Naturally Occurring Antibodies to Rumen Bacterial Species in Aging Calves

Age-related changes in agglutinating antibodies against rumen bacterial species were inves-tigated in calves from birth to 40 weeks of age. The results showed that naturally occurring rumen bacterial antibodies were routinely present in all calf sera tested. All calf sera titers of agglutinating antibody against some rumen bacterial species during the period from 4 weeks to 8 weeks of age exhibited unstable immune reaction. In particular, many rumen bacterial anti-bodies had disappeared from sera in 3-week to 4-week-old calves. It is conceivable that a rela-tionship may exist between the grouping of species of, rumen bacteria and the response capability of detectable agglutinating antibodies in sera with the aging of calves. The hypothesis presented here is that 4 types of immune. response pattern of the host ruminants against rumen bacteria can be designated; stable and continuous immune response, low immune response, unstable immune response and non-immune response patterns. On the hand, serum protein and globulin from aging calves was also investigated, and the data indicates that the age-related changes observed have similar features to agglutinating antibody titers to rumen bacteria. In addition, the role of the rumen bacteria as an immune stimulating factor in the development of the immune system with aging of calves was discussed.