EVALUATION OF PINEGRASS AS RANGE FORAGE

Abstract

Seasonal changes in the quality of pinegrass (Calamagrostis rubescens) on native forest range in southern British Columbia included declines in crude protein content and in vitro digestibility of dry matter and increases in content of lignin, acid-detergent fiber, and ash. The decline in average daily gains of beef heifers was more rapid than changes in quality of the pinegrass over the grazing period from June to October.Pinegrass contained adequate nutrients for the rapid growth of yearlings or for maintaining weanling calves until August 1, whereupon protein and phosphorus supplementation were required. Nutrient requirements of pregnant cows and replacement heifers were adequately met until September 1.Copper and zinc were inadequate throughout the season. Calcium, iron, and manganese contents, however, were satisfactory. Silica was high and must be considered a potential problem in pinegrass utilization.Digestible dry matter gave a high positive correlation with crude protein and phosphorus and a high negative correlation with lignin, acid-detergent fiber, and total ash.Crude fiber, crude fat, and total soluble carbohydrate contents of pinegrass did not closely follow changes in either animal gains or in vitro digestible dry matter.Crude protein, phosphorus, and acid-detergent fiber appear to give a good indication of animal yields on pinegrass and could be used to evaluate pinegrass quality where animal data are not available.