Oesophagostomosis is a helminthic disease caused by nematodes of the Oesophagostomum’s genus, Trichonematidae’s family, characterized by the defeat of the thin and thick intestine and the violation of the functions of the gastrointestinal tract. The main causative agents of oesophagostomosis of cattle in Belarus Republic are Oes. radiatum, Oes. columbianum and Oes. venulosum (Rudolphi, 1809). Esophagostomes in the larval stage cause a special bowel disease, known at meat-packing plants as "nodular disease".

Hematological studies can reveal hidden pathological processes, identify the occurrence of complications, monitor the status of individual organs and systems, and also the effectiveness of further treatment. Therefore, the aim of our work was to assess the effect of oesophagastomosis invasion for hematological indices of cattle.

To carry out the experiment, a group of three-month-old calves (n=12) were infected with Oesophagostomum larvae in a dose of 500 pieces per animal. The control group consisted of healthy calves of similar age. The blood test was performed before infection of the animals and at the 15th day of the experiment.

The results of the study showed that at the beginning of the observation the number of erythrocytes in the calves of the experimental group was 6.55±0.13 T/l, and on the 15th day it was 3.87±0.14 T/l (decreased by 41%, p<0.01). In the control group of animals, the index was from 6.35±0.09 till 6.17±0.37 T/l, respectively.

The concentration of hemoglobin at the beginning of the experiment was 104.13±1.67 g/l, and till the 15th day it decreased by 24 % (till 79.13±1.41 g/l, p<0.01). In the control group of animals, the index was at a level from 103.41±1.63 till 103.6±2.36 g/l.

Studying of leukocytes’ number dynamic showed that it increased by 85 % (from 9.25±0.07 till 17.07±0.35 G/l, p<0.05). In the control group of young animals the index was 9.46±0.12 and 10.24±0.32 G/l, respectively, without making a reliable difference.

After infestation with esophagus’ larvae, eosinophilia was observed in their blood, developing from 5.10±0.31 till 13.30±0.46 % (2.6 times, p<0.01). The index in the animals of the control group was in the range from 5.30±0.30 till 4.40±0.68 %.

The infestation of animals was also accompanied by a significant decrease in the total protein content in the serum from 75.09±0.82 g/l at the beginning of the observation till 50.16±1.72 g/l at the 15th day (by 33 %, p<0,01). In the control group of calves there were no reliable fluctuations of the index value – from 72.91±0.65 till 75.89±1.97 g/l.

During the experiment, a decrease of the albumin fraction in the blood of the test group’s animals was observed from 32.90±0.51 g/l at the beginning of the experiment till 21.36±1.48 g/l at the 15th day after infestation (by 35 %, p<0.01). In the control group, the albumin’s concentration remained in the range from 35.16±0.16 till 36.27±1.63 g/l.

The dynamic of aspartate aminotransferase’ activity was characterized by a significant increase from 74.22±1.09 till 97.39±4.51 U/l (31 %, p<0.01). In the control group, the activity of this enzyme was 72.6±0.8 and 72.51±1.38 U/l, respectively.

The level of activity of alanine aminotransferase in the blood serum of experimental calves increased by 38 %, and till the 15th day of observation it was 34.15±0.88 U/l (p<0.05). In animals of the control group, the activity index was in the range from 26.63±0.96 till 25.92±1.95 U/l throughout the experiment.

The level of alkaline phosphatase’s activity at the beginning of the experiment was 77.30±1.22 U/l, and by the 15th day it reached till 196.50±3.68 U/l (increased by 2.5 times, p<0.01). For animals of the control group, the activity of the enzyme was in the range from 75.63±1.1 till 81.62±3.7 U/l throughout the experiment.

After infestation, a significant reduction in glucose in the blood serum of young animals was recorded from 2.60±0.05 till 2.17±0.12 mmol/l by the 15th day after infection (by 17 %, p<0.05). There was also an increase in urea concentration by 52 % and cholesterol by 98 %. Thus, the urea concentration increased from 4.41±0.09 till 6.72±0.42 mmol/l on the 15th day of observation (p<0.05). The concentration of cholesterol increased from 2.49±0.09 till 4.92±0.17 mmol/l (p<0.01). In the blood serum of animals in the control group, it was no significant changes in these indices.

Thus, the parasitization of cattle by the Oesophagostomum larvae in the body causes profound changes in the functioning of the host’s organism. Thus, a decrease in the number of erythrocytes and hemoglobin leads to a violation of the respiratory function, the development of tissue hypoxia and as a result of intoxication of the body.

The tendency to increase the number of leukocytes is due to the fact that the products of the life of helminths, toxins and products of inflammation are a factor that activates the mechanisms of immunity, aimed at eliminating the antigen. Detected eosinophilia indicates an allergization of the animal's organism by helminths’ toxins.

Reducing the glucose concentration in calf serum with oesophagostomosis invasion leads to activation of the gluconeogenesis process – biosynthesis of glucose from substances of non-carbohydrate nature. This leads to a decrease in the concentration of total protein, including albumin, and an increase in the content of the final product of decay of proteins – urea. With this the activation of transferases with the formation of pyruvate and oxalacetate, which is the process of compensatory recovery, is connected.

An increase in the concentration of alkaline phosphatase in serum of animals and an increase in the concentration of cholesterol testifies to the disruption of the liver function of cattle with oesophagostomosis.

It was found that the parasitization of Oesophagostomum helminths in the young cattle’s body also causes complex disorders of the functions of the systems and organs of the organism.

Key words: oesophagostomosis, invasion, cattle, hematology, biochemistry, metabolism.