Effects of zinc supplementation on virus infection in pigs

The worldwide trend towards a reduced reliance on in-feed antibiotics has increased the pressure to develop alternative strategies for the management of infectious diseases in the livestock industry. Extensive research into the beneficial effects of Zn has revealed its important role in host defense and immune responses, but there have been hardly any reports concerning the effects of Zn against virus infections in pigs yet. Since the current vaccines or therapies are not successfully providing full protection against PRRSV and TGEV infections, the overall goals of this thesis were to investigate the systemic diet ZnO effects on an acute and persistent PRRSV infection and the local diet effects on a mild and self-limiting TGEV infection in pigs, and to explore the potentials of Zn as a single approach for multiple diseases. Therefore, in the PRRSV challenge infection trial, we tried to find out if high levels of Zn could influence the success of vaccination with an experimental inactivated vaccine and if it could affect the level of protection in vaccinated and/or non-vaccinated pigs challenged with a heterologous PRRSV strain. And in the trial of TGEV infection, which causes serious gastroenteritis in piglets, we sought to determine if Zn supplementation could improve systemic and/or mucosal immune responses after infection, and the possible protection mechanisms involved in the antiviral potential of Zn were investigated. The specific aims of this study are: 1. To detect if high level of Zn could improve the clinical outcome after virus infections in pigs; 2. To evaluate whether Zn supplementation has an effect on the innate and adaptive immune responses to virus infections; 3. To explore potential of Zn treatment on the immunogenicity of a PRRSV vaccine; 4. To investigate the mechanisms responsible for a protective effect of Zn against virus infections in vivo.