SummaryFailure of passive immune transfer (FPT) through colostrum absorption is still fairly frequent and responsible for a large proportion of cases of neonatal mortality in newborn foals. The most frequent causes of FPT are: low quality maternal colostrum (IgG < 40 g/l is observed in about 30% of all foaling mares) and/or a delay in ingestion (> 12 hours after birth). Colostrum quality can be measured reliably and rapidly under field conditions using a modified sugar refractometer (Colotest ® ). If maternal IgG content is too low, good quality colostrum can be given (> 1 litre) to the foal within 9-12 hours post -partum to prevent FTP. Ingestion of low quality colostrum, an artificial milk or an electrolyte solution by the foal before ingestion of good quality colostrum does not seem to prevent a correct level of protection. To date, there is no satisfactory colostrum substitute for complete colostrum replacement available on the market and the use of banked frozen colostrum is recommended. Recent research in our laboratory, however, shows that a freeze-dried extract of equine colostral IgG can provide satisfactory immune protection when used as a complete substitute for colostrum. Furthermore, the induction of lactation in selected barren mares may offer an alternative way to produce colostrum when needed.