DOMESTIC ANIMALS 



21 



and fattening. Nutrition is such an im- 

 important part of animal life, however, 

 that nearly all organs of the body are 

 concerned with it. A considerable part 

 of the animal's movements are for the 

 purpose of obtaining food. The teeth, 

 tongue and stomach reduce the food to 

 small particles. The digestive juices 

 dissolve and otherwise modify the nutri- 

 tive elements so that they may be ab- 

 sorbed. The stomach, intestines, sali- 

 vary glands, pancreas and liver take part 

 in this work. The dissolved food mate- 

 rials are absorbed directly into the veins 

 or are carried by the lymphatic vessels to 

 the blood. By means of the circulating 

 blood the food in solution is distributed 

 to all parts of the body. The excess of 



nutritive substances; viz., proteids, car- 

 bohydrates, and oils or fats. Protein is 

 an essential constituent of all animal 

 tissues and must therefore be present in 

 the ration to a greater or less degree. 

 Carbohydrates include starches, sugars 

 and their derivatives. 



The mechanical work of reducing the 

 feed stuffs to fine particles ready for the 

 action of the digestive juices is natu- 

 rally much greater with farm animals 

 than with man. For much of the food 

 is of a coarse nature and contains rela- 

 tively large amounts of cellulose and 

 crude fiber. Some advantage, there- 

 fore, is gained by cutting, cracking, 

 grinding, soaking, steaming or boiling 

 feed. The animal is thereby saved some 



Fig. 14 A GRAND CHAMPION MERINO RAM OF PRESENT DAY 



sugar is first stored tip by the liver in 

 the form of glycogen. The waste prod- 

 ucts arising from the breaking down of 

 tissues are carried in the blood to the 

 kidneys, lungs and skin where they are 

 excreted in the form of urine, carbon 

 dioxid and sweat. The whole cycle 

 which the food undergoes from diges- 

 tion to excretion in the form of a waste 

 product is known as metabolism. For 

 the farmer's purposes, therefore, animal 

 physiology is practically the same as the 

 general subject of nutrition and may 

 well be discussed from that standpoint. 

 Nutritive substances in feeds — The 

 feeds which we give our farm ani- 

 mals contain three classes of organic, 



of the mechanical work of preparing the 

 feed for digestion. The economy of 

 these processes, however, cannot be de- 

 termined by viewing them from this 

 standpoint alone. They may cost too 

 much in proportion to the advantage 

 gained. Moreover, in ruminants there 

 seems to be a natural demand for a cer- 

 tain amount of coarse feed. 



As soon as the feed is taken into the 

 mouth it is mixed with the saliva and 

 becomes thereby somewhat softened. 

 This helps in masticating and swallow- 

 ing the food. The saliva also contains 

 ferments, especially ptyalin which 

 changes a part of the starch and cane 

 sugar in the feed stuffs into dextrin, 



