Mastitis in Dairy Cows and Heifers: How to Manage Risk Before Production Loss

Mastitis remains one of the most costly and complex diseases in dairy production. The National Mastitis Council estimates mastitis costs the dairy industry more than $2 billion each year, with losses tied to reduced milk production, discarded milk, treatment costs, labor, veterinary expenses, culling and lower milk quality. (1)

However, the cost isn’t limited to cows showing obvious signs of infection. Subclinical mastitis often creates more financial loss across a herd because it can go unnoticed while somatic cell count rises and milk production declines.

Research shows the total failure cost of mastitis at $147 per cow per year, representing 11-18% of gross margin per cow per year. Mammary tissue damage and reduced milk production account for about 70% of total mastitis losses. (2) Yet, other studies estimate the total cost of clinical mastitis even higher, at around $444 per case. (3)

For dairy producers, mastitis control isn’t just about treating sick cows. It’s about reducing pathogen pressure, protecting the udder, supporting immune function and identifying problems early enough to limit long-term damage. 

What’s Mastitis?

Mastitis is inflammation of the mammary gland. It’s most often caused by microorganisms entering the teat canal and establishing an intramammary infection, although physical trauma to the udder or teat can also contribute to infection. (2) 

In simple terms, bacteria can get into the udder through the teat opening and cause swelling, abnormal milk and, in more serious cases, death. 

Some mastitis-causing pathogens are contagious and can spread from cow to cow, especially during milking, while others come from the cow’s environment, including bedding, manure, mud and wet areas. 

Mastitis Can Be Clinical, Subclinical or Chronic

Clinical mastitis is the form producers are most likely to see. The udder may be swollen, red, hot or painful. Milk may appear watery or contain flakes, clots, strings or blood. (See picture below). In more severe cases, cows may show fever, depression, dehydration or reduced appetite. (2)

Clinical Mastitis. Picture Credit: BouMatic

Subclinical mastitis is more difficult to identify. The udder and milk may look normal, but somatic cell count increases and milk yield can decline. Because it’s less visible, subclinical mastitis can spread and create losses before a producer realizes there’s a problem. (2)

Chronic mastitis is a long-term infection that can flare up repeatedly. These cows may have recurring clinical cases, persistently high cell counts or quarters that fail to fully recover and no longer produce milk.

What Causes Mastitis?

Mastitis is caused by a wide range of pathogens. These pathogens are often grouped into two categories: contagious and environmental. 

Contagious mastitis pathogens spread from cow to cow, most often during milking. They can be carried through milk, milking units, hands, towels or poor milking procedures. Common contagious pathogens include Staphylococcus aureus, Streptococcus agalactiae and Mycoplasma species.²

Environmental mastitis pathogens come from the cow’s surroundings. These pathogens are commonly found in bedding, manure, mud, water, stalls, lots and calving areas. Common environmental pathogens include E. coli, Klebsiella, Streptococcus uberis and other environmental streps. (2,3)

Mastitis can even spread when a contagious cow leaks milk in a resting area. If another cow lies in that same spot, bacteria can be transferred to the teat end and increase the risk of infection.

The pathogen involved in mastitis is important because severity, spread, treatment response and long-term impact can vary. Staphylococcus aureus can become chronic and difficult to eliminate. Mycoplasma can spread quickly within a herd and often responds poorly to treatment. Environmental pathogens like E. coli and Klebsiella can cause severe clinical mastitis, including toxic cases that may lead to rapid illness, permanent udder damage or death. (2)

Because different pathogens behave differently, culture data and veterinary guidance are important parts of an effective mastitis program. Identifying the bacteria involved helps guide treatment decisions, since certain antibiotics may not be effective against certain pathogens.

Heifer Mastitis Shouldn’t Be Overlooked

Research shows heifer mastitis can threaten udder health and milk production in the first and future lactations, especially when more damaging pathogens like Staphylococcus aureus, Streptococcus uberis, Streptococcus dysgalactiae and E. coli are involved. (4) 

Heifers can develop intramammary infections even before calving, around calving or shortly after freshening, which means they have had their first calf and entered the milking herd. Some may calve with a quarter already damaged or nonfunctional. When that happens, milk losses start before the animal has the opportunity to reach her full production potential. 

In heifers, coagulase-negative staphylococci are often associated with intramammary infection and subclinical mastitis around calving. Staphylococcus aureus and environmental pathogens tend to account for fewer infections, but they can be more damaging and are more often tied to clinical mastitis. (4)

Common Mastitis Risk Areas

Mastitis prevention looks different across stages of production, but the goal is the same: reduce teat-end exposure and limit the conditions that allow bacteria to enter the udder. 

For lactating cows, that often means focusing on stall hygiene, bedding, fly control, milking procedure, equipment maintenance and cow cleanliness. For heifers, more attention may need to be placed on fly control, cross-sucking, pasture conditions, injuries and pre-fresh management because these animals can develop udder infections before they enter the milking string. 

1. Fly control

Fly pressure is one of the most important mastitis risk areas, especially for heifers. Flies can irritate teat skin, create scabs and help move bacteria between animals. Research on heifer mastitis identifies fly control as a key prevention strategy. (4) 

A strong fly control program often requires more than one tool and may need to be adjusted throughout the season as flies develop resistance. Producers often use premise sprays, feed-through options, natural sprays, dust bags, sticky traps, manure management and pasture management to reduce fly pressure. 

2. Cross-sucking

Cross-sucking is primarily a concern in calves and young heifers. When weaned calves or young heifers are housed together in the same pen, one animal may continue sucking on another. This can irritate the teat end, create an opportunity for bacteria to enter and potentially increase mastitis risk later in life. 

Reducing inter-sucking among young stock starts with strong calf management, pen design, proper stocking density, balanced nutrition and close observation of group-housed calves and heifers. 

3. Injuries and teat damage

Cuts, scabs, stepped-on teats, rough pasture conditions or facility hazards can create an entry point for bacteria. This is especially important in heifers because teat damage can happen before calving and may not be noticed until the animal freshens. 

Regular observation of udders and teats in bred heifers can help identify issues before calving. 

4. Mud, bedding and resting areas

Environmental mastitis pressure often increases when cows or heifers are exposed to mud, manure, wet bedding or contaminated resting areas. Shade is important during heat, but shaded areas can become muddy when cows gather in the same place day after day. Tall weeds, unmanaged pasture, ponds and wet lots can also increase the chance of udders and teat ends contacting contaminated surfaces. 

For heifers, pasture and pre-fresh conditions are very important because infections can develop before they enter the parlor. For lactating cows, bedding and stall management are key control points. Sand, shavings and dried manure solids can all be used successfully, but only when they are managed well. 

Dried manure solids, including bedding from manure digesters, require close attention for the entire herd because they can carry higher bacterial loads if they’re not properly dried, stored and managed. 

Overcrowding, poor ventilation, heat stress and uncomfortable stalls can also increase mastitis risk when cows spend more time lying in alleys or resting in dirty areas. 

5. Bird control

Birds can contaminate feed, bedding, water areas and resting spaces. They can also move manure and bacteria throughout facilities, especially when roosting on cows, in feed bunks or bedding areas. 

Keep feed spills cleaned up, cover or protect stored feed when possible and reduce open water sources that attract birds. Other options include bird netting, spikes, enclosed rafters, owls, sealed openings, bird-proof roofing, noise deterrents, visual deterrents and professional control programs. 

6. Milking procedure

Milking routine is one of the most important controllable areas in mastitis prevention for lactating cows. Contagious pathogens can spread during milking if milk, equipment or hands carry bacteria from one cow to another. (2,3) 

A consistent routine should include:

• Clean gloves
• Proper forestripping (squeezing a few streams of milk from each teat to check for abnormal milk)
• Complete teat cleaning
• Correct pre-dip contact time
• Dry teats before unit attachment
• Clean and well-maintain liners and units
• Minimal liner slips and post-milking teat disinfection.

Forestripping helps milkers identify abnormal milk early. Again, watery milk, flakes, clots, strings or blood can all be signs of mastitis and should be addressed according to the herd’s protocol.

In herds with contagious mastitis pressure, additional steps such as milking infected cows last, segregating problem cows or flushing units may be needed. These decisions should be based on herd records, culture results and veterinary guidance.

Treatment Decisions Should Be Pathogen-Guided

Mastitis treatment should be built with the herd veterinarian. Antibiotics may be necessary in some cases, but treatment response depends on the pathogen, severity, stage of lactation and cow history. 

For example, some pathogens respond better to treatment than others. Chronic Staphylococcus aureus infections can be difficult to clear. Mycoplasma mastitis often requires a different herd-level response. Severe toxic mastitis may require rapid supportive care because the cow’s systemic response can be life-threatening. (2)

A complete treatment and prevention plan may include:

• Milk culture
• Veterinary diagnosis
• Antibiotic therapy when appropriate
• Supportive care for sick cows
• Anti-inflammatory therapy when directed by a veterinarian
• Dry cow therapy
• Internal teat sealants
• Vaccination protocols
• Culling decisions for chronic cases
• Milking equipment evaluation
• Bedding and facility review 

Dry cow therapy and internal teat sealants can help eliminate existing infections and prevent new infections during the dry period when used appropriately. (2)

Vaccines may also be part of a mastitis prevention strategy, especially in herds dealing with severe mastitis challenges. However, vaccination should not be viewed as a stand-alone solution. Research notes that vaccine effectiveness can vary by pathogen and herd management, which makes sanitation, milking procedure, cow comfort and treatment protocols just as important. (2)

Support Cows with Natural Approaches

Research also continues to explore how natural approaches can support mastitis control, especially as the dairy industry works to use traditional tools more responsibly. Plant-derived compounds, animal-derived compounds and bacteria-derived technologies have all been studied for their potential role in supporting udder health, immune response, microbial balance and inflammation management. (2) 

For example, research has looked at plant-derived compounds and extracts for their antimicrobial, anti-inflammatory or biofilm-related activity against mastitis pathogens. Some studies have also explored animal-derived compounds like chitosan and propolis, as well as bacteria-derived options such as bacteriocins and bacteriophages. (2) 

These studies are important because mastitis pathogens can be difficult to manage once infection is established. Some bacteria, including Staphylococcus aureus, Streptococcus uberis, E. coli and Enterococcus species, can form biofilms or persist in ways that make infections harder to clear. (2) Research has also shown that selenium and vitamin E can also support phagocytic activity, which is one part of the immune response involved in helping the cow fight infection. (4) 

Ralco’s Natural Supportive Care Program

Mastitis can show up when cows are already under pressure from calving, high production, ration changes or recovery stress. Ralco’s natural products are designed to support cows during those demanding times. 

1. Start Strong for Fresh Cows is a performance pack that supports cows immediately after calving with energy, hydration and key nutrients during the fresh period.
2. Fight Strong for Cow Stress boluses help support cows during periods of challenge when intake, recovery and normal function may be affected.
3. Fight Strong for Uterine Balance boluses support cows after calving when reproductive recovery and microbial balance matter.
4. Stand Strong for Dairy Cows is a feed additive that supports lactating cows through daily production stress and helps maintain performance during demanding periods. 

These products fit best as part of a complete dairy program that includes veterinary care, clean environments, consistent milking routines, strong transition nutrition, good records and early response when mastitis is suspected. 

A Practical Approach to Mastitis Control

Bottom line, mastitis control is built through everyday consistency. The goal is to reduce exposure, improve early detection and support cows before small problems become costly ones. 

Mastitis isn’t controlled by one product, one protocol or one treatment. It’s controlled by lowering risk at every point where bacteria can reach the udder.

When producers can reduce pathogen pressure, identify abnormal milk early and support cows through high-stress periods, they’re better positioned to protect milk production and long-term herd profitability.

Questions? Give our dairy specialists a call at 507-337-6916 or email RuminantHelp@RalcoAgriculture.com 

References

1. National Mastitis Council estimate cited in NIMSS. Mastitis Resistance to Enhance Dairy Food Safety, Milk Quality and Dairy Production Efficiency.
2. Cheng, W. N., and Han, S. G. 2020. Bovine mastitis: risk factors, therapeutic strategies, and alternative treatments. Asian-Australasian Journal of Animal Sciences.
3. Penn State Extension. Mastitis-Causing Pathogens and How They Get on Your Farm.
4. De Vliegher, S., Fox, L. K., Piepers, S., McDougall, S., and Barkema, H. W. 2012. Invited review: Mastitis in dairy heifers: Nature of the disease, potential impact, prevention, and control. Journal of Dairy Science.