Differences in Food Ingestion and Digestion Among Sheep Classified as High or Low Sagebrush Consumers

Abstract

Animals vary substantially in amount of three-tip sagebrush (Artemisia tripartita [Rydb.] tripartita) or other chemically defended plants they will voluntarily consume. This individual variation results from differences in dietary experience and inherited digestive characteristics. We conducted a series of experiments to examine behavioral and digestive traits of sheep identified as high or low consumers of sagebrush. In a pen-acceptance trial, high sagebrush consumers ate the same amount of sagebrush as low consumers when they had unrestricted access to a basal ration of alfalfa pellets (P = 0.77). However, when animals were restricted to 75% of their recommended energy requirement, sheep identified as high consumers ate more sagebrush than low consumers (P = 0.05). In a digestion trial, sagebrush reduced the dry matter digestibility when it was added to a hay-based diet. In vivo digestibility of a diet containing 10% fresh sagebrush and 90% alfalfa/grass hay was higher for high sagebrush consumers than low consumers (P = 0.02). The parameters measured in this trial suggest sheep that willingly consume high amounts of sagebrush, digest diets containing sagebrush more efficiently than low consumers.