Zinc supplementation has been shown to reduce the incidence of diarrhoea and to protect animals from intestinal diseases but the mechanisms of this protective effect against virus infection in vivo have not yet been elucidated, report Weidong Chai of Freie Universität Berlin in Germany and co-authors in a paper published in BMC Veterinary Research.

TGE virus (TGEV) causes diarrhoea in piglets with an age-dependent decrease of severity.

The researchers explain that they used 60 weaned piglets that were divided into three groups to evaluate the effect of different zinc levels added to a conventional diet (50mg zinc per kg diet, Zn-L; control group). The other groups received the diet supplemented with zinc oxide at final concentrations of 150mg zinc per kg diet (Zn-M) or 2,500mg per kg diet (Zn-H).

Oral challenge infection with TGEV was performed when the pigs had been fed for one week with the respective diet. Half of the piglets of each group were sacrificed on day 1 and day 18 after challenge infection.

Faecal consistency was improved and bodyweights increased in the Zn-H group when compared to the other groups but no direct effect of zinc concentrations in the diet on faecal TGEV shedding and mucosal immune responses was detectable.

However, in the Zn-H group, the researchers found no villus atrophy and decreased caspase-3-mediated apoptosis in the jejunal epithelium.

Furthermore, pigs receiving the Zn-H diet showed a down-regulation of interferon (IFN)-α, oligoadenylate synthetase (OAS), zinc transporter SLC39A4 (ZIP4) but up-regulation of metallothionein-1 (MT1), as well as the zinc transporters SLC30A1 (ZnT1) and SLC30A5 (ZnT5).

In addition, forskolin-induced chloride secretion and epithelial resistance were controlled at a physiological level in the Zn-H pigs but not the other groups.

Finally, in the Zn-H group, earlier and higher systemic TGEV-specific serum antibody response was observed.

These results suggest that high dietary zinc could provide enhanced protection in the intestinal tract and stimulate the systemic humoral immune response against TGEV infection, concluded Chai and co-authors.

Reference

Chai W., S.S. Zakrzewski, D. Günzel, R. Pieper, Z. Wang, S. Twardziok, P. Janczyk, N. Osterrieder and M. Burwinkel. 2014. High-dose dietary zinc oxide mitigates infection with transmissible gastroenteritis virus in piglets. BMC Veterinary Research. 10:75 doi:10.1186/1746-6148-10-75

April 2014