With the foaling season in full swing, new foals are enjoying life at farms, ranches, and breeding facilities around the country. While most foals are protected from common equine diseases by maternal antibodies in the mare’s colostrum (the mare’s first milk that antibodies that help protect the foal’s immune system) for the first few months of life, they need to start a course of vaccinations as soon as those maternal antibody levels begin to drop.

Only a veterinarian can provide guidance on when to vaccinate. Approximately four to six weeks prior to foaling, mares should be given a pre-foaling series of vaccinations to boost the antibody levels in the colostrum they produce.

Foals that receive and absorb a mare’s colostrum within 24 hours of birth receive maternal antibodies that help protect them from most infectious diseases and should not be vaccinated until these maternal antibody levels decline. If vaccinated too early, colostral antibodies can block the foal’s immune response.

"Antibodies in a mare’s colostrum can block the foal’s ability to mount an effective protective immunity, so owners and breeders need to coordinate initial vaccinations based on when those maternal antibodies drop off and when the mare was last vaccinated," said Tom Lenz, DVM, MS, senior director of equine veterinary services for Pfizer Animal Health. "Foals are most vulnerable at around three to four months old when maternal antibodies are decreasing and they have not yet been vaccinated