Estimation of the Extent of Heat Damage in Alfalfa Haylage by Laboratory Measurement

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Abstract
The potential of 30 laboratory procedures to predict forage quality was tested with 21 hay or haylage samples of known in vivo nitrogen and dry matter digestibilities. Simple regression analyses suggested that the acid-detergent insoluble nitrogen calculated as a percent of total nitrogen was the most reliable predictor for nitrogen digestibility (r2 = .86). The equation using acid-detergent fiber as a percent of dry matter (X1) and acid-detergent insoluble nitrogen as a percent of dry matter (X2) as predictors for nitrogen digestibility (Y) was found of value for practical use (R2 = .91). This equation was Y = 113.88 −.76(X1) −47.27(X2). Acid-detergent insoluble nitrogen as a percent of total nitrogen was negatively related to nitrogen digestibility to a greater extent for forages with little or no heat damage than for forages more severely damaged by heat. The relationship between acid-detergent insoluble nitrogen as a percent of total nitrogen and nitrogen digestibility was not strictly linear but logarithmic transformation of the former, however, did not result in an increased r2 value. A polynomial multiple regression improved the R2 value (.88). Among the 30 laboratory measurements, acid-detergent fiber was the most reliable predictor for dry matter digestibility (Y) (r2 = .88). The prediction equation was Y = 93.79 − .9 (acid-detergent fiber as a percent of dry matter). Using only two analytical techniques an R2 of. 96 was obtained with pepsin and hot water solubility test values and higher R2 (.98) with four test values. Copyright © 1976. American Society of Animal Science . Copyright 1976 by American Society of Animal Science.