The researchers studied different combinations of grasses and clover or nitrogen fertilization in pastures for grazing steers. They created a Species Composition Index (SCI) to track changes in pasture composition over time. The SCI was better at explaining variability in forage growth, consumption, and beef production compared to traditional methods. It can help understand how factors like season, grazing periods, stocking rates, protein content, precipitation, and temperature affect pasture and animal performance. The SCI is a useful tool for analyzing changing pasture compositions and can be applied in various situations.