Mixed supplementation of dietary inorganic and organic selenium modulated systemic health parameters and fecal microbiota in weaned pigs.

This study was conducted to evaluate the effects of dietary mixed selenium [MSe: inorganic selenium (ISe) + organic selenium (OSe)] levels on the growth performance, blood parameters, and fecal microbiota of weaned pigs. In a randomized complete block design (block = initial body weight), 156 weaned pigs were allotted to three dietary treatments (4 pigs per pen; 13 replicates per treatment) for 42 days. Dietary treatments included (1) a non-Se-fortified diet based on corn and soybean meal (CON), (2) CON + 0.15 ppm ISe and 0.15 ppm OSe (MSe3), and (3) CON + 0.25 ppm ISe and 0.25 ppm OSe (MSe5). Pigs fed both MSe diets showed no effects on growth performance or diarrhea frequency compared with those fed the CON diet. However, pigs fed MSe3 and MSe5 had higher serum interleukin-6 (p = 0.021, linear p = 0.011) on day 7 and higher Se concentrations (p = 0.002, linear p = 0.001) on day 42 than those fed the CON. In addition, pigs fed different levels of MSe exhibited quadratic (p = 0.054) and linear (p = 0.069) effects on the number of white blood cells and hematocrit on day 42 compared with those fed CON, respectively. Moreover, the MSe3 group had higher total protein concentration (p = 0.049, quadratic p = 0.026) on day 42 than the CON group, and the MSe5 group had lower blood urea nitrogen concentration (p = 0.094, linear p = 0.033). There were no differences in alpha diversity indices of fecal microbiota among dietary treatments. However, beta diversity indices based on the Bray-Curtis dissimilarity were clustered differently (r ² = 0.56, p = 0.001) among dietary treatments. Pigs fed the MSe5 diet showed an increase in the relative abundance of phylum Bacteroidetes [false discovery rate (FDR) adjusted p = 0.004], families Barnesiellaceae (FDR adjusted p = 0.006) and Veillonellaceae (FDR adjusted p = 0.006), genera Barnesiella (FDR adjusted p = 0.023) and Megasphaera (FDR adjusted p = 0.023), and species Barnesiella intestinihominis (FDR adjusted p = 0.016) and Megasphaera elsdenii (FDR adjusted p = 0.019) compared with those fed the CON diet. In conclusion, dietary MSe modulated the systemic health parameters and fecal microbial community in weaned pigs.