Browsing Journal of Range Management, Volume 48, Number 6 (November 1995) by Subjects
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Forage quality, intake, and digestibility of year-long pastures for steersThirty-six weanling steer calves (avg wt = 174 +/- 14 kg) were grazed on either wheat, irrigated improved, or native rangeland pastures from December 1989 to December 1990. Irrigated improved pastures consisted of 2 cool-season [tall wheatgrass [Agropyron elongatum (Host.) Beauv.], tall fescue (Festuca arundinacea Schreb.) 2 warm-season [bermudagrass (Cynodon dactylon (L.) Pers.], bluestem (Bothriochloa ischaemum Keng.), and annual wheat. Wheat pastures were grazed from 13 December to 11 April. Warm-season pastures were grazed from 30 May (bermudagrass) or 27 June (bluestem) until 3 October. Cool-season pastures were grazed at other days during spring and fall seasons. Rumen evacuation procedures were used to evaluate forage quality and estimate forage intake during each grazing season. Winter rangeland pastures were lower in nutritional quality (based on protein and fiber contents) and in vitro organic matter digestibility (53 vs 85%, P < 0.05) compared to wheat pasture. During spring, rangeland pastures were still lower in protein and higher in fiber but in vitro organic matter digestibility (72, 73, 72%; respectively, for wheatgrass, fescue and rangeland) was similar (P = 0.70) for all forages. Rangeland and warm-season pastures were similar in quality during summer but rangeland pastures were higher (P< 0.10) in in vitro organic matter digestibility (65, 69, and 73%; respectively, for bermudagrass, bluestem, and rangeland). Rangeland pastures were again lower in quality and digestibility than cool-season grasses during the fall. There were no difference (P>0.10) in organic matter intake (% of body weight) during winter, summer, and fall season but during spring organic matter intake was greater (P < 0.10) for steers on rangeland pasture than for those on cool-season grasses.
Mountain big sagebrush browse decreases dry matter intake, digestibility, and nutritive quality of sheep dietsA metabolism study evaluated the influence of increasing quantities (0-30% dry matter basis) of mountain big sagebrush (Artemisia tridentata ssp. vaseyana Rydb. Beetle) on dry matter intake and in vivo digestibility of wether diets. Diets consisted of hand-harvested, coarse-ground and frozen current year's growth of mountain big sagebrush leaves and twig tips mixed with chopped native grass hay. Dry matter intake decreased from 93 to 23 g dry matter day-1 kg metabolic weight-1 and in vivo dry matter digestibility from 59 to 0% with increasing levels of sagebrush in the diet. With increasing levels of sagebrush in the diet, water, lignin, and nitrogen contents increased in the diet, but decreased in the dung, while fiber components decreased in both the diet and dung. Total nitrogen intake decreased from 1.58+/-0.041 to 0.406+/-0.070 g day-1 kg metabolic weight-1, and nitrogen retention decreased from 0.80 g day-1 kg metabolic weight-1 with no sagebrush to a slight loss of nitrogen with 30% sagebrush in the diet. Mountain big sagebrush was not readily consumed by wethers when fed together with grass; as low as 10% sagebrush in the diet seems to adversely influence intake and digestibility. Therefore, when other more favorable forages are not available, sheep and other ruminants with similar physiological responses to mountain big sagebrush may not meet their nutrient requirements through increased sagebrush consumption.