Mastitis in Cattle: A Complete Guide for Dairy Farmers and Veterinary Professionals.

Mastitis is one of the most common and costly diseases affecting dairy cattle worldwide. It is responsible for significant economic losses due to reduced milk production, discarded milk, treatment costs, increased labor, and premature culling of affected animals. Beyond the financial burden, mastitis also compromises animal welfare and milk quality, making its prevention and control a top priority for every dairy farmer.
The disease occurs when microorganisms—most commonly bacteria—invade the udder through the teat canal, causing inflammation of the mammary gland. However, mastitis is not always caused by infection. Physical injuries, chemical irritation, or poor milking management can also trigger inflammation.

Some cows develop obvious signs such as swollen udders, abnormal milk, pain, and fever, while others may have subclinical mastitis, where milk appears normal but production decreases and somatic cell count rises. These hidden cases often remain unnoticed and silently reduce herd productivity.

Mastitis affects milk quality and can result in financial losses on several fronts. For instance, a high-yielding cow suffering from mastitis can experience a 3-4 kg reduction in daily milk yield,leading to a loss of Rs. 306 to Rs. 458 per cow, per day, for farmers. Besides, losses due todiscarded milk during the treatment come to be between Rs. 150 to 200.(Source: Department of Animal Husbandry and Dairyig).

What is Mastitis?

Mastitis is the inflammation of one or more quarters of the mammary gland. It is usually caused by bacterial infection but may also result from trauma or chemical irritation.During infection, bacteria multiply inside the udder and stimulate the cow’s immune system. White blood cells migrate into the milk to fight the infection, increasing the somatic cell count (SCC). As inflammation progresses, the milk-producing tissue becomes damaged, leading to reduced milk yield and poor milk quality.
Mastitis affects dairy cattle of all breeds and ages but is more common in high-producing cows, older animals, and cows kept under poor hygienic conditions.

Types of Mastitis

1.Clinical Mastitis:

Visible changes in udder (swelling, heat, pain) and milk (colour, blood,
fibrin) with a sharp drop in milk yield.

2.Subclinical Mastitis:

No visible changes, only detected by diagnostic tests. Subclinical mastitis is more important worldwide including India (varying from 10- 50% in cows and 5-20% in buffaloes) than clinical mastitis (1-10%).

3. Acute Mastitis:

Acute mastitis develops suddenly and progresses rapidly.
Affected cows may show:High fever,Severe udder swelling,Pain,Marked reduction in milk yield,Loss of appetite and Depression.

4.Chronic Mastitis :

Chronic mastitis persists for weeks or months.Affected cows may experience repeated episodes of mastitis and gradually lose milk-producing tissue due to fibrosis. Some cows become permanent carriers and may need to be culled to protect the rest of the herd.

Causes of Mastitis

Mastitis is often triggered by pathogens that can be broadly classified as
contagious or environmental:
1.Contagious Pathogens: These pathogens, such as Staphylococcus aureus and Streptococcus agalactiae, are typically spread from cow to cow during milking. Poor milking hygiene, such as using shared milking equipment without proper sanitation, is a major contributor.

2.Environmental Pathogens: These include organisms like Escherichia coli that thrive in manure, bedding, and unclean housing environments. Improper housing management, such as infrequent manure removal and poor ventilation, allows these pathogens to proliferate and infect cows.

3. Other Pathogens and Causes: Mycoplasma, fungi, virus, trauma, chemical irritant, etc.

Clinical Signs of Mastitis

The severity of mastitis depends on the causative organism, the cow’s immune status, and the stage of lactation. Clinical signs may vary from mild changes in milk to severe systemic illness.

• Local Signs
  Swollen udder or affected quarter
  Heat and redness of the udder
  Pain on palpation
  Firm or hard udder tissue
  Enlarged supramammary lymph nodes
  Reduced milk production from the affected quarter
• Changes in Milk
  Watery appearance
  Flakes or clots
  Yellowish or creamy discoloration
  Blood-stained milk
  Pus or thick secretions
  Foul-smelling milk in severe infections
• Systemic Signs
  In severe or toxic mastitis, cows may develop:
  Fever (above 39.5°C)
  Loss of appetite
  Depression
  Dehydration
  Rapid heart rate
  Weakness
  Reduced rumen motility
  Recumbency
  Septic shock (especially in acute E. coli mastitis)

Diagnosis of Mastitis

• 1. Physical Examination
  The veterinarian should evaluate:
  Udder symmetry
  Swelling and pain
  Teat injuries
  Milk appearance
  Rectal temperature
  Hydration status
  General health of the cow
  2. Strip Cup Test
  The first few streams of milk are collected in a strip cup with a black background.This simple test helps detect:
  Flakes
  Clots
  Blood
  Watery milk
  Abnormal secretions
  It is widely used before milking in dairy farms.
  3. California Mastitis Test (CMT)
  The California Mastitis Test is one of the most commonly used field tests for detecting subclinical mastitis.
  Principle
  The reagent reacts with DNA released from white blood cells (somatic cells) present in milk.Higher somatic cell counts produce a thicker gel.
  Interpretation
  Score Interpretation
  Negative Healthy quarter
  Trace Suspicious
  1+ Mild infection
  2+ Moderate infection
  3+ Severe infection
  The CMT is inexpensive, rapid, and easy to perform on farms.
• 4.Somatic Cell Count (SCC)
  Somatic Cell Count is an important indicator of udder health.
  General interpretation:
  Less than 200,000 cells/mL: Healthy udder
  More than 200,000 cells/mL: Suggests intramammary infection
  Higher SCC values are associated with reduced milk quality and production.
• 5.Milk Culture
  Milk culture is considered the gold standard for identifying the causative organism.It helps:
  Identify bacterial species
  Guide antibiotic selection
  Monitor herd infection patterns
  Reduce unnecessary antibiotic use
  Milk samples should always be collected aseptically before starting antibiotic therapy.
  6.Polymerase Chain Reaction (PCR)
  PCR is a rapid molecular diagnostic technique used to detect bacterial DNA in milk.

Treatment of Mastitis

1. Intramammary Antibiotics
These are commonly used for mild to moderate clinical mastitis.
Examples include:Cloxacillin,Cephapirin, Amoxicillin combinations (where appropriate).Other products selected according to culture and sensitivity results
Treatment should always follow veterinary advice and local regulation regarding antibiotic use.
2. Systemic Antibiotics
Systemic therapy may be indicated in:
Severe clinical mastitis
Acute toxic mastitis
Deep tissue infections
Cases with systemic illness
Drug selection should ideally be based on culture and antimicrobial sensitivity testing.
3. Non-Steroidal Anti-Inflammatory Drugs (NSAIDs)
Common veterinary NSAIDs include flunixin meglumine, ketoprofen, or meloxicam, depending on veterinary recommendation.
4. Fluid Therapy
Cows with toxic mastitis often require intravenous fluids to:
Correct dehydration
Restore blood circulation
Support kidney function
Manage shock
Oral electrolyte solutions may be useful in mild dehydration, while severe cases require IV fluids.
5. Frequent Milking
Milking the affected quarter more frequently helps:
Remove bacteria
Eliminate inflammatory toxins
Improve antibiotic penetration
Reduce pressure within the udder
This should be performed carefully to avoid spreading infection between cows.

Supportive Care

• Good supportive management improves recovery.
  Recommended measures include:
  Provide clean, dry bedding.
  Ensure adequate access to fresh water.
  Offer a balanced, nutritious diet.
  Isolate infected cows when practical.
  Maintain excellent milking hygiene.
  Follow the prescribed milk withdrawal period after treatment.
• Responsible Antibiotic Use
  Antibiotics should never be used indiscriminately.
  Good antimicrobial stewardship includes:
  Treating only when indicated.
  Collecting milk samples for culture whenever possible.
  Completing the full course of treatment.
  Avoiding unnecessary antibiotic use in culture-negative cases.
  Respecting withdrawal periods to prevent antibiotic residues in milk and meat.
  Responsible use helps reduce antimicrobial resistance and protects both animal and public health.