Alkali effects on agricultural wastes and their cell wall fraction

Publisher Website
Google Scholar
Abstract
Five experiments are reported which examine the effect of alkalis (NaOH, 0-14 g/100 g DM [dry matter]; NH4OH, 0-2.9 g/100 g DM), reaction time and temperature upon DM digestibility and related properties of mature forage waste materials. Digestion was assessed by microdigestion of test samples in the rumens of fistulated sheep fed lucerne base diets. Digestion of the DM of brewer''s grains was increased from 50.2-58.5% by application of 2.9% NaOH or NH4OH at room temperature for 24 h, and to 81.9% when heated to 80.degree. C for 24 h. Heating at 150.degree. C for 1 h produced no improvement over heating at 80.degree. C for 24 h. Average DM digestion of a range of mature grasses was improved by 6.9% by applying 1.5 g NH4OH/100 g DM at room temperature for 17 h and by 13.7% when heated to 80.degree. C for the same period. The DM digestion of mature legumes did not increase due to these treatments, but when heated with 1.5 g NH4OH/100 g DM to 130.degree. C for 4 h, increased DM digestibility by 16.6%. The digestion of unashed cell wall (CW) and acid detergent (AD) residues in mature grasses was increased by a prior extraction with neutral detergent and acid detergent. In mature legumes these pretreatments had no effect upon digestibility. The unashed (KMnO4 extracted) cellulose residues of grasses and legumes were incompletely digested compared with pure cotton. Both NaOH and the chelating agent EDTA eventually remove the CW-ash fraction and this is associated with increases in CW digestion with increasing level of their application. These chemicals also initially increase and then decrease the organic fraction of the mature forage CW, its ADF [acid detergent fiber] and lignin. The digestibility of cell walls of lucerne hay is increased from 24.3-43.3% by application of NaOH (9 g/100 g DM) for 2 h at room temperatures; the corresponding increase for cell walls of wheaten chaff is from 33.9-72.3%. Alkalis induce increases in DM digestion by degrading cell walls and the cell walls of mature grasses are more easily degraded than are the cell walls of mature legumes.

This publication has 4 references indexed in Scilit: