Acid Insoluble Ash and Permanganate Lignin as Indicators to Determine Digestibility of Cattle Rations

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Abstract
Rations composed of 0, 20, 40, 60 and 80% concentrate with the remainder being early (June 3) or late (July 7) cut mixed grass hay were fed to steers in a latin square design (five periods and five steers for each cutting date). Digestibility of ration dry matter was determined at the maintenance level of intake by total collection and by using acid insoluble ash (AIA) or permanganate lignin as indicators. Average rates of recovery of indicators were: permanganate lignin, 52.21 ± 1.79 and 59.25 ± 1.77%, and AIA, 101.19 ± 4.81 and 98.87 ± 2.98% for the early and late cutting dates, respectively. The permanganate lignin method underestimated digestibility determined by the total collection method by an average of 23.9 percentage units (P<.001). Thus, permanganate lignin is unreliable as an indicator in the ratio technique of measuring digestibility. When acid insoluble ash was used as an indicator, deviations from actual digestibility ranged from −3.62 (80% concentrate, late cut hay) to + 1.40 (40% concentrate, late cut hay) percentage units. The ration × method of determination interaction was not significant and the average deviation of -.62 was not significantly different from zero. Thus, digestibility by cattle of rations composed of hay and grain may be determined with AIA if a representative sample of feces is used. Copyright © 1979. American Society of Animal Science . Copyright 1979 by American Society of Animal Science.