Background and Aim: Progressive antibiotic resistance has become the primary threat to public health. The search for alternative substances with similar effects is now a global challenge for poultry farming. The aim of this study was to investigate the action of the probiotic Bacillus cereus (BC) and coumarin (CO) on broiler productivity, biochemical indicators of blood, and muscular and liver tissues. Materials and Methods: The trial of this study included Arbor Acres cross broiler chickens that were grown up to the age of 42 days. The experiment was conducted on 200 broiler chickens divided into four experimental groups of 50 individuals each: The control group received ration without additives (main ration [MR]), the first experimental group received MR+BC, the second received MR+CO, and the third received –MR+BC+CO. A biochemical and hematological analyzer was used to estimate elemental concentrations using inductively coupled plasma mass spectrometry and inductively coupled plasma atomic emission spectrometry. Results: Inclusion of CO and CO+BC in the diet improved growth rates and reduced feed consumption (FC) per kg of live weight gain. Decreased white blood cell count, increased creatinine and triglycerides (CO), changes in aminotransferase and transpeptidase activity, and increases in chemical elements in the liver and pectoral muscles (BC+CO) were observed. The inclusion of BC+CO in the diet contributed to increases in a greater number of chemical elements in the liver (calcium [Ca], K, magnesium, Mn, Si, and Zn) and the pectoral muscles (Ca, Na, Co, Cu, Fe, Mn, Ni, and Zn). Conclusion: The inclusion of CO and CO+BC in the diet improves growth rates and reduces FC in broilers against a background of the absence of mortality during the experiment.

A way to assess the metabolic state of bacteria of rumen microflora cells is the registration of glow kinetics including recombinant strains, which is a reflection of stress states developing in the cell. The experiment evaluated the effect of rumen fluid in combination with probiotic strains and vanillin on the luminescence of a recombinant strain Escherichia coli MG1655 and digestibility of feed. The “in vitro” method with the rumen simulation technique (Rusitec) was used to determine the digestibility of the dry substance of feed. Using the initial sample, the glow level at the 30th minute was recorded at 3,149±145 RLU, which is 32% of the control level. In the presence of rumen fluid (at the concentration of 6.25%), there was observed an improved response by E.coli against Saccharomyces boulardii’s background (by 44%). The use of vanillin in rumen fluid increases the glow level of bacterial cells in the range of concentrations up to 50%, and in combination with probiotic strains, in the range of 25-50 %. In vitro conditions against the background of rumen fluid showed that vanillin in combination with probiotic strains Bifidobacterium longum and Bifidobacterium adolescentis / Lactobacillus acidophilus contributes to an increase in the digestibility of the dry substance of feed.

Background and Aim: As an alternative to natural and chemically synthesized direct-acting bactericides, there has been an increase in the use of plant extracts, which possess a set of phytochemicals with potential for microbial disease control; this is due to the spectrum of secondary metabolites present in extracts, which include phenolic compounds, quinones, flavonoids, alkaloids, terpenoids, and polyacetylenes. The biologically active substances within plant extracts, which perform protective functions for plant tissues, can have ambiguous effects on the animal body. Therefore, the aim of this study was to assess the ability of gamma-octalactone, isolated from Eucalyptus viminalis extract, to inhibit various LuxI/LuxR quorum-sensing (QS) systems in bacteria, and to evaluate its effect on broiler chickens. Materials and Methods: Phytochemical analysis of E. viminalis extract was performed. The ability of gamma-octalactone to inhibit QS was evaluated using four different LuxI/LuxR bacterial test systems. In vivo assessments were performed on one hundred and twenty 7-day-old broiler chickens (Arbor Acres cross), split into four groups of 30 chickens: 1. Control group: Basic diet (BD); 2. experimental Group I: BD + gamma-octalactone at a dosage of 0.05 ml/kg live weight/day; 3. experimental Group II: BD + gamma-octalactone at a dosage of 0.1 ml/kg live weight/day; and 4. experimental Group III: BD + gamma-octalactone at a dosage of 0.2 ml/kg live weight/day. Hematological blood parameters were assessed using an automatic hematological analyzer (URIT-2900 Vet Plus, URIT Medial Electronic Co., China) and an automatic biochemical analyzer (CS-T240, Dirui Industrial Co., Ltd., China). Statistical analyses were performed using SPSS Statistics Version 20 (IBM); averages (M), standard deviations (σ), and standard deviation errors (m) were calculated. Results with p≤0.05 were considered significant. Results: Based on the phytochemical analysis results, libraries of compounds with putative QS inhibitory properties were compiled. Gamma-octalactone exhibited a pronounced inhibitory effect on the LuxI/LuxR QS systems, characterized by EC50 values of 0.15-0.4 mM. In the in vivo portion of this study, broiler chicken live weights increased in all experimental groups, with the most significant increase in Group III (14.0%), in relation to the control group. Blood serum from the experimental group chickens had significantly higher levels of triglycerides and uric acid (p≤0.05), in comparison to the control group chickens. With respect to blood serum enzyme activity and antioxidant status indicators, the experimental group chickens had a higher level of gamma-glutamyl transferase, an enzyme associated with amino acid metabolism, than those in the control group; this increase was especially pronounced in Group III, with 37.0% increase (p≤0.05). Superoxide dismutase and catalase levels were higher in the experimental groups than the control group, corresponding to increases of 30.4-56.2% (p≤0.05), 33.3-83.3%, and 27.9-45.5% (p≤0.05) in Groups I, II, and III (p≤0.05), respectively. Morphological blood parameters did not display significant changes due to gamma-octalactone. Conclusion: According to the results of this in vivo study in broiler chickens, gamma-octalactone, isolated from E. viminalis leaf extract and supplied at a dosage of 0.2 ml/kg live weight/day, led to an increase in the activity of blood plasma digestive enzymes, increased live weight, and had a positive effect on lipid metabolism and antioxidant status.