Dietary effects of organic selenium and zinc combination on in vitro microbial dynamics in the rumen.

Abstract

This study used an in vitro approach to investigate the effects of combined organic selenium and zinc supplementation on rumen microbial communities. A completely randomized design was employed with five dietary treatments: basal diet only (CON), CON + selenium 0.30 ppm (part per million) + zinc 60 ppm (SZ-1), CON + selenium 0.45 ppm + zinc 60 ppm (SZ-2), CON + selenium 0.30 ppm + zinc 90 ppm (SZ-3), and CON + selenium 0.45 ppm + zinc 90 ppm (SZ-4). Selenium and zinc were provided in the form of organic-chelated methionine. Analysis of rumen microbiota through 16S rRNA gene sequencing showed no significant differences in microbial diversity ( p > 0.05); however, microbial composition was significantly affected. SZ-2, SZ-3, and SZ-4 groups exhibited an increased prevalence of Bacteroidetes and Proteobacteria and a reduction in Firmicutes compared to CON and SZ-1 ( p < 0.05). The relative abundance of Patescibacteria and Euryarchaeota was also reduced in the SZ-2, SZ-3, and SZ-4 groups ( p < 0.05). At the genus level, Prevotella , Ruminococcus , and Rikenellaceae RC9 gut groups were enriched in SZ-2, SZ-3, and SZ-4, whereas Lachnospiraceae XPB1014 and Christensenellaceae R-7 group decreased ( p < 0.05). Combined selenium and zinc supplementation as organic trace minerals significantly modulates rumen microbial composition, enhancing the relative abundance of carbohydrate-degrading bacteria while reducing methanogen-related taxa.