State of local immunity of respiratory organs in calves with bronchopneumonia

Abstract

Respiratory diseases are widespread among cattle and represent a significant proportion of the causes of abandonment in dairy and beef cattle. Despite the fact that new vaccines are being developed and introduced to combat respiratory diseases, which create humoral immunity to the main specific pathogens of respiratory diseases, the problem persists. Thus, it can be assumed that a significant proportion of respiratory diseases is caused by opportunistic microflora. Previous studies have shown that in calves under the influence of adverse microclimate factors, the microflora of the upper respiratory tract migrates to the underlying parts of the respiratory tract, resulting in bronchopneumonia.The study of local immunity indicators in healthy calves and calves with bronchopneumonia was realized. The study involved 8 Holstein calves aged 4-5 months, which were divided into 2 groups. Group 1 (control, n = 3) - clinically healthy calves, group 2 (experiment, n = 5) – calves with bronchopneumonia. Nasal secretions were collected from calves to assess local protection of the respiratory tract. The level of lysozyme, mucin, alkaline phosphatase, total protein, IgM, IgA and IgG was determined in it. The study of nonspecific factors protecting the mucous membrane of the respiratory tract showed a decrease in the level of lysozyme by 27.4% (p ˂ 0.01), as well as an increase in mucin by 76.4% and alkaline phosphatase - by 2.3 times compared with healthy calves. At the same time, with the development of pneumonia, there was an increase in the level of immunoglobulins M and A by 2.5 times (p ˂ 0.05). Thus, the conducted studies have shown that in case of bronchopneumonia, the barrier functions of the respiratory tract are activated to a large extent. In the nasal mucus of sick calves, the level of secretory immunoglobulins A and M increases, the production of alkaline phosphatase and mucin is activated.