Bermudagrass, Tall Fescue, and Orchardgrass Pasture Combinations with Clover or N Fertilization for Grazing Steers. II. The Species Composition Index and Variability in Forage Growth and Consumption, and Animal Performance1

Abstract Forage growth and consumption, animal gain, and beef production were estimated in a steer (Bos sp.) backgrounding experiment concurrently with several environmental, plant, and animal characteristics. This paper describes a technique that combines the dynamic changes in species composition in pastures over time into a Species Composition Index (SCI). This index can then be related to the effects of season, grazing periods, stocking rates, forage crude protein, precipitation, and air temperature on forage growth and consumption, and beef production. The SCI was compared to the traditional classification variable treatments to describe seven differently managed pasture combinations of different forage species. It was superior to treatments in explaining variability and appeared to be a sensitive tool for characterizing dynamically changing pasture compositions. It could be a useful and flexible tool in quantifying species cover in many other situations.