Failure of Passive Transfer
Failure of passive transfer happens when a newborn animal doesn't absorb enough antibodies from its mother's first milk, leaving it poorly protected against infection.
Newborn puppies, kittens, foals, calves, lambs and kids are born with an immune system that works but has never met anything. They carry almost no antibodies of their own, because the placenta in these species lets very little antibody through to the baby before birth. Their protection has to arrive by mouth, in the first milk the mother produces. That milk, colostrum, is thick with antibodies (immunoglobulins, mostly a type called IgG), and for a short window after birth the newborn gut can absorb those large molecules straight into the bloodstream. Failure of passive transfer, often shortened to FPT or FTPI, is what vets call it when that handover doesn't happen properly and the newborn ends up with too little antibody in its blood to defend itself.
Two things make this urgent. The first is the clock. The gut's ability to absorb antibodies fades quickly and then closes: in puppies the intestinal barrier is effectively shut after roughly 12 to 16 hours of life, in kittens absorption stops after about the first 16 hours, and in calves permeability declines sharply after 12 hours and has ceased by 24 hours. Colostrum given late is still good nutrition, but the antibodies largely stay in the gut instead of entering the bloodstream. The second is the consequence. A newborn without that antibody cover is wide open to infection, and both mortality and serious neonatal disease such as blood poisoning (sepsis) are far more common in these animals.
Plenty of ordinary situations can cause it: a mother who produces little or poor-quality colostrum, who leaks or lactates before giving birth, who rejects the newborn or is too sore after a difficult delivery to let it nurse, a very large litter where the smallest are pushed off the teat, a premature or weak baby with no suck reflex, or an orphan with no access to colostrum at all. In foals, research on Thoroughbreds, Standardbreds and Arabians has found inadequate transfer in a sizeable minority of otherwise normal foals, which is why testing is routine rather than exceptional on many stud farms.
When to involve your vet
In horses and farm animals, a blood test measuring IgG is standard, and there are quick in-clinic versions. In foals, above 800 mg/dL is considered adequate, 400 to 800 mg/dL is partial failure, and below 400 mg/dL is complete failure. Puppies and kittens are harder to test directly, so vets lean on history and risk, plus indirect blood markers, and treat when the picture fits.
Call your vet the same day, not tomorrow, if a newborn:
- hasn't nursed within the first two to four hours of life
- is limp, cold, quiet or crying constantly
- is being kept away from the mother, or the mother has no milk
- is losing weight or failing to gain in the first days
Timing decides the options. Within the absorption window, colostrum from the mother, from a donor of the same species, or from a bank can still be given by bottle or tube. Once the gut has closed, antibodies have to go in another way, most commonly an intravenous plasma transfusion in foals or serum given by injection in kittens and puppies. Both are veterinary procedures. Prevention beats treatment here: watch that every newborn actually feeds early, and get help fast if one doesn't.
This is general information, not a diagnosis. A newborn that isn't thriving is always a reason to be seen.
