Model Answer
0 min readIntroduction
Failure of Passive Transfer (FPT) is a critical neonatal condition in cattle, characterized by inadequate transfer of maternal antibodies to the calf, leaving it vulnerable to infectious diseases. This deficiency occurs when immunoglobulin (IgG) levels in the calf's serum are below a threshold considered protective, typically < 150 mg/dL. The transfer of immunity from the dam to the calf occurs primarily through colostrum ingestion during the first few hours of life. The inability to achieve sufficient passive immunity significantly increases morbidity and mortality in calves, impacting farm profitability and animal welfare. Recent studies highlight the growing concern due to increasing herd size and intensive farming practices which can compromise colostrum quality and calf intake.
Etiology of Failure of Passive Transfer
The etiology of FPT is multifaceted and can be categorized into factors affecting colostrum production, colostrum quality, and calf intake.
- Dam-Related Factors:
- Breed: Certain breeds may produce lower IgG concentrations in colostrum.
- Parity: First-parity cows often produce colostrum with lower IgG concentrations compared to older cows.
- Nutrition: Inadequate protein intake during late gestation can reduce IgG synthesis in the dam.
- Disease: Systemic infections in the dam can impair antibody production.
- Genetics: Genetic predisposition plays a role in IgG levels.
- Colostrum-Related Factors:
- IgG Concentration: Low IgG concentration in the colostrum directly limits antibody transfer.
- Colostrum Quality: Factors affecting colostrum quality include storage time, temperature, and handling practices.
- Calf-Related Factors:
- Birth Order: Calves born later in a sequence often receive less colostrum.
- Strength and Ability to Suck: Weak or premature calves may struggle to suckle effectively.
- Gut Permeability: The calf’s gut has a “leaky” barrier during the first 12-16 hours of life, allowing large antibody molecules to be absorbed. This permeability decreases rapidly after that.
Pathogenesis of Failure of Passive Transfer
The pathogenesis of FPT revolves around the failure of the calf to acquire sufficient maternal antibodies, leading to a compromised immune system.
- Absorption of Immunoglobulins: After birth, calves actively absorb intact IgG from colostrum. This process requires a specialized transport mechanism in the intestinal epithelium.
- Serum IgG Levels: If colostrum intake is insufficient, serum IgG levels remain low.
- Immune System Development: Low IgG levels impair the development of the calf’s own immune system. The calf's B-lymphocytes are not adequately stimulated to produce antibodies.
- Increased Susceptibility to Infection: The calf becomes highly susceptible to common neonatal pathogens like E. coli, Salmonella, Rotavirus, and Coronavirus.
- Secondary Infections: Initial infections can lead to secondary complications and increased mortality.
Symptoms and Lesions in FPT
The clinical signs and lesions associated with FPT are often secondary to the infections that occur due to the compromised immune system.
- Early Symptoms (often subtle):
- Lethargy and weakness
- Failure to thrive
- Depressed appetite
- Advanced Symptoms (due to secondary infections):
- Diarrhea: Often severe and watery, leading to dehydration.
- Pneumonia: Difficulty breathing, coughing, nasal discharge.
- Septicemia: Fever, shivering, and general malaise.
- Umbilical Infection (Omphalitis): Swelling and discharge from the umbilical cord.
- Joint Ill (Septic Arthritis): Inflammation and pain in joints.
- Lesions:
- Necropsy Findings: Gross lesions vary depending on the specific infection. Pneumonia may show consolidated lung tissue. Septicemia can result in widespread petechial hemorrhages.
- Histopathology: Shows inflammation and tissue damage consistent with the infectious agent.
Table: Comparison of IgG Levels and Clinical Significance
| Serum IgG Level (mg/dL) | Clinical Significance |
|---|---|
| > 150 | Adequate passive immunity |
| 50-150 | Partial passive immunity; increased risk of infection |
| < 50 | Failure of passive transfer; high risk of severe infection |
Diagnosis and Management
Diagnosis involves serum IgG measurement using a colostrometer or ELISA. Management focuses on improving colostrum quality and calf intake, and treating secondary infections.
Management strategies:
- Colostrum testing and banking.
- Ensuring adequate colostrum intake within the first 6 hours of life.
- Supplemental colostrum feeding or plasma transfusions.
- Antibiotic therapy for secondary infections.
Conclusion
Failure of Passive Transfer remains a significant challenge in neonatal calf health, leading to substantial economic losses and animal welfare concerns. Understanding the multifaceted etiology, pathogenesis, and clinical manifestations is crucial for effective prevention and management. Emphasis should be placed on improving colostrum quality, ensuring adequate intake, and implementing proactive monitoring strategies. Further research into genetic factors influencing IgG production and innovative approaches to antibody delivery could significantly reduce the incidence of FPT and improve calf survival rates.
Answer Length
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