Abstract
Groups of pregnant sows were inoculated with type 01 foot and mouth disease (FMD) oil emulsion vaccine at various times before farrowing and samples of the sow's serum, colostrum and milk, and piglets serum were collected for analysis. Pregnant sows responded well to vaccination regardless of their state of gestation. Single vaccination produced protective levels of antibody in three out of four sows while double vaccination produced protective levels in all six sows tested. Although there was no evidence of a fall in the neutralizing antibody titres over one year post vaccination the IgG antibody population did show signs of a change in its heterogeneity and avidity. No FMD neutralizing antibodies were detectable in the piglets’ serum at birth but they were present 1. 5hr after suckling and peak titres were reached one to three days later. Samples of colostrum/milk collected from different teats three days after farrowing showed significant (P<0. 005) fore to hind variation. A significant correlation was also observed between the sow's serum titres and colostrum titres at farrowing (r=0. 90), and between sows colostrum titres at farrowing and their three day old piglets serum titres (r=0. 99). When sows were vaccinated 12 to 13 days before farrowing (dbf) the predominating neutralizing antibody at parturition was IgM and the observed half-lives of the maternally derived antibodies in the piglets were short (four to eight days). However, when sows were last vaccinated 30 to 32dbf, the maternally derived neutralizing antibodies in the piglets were predominantly IgG and the observed half-lives were seven to 21 days. If corrections were made for increase in blood volume the decay rates of IgM antibodies in piglets were seven to 18 days while the decay rate for IgG was greater than 408 days. The response of young pigs to FMD vaccination and the effect of maternally derived antibodies on this response was also studied. Piglets born to non-immunized sows were able to respond to vaccination when one week old, with no deleterious effect on their growth rate. However, total suppression of the vaccination response was observed in one, two and four week old piglets born to immunized sows and a partial suppression occurred in eight week old piglets. This maternal antibody suppressive effect could be mimicked by the passive transfer of neutralizing IgG antibodies into older piglets.