How to Use a Quantitative Turbidimetric Immunoassay Assay to Determine Immunoglobulin G Concentrations in Neonatal Foals

1. Introduction
Newborn foals are born immunocompetent but without circulating immunoglobulins.¹  It is crucial that the newborn foal receives immunoglobulins from the mare’s colostrum to prevent infectious disease during the first few months of life. Healthy foals ingesting good-quality colostrum will typically have immunoglobulin G (IgG) levels >800 mg/dl at 24 h of life, which is considered adequate passive transfer of immunity.²  Failure of passive transfer (FPT) is commonly defined as an IgG level <400 mg/dl after 24 h of age.²  Partial failure of passive transfer (PFPT) is defined as an IgG level between 400 and 800 mg/dl at 24 h of age.2

The incidence of FPT in foals is 10–20%, and the incidence of PFPT in foals 17–19%.^3–7  Risk factors for FPT include ingestion of colostrum with a low level of immunoglobulin, failure to ingest a sufficient quantity of colostrum, and failure to absorb colostral immunoglobulins from the gastrointestinal tract.² [...]