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.
Anti-quality factors associated with alkaloids in eastern temperate pastureThe greatest anti-quality associated with eastern temperature pasture grasses is the result of ergot alkaloids found in endophyte-infected (Neotyphodium ceonophialum) tall fescue (Festuca arundinacea Schreb.) The relationship between the grass and the endophyte is mutualistic with greater persistence and herbage mass as a result of the endophyte. Ergot alkaloids reduce growth rate, lactation, and reproduction in livestock. Significant effects are the result of elevated body temperature and reduced peripheral blood flow such that necrosis may result. Perturbations also occur in a variety of body systems. Planting new pastures with seed containing a "non-toxic" endophyte appears to be a potential solution. Ergotism results from the ingestion of the scelerotia of Claviceps purpurea containing ergot alkaloids found on seed heads. Ergotism resembles the effects of endophyte-infected tall fescue. Endophyte-infected perennial ryegrass (Lolium perenne L.) contains ergot and lotirem alkaloids that result in reduced growth and tremors. Reed canarygrass (Phalaris Anundinacba L.) contains tryptamine, hordenine and gramine alkaloids that reduce growth. Annual ryegrass (Lolium multiplorum L. may contain galls with cornetoxins which result in neurological signs.