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Effects of various physical and chemical treatments on the in virtro rumen digestibility and chemical composition of four woods. Huffman, James Grant

Abstract

Samples of sawdust from poplar, alder and Douglas fir, were ground past screens ranging in size from 2.21 mm to 0.25 mm (60 mesh). A reduction in particle size significantly increased the in vitro rumen digestibility of poplar, but had little effect on the digestibility of alder or fir. The above woods, plus sludge (a by-product of the pulping process) were treated with NaOH solutions of 2, 4 and 6%. These solutions were used at three treatment periods of 0.5, 1.0 and 1.5 hours, and all treatments were carried out at 1.05 kg/sq cm and 121° C. NaOH treatment significantly increased the in vitro cellulose digestibility of all woods except fir. The optimum treatment conditions for increasing the in vitro cellulose digestibility of all woods were 4% NaOH at the 1.5 hour treatment period, except in the case of alder which was most digestible when treated with 2% NaOH for 1.5 hours. Gamma irradiation increased the in vitro cellulose digestibility of all woods. Alder and fir were most digestible when treated with 2 x 10⁸ rads, but poplar and sludge reached their peak digestibility when exposed to 1 x 10⁸ rads. Irradiation was found to decrease the cellulose and acid detergent fibre (ADF) content of all the woods studied. Acid detergent lignin (ADL) also decreased in response to irradiation in all woods except sludge. Irradiation had no effect on the ash content of any of the samples. Three methods of cellulose analysis were used on both untreated and irradiated wood, and there was a significant difference shown among the methods. The lowest values were obtained using Van Soests' KMnO₄ method, next were the results from Van Soests' 72% Hg₂SO₄ method, and the highest values were obtained using the Crampton and Maynard procedure for cellulose. Two lignin methods were also compared and it was found that the KMnO₄ lignin values were significantly higher than those obtained using the 72% H₂S0₄ method for lignin.

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