Immune response of piglets on a PRRSV vaccination-Altered by different feed additives?

Animal performance was not affected by the experimental diets. Hematological parameters and complete blood counts displayed time-dependent changes, feed-related effects were not observed. The analysis of the expressed lymphocyte surface markers showed distinct time dependent shifts but no dietary effects. CD4−CD8α+ cells reached highest levels on day 21 post vaccination and decreased thereafter (P=0.037), the CD2+CD5− cells decreased in all groups towards day 35 (P<0.001). CD2+CD5+ cells were determined at constant levels during the observation period, while CD2−CD5+ decreased at day 21 (P=0.039) and CD4+CD8α‐ cells decreased over time (P=0.003). CD4+CD8α+-double positive cells increased age-dependently in all groups (P=0.006). CD21+ cells and CD14+ cells were not affected by age. Increasing levels of specific IgG were determined (P<0.001), but group effects could not be demonstrated as for the interferon γ producing T cells. The development of the immune system in piglets seems to follow a typical time-dependent pattern, the lack of dietary effects on the immune response in this trial might be due to a balanced diet and appropriate sanitary conditions.