BOVINE MASTITIS
Mastitis is the inflammation of the mammary gland, generally associated with an intramammary infection. It is caused by various types of bacteria, including E. coli and Staphylococcus aureus, although it can also be triggered by some species of fungi, yeasts and viruses. It is one of the most common diseases in dairy cattle and also one of the ones with the biggest financial impact on the dairy industry.
Genetic factors
Genetic selection of certain breeds to increase milk yield has been proven to have a detrimental effect on the health of mammary glands.
Mastitis is more common in intensive farming than extensive.
Mastitis tends to be less common among beef cattle than dairy cattle, as their udders are emptied naturally by the calves with less mechanical damage to their teats and acute infections.
In older cows, the teat canal is wider and can remain partially open, increasing their susceptibility to infections.
Mastitis is particularly common right after calving and during the first weeks of the dry period due to oxidative stress and less efficient antioxidant defense systems.
Lack of proper hygiene for facilities and farm equipment, above all milking machines, increases the risk of infection. The type of bedding, purine elimination, housing situation and crowding also affect mastitis frequency.
During this period the glandular tissues of the udder regenerate, so it is a time when the risk of mastitis increases.
High yield dairy cows tend to have a negative energy balance after calving, which affects their immune system and makes them more susceptible to diseases. Optimal feed during the dry period and early lactation is key.
Flies can be vectors that spread pathogens causing mastitis.
The main source of infection are the environment and direct contact with the infected mammary gland, mainly through milking machines, the hands of employees and calves that have contact with infected udders. However, there are other ways depending on the pathogen involved.
They live in mammary tissue and are spread from one cow to another. Transfer generally occurs during milking, through the milking machine, employees’ hands or towels used to clean the udders.
They can live in the mammary glands or come from the environment.
Environmental pathogens
They come from the cow’s environment: bedding, soil, manure, drinking troughs, etc. Infection occurs by contact of the udder with the source of contamination.
When a pathogen invades the udder and the immune system doesn’t produce the response necessary to eliminate it, the mammary gland becomes inflamed. The infection changes the glandular tissue, which becomes more easily permeable, leading to biochemical changes in the milk (increase in somatic cell count).
Depending on the type of the infection, there are three different types of mastitis:
Contagious mastitis
Caused by pathogens living on the animal’s skin or udders and spread through direct contact.
Caused by organisms in the environment like E. coli that get into the teat canal when the cow comes in contact with a contaminated environment. Pathogens are normally found in feces, bedding and feed.
This infection is more common when cows are in environments where they are exposed to teat damage and there are a lot of flies. It is an acute form of mastitis in dry cows and heifers, causing extensive damage and pain to their udders. Infected quarters are damaged forever. The clinical signs of summer mastitis are a warm, hard, swollen quarter, associated with a thick, malodorous secretion.
The cow seems healthy, the udders don’t show signs of inflammation and the milk seems normal. However, the biochemical properties of the milk are altered and there is an increase in the somatic cell count (SCC).
Painful, inflamed udders, altered milk (due to curds, desquamation, discolored serum or even blood), fever, accelerated pulse, loss of appetite, decreased milk production.
The inflammatory process lasts months and can continue from one lactation to another. It is subclinical but the animal can have short outbreaks of clinical symptoms periodically.
E. coli
Environmental
Mastitis caused by E. coli
Moderate
Staph. aureus
Udder / skin
Subclinical / Clinical
Acute or Chronic
High or very high
Str. agalactiae
Udder
Subclinical
Very high
Str. disgalactiae
Udder / skin / Environmental
Clinical
High
Str. uberis
Environmental / poor hygiene
Subclinical
High
Str. pyogenes
Environmental
Clinical
High
A. pyogenes
Environmental
Acute or Chronic Clinical Mastitis
Very high
Financial losses vary considerably from one country to another, based on factors like the price of milk and the cost of treatment or replacement. Nevertheless, it is clear that mastitis causes greater financial losses for dairy farms around the world than any other infectious disease.
Mastitis affects nearly half of all cows at some point in their lives, even in farms with proper hygiene. However, its prevalence varies widely from one farm to another.
This disease causes a 40% to 50% drop in net profit per cow, with most of this loss from the decreased milk yield.
Farmers tend to underestimate the costs of mastitis, above all in terms of indirect costs, which actually make up 56% to 70% of the total while direct costs are 30% to 44%.
- Cost of diagnosis and treatment: The more cases of mastitis at a farm, the higher the costs associated with detecting it (lab expenses), treatment and veterinary services.
- Discarded milk: Milk with a high SCC isn’t fit for human consumption and must be thrown out.
- Culling animals: Mastitis is one of the leading causes of culling.
- Human resources: Cows with mastitis require more care (45 minutes more per cow), which leads to more spending on human resources.
- Decreased milk yield: Mastitis always results in decreased milk yield, which can be temporary or persist throughout lactation. Estimated losses due to reduced yield fluctuate between 100 and 500 kilograms per cow per lactation. On top of this, there is also the milk lost while the cow is eliminating any medications.
- Decreased reproductive efficiency: The interval between calving and successful insemination is between 10 and 68 days in cows with mastitis.
- Increased replacement rate: It is 1.8 times higher than for a healthy animal.
Discover the financial benefits and return on investment for vaccinating.
As some mastitis causing agents have become resistant to antibiotics, it is becoming more and more difficult to cure as treatments become less effective.
So, it is increasingly important to control and prevent mastitis in cows by reducing exposure to pathogens and boosting defenses in the udders.
Control
It is difficult to control mastitis causing bacteria because they are found throughout the environment and some can be spread simply through skin contact.
Good hygiene while milking is crucial to preventing and fighting infectious mastitis. Hand washing before and after milking traditionally reduces the risk of subclinical mastitis compared to farms where this practice isn’t implemented, probably because it makes it easier to detect dirty udders.
Good environmental conditions: Bedding should always be clean, dry, warm and as comfortable as possible. Cubicles should be the right size, so the cow can lie down and get up easily, with at least one cubicle and 10 m² of space per cow. Drinking and eating troughs and paths must be kept clean at all times and active fly control is recommended to prevent them from acting as vectors.
Not too hot: In the warm season, the facilities should be designed properly with fans and sprinklers to help keep the cows cool.
Proper milking and hygiene:
- Before milking: Teats must be clean, dry and well stimulated before milking. They must be cleaned and disinfected (predipping) no more than 90 seconds before being put into the milking unit.
- Milking: The process should be done as quickly as possible, evenly and continuously in the four quarters, to prevent overmilking and keep air from getting into the system.
- After milking: Teats must be disinfected after milking. Cows should remain standing while the sphincter closes (40–45 minutes). To ensure this, make sure they have fresh feed when they leave the milking room.
Good hygiene, disinfection and biosafety: Good hygiene and regular maintenance are key, both of the facilities and, especially, the milking equipment. The milker must use disposable gloves, as humans are an important reservoir of microorganisms that cause mastitis.
Culling cows with chronic mastitis: Cows with chronic mastitis are a reservoir for the infection and can spread mastitis to the rest of the livestock.
Genetic selection: Some breeds and individuals are more resistant to this type of infections.
Diagnostic tests are key to controlling mastitis, allowing for early, effective intervention to limit financial losses and improve the health of dairy cows:
Strip cup test: A very simple way to detect mastitis. Milk the first few streams from each quarter into a strip cup. Any clots or watery, bloody or serum secretions indicate mastitis. This method is very fast and can be done by anyone.
California test (CMT): This is a fast, reliable screening for subclinical mastitis. You can assess the infection level of each quarter individually or in bulk milk samples. A small amount of milk is mixed with the CMT solution in a plastic container. The reaction indicates the somatic cell count, showing whether it is high or low.
Flow cytometry (FC): Advanced method to get somatic cell count in milk, particularly useful for detecting subclinical cases of mastitis. This method measures the physical and chemical traits of the cells or particles in suspension as they pass by a detection point.
Culture method: The safest way to diagnose mastitis, as it also allows you to isolate and identify pathogenic microorganisms in the milk.
One of the most effective prevention measures is boosting the cow’s immunity to mastitis through vaccination. Vaccination boosts udder immunity, achieving high antibody concentrations.
Vaccines protect against some of the leading causes of mastitis, although as a multifactor disease it can be complicated to achieve complete protection. This is why it is important to use a broad spectrum vaccine to reduce the chance of infection from a mastitis causing pathogen , reduce the severity and increase the cure rate as much as possible, as well as combining vaccination with other prevention strategies like those mentioned above.
Bibliography
Ashraf, A. & Imran, M. (2018). Diagnosis of bovine mastitis: from laboratory to farm. Tropical animal health and production, 50(6), 1193–1202. https://doi.org/10.1007/s11250-018-1629-0
Ashraf, A. & Imran, M. (2020). Causes, types, etiological agents, prevalence, diagnosis, treatment, prevention, effects on human health and future aspects of bovine mastitis. Animal Health Research Reviews, 1–14. doi: 10.1017/S1466252319000094
Gonçalves, J.L., Kamphuis, C., Martins, C.M.M.R., Barreiro, J.R., Tomazi, T., Gameiro, A.H., Hogeveen, H. & dos Santos, M.V. (2018) Bovine subclinical mastitis reduces milk yield and economic return. Livestock Science, 210; 25-32. doi: 10.1016/j.livsci.2018.01.016.
Heikkilä, A.M., Liski, E., Pyörälä, S. & Taponen, S. (2018) Pathogen-specific production losses in bovine mastitis. Journal of Dairy Science, 101(10);9493-9504. doi: 10.3168/jds.2018-14824
Kibebew, K. (2017). Bovine Mastitis: A Review of Causes and Epidemiological Point of View. Journal of Biology, Agriculture and Healthcare, 7, 1-14.
LUIS MIGUEL JIMÉNEZ
Specialist in mastitis control and milk quality, with over 30 years of experience advising dairy farmers in Spain and Portugal. He has published scientific papers and articles on mastitis and regularly speaks at national and international events.
We have worked with him on some recommendations to reduce the rate of intramammary inflammation on farms.
