224 THE CHEMISTRY OF CATTLE FEEDING 



it will be seen, is practically the same as that calculated 

 directly from the thermic energy of the food. That is because, 

 in stating the requirements of the animal as 6 Ibs. of starch 

 equivalent, it is assumed that the maintenance rations always 

 consist of hay or other coarse fodder, of which about 35 per 

 cent, is spent on the work of digestion. But if the fodder 

 actually used were of a less or more readily digestible kind, 

 the result would be wrong unless a corresponding alteration 

 were made in the estimate of the animal's requirements. 



For example, 7 Ibs. of maize and 50 Ibs. of wheat straw 

 respectively are equal to 6 Ibs. of starch equivalent, but the 

 quantities required to produce 35 kt. of thermic energy are 

 io'6 Ibs. of the former and 26-3 Ibs. of the latter. These are, 

 perhaps, extreme cases. They were selected merely to illus- 

 trate the point above referred to. As a matter of fact, neither 

 of these foods would, by itself, form a suitable maintenance 

 ration for oxen. 



In order to ensure that the foods selected shall be of the 

 digestibility assumed in the estimate of the animal's require- 

 ments, a further statement is necessary showing, within certain 

 limits, the amount of total organic matter in the food. Such 

 a statement would rule out both of the foods previously 

 mentioned. The importance of this datum, however, is often 

 overlooked, and rations calculated from the starch equivalents 

 alone are, therefore, sometimes erroneous and apt to prove 

 misleading. 



The rations of an animal must always include a certain 

 allowance for maintenance, and an additional quantity for any 

 work, milk, or increase produced. When the nutrients in both 

 portions are expressed in terms of starch equivalents, they can 

 be added together, and the whole stated in the form of a 

 feeding standard. As, however, the starch equivalents for 

 maintenance, work, and milk production are purely empirical 

 and of somewhat doubtful value, it does not appear that such 

 feeding standards are very reliable. They are also open to 

 question on other grounds. On the whole, the author prefers 

 to adhere to the methods previously recommended, viz. (i) to 

 determine the maintenance ration from the thermic values of 



