On the chemical nature and digestibility of roughage carbohydrates

Abstract

1. Egyptian clover, sweet lupin,Lathyrus ochrus, Eragrostis tefandVicia narbonnensishave been analysed as to their hexosan, pentosan and lignin content. The major part of the pentosan is soluble in 2 % HCl and therefore belongs to the hemicellulose fraction, whereas most of the hexosan is insoluble in 2 % HCl and forms part of the cellulose fraction.2. The digestibility of hexosan, pentosan and lignin has been determined by experiments with sheep. The digestibility of soluble pentosan and of insoluble hexosan (2 % HCl) was found to be very constant. It ranged from 64·0 to 66·2 % for pentosan and from 74·1 to 76·5 % for hexosan. ·Lignin was in all cases digested comparatively well, the digestibility coefficients being markedly variable, depending on the plant material. They ranged between 35·1 and 64·0.3. Faeces lignin yields lower methoxyl values than plant lignin. Therefore lignin appears to have been changed during passage through the animal body.4. The partition of hexosan, pentosan and lignin on crude fibre and N-free extract prepared from different plant materials is markedly variable.5. The major portion and best digestible fraction of plant lignin is soluble in alkali and is, therefore, contained in the N-free extract.