Steam Treatment of Crop Residues for Increased Ruminant Digestibility. I. Effects of Process Parameters

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Abstract
Rice straw, sugar cane bagasse and sugar cane field trash were steam treated at pressures ranging from 7.0 to 42.2 kg/cm2 with and without added chemicals. Aqueous NaOH, NH3 and urea were additives used at levels of up to 4.5% of dry weight. Effect of processing parameters was measured by an enzymatic in vitro digestibility assay. The general effect of increased pressure and (or) treatment time on rice straw was to increase in vitro digestibility over that of untreated straw. There was some indication that a maximum digestibility may be reached and then followed by a decline upon further treatment. Highest digestibilities were reached at 21.1 kg/cm2 both with and without additives. After 1.5 min at this pressure, rice straw digestibility improved to maximums of about 47%, without additives, and 64% with NaOH. Initial rice straw digestibility was 26%. Neither aqueous NH3 nor urea increased digestibility of steam-treated material, but both increased nitrogen content of the product. However, less additive was retained as the amount used increased. Moisture content of treated material was typically between 40 and 50% after steam condensation and water entrainment. Depending on treatment time and pressure, 5 to 16% of the crop residue was volatilized and lost when the reactor was vented to the atmosphere. Copyright © 1980. American Society of Animal Science . Copyright 1980 by American Society of Animal Science