20 BULLETIN 48, HAWAII AGRICULTURAL EXPERIMENT STATION. 
ing to less than 10 per cent of the total consumed. It other words, 
fully 90 per cent of the feed consumed at the more profitable en- 
terprises is home grown. The striking exception to feeding home- 
grown products at a profit is in the case of the extensive garbage- 
feeding enterprises being conducted on Oahu, where practically all 
of the feed is purchased outright at a comparatively low figure. 
Unless the swine raiser is favorably situated where garbage or 
other by-products suitable for feeding can readily be obtained at 
a cost lower than is asked for the grain equivalents, farm crops for 
feeding to market hogs should be produced at a cost that is com- 
mensurate with the returns. When highly bred stock is raised for 
selling for breeding purposes the situation is somewhat changed, 
but even then the breeder should produce forage crops as extensively 
as possible for feed. 
The swine raiser should endeavor to familiarize himself with the 
underlying principles of nutrition, as well as of feeds and feeding, 
if he would feed hogs economically and profitably in these days of 
intensive production and keen competition. In the first place he 
should know that the digestive organs of swine with their contents 
compriss only about 7.5 per cent of the total weight of the body, 
while those of cattle are more than 14 per cent. In the second place, 
he should know that horses, cattle, and sheep are normally herbivo- 
rous, living as they do on grass and herbage, while the hog is omnivo- 
rous and feeds not only on tender herbage, roots, and seeds but also 
on animal matter. The hog also, in its effort to extract feed from 
beneath the soil, swallows considerable earthy matter. Having a 
stomach of rather limited capacity and a peculiar digestive tract, 
swine require feed that is more concentrated and digestible and less 
fibrous than is needed for any other class of farm animals. 
The changes which food undergoes within the digestive tract pre- 
pare it for absorption into the circulatory system, where it is used 
to build new material, repair body waste, and to act as a source of 
energy. The true or digestible nutrients are food constituents that 
aid in supporting animal life, such as crude protein, the carbo- 
hydrates, and fat. Air, water, and mineral matter also come under 
this heading. 
A " ration " may be termed the feed allowance per day per ani- 
mal, whether it be fed at one or several meals. A " balanced ration " 
is the feed or combination of feeds containing the several nutrients 
protein, carbohydrate, and fats, in proportion and amount that will 
furnish one animal with the optimum amount of nutrition in 24 
hours. 
The relative usefulness of different feeds depends largely upon the 
digestibility of their several nutrients ; that is, upon the percentage of 
total crude protein, fiber, carbohydrate, and fat that is digested by 
the animal. After the feed is chemically analyzed, it is given in 
weighed quantities to the animal, and for a reasonable length of time 
after feeding the urine and feces of the animal are also weighed 
and analyzed. The difference between the amount of each nutrient 
fed and of that eliminated represents the digested portion. 5 
5 Data showing the determination, of the digestible nutrients in a great many feeds are 
to be found in all standard textbooks on feeds and feeding. Feeding standards that have 
been worked out experimentally to show the amounts of digestible nutrients which are 
supposed to be best adapted to different animals for maximum production do not take 
into account the element of cost. They should, therefore, be used as a guide rather than 
adhered to blindly. 
