Dietary coated copper and zinc improve growth performance by modulating immune responses and fecal microbiota of weaned pigs

In the swine industry, supplementation with high levels of zinc oxide and copper sulfate in the weaner diet could be excreted through feces without being normally absorbed in the intestine, resulting in environmental pollution. Therefore, the various forms have been proposed to address this issue. The objective of this study was to investigate the effects of a low dietary dose of coated copper sulfate (CuSO₄) and zinc oxide (ZnO) on growth performance, frequency of diarrhea, nutrient digestibility, and immune responses of weaned pigs. The four dietary treatments were (1) a basal weaner diet based on corn and soybean meal (CON), (2) CON supplemented with 2,500 ppm standard ZnO (T1), (3) CON supplemented with 100 mg/kg dietary coated CuSO₄ and 100 mg/kg dietary coated ZnO (T2), and (4) CON supplemented with 200 mg/kg dietary coated CuSO₄ and 200 mg/kg dietary coated ZnO (T3). Dietary T2 and T3 increased (p < 0.05) the average daily gain for the first two weeks and the overall experimental period compared to that with CON. In addition, the groups supplemented with Cu and Zn tended to have a decreased (p < 0.10) frequency of diarrhea. Pigs fed dietary T2 and/or T3 had lower (p < 0.10) number of white blood cells on day 7 and hematocrit on day 14 compared to those fed CON. However, no difference was observed in the number of red blood cells among the dietary treatments. Regarding immune responses, dietary T2 decreased (p < 0.10) serum tumor necrosis factor-α on day 7 and increased (p < 0.10) immunoglobulin G on day 14 compared with CON. Moreover, pigs fed dietary T2 tended to have increased Limosilacatobacilus (p < 0.10). Dietary T3 had higher (p < 0.05) relative abundance of the genus Agathobacter compared to those fed CON and dietary T1 and decreased (p < 0.05) genus Terrisporobacter compared to those fed dietary T1. These results suggested the supplementation of dietary coated ZnO and CuSO₄enhanced growth performance and modulated immune responses associated with changes in the fecal microbiota composition