Mastitis in Cows (1)

Cow Mastitis: Identify, Treat, and Prevent Infection


To the new cow owner, mastitis can often be undiagnosed and left untreated. But, this is dangerous to both the individual cow and to the entire herd. Mastitis can develop into a major and costly problem if left untreated. This article will cover how you can diagnose, treat, and help prevent mastitis in your herd.

Mastitis carries a hidden cost to dairy farmers. It often occurs due to an invisible bacteria that can infect an entire herd and drive down milk production. 

What is Mastitis? Mastitis is a common bacterial disease that commonly attacks cows. It is characterized by inflammation of the teats or udders of the cow. When left uncontrolled, mastitis can result in poor performance of the entire herd and can lead to culling cows with severe cases of mastitis.  

Dairy cattle are the most affected by mastitis because of their higher milk production. However, beef cattle and even heifers can contract mastitis.

In the United States, the economic loss attributed to mastitis is estimated by the University of Glasgow to be 2 Billion dollars each year.  In other countries, losses associated with mastitis are also significant. This article will guide you on how to prevent your farm from being part of these statistics. 

Signs and Types of Mastitis 

Mastitis is classified under two main categories:

  • Subclinical mastitis
  • Clinical mastitis

Subclinical Mastitis

Subclinical mastitis does not exhibit the usual signs and symptoms of mastitis. Your cow will appear normal, and the udder will not show any physical signs of inflammation. Subclinical mastitis often goes undetected for a very long time because the signs are not easily identified. 

Cows with subclinical mastitis produce less milk than expected. Reduced milk production may be considered to be a sign of subclinical mastitis. You should also note that the quality of this milk will below. However, to prove with absolute certainty that your cow is infected, a bacterial test must be conducted by a veterinary doctor. 

Clinical Mastitis

Clinical mastitis is the most visual form of mastitis. The naked eye can detect the signs and symptoms of clinical mastitis. A cow who has mastitis will show swelling, redness, inflammation, or a harness to the udders. You may also notice that the cow isn’t eating as much, has a sensitivity to her udders when touched, or that the udders are hot to the touch. You may notice a change in the milk. Cows may face movement issues due to the pain, or it may take longer to milk her. You may notice flaky or pasty milk excretions. 

There are varying degrees of clinical mastitis. When a cow only shows signs of mastitis periodically and seems to regain health, this is described as chronic mastitis. When a cow shows consistent signs of mastitis, this is described as acute mastitis. Despite the two varying degrees of mastitis, both should be treated with urgency.

5 Common Causes of Mastitis

Bacteria cause mastitis. Bacteria can spread from one cow to the other, leading to infection of the herd. The bacteria may also be in the cow’s environment, leading to infection. 

The mastitis-causing bacteria include Streptococcus uberis, Staphylococcus aureus, mycoplasmas bacteria, and E. coli. 

While these bacteria cause mastitis, they require certain predisposing factors to infect cows. There are predisposing factors that may lead to mastitis.

  • Poor hygiene in a cowshed
  • Injury to the udder or teats
  • Bad milking techniques
  • Inadequate milking of lactating cows
  • Infection from other animals

1. Poor Hygiene in the Barn

Cows release a large amount of waste in the form of dung and urine. Pasture remains may also end up on the floor of the cowshed.  When waste is left in the cowshed for an extended period, it begins to undergo decomposition. In this environment, mastitis-causing bacteria find optimal conditions to thrive. 

Cows use the floor of the cowshed as a place to sit and rest. In this sitting position, the cow’s udder will most likely come in contact with mastitis pathogens on the floor. The cowshed should be cleaned twice a day. Cleaning the floors and using recommended disinfectants (find on Amazon) will eliminate dangerous bacteria.

Equipment that is used when handling cows should also be cleaned. Particularly, milking equipment should be cleaned thoroughly and sterilized before and after use. If equipment is used on more than one cow, it should be cleaned after use per cow. 

2. Injury to the Udder or Teats

An injury to the udder or teats of a cow often leads to mastitis. Wounds on the udder or the teat can also act as a passageway of bacteria.

There are several ways a cow can injure her teats. Sharp objects can bruise the udder. Rough stony fields can also cause injury to the udder. External parasites, such as ticks, can also leave wounds on the soft skin of the udder. You should also note that grazing your cow in a field with thorny plants can wound the udder.

3. Bad Milking Techniques

Cows enjoy being milked. Milking provides a cow with relief by releasing the pressure of a full udder. But, care should be taken not to injure the teats. You should not milk your cows if you have long nails. Before milking, wash your hands and all the milking equipment.

To prevent friction between the fingers and the teats, apply milking jelly (find on Amazon) on the teats and your fingers. The jelly helps to protect the teats while also making the process of milking to be easier.

On larger farms, an automatic milker (find on Amazon)  is often preferred over hand milking because of the saved time and labor costs. A milking machine should be cleaned before and after use as it can hold bacteria too. A machine milks a cow by vacuuming all four teats at the same time. The chances of cows getting injured by a milking machine drastically reduce.  

Preventing Mastitis when milking (1)

4. Inadequate Milking of Lactating Cows

Mastitis is also caused by high amounts of milk left in the udder after milking. Leaving milk in the udder promotes microbial activity in the udder, leading to acute mastitis. While it may not be possible to drain all the milk from the udder, you should make an effort to leave the udder empty or almost empty.  

Another alternative is to let the calf suckle if you suspect that there is milk in the udder after milking. This facilitates milk let-down in cows, and the calf will exhaust any remaining milk in the udder.

5. Infection From Other Animals

It is easy for cows to get infected with mastitis from other animals on the farm. Remember that farm animals are social creatures who interact throughout the day on the farm. Preventing infections from spreading across your herd is not easy but is doable.

With the help of your vet, if you detect mastitis or signs of mastitis in one cow, you should isolate it from the rest of the herd. This reduces the chances of spreading the disease. 

Because detecting subclinical mastitis is difficult, always clean milking equipment and hands after use on every cow. 

Signs of Mastitis

Mastitis has several signs that, if spotted, can stop a severe infection or possible outbreak. The most common signs are:

  • Reduced milk yields
  • Reduced quality of milk
  • Loss of appetite
  • Inactivity and depression
  • Fever
  • Swollen udder

These signs are not isolated to mastitis alone but can appear when other issues are also present. To diagnose mastitis, watch for multiple signs to appear or get a bacterial test if you are uncertain. 

Lower milk yields

A reduction in milk yield occurs for both subclinical mastitis and clinical mastitis. And, this is the main sign for subclinical mastitis as it does not show other signs like clinical mastitis. 

To detect reduced milk yield accurately, measure and track the volume of milk for each cow after milking. These records will help you to identify milk production trends. 

Did you know? 

 A reduction in milk production does not automatically mean that your cow has mastitis. A variety of other reasons can cause reduced milk yield. 

A lactating cow needs to be well-fed several hours before milking, or she will experience reduced milk production. A cow will also produce low amounts of milk if it is sick with other diseases. Further, external and internal parasites can also lead to reduced milk yields.

Automatically milking cows can help prevent mastitis (1)

Reduced Quality of Milk

Apart from decreased milk yields, a mastitis-infected cow also produces low-quality milk. Good-quality milk should be free from clots, pus, flakes, or bloodstains. All or part of these impurities are usually present in the milk of a cow with clinical mastitis. 

Watch for any of these impurities when you milk. The easiest for detecting them is to milk the initial gush of milk from each teat into a black cup or surface. Examine a sample of the milk on a dark surface. Clots, pus, or blood can be seen more easily when a small amount of milk is placed on such a dark surface.

While all these are physical methods of determining milk quality, there are other methods that your veterinary doctor may recommend. These may be recommended if your milk looks okay but has an abnormal taste or clots when boiled.

Loss of Appetite

Cows with clinical mastitis experience a loss of appetite. Even a slight reduction in appetite should be interrogated. Loss of appetite does not apply to pasture grazing and feed only, but to water intake also. A healthy cow has a good appetite.

What Constitutes a Loss of Appetite? It is deemed a loss of appetite when the cow leaves a substantial amount of their feed or all the feed in the feeding trough. A cow with a loss of appetite may eat very little or even ignore her favorite treats (farm animals).

Inactivity and Depression

A healthy cow is active and curious. She responds to other farm animals nearby and occasionally moves from one end of the cowshed to another. When you stretch your hand near the nose of a healthy cow, she shows inquisitiveness and sniffs your hand. In a cow that has clinical mastitis, most of these characteristics are not exhibited.

There is general inactivity and depression in a cow with clinical mastitis. The cow is likely to maintain the same position in the cowshed or the grazing field. She will not interact freely with the rest of the herd and will appear uninterested in her surroundings.

Swollen Udder

A swollen udder is the most obvious symptom of mastitis. The bacteria that cause mastitis are hosted in the udder of the cow. 

The cow’s immune system responds to the presence of these bacteria by swelling the tissues in the udder. The skin of the udder also becomes red. When squeezed, lumps can be felt inside the udder. Any touch on the udder or the teats results in pain, and the cow will fight any milking attempts by kicking and lashing her tail near the udder.

High Temperature

A cow with clinical mastitis will experience fever. To know if your cow has a fever, you need to know the average body temperature of a cow. This is usually between 37 °C to 39 °C (98.6°F to 102.2°F). 

A cow’s temperature is best measured through the rectum. Farmers should have a rectal thermometer (Amazon) to detect fever in their herd.

Officially Diagnosing Mastitis 

For subclinical mastitis, diagnosis is made through a test called the Somatic Cell Count. Samples of milk are collected from the affected cow, and white blood cells are counted in a lab. High white blood cells indicate that a cow is fighting infection. 

Farmers can easily conduct a mastitis test using the California Mastitis Test (CMT Found on Amazon), which is available for purchase. You will also need the mastitis test board found on Amazon here

The California Mastitis Test can be used to test for mastitis, but it cannot be used to show the type of bacteria behind the infection. To establish this, laboratory tests are advised. There are also other mastitis tests that the vet can carry out in the laboratory after collecting samples from your cow.

Mastitis in Beef Cattle

Most people are aware that mastitis affects dairy cattle. But, beef cattle can be at an even higher risk of mastitis because the cows are kept in the herd longer- increasing the risk that older cows develop mastitis. Plus the trend for beef producers to breed higher milk production into beef cattle has resulted in more frequent rates of mastitis.

Calves mostly suckle the lower quantities of milk that beef cows produce. But, occasionally, beef cows produce more milk than a calf can suckle. For such cows, farmers should consider milking them to reduce the chances of mastitis. Beef cattle present unique problems in dealing with mastitis that don’t usually come up in dairy cattle. 

 Without a keen inspection of a beef cow’s udder, mastitis is likely to go unnoticed.

The Effects of Mastitis in Calves

Milk plays a crucial role in the growth and health of a calf. So, what happens when a calf suckles an udder of a cow with mastitis?

When a cow is diagnosed with mastitis, alternative feeding arrangements should be made for the calf. The calf will need to be bottle-fed (on Amazon) or bucket-fed (on Amazon)with milk from a healthy cow. Allowing a calf to continue suckling a sick cow is endangering the calf and the cow. The calf will have dangerous bacteria introduced in the gut, while the udder will be inflamed more. 

Bottle fed cows when mastitis is present in moms (1)
Bottle feed calves when the mom has mastitis

How to Treat Mastitis

Mastitis is treated using antibiotics that act against specific bacteria. If a wrong antibiotic is used or the dosage is inadequate, your cow will not get well. For this reason, you should always hire a veterinary doctor to treat a cow with mastitis.

There are two types of mastitis treatment on an infected cow. They all involve the use of prescribed antibiotics. These are;

  • Intramammary antibiotics
  • Systemic antibiotics

Intramammary Antibiotics

Intramammary treatment of mastitis targets the affected area. The prescribed antibiotics are applied directly into the affected quarter of the udder. This method is used to treat mastitis cases that are not severe. 

Intramammary antibiotics used to treat mastitis may come under different brand names. However, their core composition is mainly;

  • Tetracycline
  • Penicillin
  • Amoxicillin
  • Streptomycin
  • Cloxacillin, 
  • Ampicillin

Systemic Antibiotics

In mastitis cases where more than one-quarter of the udder is infected, systemic antibiotics therapy is used. While intramammary antibiotics tend to be used even without finding out the nature of the bacteria that caused mastitis, systemic antibiotics are prescribed after a lab test. 

The lab test identifies the exact pathogen, and the antibiotics are prescribed based on these results. In severe cases, intramammary antibiotics can be applied together with systemic antibiotics for better results. Systemic antibiotics are administered to the cow through intravenous injections or intramuscular injections.

Prevent Mastitis in Herds 

There are several simple strategies you can use to prevent your cows from contracting mastitis. They are geared towards mastitis pathogen eradication and timely detection of infection.

The first preventive measure to keep mastitis at bay is to maintain high hygiene standards on your farm. Maintain good milking practices by cleaning the equipment, udder, and teats every time before milking. Use a teat dip (on Amazon) before and after milking. A teat dip cup contains an iodine solution (on Amazon) that kills mastitis pathogens.

When hand milking, do it gently to avoid causing injury to the teats.  Remember, an injury to the teat can easily lead to mastitis. 

There are other ways that the udder or teats may sustain injuries. Remove sharp objects or surfaces that can bruise the udder and teats. Such objects include nails and timber edges. 

Lactating cows should rest from being milked for 60 days before calving and starting lactation again. This process is called drying off. This allows the tissue of the udder to heal and repair. 

Culling severely affected cows

The most extreme measure for mastitis involves culling severely sick animals. Cows with badly damaged udders should be culled. Retaining them may lead to the further spread of mastitis to other animals. 

The Effects of Mastitis on Cows

In addition to the economic cost of mastitis, it affects cows.  Long-term effects of the disease underline the need for sustained preventive measures.

Reduced Fertility and Conception Rates

Cows with a history of mastitis have reduced fertility and conception rates than cows without a history of mastitis. The link between mastitis and fertility is a result of the disease affecting the normal function of the ovaries and the reproductive system of cows.

Increased Resistance to Antibiotics

The treatments for mastitis are largely antibiotics. Recurring infections of mastitis means that antibiotics will be used repeatedly. Eventually, this leads to pathogens gaining resistance against most antibiotics. 

Increased Probability of Future Infections

Mastitis on your farm increases the risk of future infections. It is difficult to eradicate all the mastitis pathogens on your farm completely. Additionally, infected cows can carry the subclinical form of mastitis for years without detection.

Udder Deformation

A severe case of mastitis can leave your cow with a deformed udder. This deformation can be due to scar tissue formation or surgical procedures performed by the vet. In mild cases, lumps or minor scars resolve over a period of time. A dairy cow with a deformed udder loses its value and may be culled.

Frequently Asked Questions

Will mastitis clear up on its own? Minor cases of mastitis can sometimes clear up without treatment. However severe mastitis, once symptoms manifest, requires treatment to heal. Even then, cows may not fully recover from mastitis. 

Can a heifer get mastitis before calving? Heifers can get mastitis before they calf. The two weeks before calving are the greatest risk for heifers to get mastitis. It’s essential for heifers to be kept in a dry, clean environment prior and after calving to prevent mastitis. 

Can a calf nurse a cow with mastitis? In subclinical mastitis calves can nurse a cow with mastitis. At this point the mastitis is mild and the cow may recover naturally. But, as mastitis becomes painful, the cow may kicks the calf off when it nurses. Or, the calf may refuse to nurse because of the change in flavor.  

How long does it take to dry off a cow? Drying off a cow typically takes between 30-35 days. Once a cow is dry, she should have a dry period of 60-70 days. This will provide her body with enough time for the glands and udder tissue to heal. Cows without a dry period produce 20-25% less milk that cows that have a dry period (a break in lactation).


Mastitis is a serious condition in cattle that, left untreated, can have costly and severe repercussions. Fortunately, with a few steps, you can diagnose and treat cow mastitis. Even better, it is usually preventable.  

Recommended Cattle Supplies (And Dairy Supplies)

This list contains affiliate products. Affiliate products do not cost more but helps to support BestFarmAnimals and our goal to provide farm animal owners with accurate and helpful information.

This shelter is pretty easy to put together and it shelters a good number of cows. It’s sturdy and can withstand our high winds and heavy snows. And it’s cheaper than a barn and easier to build.

Colostrum is critical for calves. If you aren’t able to get some from your cows, this is a quality supplemental colostrum.

Probiotic for cattle with digestion issues in a oral tube. It works for other ruminants and is safe for goats, but is formulated especially for cattle.

A halter to lead Bessie around. This show halter also works for kids showing for 4H.

All Stock Feed is on Amazon, but you’ll pay less if you find it at your local feed store. It’s a great feed for cattle.

Electrical rope for your fencing. This keeps cattle in, but goats, alas- not so well.

Dairy Cow Recommended Supplies

Disposable towels or wet wipes are the first step in cleaning the udders.

Teat Dip and a dip cup are essential for keeping your milk clean. It lasts a while. Mine usually lasts a year to a year and a half.

I use a stainless steel bucket when I milk because it’s easy to clean and carry. These are my preferred milk filters and I use them for cow and goat milk.

This large jar funnel stays much more stable than regular funnels and can handle larger milk volumes.

I like this grain feeder while milking and use this size for the cows and goats being milked.

Balm ointment for sore udders. This cream is popular for people but formulated and created for cows’ udders.

Mastitis Test detects mastitis.

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