58 Animal Husbandry 
108. Fat. — Plants also contain fat or oil. It occurs in largest 
quantities in the seed, and varies widely, running less than 2 per 
cent in rye to 30 and 35 per cent in flaxseed.‘ Fats like carbo- 
hydrates contain carbon, hydrogen, and oxygen, but no nitrogen. 
The oil content of food is determined by extracting the fat by 
ether; hence in tables giving composition of food, the fat is often 
designated as ether extract. A given weight of fat will develop 
23 times as much heat energy as an equal weight of carbohydrates. 
If we multiply fat, therefore, by-2%, it reduces it to the starch or 
carbohydrate equivalent. Fats are not so readily digested as 
nitrogen-free extract. 
FUNCTIONS OF FOOD MATERIALS 
A knowledge of the function of the various food materials will 
enable one to choose and balance a ration more economically, 
and to adapt it to the needs of the animal. 
109. Water. — The water of the food takes the place to a cer- 
tain extent of the water that an animal would otherwise drink. 
In the case of food containing a large amount of water, the total 
consumption of water by the animal will be greater than other- 
wise. Watery foods will not, however, satisfy the animal in this 
respect, as it will still drink water. In many cases the large con- 
sumption of water is of advantage to the animal; this is partic- 
ularly true of the dairy cow, which, in addition to the water needed 
for her own body, secretes large amounts in the milk. Animals 
require much water, particularly the younger ones, whose bodies 
are more than 50 per cent water. 
110. Ash.— The ash or mineral matter is chiefly used in the 
formation of bone, but also to some extent in the tissues, 
blood, digestive fluids, and the like. Young animals fail to 
develop if given no mineral matter, and mature animals be- 
come weak and inactive if deprived of common salt. Hogs, 
if closely confined, and fed on corn alone, are likely to be 
