Browsing Journal of Range Management, Volume 54, Number 4 (July 2001) by Subjects
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Anti-quality components in forage: Overview, significance, and economic impactAlthough recognized in importance from the dawn of history, forages have too often been underestimated and undervalued perhaps in part because animal performance has frequently failed to reflect apparent forage quality. Anti-quality components, diverse impediments to quality, have evolved as structural components and as secondary metabolites. They include mineral imbalances or can be related to the presence of insects and diseases. Animal behavior and adaptation are increasingly recognized as important aspects of anti-quality factors. An anti-quality component may reduce dry matter intake, dry matter digestibility, or result in nutritional imbalances in animals. They can act as a direct poison compromising vital systems, result in abnormal reproduction, endocrine function, and genetic aberrations, trigger undesirable behavior responses, or suppress immune function leading to increased morbidity and mortality. The economic impact of anti-quality factors on individual herds can be devastating but definable. Broadscale economic impacts of anti-quality factors are far more difficult to estimate. A loss of 0.22 kg/day in potential gain of stocker cattle due to anti-quality factors during a 166-day grazing season translates into a loss of about 55/steer at 1.45/kg or over 2 billion annually when applied to the U.S stocker cattle. Economic losses to tall fescue (Festuca arundinacea Schreb.) toxicosis in the U.S. beef industry are probably underestimated at 600 million annually. Reproductive and death losses of livestock due to poisonous plants have been estimated at 340 million in the 17 western states alone. These examples of economic losses due to anti-quality factors may be upper bounds of actual losses but even if a small proportion of the expected losses were eliminated through research, the potential payoff would be extremely high.
Complementary grazing of native pasture and Old World bluestemNative pasture and Old World bluestems (Bothriochloa spp.) have contrasting herbage production characteristics that suggest potential for incorporation into a complementary forage system. We compared 2 yearling beef production systems consisting of either native pasture (Native) or Old World bluestem combined with native pasture (Old World bluestem-Native) over 5 years. Crossbred steers (initial weight 257 kg) grazed only native pasture in the Native system, but alternated between Old World bluestem and native pastures in the Old World bluestem-Native system. Production system had no effect on the frequency of any plant species in the native pastures (P > 0.16) even though stocking rate in the growing season was increased 31% in the Old World bluestem-Native system. Peak standing crop of Old World bluestem averaged 4640 kg ha(-1) but did not differ between the cultivars 'WW-Iron Master' and 'WW-Spar' (P = 0.16). Individual steer gain was higher in the Native system during the Winter (P < 0.01) and Early Native (P = 0.03) management periods, but was greater in the Old World bluestem-Native system when steers were grazing Old World bluestem in June and July (P < 0.001). Over the entire season, steers in the Native system gained 13.5 kg head(-1) more than steers in the Old World bluestem-Native system. Total livestock production was greater in the Old World bluestem-Native system (77 versus 47 kg ha(-1), P < 0.01). Relative economic returns between the 2 systems were dependent on the marginal value of livestock gain and the relative costs of production for the 2 types of pasture. With average costs for native pasture of 17 ha(-1) and for Old World bluestem pasture of 62.10 ha(-1), the Native system was often more profitable, even though livestock production per ha was much higher with the Old World bluestem-Native system. Lower costs for native pasture and high values of livestock gain favored the Native system.
Economic analysis of using sheep to control leafy spurgeLeafy spurge (Euphorbia esula L.), a widely established exotic, noxious, perennial weed, is a major threat to rangeland and wildland in the Upper Great Plains. A deterministic, bioeconomic model, incorporating relationships between sheep grazing and leafy spurge control, grass recovery, and forage consumption by cattle, and expected costs and returns from sheep enterprises was developed to evaluate the economic viability of using sheep to control leafy spurge. Various scenarios were developed depicting likely situations facing cattle ranches adding a sheep enterprise for leafy spurge control. Two levels of flock profitability, one based on a level of proficiency achieved by established sheep ranches and one substantially lower than typically achieved in the sheep industry, were combined with debt and no-debt to represent best- and worst-case scenarios, respectively. In the best-case situations, using sheep to control leafy spurge was economical in all of the scenarios examined. In the worst-case situations, the economics of using sheep to control leafy spurge were mixed across the scenarios examined. Leafy spurge control with poor flock proficiency, high fence expense, and unproductive rangeland generally was not economical. Situations with low fencing costs, moderately productive rangeland, and poor flock proficiency resulted in less economic loss than no treatment. Actual returns from leafy spurge control for most ranchers will likely fall between the extremes examined.