16 FEEDS AND FEEDING 



while plants, as we have learned, commonly store their reserve food in 

 the form of starch. 



Carbohydrates, which form such a large part of plants, make up but 

 a very small portion of the animal body. As will be discussed later, 

 altho the glucose in the blood and the glycogen, or animal starch, in the 

 liver and other organs perform exceedingly important functions, at no 

 time do they form an appreciable part of the animal's weight. (60) 



Mineral matter forms the larger part of the bony skeleton, but is also 

 distributed in small amounts thru all parts of the body, where it per- 

 forms indispensable vital functions, which will be discussed later. 



29. Composition of animals. Over 60 years ago Lawes and Gilbert, 

 famous English agricultural scientists, analyzed the entire bodies of 

 several farm animals a task involving much labor. During recent 

 years similar studies have been made at certain of the American ex- 

 periment stations. The following table, 1 which summarizes some of 

 these investigations, shows that the composition of the bodies of farm 

 animals varies greatly according to their age and degree of fatness: 



Composition of the bodies of farm animals* 



Water Protein Fat Ash 



Per ct. Per ct. Per ct. Per ct. 



Calf, wt. 100 Ibs 71.8 19.9 4.0 4.3 



Calf , wt. 300 Ibs 65.7 18.8 11.2 4.3 



Growing steer, wt. 700 Ibs 60.3 18.6 16.6 4.5 



Partly fat steer, wt. 1,000 Ibs 52.0 17.1 26.9 4.0 



Fat steer, wt. 1,200 Ibs 48.0 16.0 32.3 3.7 



Very fat steer, wt. 1,500 Ibs 43.5 15.7 37.7 3.2 



Fatlamb.. 52.3 13.4 31.2 3.2 



Sheep, before fattening 61.0 15.7 19.9 3.4 



Half-fat sheep 55.2 15.4 25.9 3.5 



Fat sheep 46.2 13.0 37.9 3.0 



Very fat sheep 37.1 11.5 48.3 3.1 



Hog, before fattening . . 58 . 1 14.5 24 . 6 2.8 



Fat hog 43.0 11.4 43.9 1.7 



* Not including contents of digestive tract. 



The table shows that 71.8 per ct. of the body of a 100-lb. calf is 

 water and that the proportion of water steadily grows less as the animal 

 matures and fattens, the body of a very fat 1,500-lb. steer containing 

 only 43.5 per ct. water. The percentage of protein remains quite con- 

 stant during growth but decreases as the animal fattens. On the other 

 hand, the percentage of fat increases gradually during growth, and more 

 rapidly while fattening. Over one-third of the carcass of the fattened 

 1,500-lb. steer is fat. The percentage of ash, or mineral matter, shows 

 the least change, but decreases as the animal fattens, since the fatty 

 tissue contains but little mineral matter. 



Similar changes occur in the bodies of sheep and swine, as the animals 

 mature and fatten. In general, sheep and swine at the same degree 



1 Data for cattle from Haecker, Minn. Bui. 193, and for sheep and swine from 

 Lawes and Gilbert, Philosophical Transactions, 1859. 



