FEEDING ANIMALS 327 



423. Carbohydrates. These substances include the sugars and 

 starches and also the cellular walls of plants called cellulose or 

 crude fiber. The cereals, such as wheat, rye, barley, and corn, 

 and such crops as kafir, milo, and sorghum, furnish a prepon- 

 derance of starchy, or carbohydrate, materials. The fat in the 

 animal body, in the milk, and in the wool is made for the most 

 part from carbohydrates and crude fiber. Starch is first changed 

 into soluble sugars, and the sugars are then conveyed in the 

 blood to the tissues, where they are used to give energy, or 

 where the various enzymes convert them into fat. 



424. Fats. Most feeds contain more or less fat or oil. Fat 

 may furnish energy for work or may be stored. It is not, how- 

 ever, stored in quite the same form in which it occurred in the 

 plant. Each species of animal makes its own special sort of 

 fat. We all recognize the difference between mutton tallow and 

 butter fat and the difference between the oily fats of the hog 

 and the hard, tallowy fats of the beef steer. 



The fats have a higher nutritive value than the sugars or 

 starches. A pound of fat when burned produces about two 

 and one-fifth times as much heat as does a pound of starch. 

 Therefore fats are estimated to be two and one-fifth times as 

 valuable as starches as a source of energy. 



425. Mineral nutrients. The mineral elements furnish build- 

 ing material for the body and add palatable, laxative, and stim- 

 ulative properties to the ration. They also furnish essential 

 constituents for the digestive juices. Calcium furnishes about 

 70 per cent of the mineral elements that enter into bone, phos- 

 phorus more than 27 per cent, and magnesium about one half 

 of i per cent. Eggshell is almost pure calcium carbonate. 

 Most cereals are deficient in calcium. This is especially true 

 of corn, and the young growing pig or lamb is unable to 

 secure enough calcium from corn. Phosphorus is another min- 

 eral element which is used in the building of bone, and for 

 rapidly growing animals many cereals are deficient in this 

 element. Potassium is another element especially important 

 in the soft tissues. 



