The purpose of this study was to determine what native forage species and parts of these species were selected and consumed by cattle grazing upon sandhill ranges. In addition, grazing habits of the animals were studied. It is an established fact that the chemical composition of range forage undergoes seasonal changes which may affect the nutrition of grazing animals (Hart, 1932; Stanley, 1938a and 1938b). Cook and Harris (1950) pointed out that preference for certain forage species was an important factor affecting the nutritive value of ingested forage. The need has been stressed for determination of botanical and nutritive composition of a grazing animal's diet so that grazing and range supplementation plans can be made (Cook and Harris, 1950; Harris et al., 1952). The many studies initiated by researchers to determine the botanical and nutritive content of the diet of grazing animals follow three general lines of methodology similar to those recognized by Lucas (1950) : (1) nutritional methods, (2) observational methods, and (3) sampling before and after grazing. The work reported herein was ac-Wolorado Agricultural Experiment Station Scientific Journal Article No. 603. Excerpt from a thesis presented to the Department of Range Management, Colorado State University, Fort Collins, Colorado, in partial fulfillment of the requirements for the Degree of Master of Science, 1957.

Frequency measured by the 3/4-inch loop technique was compared to estimates of plant basal cover, foliar cover, herbage production, and density. The relationship between loop-frequency and the other parameters were rarely significant or consistent as determined by regression and correlation. Loop-frequency unpredictably overrated foliar and basal plant cover on the basis of ratio estimates, a relative measure of bias. Therefore, frequency estimated by the 3/4-inch loop technique can be equated only to itself and not used to make inferences about other plant community parameters.

The 5-phase procedural framework uses 3-step range trend data to identify important trends in vegetation and soil characteristics and assign cause. Fieldwork is executed under strict procedural rules (phase 1), and current condition and tentative trend are determined (phase 2). Office statistical tests of change in frequency of important species groups, species, and soil surface factors are related by photointerpretation to visible changes in other important indicators of range trend (phase 3). All characteristics that indicate change are grouped and related to trends judged in the field (phase 4), and all available supplemental information is considered and most probable cause(s) of trend assigned (phase 5).

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The vigor of Idaho fescue in northeastern California was compared on plots grazed by two different approaches: one full 5-year cycle of rest-rotation grazing, at Harvey Valley; and repeated continuous grazing, at Grays Valley. Vegetative shoot lengths and numbers of flower stalks served as indicators of vigor. Vigor was higher on the Harvey Valley plots. The full-use treatments of rest-rotation grazing did not measurably reduce vigor, nor did the rest treatments improve it. Production of flower stalks appeared to depend on adequate spring precipitation and was not synchronized with the seed production phase of rest-rotation grazing. Continuous grazing at moderate intensity did not reduce plant vigor during the 5-year study period on the Grays Valley plot. The results suggest that moderate, continuous grazing permits Idaho fescue to maintain its vigor. But because rest-rotation grazing disrupts an apparent relationship between grazing use and precipitation, it may hold Idaho fescue vigor at a higher level than can continuous grazing.