Failure of passive transfer (FPT) is the inadequate intake of colostrum (from the mother’s milk) within 24 hours of birth, leading to inadequate provision of antibodies to the foal.
• Colostrum is the early milk from the mare that provides antibodies to the foal and allows for protection against infectious diseases
• FPT does not cause symptoms itself, but foals that have not nursed, or are nursing only small amounts, may develop FPT
• FPT is determined by testing plasma antibody levels
• Foals with FPT require emergency care as they are susceptible to life-threatening infections
• Foals with FPT require supplemental colostrum feeding or IV plasma transfusions to build their antibody supply
• Practices to prevent FPT include evaluating colostrum before foaling, ensuring foals nurse appropriately, and supplementing colostrum if intake or quality is thought to be inadequate
Signs of illness resulting from FPT in the foal usually occur within the first 72 hours after birth. Signs vary depending on the type of secondary infection, but may include:
• Fever • Recumbency • Extreme lethargy • Cold extremities • Pale gums • Swollen joints • Rapid breathing
• Coughing • Swollen umbilicus • Diarrhea
Mares that have underdeveloped udders or had milk leaking or streaming prior to labor may have poor quality colostrum that does not provide adequate protection, even if consumed in sufficient quantity.
FPT is common, affecting up to 25% of newborn foals. Foals with FPT require emergency veterinary care.
Foals with FPT are at risk of developing septicemia, joint and respiratory infections, and diarrhea. Foals with these complications have a poor prognosis, emphasizing the need for prompt veterinary intervention.
Colostrum is the only source of antibodies for newborn foals, making consumption of this “first milk” critical for newborn foal health. Factors that can result in FPT include:
• Reduced volume of colostrum intake (weak foals at birth with poor suckling response)
• Poor colostrum quality (due to maternal factors such as age, malnutrition, or underlying disease or infection)
• Inaccessible udder (poor mothering or rejected foal)
• Malabsorption of colostrum (foals with gastrointestinal disease that cannot absorb antibodies)
• Increased metabolism of immunoglobulins (sick foals that need more antibodies to fight an active infection)
Failure of passive transfer itself does not cause any symptoms.
Signs that a foal may not have nursed adequately include:
• Frequent, short periods of nursing • Inability to nurse properly • Recumbent and not nursing
• Failure to pass meconium • Full udder on the mare
Thorough physical examination of the foal and mare can provide clues that failure of passive transfer has occurred. A blood test for serum antibody levels in the foal can be used to confirm FPT. Tests are also available to measure immunoglobulins in the mare’s colostrum, providing an estimation of colostrum quality.
If the foal was born within the last 12 hours, oral ingestion of good quality colostrum from the dam, frozen-thawed colostrum from another source, or a colostrum replacer may suffice as treatment.
When a foal does not receive colostrum within 12 hours of birth, it requires multiple intravenous plasma transfusions. By 18-24 hours post-birth, oral colostrum is not effective as the gut closes and no longer allows immunoglobulins to pass.
Although FPT is treatable, the duration of treatment depends on how soon FPT is detected, and the presence of secondary conditions resulting from the FPT. Foals with FPT are prone to developing life-threatening conditions such as diarrhea, joint infections, pneumonias, and septicemia. These foals often have a poor prognosis and require aggressive, prolonged treatment. Foals that do not develop secondary infections have an excellent prognosis with appropriate and prompt treatment.
Methods to prevent FPT include:
• Monitor the mare pre-partum for general health and udder size • Evaluate colostrum quality before foaling
• Prepare a clean, quiet foaling area • Be present for foaling
• Help foal nurse if needed (healthy foals suckle 1-2 hours after birth)
• Tube or bottle feed foals with colostrum within 2-4 hours if failure to nurse is occurring
Failure of passive transfer is common in foals, and is thought to occur in 3-24% of foalings.
• Colostrum supplementation • Intravenous plasma transfusions
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