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Agronomy Journal Abstract -

Use of Potassium-40 as an Evaluator of Animal Response in Grazing Trials1


This article in AJ

  1. Vol. 65 No. 2, p. 335-336
    Received: May 20, 1972

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  1. J. L. Clark2,
  2. A. G. Matches3 and
  3. G. B. Thompson2



Our objective was to evaluate techniques for measuring the response of cattle grazing four pasture systems. The techniques employed were the use of the Whole Body Counter to measure potassium-40 (40K) of animals to predict body composition, visual condition scores, and body weight. The condition score is a subjective score placed on the animal to estimate the amount of external flesh.

Pasture systems were composed of orchardgrass (Dactylis glomerata L.) and tall fescue (Festuca arundinacea Schreb.) for spring grazing and the round baled hay plus regrowth of orchardgrass-Korean lespedeza (Lespedeza stipulacea Maxim.) and tall fescue for summer grazing.

Composition of gain was not influenced by pasture systems, and there was no change in condition score or FFB over the season. Approximately 66 to 74% of the gain was FFB and the remaining 26 to 34% represented body fat and gut content. There were no significant differences (P ≤ .05) in gain due to pasture systems. Since the estimation of body composition using 40K can be obtained without slaughtering the test animals, we believe the Whole Body Counter has much potential as a research tool in grazing research.

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