Evaluating Forage Quality of Pastures

Abstract

Ten irrigated pastures located in northeastern Colorado were evaluated for forage quality during the 1972 growing season. Most of the pastures used the center-pivot type of sprinkler system and consisted mainly of mixtures of alfalfa (Medicago sativa L.), orchardgrass (Dactylis glomerata L.), and smooth bromegrass (Bromus inermis Leyss.) in varying proportions. Thirteen factors for quality were evaluated from each pasture from samples obtained over a 5-month period Mg, P, K, crude protein, in vitro digestibility, cell wall constituents, cell contents, hemicellulose, cellulose, lignin, and silica showed significant fluctuations during the growing season, while calcium and ash insoluble in neutral detergent remained fairly constant. Changes that occurred during the growing season could be accounted for by time of harvest, management practices, species, and other environmental factors such as differences in climate and soil. In spite of differences between pastures, satisfactory regression functions were developed to give good estimations of forage quality using in vitro dry matter digestibility as the dependent variable. By submitting the data to the stepwise regression calculation techniques, good predictive equations for IVDMD were developed that can readily be applied to pastures in northeastern Colorado regardless of location, management, or species composition.