Influence of zinc supplementation on immune parameters in weaned pigs

Zinc is an essential trace element, highly important for a well functioning immune system. In case of zinc deficiency, proper immune functions are not ensured thus leading to various diseases. Weaning of pigs from the sow causes stress, increasing susceptibility to infections. Moreover, low feed intake during the first two weeks post-weaning, accompanied by low zinc intake, results in temporary zinc deficiency. Therefore, supporting the immune system by zinc supplementation might improve its function and thereby the pigs' health and well-being. In this study, the immune status of weaned pigs was analyzed under different conditions of zinc supplementation. More precisely, the daily porcine diet was either left unsupplemented (0 ppm), or was supplemented with low (100 ppm), or high (2500 ppm) amounts of additional zinc in the form of zinc oxide (ZnO) (Zn0, Zn100, and Zn2500, respectively). Porcine innate and adaptive immune cells of the different dietary groups were analyzed. Results revealed an improved innate immune capacity, represented by increased phagocytosis and slightly increased oxidative burst in cells from the Zn2500 pigs and Zn100 pigs, respectively. Apart from that, zinc supplementation improved adaptive immunity, as seen by increased numbers of CD3⁺ T cells as well as increased numbers of CD3⁺CD4⁺Foxp3⁺ regulatory T cells, elevated interleukin (IL)-2 production and decreased IL-10 production. Although not significant, supplementing 2500 ppm zinc slightly decreased killing activity of natural killer (NK) cells. Thus, the optimal concentration for zinc supplementation of weaned pigs two weeks post-weaning needs to be further studied, presumably establishing an optimal concentration between 100 ppm and 2500 ppm zinc. Genome comparisons indicate that the porcine genome is more closely related to the human genome than the murine genome is related to the human genome. Therefore, the pig seems to be a suitable organism to study human immunity and diseases. Results obtained in the current study might therefore be transferable to the human immune system.