Commercial poultry production growth and the increase in the number of small farms specializing in raising broiler chickens, laying hens, quails, and other poultry contribute to the spread of infectious diseases. Non-compliance with the principles of biosafety during incubation and breeding results in mass deaths of poultry and, consequently, significant economic losses for farmers. Salmonellosis is one of the most dangerous anthropozoonotic diseases of poultry, which is most often registered in private farms. Age analysis of the poultry salmonellosis in the EU countries indicates the infection of adult laying hens most often, young poultry to a lesser extent, and chickens aged up to 10 days less frequently. Although the program for the prevention and elimination of poultry salmonellosis has been approved at the legislative level in Ukraine, monitoring studies are not carefully conducted. This is especially true for private homesteads and small farms, which greatly complicates the epizootiological situation in some regions of the country. The article describes the pathological and histological changes in the liver, heart, lungs, kidneys, and spleen. The changes were detected in chickens aged 10 and 14 days infected with microorganisms of the species Salmonella pullorum. Eggs for incubation were obtained from different family flocks, and incubation was performed in a single incubator. The initial clinical signs of the disease appeared in chickens aged 7 days and included diarrhea, increased water consumption, lameness, mass concentration of chickens near heat sources, nervous phenomena in the form of circle walking, and partial blindness in some cases. The pathological autopsy revealed hepatomegaly with sharp change in the organ colour, diapedetic hemorrhage under Glisson’s capsule, and diffuse miliary necrosis. Greyish-white nodular lesions of the lungs and heart, dystrophic changes in the kidneys, and deposition of uric acid salts in the ureters were also characteristic features. Diffuse coagulation necrosis, massive perivascular infiltration by heterophilic lymphocytes and stasis were observed in the liver. Changes in the heart were characterized by significant infiltration by mononuclear cells and heterophiles, which led to atrophy, necrosis, and replacement of cardiomyocytes by connective tissue cellular elements. Delymphatization and necrosis of the lymph nodes were pronounced in the spleen.

The article presents the results of histological, histochemical searches and histomorphometric indices of villous height, depth of the crypt of the mucous membrane of the duodenum, jejunum and caecum of broiler chickens, fed a feed with probiotic additive «Probion forte» at a dose of 1 g/kg for 42 days in a row. The experiments were carried out on broiler chickens of the «Kobb-500» breed under vivarium conditions. Two experimental groups of broiler chickens were formed, with a body weight of 37–40 g, with 30 heads in each: First group was received feed with the probiotic «Probion forte» at a dose of 1 g/kg, and the second-control group, which was fed the main ration without the addition of any preparation. At 15, 30 and 42 days of the experiment, 10 chicks from each group were withdrawn from the experiment, an autopsy was carried out and samples from the duodenum, jejunum and the i caecum were taken, which were fixed in 10% neutral formalin solution, Carnoua and Buena liquid, followed by paraffin filling. Gisto-cutters were made, stained with hematoxylin-eosin, by Stidman and McManus. For the histological, histochemical, histomorphometric search of the mucous membrane of the duodenum, jejunum and caecum of chickens of the experimental group, It was established that the use of «Probion forte» in a dose of 1 g/kg with food for chicken broilers in the process of growth and development was contributed to: activation of the mitotic and synthesizing functions of cells, active hyperplastic and hypertrophic processes in the structural elements of the mucous membrane of the investigated sections of the intestines of broiler chickens, as a result of which was expressed by an increase in the height of the villi and the depth of the crypts. In the broiler chickens of the experimental group it was most likely increased the height of the villi in the duodenum at 15 and 42 days; in the jejunum, the probable increase in the height of the villi was noted at 15 and 30 days, and in the caecum - at 30 and 42 days of the experiment. At the same time, the height of columnar epitheliocytes, which was located on the villi of the jejunum of animals of the I group, was 31.5 μm and 24.9 μm in control. At the same time, active formation of mucus-like cells of the duodenum, jejunum and caecum, rich in glycosaminoglycans and glycoproteins, has been established, which contributed to the formation of a thick mucosal biofilm. The latter serves as a liquid phase in which the movement of cells is carried out, as well as an important barrier to the action of enzymes, pathogens and conditionally pathogenic microorganisms. An increase in the number of columnar epithelial cells and cello-like cells of the villi of the intestinal mucus was aimed at improving parietal digestion, absorption and enhancement of the protective function.

Liver problems of various etiologies in turkeys have been reported in many countries for the last 20 years. Poultry dies having no clinical manifestations of the disease, and at pathological autopsy, diffuse haemorrhages and marked dystrophic changes of the organ are noted. To date, there are several factors that can cause such changes, these are unbalanced amino-acid feed, insufficient calcium, biotin, selenium, the very high energy content of feed; zootechnical factors – limited mobility of birds due to cage density violations, high temperature; genetic factors – the influence of estrogens; infectious factors – E. coli, Clostridium, and viruses of Picornaviridae family. The article describes the histopathological and ultrastructural changes in the turkey liver under the influence of various factors. The material for the research was obtained from a farm where turkeys of the “Hybrid Converter” cross are grown, same age, fed with a standard diet that changed according to the technological map of cultivation. On the 50th day of life, a pathological autopsy of the dead poultry was performed, pieces of liver were selected for histological and ultrastructural examination. The visual assessment revealed significantly enlarged liver, the colour from dark red to light brown, flabby consistency. In some cases, diffuse fatty infiltrations of hepatocytes were histologically revealed, in other cases, focal necrosis with the growth of the connective tissue and the formation of massive perivascular couplings were registered. Large vacuolar fatty degeneration of hepatocytes with subsequent development of fibrosis indicates chronic intoxication, probably caused by slow breakdown of fatty acids in cells due to insufficient oxidative phosphorylation, as well as reduced levels of lipotropic factors: choline, methionine and the vitamins. At the ultrastructural level, a large number of lipid inclusions of various sizes, dystrophic changes in mitochondria were observed, which indicates a decrease in the synthetic activity of cells.

The article is dedicated to the study of the effect of a class of microorganisms and substances of microbial and other origin that are used in feeding pigs to achieve maximum growth in animal mass, as well as therapeutic purposes. Study of the effect of biologically active additives on the state of the pig's digestive system. The article considers the rational nutrition that increase the productivity and reproductive capacity of animals, and also prevent the emergence of profound disturbances of all metabolic processes which leads to a decrease in resistance to productivity, a clinically pronounced disease of adult animals and young animals. The authors pay attention to the morphometric parameters, ultrastructure and content of nucleic acids in the wall of the duodenum of pigs by forage feeding with the addition of probiotic fodder additive «Probion-forte» in dose of 1 g/kg of fodder. Research were conducted on 28 day pigs, breed «Large White». It was formed two groups of piglets per 30 heads; piglets were fed with standard mixed fodders; piglets from the first group were received standard mixed fodder with the addition of  probiotic fodder additive «Probion-forte» in dose 1 g/kg of fodder for 42 days. After the slaughter of  piglets, pieces of duodenum for histological, histochemical and ultrastructural studies were selected. Statistical significance of differences was determined by Student's t test , assuming 5% estimate error. It was shown that feeding with forage within 42 days from the addition of probiotic fodder additive «Probion-forte» at a dose of 1 g/kg, villus height is increase, crypt depth and a number of plasma cells in the lamina propria of mucosa of the duodenum, which helps the digestive process and increase the area of nutrient absorption in the intestines. The number of plasma cells are increased in the lamina propria of mucosa and testify immunomodulatory effect of fodder additives. Ultra structural alteration of microvilli and changes in the nuclei of duodenal enterocytes of piglets of the first group indicates a more pronounced acfunctional activity of enterocytes and thereby increases the activity of parietal digestion in the intestine. As a conclusion, the task by definition performed of the effective dose of probiotic in feed for pig it can be considered completed and we can state the probiotics can be incorporated, as a alternative to antibiotics and increase the weight gain of animals and also to increase the level of immune resistance of the organism.

The article covers the results of pathomorphological studies of broiler chickens' liver (Cobb 500 cross) spontaneously damaged by Group I fowl adenovirus. Clinical signs of the disease in broiler chickens appeared on the 15th day of life and were manifested by a sharp decrease in water and feed consumption. The fowl was lethargic for several days, breathing hard, mostly sitting with its head down and eyes closed. During the breeding period, the mortality rate reached 13.2 %, accompanied by significant growth retardation. A peak of mortality was observed within 20–24 days of life. Antibody titers monitored by immunoenzymatic method using BioChek ELISA tests for infectious bursal disease (IBD), infectious bronchitis (IBV), and Newcastle disease (ND) virus were within normal post-vaccination levels. Pathological autopsy of broiler chickens revealed hepatomegaly, diffuse punctate and petechial hemorrhages under the Glisson's capsule, and military necrosis in the liver parenchyma. Hydropericarditis, pulmonary edema, renal dystrophy, and catarrhal enteritis were also detected in some cases. Liver fragments were selected for histological examination, fixed in a 10 % aqueous solution of neutral formalin, washed in water, and dehydrated in an ascending series of alcohols, followed by sealing and embedding in paraffin. Deparaffinized sections were stained with Mayer's hematoxylin and eosin. Optical examination of hepatocytes revealed large, round basophilic intranuclear inclusion bodies, multifocal necrosis of hepatocytes, stasis, and fatty dystrophy. According to the molecular genetic test results of broiler chickens' liver fragments, the DNA of Group I fowl adenovirus, serotype FAdV-11, was isolated.