Effects of Stevia Straw Supplementation on Meat Quality, Nutrient Composition, and Rumen Microbiota in Sheep

This study investigated the effects of dietary <i>stevia</i> straw supplementation on meat quality, amino acid and fatty acid content, and rumen microbial diversity in sheep. A total of 50 ram lambs (3-4 months, 27.01 ± 3.8 kg) were randomly assigned to five groups. Each group received a total mixed ration supplemented with 0% (control), 5%, 15%, 25% and 35% dry <i>stevia</i> straw for 72 days. Adding 15% and 25% <i>stevia</i> straw significantly increased the pre-slaughter body weight. EE content was also significantly higher across all experimental groups (<i>p</i> < 0.01), showing a linear increase with supplementation. Glutamic acid content in the 15% group was significantly higher than that in the 25% group (<i>p</i> < 0.05). The addition of stevia straw improved the fatty acid profile: C18:1n9c content in the 5%, 15%, and 25% groups was significantly higher than that in the CK (Control) group (<i>p</i> < 0.05); C18:2n6c content in the 25% group was significantly higher than that in the CK, 5%, and 15% groups (<i>p</i> < 0.05); the content of (C20:1) was extremely significantly higher in all experimental groups compared to the CK group. Additionally, the unsaturated fatty acid content in the 25% group was significantly higher than that in the CK group (<i>p</i> < 0.05). The relative abundances of Bacteroidota and Firmicutes were increased in the 25% and 35% groups, but the differences were not significant (<i>p</i> > 0.05). In conclusion, dietary supplementation of 15-25% stevia straw to the ration can significantly improve the slaughtering performance, meat quality and muscle nutrient composition of fattening sheep. In addition, the addition of stevia straw had no negative effect on the rumen microflora, and the 15% level could increase the abundance and activity of the rumen microflora, so it is recommended to use 15% stevia straw in the ration for sheep during the fattening period.