5bU ANNUAL KlCrOKT OK I'lM-: Olt I )uc 



which the g~roup happens to be made up in a given loud, the nieclian 

 ical condition in which it exists and the proportion which the group 

 under consideration bears to the other groups of food substances 

 present in the digestive tract at the same time. Thus, so-called 

 "herbivorous" animals provided with a paunch, have greater power 

 of digesting fiber than is possessed by animals with a single, small 

 stomach like the hog; the tender fiber of voung plants, is more di- 

 gestible than the hard, ligneous fiber of old, woody plants; the pro- 

 teids of clover and timothy seeds are really quite digestible, but 

 escape digestion in a horse's stomach, because the hard seed-coats 

 of these small seeds fail to be broken by the animal's teeth and almost 

 entirely prevent access of the digestive fluids to the proteids; and 

 finall}', the digestibility of protein is decreased when large quan- 

 tities of carboh3'drates are present in a ration. The percentage of a 

 ^iven group of materials that is removed from a given food by diges- 

 tion is termed its percentage of digestibility^ or sometimes, its co- 

 efficient of digestion. 



The more important nutritive uses of the digested parts of these 

 several food constituents may be briefly noted: 



The ash materials supply the mineral salts of the bone, blood, 

 muscle and other animal tissues. 



The carbohydrates (fiber and nitrogen-free extract) and fat serve, 

 when burned in the body, to maintain its temperature and supply of 

 energy. For this purpose, the fat is 2.25 time© as valuable as the 

 carbohydrates. Both of these groups are also capable of forming 

 body-fat. The protein alone is able to supply the nitrogenous sub- 

 stances forming the organic matter of bone, blood, muscle, nerve, 

 skin, wool, milk-curd and egg-albumen. 



To permit a more perfect distinction of food values in the com- 

 mercial feeding stuffs, the average compomtion of a number of the 

 more common cattle food products of a Pennsylvania farm is given 

 below; 



