A Method for Determining Total Digestible Nutrients in Grazed Forage

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Abstract
A method is presented for determining the TDN content of grazed forage. Digestibility of the organic matter is determined by the chromogen ratio technique by use of the formula: [image] where D is the digestion coefficient for organic matter, A and B are the organic matter per gram of dry matter in feces and forage, respectively, and X and Y are the chromogen per gram of dry matter in feces and forage, respectively. TDN is determined by multiplying digestion coefficient for organic matter, D, by a conversion factor calculated by the formula: F = M (0.01 + 0.000125 E) where M is the percent organic matter in the dry matter of the feed and E is the ether extract as percent of organic matter. Data are presented in support of the validity of the method. Evidence is shown which inidcates that selective grazing may be more pronounced with mature than with immature forage.