Specific immune response of mares and their newborn foals to Actinobacillus spp. present in the oral cavity

Oral swab samples, serum and colostrum was taken from 15 mares and 14 of th eir foals, within 24 h of birth. The presence of antibody against Actinobac illus spp. isolated from the oral cavity was investigated using agar gel im munodiffusion. Antibodies against 48 out of the 77 Actinobacillus isolates from all horses in the study were present in the respective sera of 13 mare s and 9 foals. In 11 mother-foal pairs, the antibody content of the foal se rum was similar to that of the mare, and in 9 cases this was reflected in t he antibody content of colostrum from the mare. The results indicate that a n immune response to Actinobacillus spp. colonising the oral cavity is pres ent in many adult horses and that this immune response can be transferred f rom mother to foal via colostrum.