Passive immunity in piglets : the acquisition of immunoglobulin G (IgG) from colostrum
Foetal piglets do not obtain immunoglobulins during pregnancy and rely on colostrum immunoglobulins until active immunity develops. The amount of immunoglobulin that piglets obtain depends upon: colostrum immunoglobulin concentration; quantities of colostrum ingested and when closure occurs. Closure describes the change that takes place between 12-36h of life, when the piglet gut can no longer absorb immunoglobulins. A series of studies were undertaken to examine colostrum IgG concentrations and IgG acquisition by piglets. The first two trials demonstrated that IgG concentration between sows and piglet IgG intake was very variable. Piglet plasma IgG concentrations were remarkably consistent however, suggested that piglets were regulating IgG uptake. The third trial reduced piglet IgG intakes by delaying suckling. Results showed that piglets with reduced IgG intakes had reduced plasma IgG concentrations and could not compensate for lowered IgG intake. The results suggested that piglets regulated IgG uptake when IgG was in excess, but had only limited ability to regulate IgG uptake when IgG supply was limited. The fourth trial set out to examine the effects of maternal diet and vaccination on piglet IgG acquisition. A 2x2 factorial design, sows were fed diets either with vitamins A, C and E at recommended amounts or 3-5 times recommended amounts and either vaccinated or not. Results showed that maternal vaccination or diet did not affect maternal plasma IgG concentration or colostrum IgG concentration. Supplementing maternal diet with vitamins significantly increased piglet plasma IgG concentrations, as did maternal vaccination. Of ingested IgG, approximately 0.6-0.7 appeared in piglet plasma. It was possible to influence piglet plasma IgG concentrations by manipulating maternal diet and immune status. With increasing pressure on the use of antibiotics in agriculture and increasing animal welfare/health demands, the effects of other macro and micronutrients on piglet IgG status need to be investigated.