Ewe-lamb pairs were grazed within a conifer plantation in northern Idaho for three summers. Botanical composition of sheep diets was estimated using microhistological analysis of fecal samples. Diet selection by sheep strongly favored grasses and sedges (i.e., graminoids) vs. forbs or shrubs, regardless of grazing season. Overall, sheep diets averaged 58% graminoids. Sheep generally selected forbs more in late summer than in early summer. Sheep consumed shrubs more in late summer during a hot, dry year, but during a wet, cool year sheep ate more shrubs in early summer than in late summer. Sheep consumption of conifers was not affected by grazing season, and conifers averaged 4% of sheep diets. Nutritive quality of sheep diets was evaluated based on levels of nitrogen and diaminopimelic acid (DAPA) in sheep feces. Higher levels of fecal N and fecal DAPA generally correspond to greater nutritive quality in sheep diets. Both fecal N and DAPA tended to be greater in early summer vs. late summer. Predictive equations based on these indices suggested that sheep performance suffered during the late summer grazing period.
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