Crude Terpenoid Influence on In Vitro Digestibility of Sagebrush

Abstract

The influence of crude terpenoid content on in vitro organic matter digestibility (IVOMD) was determined for basin big sagebrush (Artemisia tridentata Nutt. ssp. tridentata), Wyoming big sagebrush (A.t. ssp. wyomingensis Beetle and Young), mountain big sagebrush (A.t. ssp. vaseyana [Rydb.] Beetle), and black sagebrush (A. nova Nels.). IVOMD was determined using mule deer (Odocoileus hemionus hemionus), sheep (Ovis ammon aries), and steer (Bos taurus) rumen inocula with current year's growth collected from the 4 taxa at a common site on 1 Jan., 15 Feb., and 1 Apr. 1981. All inocula had similar digestive efficiency. Extracting crude terpenoids from foliage increased IVOMD by an average of 12.3% overall. Few differences in IVOMD among taxa and dates were evident in foliage after crude terpenoids had been extracted. Order of increasing digestibility among taxa without crude terpenoids extracted was black sagebrush, mountain, Wyoming, and basin big sagebrushes, respectively. IVOMD generally increased from January to April as crude terpenoids decreased. Crude terpenoid concentrations were lowest in mountain big sagebrush, intermediate in black sagebrush and Wyoming big sagebrush, and greatest in basin big sagebrush.