Estimating Net Energy Lactation from Components of Cell Solubles and Cell Walls

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Abstract
A summative equation was developed for predicting net energy for lactation of feeds from known chemical content for ration-evaluation programs. Encrusted area from lignification and inhibition of digestion was estimated by computing the relative surface areas of lignin and cell walls. The multiple-term equation sums net energy of cell solubles and cell walls. The coefficient for suppression of digestibility of energy in cell walls was a function of ratios of surface areas of lignin and neutral detergent fiber computed from their masses. Feeds with net energy contents between cottonseed hulls and shelled corn fit the regression line with equal precision, and the equation accounted for 98% of the variance. An expanded equation included differential effects of protein and lipids in cell contents, silicates, and an exponential term for acid-detergent insoluble N, to account for loss of protein digestibility. From chemical composition of 28 feeds the standard error was 16 kcal/kg for a prediction. Net energy intake of 12 cows in individual trials was predicted with similar precision.