The Role of Supplementing a Complex Phytobiotic Feed Additive Containing (Castanea sativa mill) Extract in Combination with Calcium Butyrate, Zinc–Methionine and Essential Oils on Growth Indicators, Blood Profile and Carcass Quality of Broiler Chickens

SIMPLE SUMMARY: Environmental microorganisms are always present in poultry farming and may be associated with a high concentration of organic dust, microorganisms in feces, litter, dust and air, as well as the release of volatile odorous compounds, feathers, dandruff (skin material), mites, bacteria, fungi and fungal spores and endotoxins, depending on the type of bird and stages of the production cycle. Moreover, highly productive poultry raised on private farms always have a lower level of immunity compared to backyard poultry flocks. This is due to high productivity, forage stresses during rearing, cohesive plantings and extensive contact between individuals; all these are the result of a decrease in productivity and, possibly, the development of infectious diseases. However, the use of antibacterial drugs for the prevention and treatment of infectious diseases is associated with a number of undesirable risks, the main of which are the contamination of poultry products and the development of resistance of microorganisms to antibiotics. Thus, we assume that plant-based extracts and phytobiotics used as feed additives can be used as alternatives to antibiotics and can definitely affect the productivity, health and product quality of broiler chickens. The complex phytobiotic feed additives (CPFA) contain the following: tannins, eugenol, cinnamon aldehyde, zinc–methionine, calcium butyrate, silicon dioxide and dextrose. ABSTRACT: The purpose of this study was to determine the level of application and effectiveness of the use of vegetable feed additives from complex phytobiotic feed additives (CPFA) in the diets of broiler chickens, as well as their effects on growth indicators, carcass characters and blood profile. A total of 258 Ross 308 chicks were divided into six dietary regimens, including: a basal diet without additives as a first control group (CON); the second group received a basal diet supplemented with 200 g/t in the starter phase and 100 g/t in the grower and finisher phase; the third group—400 g/t and 200 g/t; the fourth group—600 g/t and 300 g/t; the fifth group—800 g/t and 400 g/t; and the sixth group—1000 g/t and 500 g/t of a complex phytobiotic supplement based on tannins, respectively. The CPFA contains the following: tannins 36.8–55.2%, eugenol 0.4–0.6%, cinnamon aldehyde 0.8–1.2%, zinc–methionine 1.6–2.4%, calcium butyrate 8–12%, silicon dioxide 1.2–1.8% and dextrose up to 100%. The maximum introduction of phytobiotics (1000 g/t) at 7 days of age leads to a decrease in the live weight of broilers which reduced by 8.27% (p < 0.05) compared to the minimum level of phytobiotics (200 g/t). From 15–21 days, the live weight was significant between the supplemented and control groups and represented 396.21, 384.81 and 384.16 vs. 316.91 g for the CPFA 4, CPFA 5, CPFA 1 and control group, respectively. Furthermore, the same trend was recorded in the average daily gain during the periods between 15–21 and 22–28 days of the experiment. Feeding CPFA had a positive effect on the carcass indicators, except for the feeding of CPFA 3 in the amount of 600 g/t in the starter phase and 300 g/t in the grower and finish phases, which recorded the lowest weight in relation to the CPFA 1 and 2 groups and represented 1309.58 vs. 1460.06 and 1456.52 g, respectively, and the difference was significant. The inclusion of CPFA in poultry diets contributed to an increase in lung mass in the experimental groups relative to the control group, except for the CPFA 5 group which represented the lowest weight of lung mass (6.51 g) and the differences were significant between the CPFA 2 and CPFA 3 and the control groups. The highest concentration of leukocytes was observed during the experiment period in the group of poultry receiving phytobiotics (CPFA 3), which significantly exceeded the control group by 2.37 × 109/L. A significant decrease in the level of cholesterol was recorded in the CPFA groups when compared to the control group and represented 2.83 vs. 3.55 mmol/L, respectively. Consequently, the introduction of vegetable feed additives from complex phytobiotic feed additives (CPFA) in the diets of Ross 308 chicks had a positive effect on the growth production, the carcass yield, the mass of the pectoral muscles and the mass of the lungs. Moreover, it did not cause a harmful effect on the biochemical parameters of the blood.