Colostrum and milk, secretions of mammary gland (MG) are the two components of the post-natal delivery of maternal immunity to the neonate. In monogastrics, slgA is the predominant colostrum or milk immunoglobulins depending upon to the degree of prenatal Ig transfer, whereas in ruminant IgG 1 predominate. In ungulate as swine and ruminant absence of prenatal Ig transfer is compensated for by IgG enriched colostrum.These immunoglobulins, typically absorbed within the first 36 hours of life, by entering in blood; provide the newborn with the antibodies that arose from antigenic stimulation of the mother's systemic immune system and sustain the systemic protection of the neonate against invasive pathogens. In contrast, the passive mucosal protection of neonate mammals is dependent on the continuous supply until weaning of maternally secretory dimeric IgA (Monogastric) and IgG1 (ruminants), the so-called lactogenic immunity.The plasma cells (clgA+ cells) of the mammary gland produces slgA, which is, then secreted into the milk via the poly-Ig receptor of mammary epithelial cells. These antibodies are produced in response to intestinal and respiratory antigens, including pathogens and commensal organisms likely to be encountered by the neonate shortly after birth. Protection is also mediated by cellular immunity, which is transferred via maternal cells present in mammary secretions. The mechanisms underlying the various immunological links, that is cell (cigA+ cells) trafficking from inductor sites (mucosal surfaces) to MG, involve hormonally regulated addressins and chemokines specific to these compartments. As the same pattern of adhesion molecules -vascular adressin/homing receptor- MadCAM-1/alpha4 beta7 in one hand, VCAM-l/alpha4 beta1 in another and CCL20 chemokine was observed in small gut and nasal mucosa indicate the existence of cellular link between upper respiratory tract and MG in addition to the cellular enteromammary link. By comparison, absence of MadCAM-1 in ruminant MG, in agreement with the absence of cellular link with the intestinal immune system together with the low blood sigA translocation to MG explain the low levels of IgA in bovine mammary secretions. The enhancement of colostrogenic immunity therefore depends on the stimulation of systemic immunity, whereas the enhancement of lactogenic immunity depends among other means of appropriate stimulation at induction sites, gut and upper respiratory tract. In addition, mammary secretions provide factors other than immunoglobulins that protect the neonate and regulate the development of mucosalimmunity.