Composition and Digestibility of Alfalfa and Orchardgrass Hemicellulose Monosaccharides by Holstein Steers

Abstract

This research was to determine hemicellulose monosaccharide composition of alfalfa and orchardgrass hay and to compare digestibilities and in situ rates of disappearance of alfalfa and orchardgrass hay hemicellulose monosaccharides in Holstein steers. Orchardgrass contained more xylose and less galactose than alfalfa. Mannose in orchardgrass was more digestible than that in alfalfa, and uronic acids tended to be more digestible in orchardgrass. Xylose to glucose ratios were higher in orchardgrass than in alfalfa and were higher in feed than in feces. Xylose to arabinose ratios increased linearly with in situ removed time for alfalfa; however, orchardgrass ratio did not change significantly during the 72-h in situ studies. Xylose to glucose ratios increased with in situ fermentation time for both alfalfa and orchardgrass hay. Alfalfa hay had a higher rate of dry matter and neutral detergent fiber digestibility as compared with orchardgrass hay; however, no significant differences were detected in extent of cell wall digestion. © 1986, American Dairy Science Association. All rights reserved.