No abstract

The effects of avilamycin, zinc bacitracin, and flavophospholipol on broiler gut microbial community colonization and bird performance in the first 17 days posthatch were investigated. Significant differences in gut microbiota associated with gut section, dietary treatment, and age were identified by terminal restriction fragment length polymorphism (T-RFLP), although no performance-related differences between dietary treatments were detected. Similar age-related shifts in the gut microbiota were identified regardless of diet but varied between the ilea and ceca. Interbird variabilities in ileal bacterial communities were reduced (3 to 7 days posthatch) in chicks fed with feed containing antimicrobial agents. Avilamycin and flavophospholipol had the most consistent effect on gut microbial communities. Operational taxonomic units (OTU) linked to changes in gut microbiota in birds on antimicrobial-supplemented diets were characterized and identified. Some OTUs could be identified to the species level; however, the majority could be only tentatively classified to the genus, family, order, or domain level.

BBn (BioBreeding) rats were fed casein-based diets supplemented with barley flour, oatmeal flour, cellulose, or barley ␤-glucans of high [HV] or low viscosity [LV] in order to measure the prebiotic effects of these different sources of dietary fiber. The dietary impact on the composition of the cecal microbiota was determined by the generation of denaturing gradient gel electrophoresis (DGGE) profiles of PCR-amplified 16S rRNA gene sequences. The DGGE profiles produced from the cecal microbiota of rats within each dietary group were similar, but consensus profiles generated from pooled bacterial DNAs showed differences between rat groups. Animals fed HV glucans (HV-fed rats) had DGGE consensus profiles that were 30% dissimilar from those of the other rat groups. A 16S rRNA gene fragment that was more conspicuous in the profiles of HV-fed animals than in those of cellulose-fed rats had sequence identity with Lactobacillus acidophilus. Measurements of L. acidophilus rRNA abundance (DNA-RNA hybridization), the preparation of cloned 16S rRNA gene libraries, and the enumeration of Lactobacillus cells (fluorescent in situ hybridization) showed that lactobacilli formed a greater proportion of the cecal microbiota in HV-fed rats. In vitro experiments confirmed that some lactobacilli utilize oligosaccharides (degree of polymerization, 3 or 4) present in ␤-glucan hydrolysates. The results of this study have relevance to the use of purified ␤-glucan products as dietary supplements for human consumption.

The microflora of the crop was investigated throughout the broiler production period (0 to 42 days) using PCR combined with denaturing gradient gel electrophoresis (PCR-DGGE) and selective bacteriological culture of lactobacilli followed by amplified ribosomal DNA restriction analysis (ARDRA). The birds were raised under conditions similar to those used in commercial broiler production. Lactobacilli predominated and attained populations of 10 8 to 10 9 CFU per gram of crop contents. Many of the lactobacilli present in the crop (61.9% of isolates) belonged to species of the Lactobacillus acidophilus group and could not be differentiated by PCR-DGGE. A rapid and simple ARDRA method was developed to distinguish between the members of the L. acidophilus group. HaeIII-ARDRA was used for preliminary identification of isolates in the L. acidophilus group and to identify Lactobacillus reuteri and Lactobacillus salivarius. MseI-ARDRA generated unique patterns for all species of the L. acidophilus group, identifying Lactobacillus crispatus, Lactobacillus johnsonii, and Lactobacillus gallinarum among crop isolates. The results of our study provide comprehensive knowledge of the Lactobacillus microflora in the crops of birds of different ages using nucleic acid-based methods of detection and identification based on current taxonomic criteria.The digestive tracts of mammals and birds are home to a diverse collection of bacterial species, collectively referred to as the gut microflora (28). From gnotobiotic animal studies, the microflora is known to influence the biochemistry, immunology, physiology, and nonspecific resistance to intestinal infection of the host (9). The impact of the gut microflora on the nutritional status of farm animals is of particular interest, especially where intensive farming practices are used (4).The crop, ileum, cecum, and colon of poultry are known to harbor bacterial populations (16,27). Recent reports have investigated the composition of the ileal (13) and cecal (35) microflora using bacteriological culture and culture-independent methods. Lactobacilli are numerous in the ileum of broilers, whereas the cecal microflora is dominated by obligately anaerobic bacteria and bacteria yet to be cultivated. From the results of culture-based studies, it has been determined that the microflora of the crop has a simple composition and is dominated by lactobacilli (16,27). Colonization of the surface of the stratified, squamous epithelium of the crop by lactobacilli has been reported by Fuller (6) and Morishita et al. (18). Lactobacillus salivarius, Lactobacillus fermentum or Lactobacillus reuteri, and Lactobacillus acidophilus were the species most commonly detected (16,27). These studies were conducted prior to the reclassification of L. acidophilus, which has been divided into two DNA homology groups containing six related species (5,11,15). DNA homology group A consists of L. acidophilus (A1), Lactobacillus crispatus (A2), Lactobacillus amylovorus (A3), and Lactobacillus gallinarum (A4); DNA homology gr...