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Effectiveness of Physical and Chemical Pretreatments in Enhancing Cotton Gin Trash In Vitro Ruminant Digestibility

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  026057,  2002 ASAE Annual Meeting . (doi: 10.13031/2013.10548) @2002
Authors:   Samuel J. Ray, Lester O. Pordesimo, Michael J. Buschermohle, John C. Waller, John B. Wilkerson
Keywords:   cotton gin trash, ruminant digestibility

Cotton gin trash (CGT) in the raw form has poor ruminant digestibility due to lignocellulosic complexes. These structures must be broken down before adequate digestion can occur. This may be performed by physical and/or chemical means. Two methods for improving digestibility are particle size reduction and/or treatment with sodium hydroxide (NaOH). To evaluate the effectiveness of each method, three experiments were performed in which different CGT types were tested. Each type represented trash from a particular cleaning stage in the cotton ginning process. First, each type was ground with a knife-type grinding mill using screen sizes 0.5, 1.0, and 2.0 mm. For the second experiment, particle size was held constant, and all CGT types were treated with 4 and 6% NaOH (w/w) at room temperature. An agitation cycle of 5 minutes on and 10 minutes off was used, with the total mixing time being 4 hours. Lastly, particle size and chemical concentration were held constant, and treatments were performed at room temperature, 40C, and 50C. The total mixing times were 2 and 3 hours for 50 and 40C, respectively. For all experiments two subsamples of each treatment were tested for in vitro ruminant digestibility. From grinding alone, digestibility increased as particle size decreased. Digestibility also improved with a greater NaOH concentration. An average of 70.5% was achieved with 6% NaOH (w/w) treatment, essentially doubling that of the raw CGT. Increasing the reaction temperature did not result in increased digestibility because the mixture dried out and with a consequent reduction in chemical distribution and uniformity in heat transfer. There are still chemical residues in the CGT, and elimination/reduction of these is an issue that needs to be addressed in further research.

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