Metagenomic analysis of intestinal microbiome and biochemical composition of broiler meat upon use of Quercus cortex extract dietary additive

Today, the use of antibiotics in veterinary medicine, as well as growth stimulants in animal husbandry, is considered the main reason for the development of bacterial resistance to antibiotics. Plant-based water extracts can provide simple new approaches to control pathogenic bacteria. Active search for natural alternative sources of antimicrobials, including wild plants, are almost unlimited source of phytochemicals. Plant-based water extracts can also provide simple new approaches to controlling pathogenic bacteria. Some authors suggest that an increase in broiler growth after adding active components of plants may be associated with an improvement in the microbial composition of the intestine and metabolic function. Other plant substances can improve the profile of unsaturated fatty acids and amino acids in meat. Thus, in order to get a more complete picture of the potential use of plant extracts for the prevention or control of bacterial infections, the most significant studies concern the evaluation of the activity of plant extracts in relation to the quality of products and the intestinal microbiome of farm animals and poultry. The aim of our experiment was to study the effect of Quercus cortex extract on biochemical composition of broiler chicken meat and intestinal microbiomes. The studies were carried out with Smena 8 broiler chickens (the Common Use Center for the scientific equipment of the BST RAS, in 2019). In the experiment, 120 broiler chickens aged 7-day were randomly assigned to 4 groups ( n = 30 each, in 4 repetitions). The control broilers were fed the Basic Diet (BD); group I - BD + Quercus cortex extract 1 (1 ml/kg lw); group II - BD + Quercus cortex extract 2 (2 ml/kg lw); group III - BD + Quercus cortex extract 3 (3 ml/kg lw). Analysis of chemical composition of broiler chicken meat showed that the additional inclusion of oak bark extract at a dose of 1 ml/kg of live weight in the diet of the studied poultry helps to improve the quality of meat due to a 27.3 % (р ≤ 0.01) increase in moisture, crude protein and ash, while reducing the level of crude fat. The dietary oak bark extract contributed to an increase in the amount of essential amino acids, for lysine by 1.63-3.43 % (p ≤ 0,01, for leucine-isoleucine by 2.20-5.00 % (p ≤ 0.05), for methionine by 0.55-1.93 % (p ≤ 0.05), for valine by 1.06-1.95 % (p ≤ 0.05), for phenylalanine (group I and II) by 0.45 % and 1.14 %, respectively (p ≤ 0.05), for threonine (group I and II) by 1.07 % (p ≤ 0.05) and 1.82 % (p ≤ 0.01). Levels of non-essential amino acids in the pectoral muscles of broiler chickens compared to control also changed, with the maximum observed for a dosage of 2 ml/kg lw of oak bark extract. The content of unsaturated fatty acids in groups I and III increased compared to the control (for palmitoleic acid by 1.00 and 0.70 %, respectively, p ≤ 0.05). Different dosages of dietary Quercus cortex extract have a significant effect on microbiota of the blind intestine. Changes affect phyla Firmicutes and Bacteroidetes , involved in metabolic energy resorption and degradation of proteins and polysaccharides. The abundance of phylum Bacteroidetes increased 3.96-fold and 2.10-fold in groups I and III compared to the control (p ≤ 0.05), while in group II these bacteria were not found. The number of members of Firmicutes phylum decreased 3.60-fold and 1.47-fold (in groups I and III vs. the control, p ≤ 0.05) while increased 1.26 times in group II vs. the control, p ≤ 0.05 ) Thus, broilers fed 1-3 ml/kg dietary Quercus cortex extract were superior to other birds in terms of amino acid and unsaturated fatty acid levels in carcass due intensification of digestion in intestine, which improves consumer quality of meat.