Effect of age on absorption and immune responses to weaning or introduction of novel dietary antigens in pigs

Pigs weaned at three weeks old absorb food protein antigens from the intestine. The amount of antigen absorbed declines over the next three weeks, and this decline is associated with an increasing level of serum antibody to the fed proteins. There was no difference in the rate of immune elimination of intravenously injected antigen in fed and unfed controls. The reduction of serum antigen is thus likely to reflect reduced absorption, possibly mediated by locally produced antibody. Pigs weaned at 10 weeks old also absorbed antigens and produced an antibody response when introduced to soya; and after three weeks of feeding soya the absorption of antigen was substantially reduced. This latter exclusion was specific for soya as a second novel protein (ovalbumin) was absorbed when introduced to the diet at this time. At six months, pigs no longer absorbed soya proteins when they were introduced to the diet. Furthermore, pigs of this age had serum 'antibody' to soya and other proteins such as keyhole limpet haemocyanin to which they had never been exposed.     

Comparative virulence of NAD-dependent and NAD-independent Actinobacillus pleuropneumoniae strains.

The virulence of a NAD-independent Actinobacillus pleuropneumoniae serotype 2 strain and NAD-dependent serotype 2, 3 and 9 strains was compared under experimental conditions. Hysterectomy-derived piglets were inoculated endobronchially with 50-500 cfu of these strains. All 23 piglets inoculated with the NAD-dependent strains developed acute disease within 12 hours post inoculation. Twenty-two of these piglets died within 24 hours after the first clinical signs. Three of nine piglets inoculated with the NAD-independent strain did not develop clinical disease. In the other six piglets, disease signs were similar as in the piglets inoculated with the NAD-dependent strains. No differences in clinical disease were observed between colostrum deprived piglets and piglets that obtained colostrum from a SPF sow.