GROWTH AND FATTENING 65 



tary canal of accumulated waste matter and properly starting the 

 work of digestion. During the week following birth the composi- 

 tion of the milk gradually changes to normal. 



Tho normal milk is lower in protein than colostrum milk, it con- 

 tains an abundant supply compared with the cereals. For example, 

 Appendix Table III shows that the nutritive ratio (i.e., the propor- 

 tion of protein to other nutrients) is 1 A A for cow's milk, while it is 

 1 :10.4 for corn. Milk is also much richer in ash, or mineral matter, 

 than are the cereal grains. While only 1.7 per ct. of the dry matter 

 of corn and 3.9 per ct. of the dry matter of oats is mineral matter, the 

 dry matter of cow's milk contains 5.5 per ct. The supply of calcium 

 (lime) and phosphorus, needed in large amounts in the growing skel- 

 eton, is especially liberal, these two constituents forming over half the 

 total mineral matter. 



These studies of the composition of milk teach that after weaning 

 young animals should be given feeds similar to milk in composition ; 

 i.e., rich in protein and mineral matter. For this reason, such feeds 

 as hay from clover, alfalfa, or other legumes and protein-rich concen- 

 trates, like wheat bran, wheat middlings, and linseed meal, are of high 

 value for growing animals. 



Protein must be of proper quality. — Only a few years ago scien- 

 tists believed that an ample quantity of protein was all that was neces- 

 sary for normal growth. Many recent experiments show, however, 

 that not only must the quantity of protein in the food be abundant, 

 but it must also be of the proper kind or quality, if the animal is to 

 grow thriftily. We have seen in Chapter I that the proteins are 

 made up of many different amino acids (the protein building stones) 

 and that the amounts of these different amino acids in various plant 

 proteins differ widely. Some are well-balanced, containing consid- 

 erable amounts of all the amino acids, while in others certain of the 

 amino acids may be entirely lacking. All the different amino acids 

 are needed to form the proteins of the body, but animals are able to 

 manufacture only one of these amino acids in their bodies from other 

 compounds of the food. Therefore, for normal growth the food must 

 furnish all the necessary amino acids, with the possible exception of 

 a single one. 



The following illustration will show the conditions an animal may 

 meet in forming body proteins from the mixture of amino acids re- 

 sulting from the digestion of the food protein : Suppose we are build- 

 ing a brick wall in a certain pattern which requires that 1 brick in 10 

 have a green end. If we are using as our source of material a pile 

 of bricks resulting from the taking down of another wall, in which 

 only 1 brick in 50 had a green end, it is evident that we will soon 



