Differences in intestinal mucin dynamics between germ-free and conventionally reared chickens after mannan-oligosaccharide supplementation.

A germ-free (GF) chicken model was used to test 2 hypotheses: 1. microbial colonization of the gastrointestinal tract (GIT) influences mucin gene expression and mucin types; and 2. mannan oligosaccharide (MOS) supplementation affects GIT cells directly, without bacteria mediation, compared with bacterial-mediated effect (i.e., indirectly). Gnotobiotic isolators were used: 1) GF, 2) with a single bacteria population, and 3) conventionalized by exposure to cecal bacterial contents. Each was divided to 2 diet groups: with or without MOS (2 kg/t) for 1 wk. Results show that the absence of bacteria in the GIT caused a reduction in neutral and acidic goblet cell (GC) number and density, an increase in sulfated mucin, absence of sialylated GC, and reduced mucin 2 mRNA expression in the small intestine of GF compared with conventional birds. These results indicate a reduced development of mucin production and secretion in the absence of GIT bacteria implying a less mature small intestine mucosa, supporting our first hypothesis. Results from the single bacteria population group were not conclusive and did not support any of the hypotheses. Supplementation of MOS, regardless of microbial presence, caused a reduction in neutral GC number and density but increased neutral GC area. The MOS caused different effects on acidic mucins in conventional and GF birds, causing a reduction in sialylated GC number (conventional) and a reduction in sulfated GC density (GF), all supporting a direct effect of MOS in GF animals, in addition to an indirect effect via gut microflora.

The effect of in ovo administration of mannan oligosaccharide on small intestine development during the pre- and posthatch periods in chickens.

Early intestinal development is essential for chicken embryos to fulfill their maximal growth potential. Mannan oligosaccharide (MOS) is known to improve gut morphology, function, and innate immunity; therefore, we hypothesized that its administration in the prehatch period to the sterile intestine of embryos would affect intestinal development and functionality without mediation of gut microflora. The MOS was administered by in ovo feeding procedure to embryos 3 d before hatch. the effects of MOS administration on intestinal morphology, activity of the brush-border enzymes amino peptidase (AP) and sucrase isomaltase (SI) and mRNA abundance of AP, SI, sodium-dependent glucose cotransporter 1 (SGLT1), peptide transporter 1 (PepT1), secreted mucin (MUC2), and toll-like receptors (TLR2 and TLR4) were examined and compared with saline-injected and noninjected controls. Results show that on embryonic d 20 the only parameter affected was MUC2 mRNA abundance, which exhibited a 3-fold increase in the MOS group versus controls. On day of hatch more parameters were affected: a 20 to 32% increase in villus area was found in the MOS group compared with controls; crypt depth and number of goblet cells per villus were higher by 20 and 50%, respectively, compared with the saline group; and AP and SI activities were higher by 44 and 36%, respectively, compared with the noninjected control. In addition, an increase in fold change mRNA abundance of AP, SI, and TLR4 was observed in the MOS group compared with controls. However, on d 3 posthatch, a decrease in MOS effects was noted, indicating a temporally limited effect after administration of 1 dose. In ovo administration of MOS prehatch resulted in a hatching chick with more mature enterocytes and enhanced epithelial barrier and digestive and absorptive capacity at day of hatch. Results imply that the mechanism underlying the observed changes is not mediated through gut microflora but rather involves a direct effect of MOS on intestinal cells.

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.

Microflora ecology of the chicken intestine using 16S ribosomal DNA primers.

The microflora in the gastrointestinal tract of broiler chickens influences digestion, health, and wellbeing. Analysis of chicken gut microflora has been mainly by culture-based methods. Studies using these techniques have been useful for identification and analysis of specific groups of bacteria, however, the use of enrichment medium precludes even relative quantitation of bacterial species. Recent advances in ribosomal DNA-based molecular techniques make it possible to identify different bacterial populations in environmental samples without cultivation. In this study, the intestinal microflora was examined using 16S ribosomal DNA (rDNA) targeted probes from bacterial DNA isolated from intestinal and cecal contents of chickens at 4, 14, and 25 d of age. The ribosomal gene sequence was amplified using PCR with universal primers to determine total bacterial DNA and specific primers directed at 6 bacterial species: Lactobacillus, Bifidobacterium, Salmonella, Campylobacter, Escherichia coli, and Clostridium. The use of universal primers extends these methods to allow determination of relative proportions of different bacterial species. The results indicated that in young chicks the major species present in the small intestines and ceca was Lactobacilli, with a Bifidobacteria population becoming more dominant in the ceca at older age. Clostridium was detected in some segments of the small intestine in young chicks. In older chickens, Salmonella, Campylobacter, and E. coli species were found in the ceca. This study has demonstrated the use of molecular techniques for determining relative proportions of bacterial species and monitoring pathogens in the chick gastrointestinal tract.