160 



MASS. EXPERIMENT STATION BULLETIN 230 



IMPROVING THE FEEDINC; VALUE OF GRAIN HULLS 

 AND SAWDUST 



13j J. G. ARCHIBALD 



I 



FORKWOUD 



A great deal of study has been devoted by numerous investigators in differ- 

 ent countries to improving the digestibility and consequently the feeding value 

 of straws and other fibrous or woody materials. Straw of various kinds is, 

 only from 46 to 52 per cent digestible, oat hulls scarcely 40 per cent and 

 cottonseed hulls 53 per cent digestible, while rice hulls, flax shives and saw- 

 dust show little if any digestibility. Furthermore, so niucii energy is required 

 in the digestive processes that these materials, in their natural state, have but 

 little net energy or actual nutritive value. Attempts to improve the feeding 

 value by fine grinding, soaking in water and steaming under pressure have 

 proved to be useless; so also has mixing the fine material with such a palat- 

 able substance as molasses. 



The straws have also been treated with various chemicals such as dilute 

 sulfuric and hydrochloric acids, lime in the form of the sulfide and oxide, 

 sodium carbonate and sodium hydrate, both by boiling in open kettles and 

 under pressure. Many of these methods have greatly improved the feeding- 

 value of the straws. 



Why Wood, Straws, Grain Hulls and vSimilar Fibrous Materials Have 

 Low Feeding Values. 



Plant fibers (crude cellulose) are an aggregation of cell walls of certain 

 specialized cells occurring in the plant. These cell w\alls become elaborated, 

 enlarged and strengthened with age until maturity is reached, at which time, 

 in high fiber plants at least, they constitute the major portion of the indi- 

 vidual cells, the cell contents or protoplasm having been almost, if not alto- 

 gether, absorbed or transported to the seeds. 



In the early stages of growth, the cell wall consists of pure cellulose and 

 hemi-cellulose and is soft and reasonably well digested, but as growth pro- 

 ceeds and maturity is reached, it becomes changed to a compound known as 

 iigno-cellulose and tlie process is known as lignification. This ligno-cellulose 

 complex cannot be digested to any extent because tlie digestive fluids cannot 

 penetrate it. Some silicic acid also incrusts the complex and still further 

 hinders the action of the digestive fluids and micro-organisms. The action 

 of chemicals, particularly the alkalies, dissolves out the silicic acid and also, 

 breaks the bonds holding the cellulose and lignin together, and the cellulose 

 thus set free can be acted upon and converted into nutritive material. As 

 a result of the process, the lignin is more or less decomposed but is of little, 

 if any, nutritive value. 



