Taxons of chicken cecum microbiom are abundant, and influenced by the combined feed composition and decreased metabolizable energy

Currently the processed sunflower products as the cheapest source of vegetable protein are considered an alternative to soybean cake and meal in the poultry diet. However, in sunflower meal the energy value is lower, lysine rate is less than required, and the level of non-starch polysaccharides not digestible in poultry gut because of absence of specific enzymes (i.e., amylases, cellulases, etc.) are rather high. Digestion of these components is possible due to microbial enzymes. Gut content is detained in the poultry caecum for the longest time, wherein the basic processes of microbial proteolysis, and cellulose and starch destruction are performed. Using modern molecular methods of NGS-sequence analysis and real-time PCR, we investigated the number of bacteria and the structure of bacterial community in cecum of 36-day-old Cobb 500 broiler chickens fed with diets containing soybean meal or sunflower meal. Contrary to traditional view, the composition of caecum microbiom was very abundant and divers, and included the obligate gut microflora ( Clostridiaceae, Eubacteriaceae, Lactobacillaceae, Bacteroidetes ) and non-identified taxons. Moreover, the typical gut microorganisms (i.e., enterococcus, bifidobacterium) were minor and the pathogenic bacteria of genera Camphylobacter sp., Staphylocoссus sp. were not detected. Our results first characterized in detail the caecum microbiome as influenced by the combined factors such as specific composition and decreased metabolizable energy in feed. This study showed that the feed containing 25 % sunflower meal caused a 14.7-fold increase in total number of bacteria while the number of phylum Bacteroides amylolytics was 1.4-times lower, the family Clostridiaceae was 1.2-times less abundant and the cellulosolytics families Ruminococcaceae and Lachnospiraceae were 1.16-times and 1.48-times depressed, respectively, thus indicating limitations in the metabolism of hydrolysable components and cellulose in the poultry gut. Moreover, the obligate bacterial intestinal flora changed in number. Particularly, there were a 3.04-fold increase in genera Lactobacillus sp., a 1.5-fold increase in order Bacillales, 3-fold decrease in genera Bifidobacterium sp. and 10-fold decrease in genera Enterococcus sp. Also the bacterial number in genera Escherichia sp. was found to be 55-fold lower, and families Sutterellaceae and Erysipelotrichaceae, including species that might cause disbiotic diseases, were depressed 2.5 times and 1.8 times, respectively. Moreover, our research showed that the changes in the cecum bacterial community due to the sunflower meal containing feed depressed the chickens' performance. Thus, the weight of 36-day-old chickens (males and females) was the highest in the control group not fed with sunflower meal (2142.0±45.40 g) compared to the experimental poultry (2017.0±53.30 g) in which the feed consumption increased by 13 %.