Feeding sheep a pelleted total mixed ration with 1% yeast culture can improve fiber degradation in their rumen. This is because the yeast culture helps stabilize the rumen pH, which is important for breaking down fiber. The study found that the highest fiber degradation occurred with 1% yeast culture supplementation. Additionally, the levels of certain bacteria in the rumen were positively affected by the yeast culture, further aiding in fiber breakdown. Overall, supplementing sheep's diet with 1% yeast culture in pelleted total mixed ration is optimal for improving fiber degradation in their rumen.