Primary factor affecting animal performance is intake. Approximately 70% of the variation in animal performance can be explained by intake, while 30% can be explained by variation in digestibility. what factors affect intake of forages, particularly on pastures. studies of individual components may be of little use because the components can be interdependent. As pastures were grazed, the pastures were changed and the animals responded to those changes by altering their grazing behavior If we understand the relationships then we can design management systems that maintain the pastures and improve animal performance