The gastrointestinal tract is a dynamic ecosystem containing a complex microbial community. In this paper, the indigenous intestinal bacteria and the microbial fermentation profile particularly short chain fatty acids (SCFA), lactate, and ammonia concentrations are reviewed. The intestinal bacterial composition changes with age. The bacterial density of the small intestine increases with age and comprises of lactobacilli, streptococci, enterobacteria, fusobacteria and eubacteria. Strict anaerobes (anaerobic gram-positive cocci, Eubacterium spp., Clostridium spp., Lactobacillus spp., Fusobacterium spp. and Bacteroides) are predominating caecal bacteria in young broilers. Data from culture-based studies showed that bifidobacteria could not be isolated from young birds, but were recovered from four-week-old broilers. Caecal lactobacilli accounted for 1.5-24% of the caecal bacteria. Gene sequencing of caecal DNA extracts showed that the majority of bacteria belonged to Clostridiaceae. Intestinal bacterial community is influenced by the dietary ingredients, nutrient levels and physical structure of feed. SCFA and other metabolic products are affected by diet formulation and age. Additional studies are required to know the bacterial metabolic activities together with the community analysis of the intestinal bacteria. Feed composition and processing have great potential to influence the activities of intestinal bacteria towards a desired direction in order to support animal health, well-being and microbial safety of broiler meat.

SummaryThis study was designed to evaluate the effect of dietary supplementation of prebiotics, mannanoligosaccharides (MOS) and/or probiotics (LBP) on intraepithelial lymphocytes (IEL) count, goblet cells (GC) count and differentiation and intestinal micro-architecture in broilers reared under cyclic heat stress. Day-old broilers (n = 250) were randomly divided into five groups. Fifty birds were reared within the thermoneutral zone (TNZ). Remaining birds were subjected to cyclic heat stress from day 21 to 42 (35°C, 75% RH, 8 h/d). The birds were fed cornsoy-based basal diet or the same diet supplemented with 0.5% MOS (HS-MOS), or 0.1% LBP (HS-LBP), or their combination (HS-SYN). The birds were slaughtered on day 42. Tissue samples were collected from midduodenum, jejunum and ileum, and stained with haematoxylin and eosin or combined Alcian blue and PAS technique. All differences were considered significant at p < 0.05. The IEL count increased in all intestinal segments of the HS group compared with the TNZ group and decreased in all supplemented groups compared with the HS group. Compared with the TNZ, heat stress reduced villus height, crypt depth and surface area in duodenum and ileum, and increased crypt depth in ileum. Villus width decreased in duodenum and jejunum compared with the TNZ group. Supplementation of LBP, MOS and SYN reversed all these changes in duodenum, while only increased villus height and surface area in ileum. In jejunum, the villus height and surface area increased with HS-LBP, and crypt depth increased with HS-MOS. The number of GC containing acid mucins (duodenum and ileum) and mixed mucins (ileum) were increased in the HS compared with the TNZ. Supplementation of MOS, LBP and SYN maintained the enhanced activity of goblet cells. In conclusion, dietary supplementation of MOS and/or LBP may be helpful in alleviating some of the detrimental effects of heat stress on microstructure of the broiler gut.

ObjectiveThis study aimed to examine the effect of sodium butyrate (SB) on growth performance, immune status, organs weights, and microarchitecture of lymphoid organs and small intestine.MethodsA total of 120, 1-d-old broiler chicks were distributed into the following four treatment groups: corn-soy based basal diet (BD) without supplement (control), or the same BD supplemented with 0.1 g/kg zinc bacitracin (ZnB), 0.5 g/kg SB (SB-0.5), or 1.0 g/kg SB (SB-1), respectively. Six birds/group were killed on d-21 and d-35, and samples were collected.ResultsCell-mediated immune response at 48 h post-Phytohemagglutinin-P injection, and antibody titer against Newcastle disease vaccine and sheep red blood cells on d-35 was noted higher (p<0.05) in SB-1 compared to ZnB and control. Lower (p<0.05) feed conversion ratio (FCR) was attained by the supplemented groups. Thymus and spleen weighed more (p<0.05) in SB-1, and bursa registered more (p<0.05) weight in both SB groups compared to control. On d-21, areas of thymus medulla and spleen germinal centers were noted higher (p<0.05) in SB-1 group. The villus height and villus surface area increased (p<0.05) in duodenum and jejunum in both SB groups on d-21, and in SB-1 on d-35, respectively compared to ZnB and control. On d-21, number of goblet cells containing mucins of acidic nature increased (p<0.05) in all the segments of small intestines in SB-1 group compared to control, and on d-35 in ileum compared to other groups.ConclusionIn conclusion, SB improved growth performance and immunity as well as modulated morphology of lymphoid organs and gut mucosa in broiler chickens.

Inulin, a prebiotic, is a fermentable oligosaccharide that may affect the intestinal mucosal architecture and the electrophysiological parameters. The effects of a diet with added inulin were tested on the jejunal morphology and electrogenic transport of Glc and Gln from the jejunal mucosa in broilers. Short-circuit current and transmucosal tissue resistance of jejunal flaps were measured in Ussing chambers. The feeding experiment was carried out in broilers (n = 40) using 1% inulin with an application period of 5 wk. The inulin-containing diet resulted in longer jejunal villi (P < 0.05) and deeper crypts (P < 0.01) than in control birds without affecting villus:crypt depth. Basal short-circuit current value remained unaffected by dietary treatment. Inulin supplementation did not modify the electrogenic transport of Glc and Gln in the jejunal mucosa. The basal value of transmucosal tissue resistance was significantly lower (P < 0.001) in the inulin-fed group compared with the control group. In conclusion, inulin supplementation affected the jejunal mucosal architecture but did not modify the electrogenic transport of Glc and amino acid under present experimental condition.

The gastrointestinal tract commensal microbiome is important for host nutrition, health and immunity. Little information is available regarding the role of these commensals at other mucosal surfaces in poultry. Tracheal mucosal surfaces offer sites for first-line health and immunity promotion in broilers, especially under stress-related conditions. The present study is aimed at elucidating the effects of feed supplementations with mannanoligosaccharides (MOS) prebiotic and a probiotic mixture (PM) on the caecal and tracheal microbiome of broilers kept under chronic heat stress (HS; 35 ± 2°C). Day-old chickens were randomly divided into five treatment groups: thermoneutral control (TN-CONT), HS-CONT, HS-MOS, HS-PM and HS synbiotic (fed MOS and PM). Caecal digesta and tracheal swabs were collected at day 42 and subjected to DNA extraction, followed by polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE) and pyrosequencing. The PCR-DGGE dendrograms revealed significant (49.5% similarity coefficients) differences between caecal and tracheal microbiome. Tracheal microbiome pyrosequencing revealed 9 phyla, 17 classes, 34 orders, 68 families and 125 genera, while 11 phyla, 19 classes, 34 orders, 85 families and 165 genera were identified in caeca. An unweighted UniFrac distance metric revealed a distinct clustering pattern (analysis of similarities, P = 0.007) between caecal and tracheal microbiome. Lactobacillus was the most abundant genus in trachea and caeca and was more abundant in caeca and trachea of HS groups compared with the TN-CONT group. Distinct bacterial clades occupied the caecal and tracheal microbiomes, although some bacterial groups overlapped, demonstrating a core microbiome dominated by Lactobacillus. No positive effects of supplementations were observed on abundance of probiotic bacteria.