Symposium on Forage Evaluation: V. Intake and Digestibility Techniques and Supplemental Feeding in Range Forage Evaluation 1

TN THE Intermountain Area a major portion of the sheep -*• and cattle subsist on open range (31). In the winter, they graze on semi-deserts (figure 1), in the spring and fall on foothills, and in the summer on the higher mountains. These ranges have a diversity of soil, climate, topography, and vegetation. Therefore, the animal's diet is usually highly variable. The diet may be deficient in essential nutrients or may actually contain an excess of certain constituents that are toxic or poisonous. There are two main approaches to nutritional problems on range lands. The first is to measure the nutritive value of the plants which the animals consume. The phases included in this approach have been outlined by Harris et al. (30). They include (1) the determination of factors that affect the chemical composition of a given plant species on the range (13), (2) the botanical composition and nutritive content of the animal's diet (12, 16, 17, 18, 36, 54), and (3) the feeding of supplements to correct dietary deficiencies or toxicities (30, 56). The second approach is to obtain animal measures which reflect the nutritive state of the animal, such as the nitrogen-