Optimizing ruminant feed efficiency: The synergistic effects of BMR sorghum and <em>Tithonia diversifolia</em> on nutrient digestibility, rumen function, and methane mitigation

The objective of this study was to determine the optimal ratio of BMR sorghum, which has a low lignin content, and T. diversifolia, which has a high protein content, as an alternative forage for ruminant feed. The study employed a fully randomized design comprising four treatments and four replications. The experimental treatments included T1 (80% BMR sorghum + 20% T. diversifolia), T2 (70% BMR sorghum + 30% T. diversifolia), T3 (60% BMR sorghum + 40% T. diversifolia), and T4 (50% BMR sorghum + 50% T. diversfolia). This study evaluated diet treatments by observing in vitro nutrient digestibility (including dry matter, organic matter, and crude protein), as well as fiber fraction digestibility (NDF, ADF, cellulose, and hemicellulose), rumen fluid characteristics (pH, NH3, and VFA), gas production (methane gas and total gas), total protozoan population, microbial biomass, and microbial protein synthesis. Compared with the other dietary treatments, the combination of 60% BMR sorghum and 40% T. diversifolia resulted in significantly (P>0.05) greater levels of in vitro nutrient digestibility; NH3, volatile fatty acid (VFA), and total gas production; microbial protein synthesis; and microbial biomass. However, 50% BMR sorghum and 50% T. diversifolia tended to decrease all of the parameters. In conclusion, the combination of 60% BMR sorghum and 40% T. diversifolia as ruminant feed impacts optimal nutrient digestibility, microbial protein synthesis, rumen fluid characteristics, and microbial biomass. Furthermore, this combination effectively decreased methane gas production and protozoan populations.