262 THE CHEMISTRY OF CATTLE FEEDING 



The chemical composition of all kinds of cereal straw is 

 extremely variable. In fact, the variation due to the influence 

 of accidental circumstances, such as climate, season, etc., is so 

 great that it often obscures the characteristics of the different 

 kinds. Of two samples of the same kind of straw, one may 

 contain nearly twice as much nutritive matter as the other. 

 Still, when the averages of large numbers of so-called normal 

 samples are considered, it is generally found that oat and 

 barley straws are more nutritive than those of wheat and rye. 

 The straw of spring wheat, however, is generally somewhat 

 superior to that of the autumn sown crop. 



At best, cereal straws form poor feed. The ratio of 

 dynamic to thermic energy is very low. They are only fit for 

 use as maintenance rations, and, even for this purpose, 

 should only form a portion of the whole. Larger quantities 

 may be given to ruminants than to horses. When large 

 amounts are used, the high percentage of fibre in the straw 

 tends to depress the digestibility of the nutrients in the other 

 foods. 



In the rations prescribed by practical men, emphasis is 

 generally laid on the fact that the straw was or was not 

 chaffed, i.e. chopped into small pieces. The practical im- 

 portance .of this probably lies in the facility with which chopped 

 straw may be mixed with other foods, e.g. pulped roots, meals, 

 etc. Such admixture may possibly lead to more thorough 

 mastication of the meals, etc., and so increase their digestibility } 

 or it may act merely as an inducement to the animals to 

 consume the straw. So far as the straw itself is concerned, it 

 cannot make any considerable difference whether it is chopped 

 or not, provided the same amount is actually consumed. 



The term " chaff" is often applied, as indicated above, to 

 chopped straw. Strictly, it refers only to the membranous 

 outer husks or ears in which the grain is enclosed. These 

 consist mainly of lignified cellulose together with a large 

 proportion of siliceous ash. Chemical analysis reveals the 

 presence of a certain amount of nutritive matter, but there 

 are many objections to the use of this material for feeding 

 purposes. The chaff of cereals includes the awns, if any, 



