218 THE CHEMISTRY OF CATTLE FEEDING 



Some writers give the " total dry matter " instead of the 

 amount of moisture. This, of course, comes to the same 

 thing, as the total dry matter is obtained simply by deducting 

 the percentage of moisture from 100. 



The percentage of ash or so-called mineral matter is of little 

 importance because the proportion of these ingredients in all 

 natural feeding stuffs is more than sufficient to provide for the 

 requirements of the animals in this respect. The percentage 

 of ash is, therefore, sometimes omitted from a statement of 

 the composition of feeding stuffs. But if the percentages of 

 total dry matter, and of protein, fat, soluble carbohydrates 

 and fibre are known, the percentage of ash can be inferred. 

 By deducting the percentage of ash and moisture from 100 we 

 get the amount of " dry organic matter." 



Prescriptions for feeding farm animals generally show what 

 amount of dry organic matter as well as what amounts of 

 nutrients the rations should contain. In other words, they 

 show the degree of concentration, as well as the amounts of 

 the nutrients, that are suitable for the different kinds of animals. 

 This, of course, is a matter of physiology rather than of 

 chemistry, but it is one that must be taken into account in 

 practical feeding. In short, the food of the animal must be 

 suitable in kind as well as in quantity. 



If the composition and the coefficients of digestibility of a 

 food are known, the amounts of digestible nutrients and the 

 thermic and dynamic values of the product can be easily 

 calculated by the methods previously described. These data 

 for all the commoner feeding stuffs are given in the tables 

 (pp. 1 66, 213). It is obvious, however, that, so far as purchased 

 foods are concerned, they will be of little use to a farmer 

 who persists in buying " mixed meals " and " compound 

 cakes " unless he knows exactly what they contain ; and this 

 is just the information he is not likely to obtain from the 

 seller. 



Starch Value. The starch value of a food may be denned 

 as the amount of starch that is equivalent to the total fat- 

 forming power of all the nutrients in it. This definition 

 contains no direct reference to the digestibility of the food, 



