i9i i.] Starch Equivalents of Feeding Stuffs. 727 



withdrawn, and what is left is not so valuable from the point 

 of view of the availability of the nutrients contained therein. 

 Potatoes have a full value because they contain a large 

 amount of starch in a form which is easily prepared by the 

 digestive apparatus for assimilation, and so no deduction 

 need be made for the energy expended in these processes. 

 Sugar, on the other hand, is not a full-value nutrient, because 

 of the fermentative changes which it undergoes in the body 

 and the consequent loss. For' feeding purposes sugar is 

 inferior to starch, and figures which will be quoted later give 

 a direct comparison of these two materials for the formation 

 of fat. Foods which contain much sugar in the dry matter, 

 e.g., mangolds, turnips, swedes, carrots, sorghum, and sugar- 

 beet, are not equal to foods in which the chief carbohydrate 

 material is in the form of starch. 



Importance of Form in which the Digestible Nutrients 

 are Present. — Kellner and those who have worked on similar 

 lines have contributed a great deal towards founding a more 

 rational system of valuing the various foodstuffs, for it will 

 now be seen that if attention is paid solely to the digestible 

 nutrients without any reference to their origin and the foods 

 in which they are contained, very serious errors can be intro- 

 duced in estimating their relative feeding values. If rations 

 are made up without consideration being given to the origin 

 of the digestible nutrients, it might easily happen that 

 although the ration was theoretically sufficient for the needs 

 of the animal, it might nevertheless prove to be inadequate 

 owing to the fact that too much food of a low value (i.e., 

 food in which the nutrients were not full value or nearly so) 

 was used. When the ration is composed of high value 

 feeding stuffs the digestible nutrients behave practically the 

 same as pure material of the same class. It is a matter of 

 common knowledge that rations containing the same quan- 

 tity of digestible food material do not behave alike in actual 

 practice, and in some cases, probably in most, this failure 

 is due to the form in which the nutrients are present in the 

 foods composing the ration. Attention to this point, and, 

 better still, the exact working out of the feeding value of the 

 ration, will often show the reason for the failure to obtain the 

 most satisfactory results. 



