684 PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



of the albumen, as is generally acknowledged to be the case in the car- 

 nivora, or whether fat may not also be formed from the carbohydrates 

 directly. It thus seems clear that the addition of carbohydrates to the 

 diet spares the waste of tissue-albumen and body fat, and the attempt 

 has been made to determine the amount of carbohydrates which in their 

 nutritive value are equivalent to a given amount of fat. This has been 

 fixed by Yoit at the ratio of one hundred and seventy-five to one hun- 

 dred ; in other words, one hundred and seventy-five grammes of starch 

 are equivalent to one hundred grammes of fat. 



V. THE FOOD KEQUIKED BY THE HERBIVORA UNDER DIFFERENT 



CONDITIONS. 



The nutritive processes in the herbivora differ in many respects from 

 those of the carnivora. In the first place, less albumen is destroyed 

 during fasting by the herbivora than is the case in the carnivora. Thus, 

 while in the example given above a dog weighing thirty-five kilos de- 

 stroys daily one hundred and sixty-eight grammes of albumen, an ox 

 weighing five hundred and twenty-two kilos only destroys twelve hundred 

 and seventy grammes. So, also, the herbivora on feeding with carbo- 

 hydrates and fat show much less tissue waste than the carnivora. In 

 other respects, with allowances for the different digestive peculiarities of 

 carnivora and herbivora, the nutritive process may be said to be similar. 



It has been already stated that foods must not only contain repre- 

 sentatives of the proteid, carbohydrate, and fat groups, with salts and 

 water, but the different constituents must be present in definite propor- 

 tions, which may, however, vary according to the demands on the animal. 

 The proportion of albuminous to non-nitrogenous matter in food, i.e., the 

 proportion of albumen to starch and fat, is spoken of as the nutritive 

 proportion. The average nutritive proportion is attained when the food 

 contains one part proteid to from five to eight parts of non-nitrogenous 

 matter, it being remembered that one hundred parts fat may be replaced 

 by one hundred and seventy-five parts carbohydrates ; 1 : 2-4 is spoken 

 of as a narrower nutritive proportion, and 1:8-12 as a wider nutritive 

 proportion. 



The natural food of the domesticated herbivora has a nutritive pro- 

 portion of 1:4-1:7; thus, ordinary hay has a proportion of 1:5-1:Y, 

 and, although it may be regarded as the normal food of ruminants, is not 

 suitable when there is a demand for rapid fat, milk, or work production. 

 In grass the proportion is only 1 :4-6, and on such foods cattle produce 

 the most milk ; young cattle thrive on it and rapidly put on flesh. Clover 

 has a proportion of 1:5-6, but on account of its large percentage of 

 cellulose is not completely digested, so it is usually combined with some 

 more concentrated food. Before blossoming clover has a proportion of 



