Mastitis in Cows: Causes, Symptoms, Treatment and Prevention

Mastitis is an inflammation of the mammary gland, usually of bacterial origin, although physical factors (mechanical injuries, environmental conditions) can also influence the development of inflammation. Bacteria enter the udder through the teat canal, releasing toxins that damage the milk-producing tissues, and causing inflammation, which reduces milk production and quality. Mastitis in cattle can be detected at all stages of lactation, including the weaning period, but is most common in fresh milk and late lactation cattle. Although much attention is paid to the prevention of this disease, it still remains the main cause of economic losses on farms.

Most often, mastitis in cows occurs due to poor environmental conditions, health problems of the animal itself or deficiencies in herd management. Attention should be paid to the hygiene of milking equipment and animal housing, completeness of rations, gynaecological diseases, injuries and other factors. Therefore, an effective mastitis prevention and control strategy should include not only the treatment of the disease, but also the management of the entire farm.

Inflammation of the mammary gland is clinical (noticeable) and subclinical (hidden).

Clinical mastitis

The first symptoms in the manifestation of the clinical form of the disease are the thickening and elongation of the teats of the affected quarter or several quarters of the udder. Flies fly around the affected quarter, causing irritation that often causes cows to kick the udder. Clinical mastitis can be suspected from a change in udder temperature. The affected quarter of the udder becomes swollen, red, and painful. Due these reasons cows move less, their gait changes. They seem to be trying to walk more carefully to minimise irritation to the udder. As a result, sprains of the foot joints may develop, and the animals begin to limp. Sick cows look tired, lose weight, have a high body temperature, and may even abort.

In the case of clinical mastitis, after milking the first spurts of milk into a container (special purpose containers are usually used), mucus, clots, flakes are visible, traces of blood may be visible in the milk. The colour of milk also changes. When examining milk samples by laboratory methods, large amounts of somatic cells are detected, the concentrations of the main components of milk are altered and the electrical conductivity of milk changes, etc.

If only changes in milk are seen in the milk, clinical mastitis of cows is described as mild. If other symptoms also appear, clinical mastitis can be described as moderate or severe, depending on their severity.

Subclinical mastitis

Subclinical mastitis is characterised by inflammation of the udder, when visually the milk appears to have a normal consistency and colour, there are no udder or other signs characteristic of a sick animal, and the inflammation is determined only by changes in the composition of the milk. In order to detect latent mastitis, dairy cows should be examined at least once a month, 10-14 days before weaning and 8-10 days after calving. During the weaning period, the udder and general health of cows should be monitored.

An increased number of somatic cells, a change in the electrical conductivity of milk and a decreased concentration of lactose are the main indicators of milk for the diagnosis of subclinical mastitis. Monitoring changes in milk composition and quantity can help identify cows with mastitis effectively and quickly. The content of the main components in milk decreases by 5-15 percent, the composition of fat and protein changes. Modern milking lines increasingly integrate various systems, “mini-laboratories” that help identify sick animals and ease the burden of people working on the farm. It can be an excellent alternative to tests performed in conventional laboratories, because the data is obtained immediately, there is no need to worry about sampling or logistics, and the risk of obtaining false data due to an improperly collected sample or other influencing factors is reduced. However, not all systems of this type are easily applicable to many farms. Some of them can only be installed on certain milking lines, so a significant number of farms cannot adapt it to their existing equipment, while others lack accuracy and reliability.

Mastitis can increase costs for dairy farmers by 43 percent. It is estimated that the losses currently caused by mastitis can reach ~EUR 185/animal per year and it is the second most frequent reason for the failure of cows.

It was observed that when SCC is present in milk at 100 thousand/ml, the productivity of cows from one quarter of the udder per day decreases by 25-35 percent, during the entire lactation – by 10-15 percent. On average, about 650 kg of milk is not obtained from a sick cow during lactation. Sick animals produce less milk for the rest of their lives.

Most often, subclinical mastitis prevails in farms. It is said that the most losses in dairy farms, which can be as much as 70 percent, are precisely caused by subclinical mastitis. Therefore, it is very important to detect subclinical mastitis as early as possible before the course of the disease has passed into a clinical form. This can be done effectively only with the help of modern diagnostic tools.

Determination of SCC

One of the most popular tests for the diagnosis of subclinical mastitis is the determination of the somatic cell count (SCC) in milk. Higher than 200 thousand/ml SCC is the main indicator showing that the cow already has mastitis. This test is not always practical and fast, as it requires additional equipment and reagents. In most cases, the accuracy of the results is determined by the competence of the person who took the samples and performed the test. When samples are sent to the laboratory, test results are obtained only after some time, which increases the time until diagnosis and treatment of the disease, so it incurs greater losses. When using commercial tests, the test can be carried out directly on the farm. Such tests are quite popular, but not always practical, especially on large farms, as each animal must be tested individually. This requires additional labour costs, and the accuracy of the results depends on the diligence and attention of the worker. Some manufacturers have developed automated systems for determining somatic cells in milk, but not all milk lines have the possibility to apply them. Such systems are convenient in that employees no longer need to take care of sampling and evaluation of results, saving a lot of time, but require additional care and reagents for conducting tests.

Most SCC detection studies are based on the “California mastitis test” methodology. Active surfactants break down the nuclei of cells in milk, release DNA, and change the viscosity of milk. An indicator is also often used, which changes the colour of the mixture due to a change in the pH of the milk. For commercial tests, a few squirts of milk from each quarter are milked into special plates with a reagent, and taking into account changes in the consistency and colour of the milk, the test result is assessed and it is determined whether the cow has mastitis.

Undiagnosed or untreated latent mastitis can develop into clinical mastitis, which can be seen externally from changes in the udder, milk secretion and general deterioration of the animal’s body condition. The veterinarian will prescribe treatment based on the established severity of the disease and the causative agent. In the case of subclinical mastitis, quite simple treatment may be sufficient, so it is not necessary to separate and utilize the milk of such cows. Fewer losses are incurred. In the case of clinical mastitis, treatment usually involves antibiotics, anti-inflammatory, other special preparations and their combinations. Therefore, it is very important to diagnose the disease as early as possible, as this will determine the nature of the treatment. The effectiveness of treatment during the weaning period is several times more effective than during lactation. It is effective to treat all quarters of the udder with specially prepared, long-acting drugs intended for the treatment of dry period cows.

Antibiotic treatment must be used in accordance with certain principles:

• A veterinarian must examine the animal before choosing a treatment.
• Before prescribing drugs for treatment, the causative agent of the disease should be determined and then the appropriate drug should be selected.
• Antibiotic selection should be based on antimicrobial susceptibility testing.
• Treatment cannot be stopped prematurely, at the first sign of the condition improving; and one treatment cannot be suddenly changed to another.

From a practical point of view, it is impossible to completely eliminate mastitis from the herd, but its occurrence can be reduced to a minimum. Cows with chronic mastitis are a source of mastitis infection for the whole herd. It is recommended to cull cows:

• Which cannot be cured.
• The udders of which are severely damaged.
• Infected in the previous lactation and not recovered after treatment during the dry period.
• The udder of which is drooping, or udder quarters are hard or deformed.
• Cows with injured teat tips.
• Cows that had clinical mastitis 3 times during lactation.

In order to prevent mastitis and maintain good milk quality, comprehensive prevention is very important:

• Dirty cattle, bedding areas, floors, milking machines and areas, improper hand hygiene of milkers create conditions for the spread and reproduction of pathogenic microorganisms.
• Adequate ventilation in barns ensures optimal microclimate conditions and prevents the reproduction of pathogenic microorganisms.
• Drafts should be avoided in cow housing. They cool the udder, weaken the protective barrier and increase the possibility of microorganisms entering the udder.
• Corrals and walking paths must be comfortable, neat, meet the physiological needs of the animals, so that there is as little chance of udder injuries as possible.
• Beds must be dry, clean and periodically disinfected. The holding areas must not be overcrowded and all animals must have a place to rest.
• High-quality raw materials and complete nutrition are a very important factor in the prevention of cattle diseases.
• If the farm has >5% animals with dirty udders, teats and feet, it is an indicator of bad environmental conditions.
• It is important to check that the teats are healthy, clean and dry before putting on the milkers.
• Use disinfectants before and after milking as effective control measures against disease-causing pathogens.
• When milking is completed after the teats have been properly treated, the udder massage speeds up the milking process and the udder is fully milked.
• Some researchers declare that antibiotic treatment of dry period cows can reduce the occurrence of infection by up to 82 percent.