ECOXOMICAL FEEDING OF ANIMALS. 33 



starch, which is representative of the class of nutritive elements 

 called carbohydrates, into its chemical elements, finding that 

 it contains carbon, hydrogen and oxygen ; hence the name, carbo- 

 liydrates. 



There are other substances similar in chemical composition 

 grouped with this in the class called carbohydrates. The prin- 

 cipal ones are sugar and gum. Vegetable oil, called fat, also 

 contains the same chemical elements, but in different proportions. 

 Having more carbon, it is more valuable pound for pound, hence 

 is usually given as a separate element in the analysis of feeding 

 stufifs, but when eaten by animals it serves the same purposes 

 as the carbohydrates, hence is classed with them. 



This group of nutritive elements when eaten by animals server 

 one or more of three purposes. The first demand is to supply 

 the heat of the animal body. For this carbon is burned after 

 being digested and assimilated and coming into contact with the 

 oxygen in the lungs in a very similar way to which carbon is 

 burned in any of the fuels we use for heating our homes. This 

 demand upon the food is variable, just as the demand for fuel 

 for heating a stove is variable, depending upon the conditions 

 under which either the animal or the stove is placed. And 

 here is the value of this rather technical discussion of the uses 

 of food. An animal exposed to low degrees of temperature and 

 high winds uses a much larger proportion of its food to keep its 

 body warm than an animal that is comfortably housed. This 

 explains why taking two animals equally well bred, in equal 

 degrees of health, of equal age, differing only in condition, and 

 placing them in an open yard in the winter and feeding them 

 exactly the same kinds and amounts of food, the poor animal 

 will become poorer and the fat animal become fatter. 



The second use to which this carbonaceous food, or carbo- 

 hydrates, is put is in the production of working energy or power. 

 Thus we see why it is that a working horse requires more food 

 than an idle one. 



The third way in which this class of nutrients is utilized is 

 in the production of fatty tissue, fat not being produced until the 

 other two demands are met. We understand why it is that it 

 i? more difficult to fatten an animal in winter than in summer. 



