Passive Transfer

Passive Transfer



Basic Information image



Definition




• Measurement of the antibody (IgG) concentrations in the neonate to determine if adequate absorption of maternal antibodies has occurred following ingestion of colostrum.


• The radial immunodiffusion assay (RID) is considered to be the most accurate method for quantitative assessment of plasma IgG concentrations in foals. However, RID assay results typically have a 24-hour turnaround time, making them clinically impractical for critically ill foals.


• Most clinics utilize semiquantitative foal-side tests including turbidimetric immunoassays, latex agglutination tests, enzyme immunoassays, zinc sulfate turbidity tests, and glutaraldehyde coagulation tests. Though rapid and clinically applicable, these tests appear to be less reliable than the RID assay.



Synonym(s)




Neonatal immunoglobulin (IgG) levels



Typical Normal Range (US units; SI units)




• Most foal-side tests are semiquantitative.


• <200 mg/dL = complete failure of passive transfer


• <400 mg/dL = failure of passive transfer


• 400 to 800 mg/dL = partial failure of passive transfer


• >800 mg/dL = adequate passive transfer



Physiology


Transplacental transfer of antibodies does not occur in horses and cattle. These animals rely on immunoglobulin-rich colostrum in the early post-partum period. Failure of passive transfer (FPT) occurs when foals fail to consume or absorb sufficient amounts of colostrum during this critical period. Alternatively, FPT may occur if the mare produces poor quality colostrum or if colostrum is lost through premature leakage of milk. In the foal, specialized enterocytes responsible for immunoglobulin absorption are present within the small intestine. Immunoglobulin absorption is greatest in the first 6 to 8 hours of life. Absorption ceases at 24 to 36 hours as the specialized enterocytes are replaced by normal gastrointestinal epithelial cells. Because of the narrow window for colostrum absorption, IgG level testing at 8 to 12 hours is recommended. Tests performed during this window allow for oral supplementation with colostrum or a colostrum substitute in time for gastrointestinal absorption. Postsupplement IgG testing is recommended. Foals with FPT due to malabsorption of colostrum or identification after the 24- to 36-hour time period may require intravenous supplementation.



Causes of Abnormally Low Levels




• Poor colostral quality in the mare (low IgG levels; <1000 mg/dL)


• Inadequate consumption of maternal colostrum: Inability or lack of desire to nurse in the foal and foal rejection by mare


• Premature lactation or milk loss in the mare


• Gastrointestinal malabsorption of ingested colostrum in the foal

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Jul 24, 2016 | Posted by in SMALL ANIMAL | Comments Off on Passive Transfer

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