N.E. Muggli, P.L. Berggren-Thomas and L.M. Norman Department of Animal Science, Oregon State University, Corvallis, Oregon 97331, USA Proceedings of the New Zealand Society of Animal Production. The active immune system involves phagocytic, cell mediated and humoral processes plus complement proteins, all interacting to protect the individual from pathogenic organisms.
Passive immunity is acquired by new-born ungulates by ingestion of immunoglobulins from colostrum.
Research in laboratory animals has established that peak antibody synthesis following challenge with a foreign antigen responds readily to directional selection. The increased titre frequently results in enhanced resistance to some diseases but enhanced susceptibility to others. Oregon State University research has produced conflicting results as to the heritability of the ability of new-born calves and lambs to acquire and absorb colostral immunoglobulins and as to the heritability of this passive immunity considered as a trait of the dam. The authors speculate that stabilising selection for immune system traits might be most effective to improve generalised disease resistance and overall livestock production efficiency.