602 Journal of Agriculture, Victoria. [15 Oct., 1919. 



Amides serve simply as a source of heat; although .containing nitro- 

 gen they do not form tissue. By producing heat they save the proteids, 

 but for this purpose they are of only half the value of the carbo- 

 hydrates proper. 



Nitrogen-free Extract. 



Nitrogen-free extract is a term including all those substances soluble 

 in dilute hydrochloric acid. It includes (a) starches, (6) sugars, 

 (c) vegetable gums, (</) vegetable acids. Carbo-hydrates strictly speak- 

 ing are substances containing carbon, hydrogen and oxygen, the latter 

 in the proportion to form water. Nitrogen-free extract does not include 

 all the carbo-hydrates found in food; cellulose is not included, being 

 insolvible in dilute hydrochloric acid. 



Starch Group. 

 Starch is found widely distributed in plants as a reserve foodstuff, 

 and exists in grains which are structurally characteristic of the species 

 of plant producing them. It is scarcely found in coarse fodders. The 

 grains are insoluble in cold water, but swell c"nd burst with hot water 

 forming starch paste. Starch is converted by enzymes (diastase and 

 ptyalin) into maltose and dextrine. Acids hydrolise starch to glucose 

 and dextrine. 



Sugar Group. 

 This consists of (a) Grape sjigar group — glucoses, (b) Cane sugar 

 group — saccharoses. 



Glucoses — Grape sugar as found in the juice of fruits and in the 



sap of plants. 

 Saccharoses — (1) Cane sugar found in sugar cane, grasses, beet- 

 root and mangold. 



(2) Malt sugar found in malted barley and germinated 



grains. 



(3) Milk sugar found in milk and whey. 



Functions of Carbo-hydrates. 



Usually described as the fuel portion of the food, or that portion 

 which goes to the production of energy. They may also be utilized for 

 the formation of animal fat. 



Fat — Ether Extract. 



This consists of compounds out of finely ground feed stuff dissolved 

 by ether. 



The term " fats " or " fats and oils " is technically incorrect as 

 the ether dissolves out free fatty acids, wax, and chlorophyll besides 

 true fats. 



The function of fats is to serve as a source of heat and energy as 

 well as a source of animal fat, and as a source of heat are two and a 

 quarter times more valuable than carbo-hydrates. 



Fibre. 

 Fibre is the tougher or woody portion of plants, consisting largely 

 of cellulose. The proportion of fibre digested depends on the part and 

 age of the plant, and also on the animal eating it. Fowls practically 

 digest no fibre. Sometimes more energy is required for its digestioji 

 than the fibre itself can supply. The portion digested has the same 

 uses as the carbo-hydrates. 



