Discuss in detail the etiology, pathogenesis, symptoms, diagnosis and control of mastitis in a high-yielding crossbred Jersey cow.

Etiology of Mastitis in High-Yielding Crossbred Jersey Cows

The etiology of mastitis is multi-factorial, involving a combination of infectious and non-infectious factors. High-yielding Jersey crosses have larger, more vascular mammary glands, creating a more favorable environment for microbial invasion.

• Infectious Agents: The most common causative agents include bacteria (Staphylococcus aureus, Streptococcus agalactiae, Streptococcus dysgalactiae, Escherichia coli, Klebsiella pneumoniae), fungi (rare), and viruses (less common). E. coli is often associated with acute, clinical mastitis, while Staphylococcus aureus is a common cause of subclinical mastitis.
• Non-Infectious Factors: These include:
  • Teat Morphology: Jersey crosses often have teat canals that are wider and shorter, making them more prone to bacterial invasion.
  • Nutrition: Deficiencies in vitamins (A, D, E) and minerals (selenium, zinc) impair immune function and increase susceptibility.
  • Management Practices: Poor hygiene during milking, inadequate teat dipping, overcrowding, and stress contribute to mastitis.
  • Stage of Lactation: Mastitis incidence is generally higher during the transition period (late pregnancy to early lactation) due to physiological changes.

Pathogenesis of Mastitis

The pathogenesis involves a complex interplay of microbial invasion, immune response, and tissue damage.

1. Microbial Invasion: Bacteria enter the mammary gland through the teat canal, often facilitated by poor milking practices or teat damage.
2. Initial Response: The cow's innate immune system (neutrophils, macrophages) attempts to eliminate the invading bacteria.
3. Inflammatory Response: If the bacteria overcome the initial defenses, a robust inflammatory response is triggered, characterized by vasodilation, edema, and infiltration of immune cells.
4. Tissue Damage: The inflammatory response, while intended to eliminate the infection, also causes damage to the mammary gland tissue, leading to reduced milk production and altered milk composition.
5. Chronic Mastitis: Repeated or unresolved infections can lead to chronic mastitis, characterized by fibrosis and permanent damage to the mammary gland.

Symptoms of Mastitis

Symptoms can be categorized as clinical (obvious signs) and subclinical (no visible signs but altered milk composition).

Clinical Mastitis

• Severe Cases: Fever, loss of appetite, depression, swelling and redness of the udder, abnormal milk (clots, flakes, watery appearance), pain upon palpation.
• Mild Cases: Slightly abnormal milk, mild udder swelling.

Subclinical Mastitis

• Milk Changes: Elevated somatic cell count (SCC) – a key indicator (SCC > 200,000/mL is generally considered indicative), altered milk protein profile, increased somatic cell composition.
• Production Decline: Reduced milk yield.
• No Visible Udder Changes: Often, no outward signs are present.

Diagnosis of Mastitis

Diagnosis involves a combination of clinical examination, milk sampling, and diagnostic tests.

• Clinical Examination: Palpation of the udder for swelling, hardness, and pain. Visual inspection for abnormal milk.
• California Mastitis Test (CMT): A rapid, inexpensive test that detects the presence of somatic cells in milk.
• Somatocoagulation Test (SCT): Similar to CMT but uses a different reagent.
• Microbiological Culture and Sensitivity: This is the gold standard for identifying the causative agent and determining its antibiotic susceptibility.
• SCC Measurement: Routine monitoring of SCC in bulk milk tank milk.

Control of Mastitis

A comprehensive approach encompassing preventative and therapeutic measures is essential.

Preventative Measures

• Pre-Milking Teat Preparation: Thorough cleaning and disinfection of teats with appropriate teat dips.
• Milking Hygiene: Maintaining clean milking equipment and environment.
• Post-Milking Teat Dipping: Using effective teat dips to kill residual bacteria.
• Dry Cow Therapy: Administering intramammary antibiotics to dry cows to eliminate existing infections.
• Culling of Chronic Cases: Removing cows with persistent mastitis to prevent spread.
• Nutrition Management: Providing a balanced diet with adequate vitamins and minerals.
• Housing and Ventilation: Ensuring proper ventilation and hygiene in the barn.
• Genetic Selection: Selecting bulls with high breeding values for mastitis resistance.

Therapeutic Measures

• Intramammary Antibiotics: Used for treating acute mastitis. Requires careful antibiotic sensitivity testing to avoid resistance.
• Systemic Antibiotics: May be necessary for severe cases with systemic signs.
• Anti-inflammatory Drugs: To reduce inflammation and pain.

Control Method	Description	Effectiveness
Teat Dipping	Pre and post-milking disinfection of teats.	High; reduces bacterial load.
Dry Cow Therapy	Intramammary antibiotic treatment during the dry period.	High; prevents new infections.
Genetic Selection	Selecting animals with genetic resistance.	Moderate; long-term improvement.