Некоторые аспекты эпизоотологии и патогенеза субклинического и клинического мастита

Abstract

Clinical and subclinical forms of mastitis are widespread in dairy cows and cause premature slaughter of animals due to lack of milk, agalactia, atrophy and hardening of the udder. The incidence of mastitis in dairy cows averages about 25 %, but the manifest form of mastitis occurs in 50 % of lactating cows. Culling large numbers of dairy cows can have a negative impact on production profits. The early slaughter of dairy cows is influenced by various factors, mainly violations of veterinary and zootechnical husbandry rules. It should be noted that veterinary measures for the prevention and treatment of mastitis are not always effective. Statistics from the veterinary department show that the average age of Russian dairy cows is 2,7 lactations. The decisive role in the etiology of mastitis depends on three interrelated factors (infectious agent, protective properties of the macroorganism and environmental influences). At the onset of the disease, a sterile inflammatory process occurs, which is then complicated by the microbial community. Opportunistic microorganisms accumulate in the tip of the nipple and the nipple canals, penetrate the nipple and suprapapillary cisterns and cause an infectious process. Inflammatory processes in the intestines, organs of the reproductive system, etc. can also lead to infection of the mammary glands. The part of the udder that produces the most milk is most often affected. Microorganisms penetrate the mammary gland in three ways (mammary, hematogenous and lymphatic). During the inflammatory process, under the influence of microorganisms, milk proteins are destroyed, the pH of the environment changes, and clots and flakes appear. Subsequent changes depend on the severity of the inflammatory process. If timely measures are taken, the physiological processes and structure of the breast tissue can be restored, otherwise atrophy of one lobe (quarter) of the mammary gland will occur. The clinical symptoms of subclinical mastitis are unknown. Serous-catarrhal exudate appears in the alveoli, the components of which are lymphocytes, plasma cells and multinucleated cells. The protein composition of milk undergoes significant changes, which are characterized by a decrease in the content of total protein and casein, an increase in the concentration of whey protein, an increase in the alkalinity of milk, and an increase in the number of somatic cells. If cows with subclinical mastitis are left untreated, they resolve spontaneously in 12–20 % of cases and develop clinical signs in 15–20 %.