Early summer vs. late summer diets of sheep grazing in a conifer plantation
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Authors: T. Mbabaliye, J. L. Kingery, and J. C. Mosley
Date: 1999
Journal: Sheep and Goat Research Journal
Volume: 15
Number: 1
Pages: 34-40
Summary of Methods: 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.
Article Summary / Main Points: None
Vegetation Types:
MLRA Ecoregions:
Agrovoc Control Words: Riparian zones Rangelands Wildlife
Article Review Type: Refereed
Article Type: Experimental Research
Keywords: prescribed grazing, fecal nitrogen, diaminopimelic acid, nutrition, forage selection, sheep
Annotation: The grazing treatments were applied within a 4.5 ha enclosure. The site was divided into 3 blocks, each of which was subdivided into two 0.25 ha treatment pastures. Each pasture within each of the 3 blocks was randomly assigned either an early summer or late summer grazing treatment. An adjacent 1.5 ha holding pasture was used to acclimate sheep to the forage on the study site before the sheep entered the treatment pastures. Early summer grazing was in early June and lasted 11, 8, and 6 days in 1993,1994, and 1995, respectively. Late summer grazing was in early August and lasted 9, 7, and 10 days in 1993, 1994, and 1995, respectively. Vegetation was sampled in each pasture before and after sheep grazing . The current annual growth of grasses, forbs, and shrubs were separated by life form and clipped from 2.5 cm above ground level within quadrats. Total usable forage was considered to be 50% of the total forage available as estimated from the clipped quadrats.
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