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The April issue article, “The Grass Tetany Puzzle,” generated some reader concern over its reliance on anecdotal observations as opposed to peer-reviewed research. The article highlights the work and observations of veterinary pathologist Thomas Swerczek regarding the potential of loose salt to prevent and treat grass tetany in grazing cattle. What follows is a letter of rebuttal to the article by four Kentucky specialists, followed by further information by Swerczek and Holger Martens. The latter is an authority on the topic from Germany.
May 24, 2012
We read with alarm the article entitled “The Grass Tetany Puzzle: Research by a veterinary pathologist indicates salt is a big factor in preventing and treating grass tetany” by Heather Smith Thomas in the April 2012 edition of BEEF (page 22). While the theories put forth by Thomas Swerczek are thought-provoking, to our knowledge he has not performed any science-based controlled studies to research these ideas, and has not published data supporting these theories in any peer-reviewed scientific journal. The majority of the information provided in the article is anecdotal in nature.
We recommend that producers do not adopt the practice of feeding solely white salt, and especially not force-feeding white salt, to cattle for a number of reasons:
• Too much salt, as with any substance, can be dangerous, and fatal salt intoxication can occur if excessive amounts of salt are force-fed.
• Trace minerals such as copper, selenium, and zinc are all essential nutrients vital for proper growth and production. Trace mineral deficiencies that may be exacerbated by eliminating them from supplements when needed can predispose animals to serious and sometimes fatal disease conditions.
• Interactions occur between all the various metals, minerals, and other elements in the diet, and optimal amounts of all elements are essential for proper nutrition.
• Regional soil types, soil fertility and forage species can result in different mineral intakes of grazing livestock and to make a blanket statement disregarding these factors is oversimplifying a complex situation.
• Grass tetany, or hypomagnesemia, is a well-recognized condition, with well-researched and proven treatment and prevention strategies published in peer-reviewed scientific journals. Recommendation to replace these practices with unproven theory is irresponsible and can be detrimental to the health and well-being of livestock.
We would recommend that before publishing materials that could potentially be harmful to animal health and herd production, the editors should determine if the information provided can be supported by research and appropriate peer-reviewed publications. We also advise that all producers consult with their veterinarians and livestock nutritionists before making any management changes of this scope.
Michelle Arnold, University of Kentucky (UK) Veterinary Diagnostic Lab Extension ruminant veterinarian
Roy Burris, UK Extension beef specialist
Cynthia Gaskill, UK Veterinary Diagnostic Laboratory veterinary toxicologist
Jeff Lehmkuhler, UK Extension beef cattle specialist
The April issue article by Heather Smith Thomas was based on interviews she conducted with me on the grass tetany syndrome. While she did an admirable job of addressing the topic in a limited amount of space, the references provided to her unfortunately could not be included. Greater detail and scientific references on the importance of salt in the prevention of grass tetany are available here, here & here.
Research from Europe has been published in scientific peer-reviewed journals for many years, and those findings were discussed in Thomas’s article, along with my observations. It’s important to note that the research findings are consistent with my observations and findings on many farms over the course of several years.
Furthermore, a leading authority on grass tetany, H. Martens, DVM, faculty of veterinary medicine, Free University of Berlin, Berlin, Germany, reviewed my findings and commented that my observation and conclusions about a possible role of sodium deficiency in the pathogenesis of grass tetany “are very important from a practical standpoint. Though the relationship has been long known, sodium deficiency is still an overlooked factor in the pathogenesis of grass tetany, especially in grazing beef cattle. Sodium supplementation is an easy, inexpensive and a simple prophylactic tool for the prevention of an important metabolic disease of cattle.”
The use of sodium for the prevention of grass tetany has been practiced in Europe for many years, but this information hasn’t been given to U.S. cattlemen. Consequently, grass tetany remains a costly but very preventable disease of cattle.
Thomas Swerczek presents these supporting documents:
In addition, Holger Martens, Free University of Berlin veterinary physiologist, offers this general response to the April article, as well as a more detailed paper on Grass Tetany: Aetiology and Prevention.
Na deficiency is indeed an overlooked factor in the pathogenesis of grass tetany. It is well established that Na deficiency is causing a replacement of Na by K in saliva. The high rate of saliva in connection with the high concentrations of K in saliva during Na deficiency leads to a significant inflow of K into the rumen which can be even higher than on a K rich diet (3 – 4 % K in DM) (H. Martens, O.W. Kubel, G. Gäbel, H. Honig: Effects of low sodium intake on magnesium metabolism in sheep. J. agric. Sci. 108, (1987), 237-243). Furthermore, Na deficiency reduces feed intake, which could exacerbate Na deficiency and latent hypomagnesaemia (Morris and Gartner: The sodium requirement of growing steers given all-sorghum grain ration. Br. J. Nutr. (1971) 25: 191-205).
Supplementation of Na as NaCl in combination with MgO is practicable with lick stones. Na supplementation is no reason to give up necessary intake of trace elements.
Free choice of Na could be a risk if the animals are in severe Na deficiency and Na is suddenly offered. Under these conditions the animals will take up more Na than really needed which could even disturb Mg metabolism (renal loss of Mg).
Na intake according the requirement is an obligation, but Na is no miracle drug or panacea which solves all the problems. Na supplementation is no reason to give other well established means of prevention of grass tetany as pasture dusting with Mg or Mg supplementation with the drinking water.
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