THE INCIDENCE AND CONSEQUENCES OF FAILURE OF PASSIVE TRANSFER OF IMMUNITY ON A THOROUGHBRED BREEDING FARM

Circulating IgG concentration was determined between 12 and 24 hours a fter birth for 323 foals born on a Thoroughbred breeding farm over 3 c onsecutive years, The incidence of failure of passive transfer (FPT) o f maternal immunoglobulins (foal circulating IgG concentration < 8 g/L ) was found to be 9.6%. Foals born late in the season (October to Dece mber) were found to be at increased risk for the development of FPT, T he degree of assistance required at parturition and the presence of a periparturient problem in the mare or foal also significantly influenc ed the subsequent incidence of FPT, Passive immune status significantl y influenced the likelihood of foals developing septic illness (joint ill, septicaemia, pneumonia) in the first month of life, but had no si gnificant effect on the development of diarrhoea or Rhodococcus equi p neumonia. The results of the current study support the value of routin e monitoring of passive immune status and the early speculative treatm ent of foals considered to be at risk for the development of FPT.