ABSTRACT
The immune defense is immature in newborn animals, which depend on passive immunization from their mothers. Transmission of passive immunity from mother to young varies among different species (Table 3). In certain species (e.g., primates and rabbits) passive immunity is passed from the mother to the young through the placenta before birth. However, in most farm-animal species (e.g., cattle, sheep, pig, and horse), the newborn depends on the intestinal transmission of colostral immunoglobulins and other immunity-modulating factors for passive immune protection. Besides immunoglobulins, colostrum contains neutrophils, lymphocytes, cytokines, nucleotides, and various growth factors, and these colostrum-borne immune factors may affect the development of the immune system in the suckling young.
