The acquisition of passive immunity in the new-born piglet

Because of the epitheliochorial nature of the porcine placenta, the new-born piglet must acquire maternal immunoglobulins from ingested colostrum and milk for passive immune protection until the immune system of the piglet becomes fully developed. Concentrations of IgG in piglet plasma depend on the amount of colostrum ingested, IgG concentrations in colostrum and the timing of gut closure (when intact IgG can no longer be absorbed by the gastro-intestinal tract of the piglet). Much of the available information concerning IgG absorption by the piglet and the mechanism and timing of gut closure has been derived from studies using artificially-fed piglets. It is now recognised that, in addition to changes in colostrum IgG concentrations in the first 24 h of life, colostrum contains many bio-active compounds whose concentrations also change rapidly in the first 24 h of life. Modem sows are expected to rear increased numbers of physiologically less mature piglets and producers are faced with pressures to reduce antibiotic usage. Therefore it is critical that piglets absorb adequate amounts of IgG for disease protection. The review assesses the maternal supply of IgG and piglet absorption of IgG in naturally suckling piglets of modem genotype. Nutritional and other factors which may influence acquisition of IgG by the piglet are discussed and relationships between acquisition of passive immunity and development of active immunity addressed. (C) 2002 Elsevier Science B.V. All rights reserved.