FEEDING OF ANIMALS. 351 



according to its amount and other circumstances, there will, 

 of course, be more or less stock-food available in addition to 

 that produced on the arable land. So far as manure is con- 

 cerned, in some cases the grass-land, and in others the arable, 

 will be the gainer by the admixture of the two, accordingly 

 as the one or the other receives back more or less than the 

 amount derived from the consumption of its own produce. 

 Then, again, the influence of the growing modern practice of 

 selling more than the grain, and of importing cattle food and 

 manure from external sources, has to be taken into account. 

 Nevertheless, the illustration derived from a consideration of 

 the proportion of the constituents of the crops grown under 

 a particular system of rotation, which will probably be 

 available for feeding purposes, is not without interest and 

 utility. 



The facts and arguments which have been adduced may be Relative 

 very briefly summarised as follows. It has been shown that ofnTttogm- 

 the amount of food consumed, both for a given live-weight of ous and 

 animal within a given time, and for the production of a given "^m^co«- 

 amount of increase, is, as our current food-stuffs go, measur- stituents. 

 able more by the amounts they contain of digestible and 

 available n on- nitrogenous constituents, than by the amounts 

 of the digestible and available nitrogenous constituents they 

 supply. 



That this should be the case, so far as the consumption for 

 a given live-weight within a given time is concerned, seems 

 consistent enough when the prominence of the respiratory 

 function in the maintenance of the body, and the large re- 

 quirement for non-nitrogenous constituents of food to meet 

 the expenditure by respiration, are borne in mind. But, at 

 first sight, it seems less intelligible that the quantities con- 

 sumed to produce a given amount of increase in live-weight, 

 should also be much more dependent on the supplies of the 

 non-nitrogenous, than on those of the nitrogenous constituents 

 of food. 



It has been shown, however, that store animals may contain Proportion 

 as much, or even more, of the non-nitrogenous substance — %[?oqmLs 

 fat — than of nitrogenous substance ; whilst the bodies of fat- matter in 

 tened animals may contain two, three, four, or more times as ^^ ™ 

 much dry fat as dry nitrogenous matter. Obviously, there- 

 fore, the proportion of fat to nitrogenous substance in the 

 increase in live-weight of the fattening animal, must be much 

 higher than in the entire bodies of the animals. 



Then, it has been further shown that the non-nitrogenous Source 

 substance of the increase — the fat — is at any rate in great °ff at - 

 part, if not entirely, derived from the non-nitrogenous con- 

 stituents of the food. 



