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Abstract
Effects of treating wheat straw and corn cobs with various sources and levels of alkali on the in vitro rates and extents of fiber digestion were investigated. Alkali sources used were NaOH, Ca(OH)(,2) and NH(,4)OH at levels of 0, 3, 6, 9 and 12% of the dry matter. Neutral detergent fiber (NDF) of both straw and corn cobs decreased (p < .05) and rates and extents of digestion of NDF increased (p < .05) with increasing treatment level. Acid detergent fiber (ADF) of straw and corn cobs decreased with increasing NaOH and Ca(OH)(,2) treatment levels but was unaffected by NH(,4)OH treatment. Rates and extents of digestion of straw and corn cob ADF increased with increasing treatment level (p < .05).<p> Qualitative and quantitative measures of cell wall monosaccharides solubilized by alkali treatments were measured. Monosaccharides solubilized were xylose and arabinose with lesser quantities of galactose, glucose and mannose. As treatment levels increased the amounts of individual monosaccharides and total monosaccharides released increased (p < .05). Second order derivative spectra of neutral detergent extracts of the treated samples indicated absorbance peaks at 324, 310, 298, 278 and 268 nm. Absorbances increased with increasing treatment levels. Rates and extents of digestion of straw and corn cob NDF and ADF were significantly (p < .05) correlated to xylose, arabinose and total monosaccharide released by alkali treatment and with absorbance values at all wavelengths.
Wheat straw treated with 4 or 8% NaOH or NH(,4)OH had higher in vivo organic matter, NDF, ADF and hemicellulose digestibilities compared with untreated straw when fed to steers. Wheat straw treated with 8% NaOH or NH(,4)OH had higher digestibilities compared to 4% treated wheat straw. Treatment with Ca(OH)(,2) did not improve the digestibility of straw. Rumen osmolarity and fluid turnover rates were significantly (p < .05) increased by feeding NaOH treated straw. Particulate turnover rates and rates of digestion of NDF, ADF and hemicellulose in situ were not significantly (p < .10) affected by feeding alkali treated wheat straws.
