Three broiler feeding trials were investigated in order to identify gut bacteria consistently linked with improvements in bird performance as measured by feed efficiency. Trials were done in various geographic locations and varied in diet composition, broiler breed, and bird age. Gut microbial communities were investigated using microbial profiling. Eight common performance-linked operational taxonomic units (OTUs) were identified within both the ilea (180, 492, and 564-566) and ceca (140-142, 218-220, 284-286, 312, and 482) across trials. OTU 564-566 was associated with lower performance, while OTUs 140-142, 482, and 492 were associated with improved performance. Targeted cloning and sequencing of these eight OTUs revealed that they represented 26 bacterial species or phylotypes which clustered phylogenetically into seven groups related to Lactobacillus spp., Ruminococcaceae, Clostridiales, Gammaproteobacteria, Bacteroidales, Clostridiales/Lachnospiraceae, and unclassified bacteria/clostridia. Where bacteria were identifiable to the phylum level, they belonged predominantly to the Firmicutes, with Bacteroidetes and Proteobacteria also identified. Some of the potential performance-related phylotypes showed high sequence identity with classified bacteria (Lactobacillus salivarius, Lactobacillus aviarius, Lactobacillus crispatus, Faecalibacterium prausnitzii, Escherichia coli, Gallibacterium anatis, Clostridium lactatifermentans, Ruminococcus torques, Bacteroides vulgatus, and Alistipes finegoldii). The 16S rRNA gene sequence information generated will allow quantitative assays to be developed which will enable elucidations of which of these phylotypes are truly performance related. This information could be used to monitor strategies to improve feed efficiency and feed formulation for optimal gut health.Because feed constitutes approximately 70% of the cost of raising broiler chickens (1), the most common measures of bird performance have been linked to weight gain and feed efficiency. Broiler performance is closely linked to the genetics, diet, age, and rearing environment of the bird (1,23,32,54). Genetic selection has largely driven the vast improvements observed in weight gain and feed efficiency in meat chickens over the last 50 years, although a small proportion of these improvements have been attributed to nutrition and other management practices (32). The genetic changes associated with improved weight gain and feed efficiency have also resulted in changes to the gut physiology and gut microbial community composition of birds (44). Diet, age, and environmental factors have also been reported to influence the gut microbiota (43,71,72). Therefore, there appears to be a clear link between bird performance and gut microbiota composition.In medicine, much interest has already focused on the influence of the gut microbiota in human health (35,78) and energy metabolism (73,74,83).

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.Human food-borne disease outbreaks are a public health concern and have economic importance to the food-producing industry. Subclinical Salmonella enterica infections in pig herds are recognized as an important source of human salmonellosis in Denmark (29). A Danish Salmonella surveillance and control program in pig herds and slaughterhouses has been applied nationally since 1995, and the goal is to reduce the Salmonella prevalence in pork meat to 0.5% (23). In year 2002, the incidence of Salmonella-positive carcass samples in Danish slaughterhouses was 1.4% and the corresponding Salmonella prevalence at herd level monitored by serological testing was 3.2% (1).There is a growing awareness that it is only possible to reduce the prevalence of Salmonella in pork, and consequently the number of infections in people consuming pork and pork products, through an integration and cooperation of all sta...

A study was conducted to investigate the effect of the key cereal grains and a microbial enzyme supplement on broiler chicken performance, gut microflora and intestinal function. Ingestion of the barley-based diet was associated with low 28-day body weight, decreased feed intake and high FCR. The supplemental enzyme increased feed intake and weight gain of the chickens on a wheat-based diet. The pH of the gizzard and caecal contents varied with the grain type. Enzyme supplementation reduced ileal viscosity, particularly in birds that received the diet based on wheat. The birds on the barley-based diet had lower ileal digestibility of dry matter, protein and energy than those given maize and sorghum-based diets. The ileal digestibility of starch was increased by enzyme supplementation. Enzyme supplementation increased the number of total anaerobic bacteria in the gizzard of birds fed on sorghum and increased lactobacilli in the gizzard of those fed both sorghum and wheat. The birds fed the sorghum-based diet had the lowest counts of caecal total anaerobic bacteria and lactobacilli. Jejunal villus height and villus:crypt ratio of birds fed the barley-based diet were the lowest when compared with those fed the other diets. Enzyme application induced an increase in villus height and villus:crypt ratio of birds on wheat, crypt depth on barley and a reduction in crypt depth of chickens on the sorghum-based diets. The highest activity of maltase and the lowest activity of sucrase were observed in tissue from birds fed on maize and sorghum-based diets respectively. The differences in the performance of broilers on cereal grains could be explained by changes in intestinal morphology, enzyme activities and gut microflora as well as nutrient digestibility. The improved performance by supplemental enzyme in wheat-fed chickens was associated with beneficial changes in intestinal morphology and digesta viscosity.

1. A study was undertaken to evaluate the effects of mannanoligosaccharide (MOS, Bio-MOS, Alltech Inc.) on the growth performance, energy utilisation, nutrient digestibility and intestinal microflora of birds given a sorghum-wheat based diet. Two MOS levels (1 and 2 g/kg) were included in the diet. 2. Inclusion of MOS at both levels in the diet improved the apparent metabolisable energy (AME) values of the diet. However, these effects were not as pronounced as those of zinc bacitracin (ZnB) treatment. Dietary ZnB also significantly improved the net energy value of the diet. No significant differences between the different levels of MOS were noticed in the growth performance, AME and net energy values of the diet. Compared to the negative control, inclusion of 2 g/kg MOS tended to improve feed conversion efficiency (FCE) in the starter phase. 3. Dietary MOS did not affect the apparent total tract digestibility of nutrients compared to the negative control. In contrast, ZnB significantly improved the protein digestibility and tended to increase the starch digestibility. The addition of MOS reduced the concentration of arabinose in the soluble non-starch polysaccharides (NSP) fraction in the excreta of birds; whereas, the concentrations of individual sugars in the insoluble NSP and free sugar fractions were increased by ZnB. 4. A decrease in the populations of lactobacilli and coliforms in the ileal and caecal lumen was observed for MOS and ZnB treatments. Correspondingly, pH and microbial fermentation in the gut was altered. The addition of MOS tended to reduce the coliform load at the gut mucosa. 5. Results from the current study suggest that MOS can improve the apparent energy utilisation of the diet and tend to improve FCE of birds in the first three posthatch weeks, which may be partly related to the modulatory effects of MOS on the gut microflora.