The somatic cells content is one of the most significant indicators of quality in milk. Somatic cells are the dying cells of the cylindrical, squamous and cuboidal mammary epithelium, leukocytes and electrocytes. Somatic cells produce enzimes, which are resistant to pasteurization and are capable of breaking down fats and proteins of which milk consists. As a result of these processes, milk can acquire an unpleasant taste or smell, which negatively affects its consumer properties and shelf life. Even in a refrigerator, such milk spoils very quickly and becomes unfit for consumption and processing.
In the udder, there is constant renewal of epithelial cells. As a result, somatic cells are always present in milk. Udder quarters with somatic cells up to 100 thousand per milliliter are considered healthy. This indicator can vary from 50 to 170 thousand per milliliter depending on the age of the cows, nutrition and conditions in the barn, but on average it is about 100 thousand per milliliter.
The content of somatic cells from 300 to 800 thousand cells in 1 milliliter of milk from a quarter indicates subclinical mastitis. Subclinical cases are noted when about 5 - 35% of the udder quarters of the entire herd are infected with pathogenic bacteria. Subclinical mastitis is more difficult to detect because the milk and udder appear clear, while the milk has a higher somatic cell count.
A somatic cell count above one million per milliliter indicates clinical mastitis. Clinical mastitis is relatively easy to detect. The symptoms are coagulation and discoloration of the milk, the mammary gland becomes painful, dense, red and swollen, and in severe cases the animal has a fever and reduced appetite.
In addition to the decrease in the milk productivity of the cows, there is a deterioration in the quality of the milk. The pathological consequences of mastitis are tissue damage, changes in secretory function. The degree of the disease has a significant effect on the composition of the milk.
In mastitis, the content of seroproteins increases and the proportion of cosines decreases, which worsens the quality of milk as a raw material for cheese production. The concentration of hydrogen ions in milk increases, shifting to the alkaline side, and its specific conductivity increases. The content of dry matter, milk fat, casein, lactose, calcium salts, phosphorus, potassium, magnesium and vitamins in milk is reduced. In parallel, the content of water-soluble protein fractions (albumin, globulin), chlorine, sodium and enzymes (catalase, reductase, phosphatase) increases.
The above factors worsen the technological properties of milk and disrupt the microbiological and biochemical processes of its processing. Such milk is a poor substrate for the development of lactic acid microorganisms used in the dairy industry in sourdough starters. First of all, mastitis milk loses the ability to form normal cheese curds, and due to the slow development of starter cultures in the cheese mass, the required level of acidity is not achieved. The low activity of the leaven and the acidity of the cheese mass, combined with high humidity due to the looseness of the cheese, create prerequisites for the development of foreign, harmful microorganisms in the cheese. Due to the disruption of microbiological and biochemical processes during the production of cheese, the taste, smell, color and consistency deteriorate, that is, it is impossible to obtain a product of good quality from such milk.
Staphylococci and streptococci are most often isolated in the milk of cows with mastitis. These types of bacteria deteriorate the taste of the product and its shelf life. Cheeses made from milk contaminated with these microorganisms do not ripen well. In order to reduce bacteria levels in dairy raw materials and dairy products, it is necessary to maintain high hygiene standards on the farm, as well as during the transportation and processing of the raw materials. It is very important to use modern cooling units that keep the temperature of the milk no higher than 4ᵒC, because under these conditions most bacteria die or do not develop.
The high content of somatic cells and whey proteins in mastitis reduces the heat resistance of milk. This is reflected in the technological process of preparation and the quality of condensed and sterilized milk. Antibiotics used to treat and prevent various livestock diseases often cause allergic reactions in humans. As a rule, antibiotics are used for the treatment and prevention of mastitis in dairy and dry cows. And if in dairy cows antibiotics are eliminated from the body in 1 - 4 days, then in dry cows this happens in 4 - 6 weeks. In such cows, drugs may be excreted in milk even after calving. As a rule, drugs are used according to the instructions. But it is impossible to take into account the current situations on farms: incorrect labeling of cows, errors in record keeping, uncoordinated actions of staff, non-compliance with milking deadlines, difficult to predict the time to remove antibiotics. f used incorrectly or repeatedly, the risk of receiving milk containing antibiotics increases.
Such milk reduces the quality of the product during its processing. In this regard, dairies strictly control their availability and refuse to accept such raw materials. It is therefore necessary to use a full-fledged system of strict control of accounting and reporting throughout the farms. Lactating cows treated with antibiotics are milked separately, and the milk obtained from them is not sent for processing.
Various tests are currently used to determine antibiotics in milk from individual cows, in collection tanks, milk tanks, in storage tanks and to test the final product for compliance with standards. Testing at the early stages significantly reduces the risk of poor quality products at the end of milk processing and allows the farm to obtain the status of a reliable producer of raw materials.
The total number of somatic cells measured in milk from a healthy udder varies from 10 to 100 thousand per milliliter and depends on the physiological state of the animal, its health and genetics, feeding and maintenance conditions. The total number of somatic cells in milk increases in the first days after calving, before calving, during estrus and when cows are sick. An indicator of the total number of somatic cells from 300 to 800 thousand in 1 ml of milk indicates subclinical mastitis, and more than 1 million / ml indicates its clinical form.
With mastitis, the content of dry matter, lactic acid, casein, lactose, calcium salts, phosphorus, potassium, magnesium and vitamins in milk decreases, the concentration of water-soluble fractions of protein, chlorine, sodium, enzymes increases and the pH shifts to the alkaline environment. These factors worsen the technological properties of milk and disrupt the microbiological and biochemical processes of its processing.
Preventing mastitis is the key to producing high-quality milk. Every monetary unit invested in prevention brings 5 to 10 monetary units of savings. At the same time, success directly depends on the availability of competent specialists and the qualification of the personnel who directly serve the dairy herd. Employee hygiene is of great importance. The most effective way of diagnosing subclinical mastitis and its timely treatment is the constant measurement of the total number of somatic cells in the milk. Invaluable in this respect is the somatic cell analyzer of the company Milkotester.