Poultry

Bacterial colonization of the intestinal tract of poultry occurs after hatching when the young bird starts to receive the feed. The esophagus of gallinaceous poultry creates the crop, which serve as a store of the feed. The ingested feed in the crop is softened by water and by secretion of salivary glands and the glands of esophagus. In water poultry, the esophagus is able to widen throughout its length. The gastric juice produced in the gizzard helps in chemical digestion of the feed. The gut of poultry is short and the caecum is doubled. Soft feed passes through the digestive tract very fast (2 to 4 hours), crude feed takes much longer (up to 20 hours). The poultry should be fed with feed of high nutritive value due to the shortness and fast transit time of the intestinal content.

Lactobacillus microbiota lining the crop of the chicken gastrointestinal tract becomes established within a few days after hatching and the specific adherence of avian associated lactobacilli onto the crop epithelium plays a role in the colonization (24). From the third day of life, large numbers of lactobacilli are present throughout the alimentary tract (25). Recent research showed that freshly isolated lactobacilli from chickens are able to adhere to the epithelium of crop, as well as to the follicle-associated epithelium and the apical surface of mature enterocytes of intestinal villi (26).

Enterobacteriaceae and enterococci are present in large numbers in 3-day-old broilers but they start to decrease with the age. Lactobacilli, however, remain stable during the growth of broilers. The presence of volatile fatty acids is responsible for the reduction of Enterobacteriaceae in the broiler chicken. The amounts of acetate, butyrate and propionate increase from undetectable amounts in 1-day-old broilers to high concentrations in 15-day-old broilers (27). Facultative anaerobic microbiota (streptococci, lactobacilli and E. coli) comprise the predominant microbiota of the small intestine and Salanitro and coworkers (28) found that the above-mentioned bacteria represent 60-90% of the isolated bacteria. While the number of aerobic and anaerobic bacteria in duodenum and ileum were in their study very similar, they found 1011 anaerobic bacteria per g of dry tissue in the caecum and the latter exceeded aerobe plate count by at least a factor 100. The use of anaerobic methods developed for rumen bacteria have shown that the dominant microbiota of the caecum is composed of strict anaerobes and the most frequently isolated genera were Eubacterium, Clostridium, Fusobacterium, Bacteroides, Bifidobacterium, Peptostreptococcus, and Lactobacillus (28,29). Scanning electron microscopy of the intestinal epithelia of 14-day-old chickens revealed populations of microbes on the duodenal, ileal and caecal mucosa surfaces (28).

The study of intestinal microbiota composition has relied almost exclusively on the quantitative cultivation of microbes from samples. Culture results obtained in these studies compose between 50 and 80% of total microscopic counts (30). Culture-based techniques can be very selective, but never capture the total microbial community of complex anaerobic habitats such as the avian gastrointestinal tract. Apajalahti and coworkers (31) analyzed broiler chickens from eight commercial farms in Southern Finland for the structure of their gastrointestinal microbial community by a non-selective DNA-based method, percent G + C-based profiling and, in addition, a phylogenetic 16S rRNA gene-based study was carried out to aid interpretation of the percent G + C profiles. Most of the

16S rRNA sequences found could not be assigned to any previously known bacterial genus or they represented an unknown species of one of the taxonomically heterogeneous genera such as Clostridium, Bacteroides and Eubacterium. Bacteria related to ruminococci and streptococci were the most abundant members observed. The source of the feed and feed amendment changed the bacterial profile significantly.

Pregnancy And Childbirth

Pregnancy And Childbirth

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