been accompanied by correlated changes in other physiological systems and this can predispose some birds to developmental anomalies (i.e. ascites; Pavlidis et al., 2007; Wideman et al., 2013). Over the last decade, there has been increased interest in intestinal growth/health as poultry nutritionists have attempted to adopt new approaches to deal with the broader changes in the overall nutrition landscape. This landscape includes not only the aforementioned genetic changes but also a raft of governmental policies that have focused attention on the environment (phosphorus and nitrogen excretion), consumer pressure on the use of antibiotics, and renewable biofuels with its consequent effects on ingredient costs. Intestinal morphology has become a common research tool for assessing nutritional effects on the intestine but it is only one metric among many that can be used and histological results can often be interpreted in a variety of ways. This study will address the broader body of research on intestinal growth and development in commercial poultry and will attempt to integrate the topics of the intestinal: microbial interface and the role of the intestine as an immune tissue under the broad umbrella of intestinal physiology.

Formulating poultry diets based on their indigestible components

Since it started as an organized economic activity, poultry production has been undergoing an evolution toward the optimization of its feed formulation features. Notably, advances in the knowledge of birds' nutrient requirements have allowed recommendations that are increasingly closer to the needs of the birds. Over time, availability of nutrients and energy has been incorporated into those recommendations, especially to compensate for the variability in the digestibility of nutrients originating from variable feed ingredient sources. Instead of using the total energy and nutrient content, current tables of nutrient recommendations provide an estimate of the digestible fractions of the nutrients in ingredients. For instance, nonphytate P is preferred instead of total P to account for the unavailable phytate P, and digestible amino acids to account for the differences in digestibility of amino acids in different ingredients, whereas energy is usually expressed as a proportion that has been digested and metabolized (AME). With the increasing interest in the use of exogenous enzymes in poultry feeds, special attention is directed to the feed substrates such that an added enzyme can match it, forming an enzyme-substrate complex that will be followed by a chemical reaction within the gastrointestinal tract. As a consequence of a degradation reaction, nutrients released can be absorbed and metabolized. In general, nutritional data banks used in linear feed formulation software have limited data on the proportions of fractions of ingredients that are indigestible. Therefore, estimations of the presence of many substrates in the feeds, and therefore the benefits of adding exogenous enzymes, are frequently limited because of the scarcity of adequate information. The objective of this review paper is to provide insights into the use of expanded nutrient databanks to include all the molecules considered potentially indigestible for poultry such that the inclusion of exogenous enzymes allows the estimation of the values of the product originated by their hydrolysis.

Effect of viscosity on digestion of nutrients in conventional and germ-free chicks

A study was conducted with conventional and germ-free broiler chicks to obtain more information on the role of the intestinal microflora in the anti-nutritive effects of NSP in broiler chicks. As the NSP source, highly methylated citrus pectin (HMC) was used at a dose level of 30 g/kg in a maize-based diet. The diets fed to the germ-free chicks were γ-irradiated, whereas those fed to the conventional chicks were not. Feeding the HMC diet to conventional birds depressed weight gain and food utilization (P < 0·05), whereas in germ-free birds only weight gain was reduced (P < 0·05). Feeding the HMC diet to conventional birds reduced digestibilities of energy and starch at the end of the jejunum. Ileal digestibilities of starch and energy were not strongly affected when birds were fed on the HMC-containing diet. Faecal digestibilities of organic matter, crude fat, starch and amino acids, N retention and metabolizable energy were reduced when conventional chicks were fed on the HMC diet. Feeding the HMC diet to germ-free birds hardly affected faecal digestibility of nutrients and N retention, whereas metabolizable energy was increased. Feeding the HMC diet to conventional or germ-free birds increased the viscosity of the digesta in the small intestine. This increase in digesta viscosity was more pronounced in conventional than in germ-free birds. The pH of ileal digesta was reduced when HMC was added to the diet of conventional chicks, but not in germ-free chicks. Feeding the HMC diet to conventional birds markedly affected morphology of the gut wall, whereas in germ-free chicks very little effect was found on gut morphology. Based on the results of the present study, it is concluded that the gastrointestinal microflora mediates the magnitude of the anti-nutritive effects of HMC in broiler chicks. However, the exact role of the microflora in chicks in the magnitude of the anti-nutritional effects of HMC could not be derived from the present study, since the results might have been influenced by γ-irradiation of the diets fed to the germ-free chicks.

Mucin dynamics and microbial populations in chicken small intestine are changed by dietary probiotic and antibiotic growth promoter supplementation

The mucous layer that covers the intestinal absorptive surface acts as a barrier against bacterial translocation. The chicken gut contains a diverse bacterial population which interacts with the mucous layer. In this report, we studied the effect of changing the intestinal microbial populations on mucin dynamics by feeding 1-d-old chicks a control diet or that diet containing either antibiotic growth promoter (AGP) or a probiotic product for 14 d. Dietary AGP increased the proportions of Bifidobacterium species in the duodenum compared with the other groups. In AGP-fed chicks, the villous surface area was increased in the jejunum, goblet cell density was greater in the jejunum and ileum, and mucin glycoprotein levels in the duodenum were lower than in the other groups (P < 0.05). Feeding AGP increased the expression of mucin mRNA in the jejunum and ileum compared with controls. The dietary probiotic increased the proportion of Lactobacillus species in the ileum compared with the controls (P < 0.05) and significantly enlarged the goblet cell "cup" area throughout the small intestine compared with the other groups. Expression of mucin mRNA and the levels of mucin glycoprotein were greater in the jejunum of the probiotic-fed chicks compared with controls (P < 0.05). Neither the probiotic nor AGP treatments affected the thickness of the mucous adherent layer. These results indicate that both probiotic and AGP altered processes of mucin biosynthesis and/or degradation mediated via changes in the intestinal bacterial populations. These modifications in mucin dynamics influence gut function and health and may change nutrient uptake.

Effects of mushroom and herb polysaccharides, as alternatives for an antibiotic, on the cecal microbial ecosystem in broiler chickens

An in vivo experiment was conducted to study the potential prebiotic effects of mushroom and herb polysaccharide extracts, Lentinus edodes extract (LenE), Tremella fuciformis extract, and Astragalus membranaceus Radix extract, on chicken growth and the cecal microbial ecosystem, as compared with the antibiotic Apramycin (APR). This investigation was carried out in terms of a dose-response study. The chickens were naturally infected with avian Mycoplasma gallisepticum prior to the experiment. The BW gain, cecal pH, viscosity, and predominant microbial populations were measured 1 wk after the extract and APR treatments. The extracts and APR significantly stimulated growth of the chickens infected with avian Mycoplasma gallisepticum. The average BW gain of the groups fed with the extracts was significantly lower than that of the antibiotic group. The extracts had no significant effect on cecal pH. However, cecal viscosity and microbial populations were significantly affected by feeding extracts and antibiotic. In contrast to APR, the extracts stimulated the number of the potentially beneficial bacteria (bifidobacteria and lactobacilli), while reducing the number of the potentially harmful bacteria (Bacteroides spp. and Escherichia coli). Of the 3 extracts, LenE was associated with the most cecal bifidobacteria and lactobacilli. With each increase in the LenE dose, birds tended to have higher BW gain and total aerobe and anaerobe counts. Numbers of predominant cecal bacteria, in particular, E. coli, bifidobacteria, and lactobacilli, were significantly increased with increases in the LenE dose. It would seem that these specific mushroom and herb polysaccharide extracts hold some promise as potential modifiers of intestinal microbiota in diseased chickens.

Xylanase and beta-glucanase supplementation improve conjugated bile acid fraction in intestinal contents and increase villus size of small intestine wall in broiler chickens fed a rye-based diet

This study was performed with growing chickens (4 to 22 d of age) to evaluate the effects of feeding a rye-based diet supplemented with commercial enzyme preparation containing xylanase and beta-glucanase (Quatrazyme HP, Nutri-Tomen, France) on small intestine wall morphology, bile acid composition, nutrient digestibility, and bird performance compared with unsupplemented rye- or corn-based diets. The rye-based diet decreased (P < or = 0.05) weight gain, feed intake, and feed efficiency and increased water intake compared with the corn-based diet. Moreover, rye consumption reduced crude fat and protein digestibility as well as apparent metabolizable energy (P < or = 0.05). The small intestine wall showed that villus length, width, and surface were decreased in broiler chickens fed the rye-based diet compared with those fed the corn-based diet. However, crypt morphometry parameters were not affected by diet type. The concentration of conjugated bile acids in the small intestine contents of broiler chickens fed the rye-based diet was decreased (P < or = 0.05) compared with those fed the corn-based diet. These findings suggest that feeding a rye-based diet reduces villus capacity for nutrient absorption and bile acid capacity for fat solubilization and emulsification, resulting in decreased bird performance. The addition of xylanase and beta-glucanase to the rye-based diet improved (P < or = 0.05) weight gain, feed intake, and feed efficiency, and decreased water intake. The digestibility of nutrients and apparent metabolizable energy were also increased (P < or = 0.05). Addition of xylanase and beta-glucanase increased (P < or = 0.05) villus size and the villus height-to-crypt depth ratio, as well as the concentration of conjugated bile acids (P < or = 0.05) in the small intestine contents. Exogenous enzymes improved nutrient digestibility and broiler chicken performance, probably by improving the absorption capacity ofthe small intestine through increased villus surface and intestinal concentration of conjugated bile acids.

Bacterial responses to different dietary cereal types and xylanase supplementation in the intestine of broiler chicken

Several studies were carried out to investigate the influence of dietary cereals differing in soluble non starch polysaccharides (NSP) content and a xylanase preparation on selected bacterial parameters in the small intestine of broiler chicken. Compared to a maize diet colony forming units (CFU) of mucosa associated bacteria were higher in a wheat/rye diet, most notably for enterobacteria and enterococci. Xylanase supplementation to the wheat/rye diet generally led to lower CFU, especially in the first week of life. However, xylanase supplementation also displayed higher in vitro growth potentials for enterobacteria and enterococci. Bacterial growth of luminal samples in minimal media supplemented with selected NSP showed that the wheat/rye diet enhanced bacterial capacities to utilize NSP only in ileal samples. The xylanase application generally shifted respective maximum growth to the proximal part of the small intestine. The presence of soluble NSP from wheat or rye in the diet per se did not enhance bacterial NSP hydrolyzing enzyme activities in the small intestine, but xylanase supplementation resulted in higher 1,3-1,4-beta-glucanase activity. Compared to a maize diet the activity of bacterial bile salt hydrolases in samples of the small intestine was not increased due to inclusion of wheat/rye or triticale to the diet. However, xylanase supplementation led to a reduction with a corresponding increase of lipase activity. It was concluded that dietary cereals producing high intestinal viscosities lead to increased overall bacterial activity in the small intestine. The supplementation of a xylanase to cereal based diets producing high intestinal viscosity, changes composition and metabolic potential of bacterial populations and may specifically influence fat absorption in young animals.

Effect of wheat content, fat source and enzyme supplementation on diet metabolisability and broiler performance

1. A 3x3x2 factorial experiment studied the interactions of fat source (tallow, soya, tallow:soya [2:1] blend), wheat level (700, 350, 0 g/kg) and enzyme inclusion (Avizyme 1300, absent, present) in diets for broilers fed ad libitum in individual cages from 7 to 35d. Bird performance, fat digestibility, viscosity of ileal contents and diet metabolisability (AME) were measured. 2. There were no significant effects of fat source on bird performance. However, there was a significant effect on fat digestibility, which was highest for soya and lowest for tallow. Diet AME content was also significantly affected by fat source and reflected differences in fat digestibility. 3. Dry matter (DM) intake, liveweight gain (LWG) and gain:food were all reduced at 700 g wheat/kg. Viscosity of ileal contents increased with increasing wheat inclusion. 4. There were no significant effects of enzyme on DM intake or LWG but gain:food was improved by 2%. Diet AME content was increased with enzyme addition, the effect being greatest (9%) with tallow at 700 g wheat/kg. 5. Viscosity of ileal contents was reduced and fat digestibility increased with enzyme addition and there were significant wheat enzyme interactions attributable to no differences with zero wheat but marked responses to enzyme at 700 g wheat/kg. 6. The results confirm important interactions between wheat content and fat composition in relation to fat digestibility, AME content and food efficiency.

The effects of adding xylanase, vitamin C and copper sulphate to wheat-based diets on broiler performance

1. The study used a 3 x 3 factorial design to evaluate the effects of 3 additives (none; vitamin C [250 mg/kg]; copper sulphate [250 mg/kg]) and 3 enzyme additions (none; Avizyme 1300 [Finnfeeds Ltd, 1 g/kg in food]; Avizyme 1310 [liquid spray, post-pelleting, 0.5 g/kg]). All experimental diets were mixed, heat-conditioned (80 degrees C for 2 min) and pelleted. Copper sulphate (diets NCu; DCu; LCu) and Avizyme 1300 (diets DN; DC; DCu) were added during mixing. Vitamin C was sprayed at 10 ml per kg (diets NC; DC; LC) and the liquid enzyme was diluted 20-fold and sprayed at the same rate (diets LN; LC; LCu), post-pelleting. 2. Additive or enzyme addition did not significantly affect DM intake or liveweight gain (LWG). Enzyme addition improved gain:food (P=0.014), AME:GE (P<0.001), ileal apparent digestibility of DM (P=0.008) and starch (P<0.001), faecal apparent digestibility of starch, crude fat and NDF (P=0.008; <0.001; <0.001 respectively) and reduced in vivo viscosity (P<0.001). 3. Copper sulphate addition depressed gain:food (P=0.047), AME:GE (P=0.002), ileal apparent digestibility of starch (P<0.001) and faecal apparent digestibility of starch (P=0.003) and crude fat (P<0.001) due to a negative additive x enzyme interaction when copper sulphate and dry enzyme were included together. 4. Vitamin C decreased in vivo viscosity by 20% but failed to have any effect on performance. Both enzyme forms gave similar improvements in performance in the absence of copper sulphate.

The effect of dietary wheat middlings and enzyme supplementation II: apparent nutrient digestibility, digestive tract size, gut viscosity, and gut morphology in two strains of leghorn hens

An experiment was conducted with two strains of Leghorn hens, DeKalb Delta (D) and Hisex White (H), to investigate the effect of a commercial poultry enzyme preparation (EZ; xylanase plus protease) on the digestibility of protein, fat, Ca, and P and to determine any changes in the relative size of the digestive tract, gut morphology, and gut viscosity (GV) of birds fed wheat middlings (WM) over an 18-wk period. Three hundred birds (150 birds per strain) were randomly assigned to six diets: Diet 1, control (corn-soybean); Diets 2 and 3, 8% and 16% WM, respectively; Diet 4, 8% WM and 0.1% enzyme (EZ); and Diets 5 and 6, 16% WM and 0.1% and 0.2% EZ, respectively. There were five replicates per diet per strain. At 50 wk, protein digestibility increased significantly with supplementation of EZ, but, at 60 wk, all responses were similar. Protein digestibility was greater in DeKalb Deltas for WM with EZ compared with Hisex on the same treatment. Fat digestibility was greater for Diet 1 than the other diets at 50 wk but showed a similar response at 60 wk. The H strain showed a reduction in fat digestibility with WM diets with EZ. The control diet showed greater Ca digestibility than the other diets at 50 wk but did not differ at 60 wk. Phosphorus digestibility increased significantly for WM diets with or without EZ at 60 wk. Intestinal weight was significantly higher for WM with or without EZ at 50 wk, but was equal to the control diet at 60 wk. At 60 wk, gizzard weights (GW) were also lower in birds fed WM and WM with EZ compared with birds fed the control, but GV was not affected by dietary treatments. Histological observations on jejunum of birds fed WM without EZ showed shortening, thickening, and atrophy of the villi, all of which improved when EZ was included in the diet. Availability of some nutrients in WM diets was improved with supplementation of enzyme. Gastrointestinal (GI) tract and organ size were increased, and gut morphology appeared to be improved.

Effects on chick performance and nutrient digestibility of an endo-xylanase added to a wheat- and rye-based diet in relation to fat source

1. A study with growing chicks investigated the effects of an inclusion of an endo-xylanase preparation (LYXASAN) to a wheat- and rye-based diet on performance and nutrient digestibility in relation to the fat source. 2. The basal diet contained 500 g wheat and 100 g rye/kg of diet. The basal diet was supplemented with either 65 g soya oil/kg or 60 g blended animal fat and 5 g soya oil/kg. 3. Endo-xylanase added to the soya oil diet did not affect weight gain, but there was a numerical improvement in food conversion efficiency which was not statistically significant. When the endo-xylanase preparation was added to the blended animal fat diet, both weight gain and food utilisation were improved by 9.5% and 6.0%, respectively (P < 0.05). 4. Digestibilities of organic matter, crude fat, crude fibre and NFE were not significantly affected by adding endo-xylanase to the soya oil diet. However, when endo-xylanase was included in the blended animal fat diet, digestibility of organic matter, crude fat, crude fibre and NFE were improved (P < 0.05). The improvement in fat digestibility was the most pronounced, amounting to 9.4%. Nitrogen retention and metabolisable energy content were improved significantly by the addition of an endo-xylanase to the animal fat diet (P < 0.05), by 6.6% and 6.5% respectively. 5. From the results of this study, it can be concluded that the effects on chick performance and nutrient digestibility of a dietary endo-xylanase in a wheat- and rye-based diet are influenced to a considerable degree by the type of fat in the diet.

Growth, viscosity and beta-glucanase activity of intestinal fluid in broiler chickens fed on barley-based diets with or without exogenous beta-glucanase

1. Three groups of birds were fed for up to 35 days on diets containing 500 g barley (cv. Condor)/kg diet, with or without exogenous beta-glucanase, either a commercial preparation or a recombinant endoglucanase. 2. Birds which received diets containing the exogenous enzymes grew faster for the first 3 weeks but after that there was no apparent difference in rate of growth. 3. beta-Glucanase activities in the crop and small intestine of birds given exogenous enzymes were generally higher than those of birds given only the basal diet. 4. Viscosity of intestinal fluid in birds given only the basal diet decreased with age but there was no corresponding increase in beta-glucanase activity. This discounts bacterial beta-glucanase as a contributory factor in the adaptation to beta-glucanase apparent in older birds.

Influence of dietary enzyme complex on the performance of broilers fed on diets with and without antibiotic supplementation

1. The aim of the experiment was to test the possible interactions of an enzyme complex and a food antibiotic on the growth and metabolism, carcase yield, whole body composition and nutrient deposition in broilers. The basal diet contained 400 g/kg barley. The four treatments were as follows: O--without supplements (control), E--enzyme complex Roxazyme G, 200 mg/kg, A--antibiotic avoparcin, 10 mg/kg, EA--Roxazyme G, 200 mg/kg plus avoparcin, 10 mg/kg. 2. Roxazyme G positively influenced weight gain, food conversion efficiency, energy metabolisability, fat and nitrogen utilisation and the dry matter content of droppings. Fat and energy deposition in the whole body were also increased, whereas protein deposition and carcase yield were not influenced. 3. Avoparcin increased energy metabolisability and fat utilisation, but had no influence on nitrogen utilisation. No significant improvements from avoparcin were seen in growth or in nutrient deposition in the body. The fibre degradability (NDF and ADF fraction) was significantly depressed by antibiotic supplementation. 4. The inclusion of both supplements to the diet did not have a fully additive effect on growth, energy metabolisability, or fat and nitrogen utilisation. The interaction between enzyme and antibiotic for food conversion efficiency during the first experimental period (7 to 21 d) was nearly significant (P = 0.053). Except for fibre degradability (P < or = 0.01), no other significant interactions between enzyme and antibiotic were found.

Changes in the transport of 14C-leucine in tissue rings and activity of alkaline phosphatase and (Na+, K+) ATP-ase in mucosa of small intestine in broiler chickens fed on mixtures treated with gamma irradiation

The effect of treating the combined feeds with gamma rays (0.35, 0.7 and 1.0 Mrad) was studied on the transport of 14C-leucine in intestinal rings and activity of alkaline phosphatase and (Na+, K+) ATP-ase in mucosa of small intestine of broiler chicks. It was established that in treating the combined feeds with gamma rays the transport of 14C-leucine increases in intestinal rings, being this effect most significant in treating with 0.35 Mrad. Activity of both alkaline phosphatase and (Na+, K+) ATP-ase in intestinal mucosa increases on feeding combined feeds treated with 0.35 Mrad, remains unchanged with 0.7 Mrad and decreases significantly with 1.0 Mrad.

Gnotobiotes in nutritional studies

Studies with gnotobiotic animals have demonstrated extensive synthesis of vitamins, involvement in the metabolism of nitrogenous compounds and modification of lipids among the activities of the conventional microflora. The extent to which they affect the host depends on factors such as the structure of the gut, the position of the sites of bacterial proliferation and the host's nutritional status. Thus the findings in experimental animals may not always be applicable to man. Results so far indicate that in circumstances of dietary inadequacy bacterial activity may be detrimental or beneficial. However, these effects are small, and it seems reasonable to conclude that the influence of the indigenous microflora on the host's nutrition is of relatively minor importance compared with its role as a barrier against invasion by undesirable organisms.

Bile acid deconjugation and attachment of chicken gut bacteria: their possible role in growth depression

Bacteria isolated from the chicken gut were tested for their ability to deconjugate bile acids and attach to chicken epithelial cells (crop squamous cells and duodenal brush borders). Clostridium perfringens, streptococci and some of the bifidobacteria and lactobacilli were able to deconjugate all 4 substrates whereas the bacteroides deconjugated only the taurine conjugates and the coliforms were completely inactive. None of the strains of Escherichia coli or streptococci attached to squamous cells, but the anaerogenic coliform, the strain of Klebsiella aerogenes and the lactobacilli did show attachment. Attachment to brush borders was obtained with the anaerogenic coliforms, K. aerogenes, 2 out of 5 of the lactobacilli, and 4 out of 9 of the streptococci, but none of the strains of E. coli.

Effect of fat retention on the rachitogenic effect of rye fed to broiler chicks

Two experiments were conducted to determine the influence of fat retention on bone mineralization and amino acid retention for broiler chicks fed rye diets containing marginal levels of vitamin D3. In Experiment 1, rye diets containing tallow were supplemented with high vitamin D3, bile salt (sodium taurocholate), or a detergent (sodium lauryl sulphate). Fat retention and tibia ash were improved (P less than .05) with bile salt addition, and tibia ash alone (P less than .05) was improved when high vitamin D3 or the detergent was added to the diet. In Experiment 2, rye diets contained tricaprylin (TC), tristearin (TS), or triolein (TO) as a fat source. Both fat retention (TS less than TO less than TC) and tibia ash (TS less than TC less than TO) showed a significant (P less than .05) treatment effect. The results of both experiments support the hypothesis that the rachitogenic effect of feeding rye may be related to inadequate fat digestion. There was no significant treatment effect on amino acid retention in either experiment. A third experiment indicated a similar bile acid pool size for chicks fed rye as opposed to wheat; however, bile acid concentration of jejunal fluid was lower (P less than .05) for chicks fed rye. A possible microbial involvement in the disturbance of bile acid metabolism was indicated by the capacity of Streptococcus organisms derived from chick small bowel to degrade sodium taurocholate.

Effects of diet, bacitracin, and body weight restrictions on the intestine of broiler chicks

Six experiments were conducted to evaluate the effects of diet, bacitracin, and body weight restrictions on the intestine of the broiler chick. Bacitracin, at levels of 11 and 55 ppm, significantly increased body weight, significantly reduced small intestine weight, but had no significant effect on liver weight of chicks fed a soybean protein and sucrose-based diet. The greatest effects were observed in the ileum where weight, moisture, length per unit of body weight, and dry matter per unit of length were all significantly reduced. The least effects were observed in the duodenum where weight and length per unit of body weight were significantly reduced and dry matter per unit of length was significantly increased. Intestinal weight, as a percent of body weight, was not significantly affected when body weight was suppressed with a high level of nicarbazin added to a practical diet, but it was significantly reduced when bacitracin was added to the semipurified diet and chicks were restricted in food intake to 70% of controls. A level of 55 ppm of bacitracin added to the practical diet had no significant effect on body weight, intestinal weight, or liver weight. As discussed, the observed changes in the intestine, due to bacitracin, are probably indirect and most likely reflect the action of the antibiotic on the intestinal microflora.

Utilisation of rye by chickens: effect of microbial status, diet gamma irradiation and sodium taurocholate supplementation

Several experiments were conducted to determine the influence of intestinal microflora when rye diets are fed to young chicks. In a conventional environment dietary rye severely depressed growth, amino acid and fat retention, and metatarsal bone ash. These conditions could be effectively alleviated by gamma irradiation of the diet and maintenance in a germ-free environment. In gnotobiotic chicks associated with streptococci dietary rye caused effects similar to those seen in a conventional environment, however the responses were less severe. Since addition of sodium taurocholate improved fat retention from a rye diet to a greater extent than from a wheat diet, a deficiency of conjugated bile salts might contribute to the steatorrhea observed in rye-fed chicks.