Blood indices and immune organs morphological structure of broiler chickens under the influence of different doses of probiotic feed additives

In the development of effective methods of prevention and treatment of poultry today, importance is given to probiotics based on microbial cultures, in particular, lactobacilli, bifidobacteria, yeast, etc. In contrast to antibiotics, the use of probiotics stimulates the immune response of animals, restores the microflora of the gastrointestinal tract, and ensures its optimal ratio. At the same time, livestock products remain safe for the consumer. The purpose of our work was to conduct comparative clinical trials of the efficiency of the probiotic feed additive Probion-forte in terms of productivity, blood indices, and histological structure of immune organs of chicken broilers during fattening. The clinical studies were carried out with broiler chickens of “Cobb-500” cross at the age of 2 days, which were formed into four groups (300 units in each one). In order to determine the efficiency of application, probiotic feed additives were given to chickens in different concentrations during the growing period, together with the main diet. The first group (1st) was given probiotic Probion-forte in the dose of 1 g/kg of feed, the second group (2nd) – Probion-forte in a dose of 0.5 g/kg, the third (3rd) one – a probiotic-analog “Bio plus 2B” in a dose of 0.4 g/kg; the forth (4th) group was a control group – chickens received an essential diet, without adding any feed additives. The compound feed was provided according to norms recommended for the cross “Cobb-500”, considering age. On the 15th, 30th, and 43rd day of the test, 20 units were selected for hematological, pathomorphological and microbiological tests. The productivity of birds of all studied groups was evaluated by the average daily gains, safety, feed conversion, and slaughter output. The stabilized with EDTA chicken blood was used for morphological studies, and blood serum – for biochemical and immunological studies. Comparative clinical studies have shown that adding to the main diet of broiler chickens probiotic feed additive Probion-forte at a dose of 0.5 and 1.0 g/kg throughout the growing period increases the safety and improves feed digestibility, and increases the bird’s European Efficiency Index. Based on the obtained hematological, biochemical, and immunological parameters of blood, it can be argued about the activating effect on the body of broiler chickens probiotic feed additives, namely the intensification of reanimation of free amino acids, which increases the content of the studied metabolites of lipid metabolism, which chickens use as energy and plastic material. Stimulating cellular and humoral protection, nonspecific resistance is established, confirmed by a high level of lysozyme activity in blood serum and significantly higher content of T- and B-lymphocytes, NK-cells, and γ-globulins. The macro- and microscopic structure of the studied immune organs is preserved in all groups of broiler chickens. Compared with the control group, morphometric examination in the immune organs of broiler chickens of the first and second groups revealed an increase in the area and density of lymphoid elements, an increase in the number of plasmablasts and plasma cells, much higher structural and functional capacity of cells, which was reflected at the ultrastructural level. The most significant difference was found in the 1st group of chickens fed with the feed additive Probion-forte at a dose of 1.0 g/kg of feed.