|Vavra, Marty - USDA-USFS|
Submitted to: Eastern Oregon Agricultural Research Center
Publication Type: Experiment Station
Publication Acceptance Date: January 1, 2005
Publication Date: January 1, 2006
Citation: Ganskopp, D.C., Svejcar, A.J., Vavra, M. 2006. Improving late-summer and winter forage quality with livestock grazing. Eastern Oregon Agricultural Research Center. SR1057:57-58. Interpretive Summary: Pacific Northwest grasses that go ungrazed during the growing season become nutritionally deficient at maturity and will not sustain animal gains. We investigated the effects of exclusion and light and heavy spring cattle stocking on fall and winter nutritional characteristics of 3 rangeland forages. Light and heavy stocking reduced fall standing crop by 32 and 67%, respectively, but elevated crude protein content and digestibility in September and December. This showed that controlled spring cattle grazing can be used to improve fall and winter nutritional indices of grasses with findings benefitting rangeland managers striving to generate high quality, late season forage.
Technical Abstract: Tests of the hypothesis that spring cattle grazing can positively affect subsequent nutritional characteristics of grasses have generated mixed results. Our objectives were: 1) to evaluate fall/winter nutritional indices of bluebunch wheatgrass, Idaho fescue, and bottlebrush squirreltail in ungrazed, lightly grazed (33 percent utilization), or heavily grazed (69 percent utilization) pastures stocked with cattle at the boot stage of growth; and 2) to quantify costs of applying those treatments on fall standing crop. Compared with ungrazed stands, light and heavy spring grazing decreased September standing crop by 32 and 67 percent, respectively. September/December crude protein (CP) among heavily grazed grasses (mean=6.9 percent) exceeded ungrazed controls (mean=3.9 percent) for 11 of 12 comparisons. Crude protein of lightly grazed grasses (mean=5.2 percent) was higher than ungrazed controls for 6 of 12 comparisons. Grass was more nutritious during the drier of the 2 years sampled. Among grazed treatments, fall/winter CP measures were highest for bottlebrush squirreltail (mean=7.4 percent), intermediate for Idaho fescue (5.9 percent), and lowest for bluebunch wheatgrass (mean=4.9 percent). In fall/winter, herbage was most digestible in heavily grazed paddocks (mean=59 percent), intermediate in lightly grazed paddocks (mean=53 percent), and least digestible in ungrazed areas (mean=49 percent). Light and heavy spring cattle grazing can augment fall/winter forage quality of bluebunch wheatgrass, Idaho fescue, and bottlebrush squirreltail. Spring grazing reduces subsequent standing crop, but remaining forage will be nutritionally superior to herbage in ungrazed stands.