GENERAL CHEMISTRY OF MILK 125 



shine have a stimulating effect on their general health, and this 

 tends to increase their milk production. 



When cows feed throughout the year on nature's balanced 

 ration in the open air a difference is observable between the milk 

 production of the winter months and that of the spring and sum- 

 mer months. During the former food is scarce and not in as good 

 a condition as in the latter months. In countries where climatic 

 conditions make this possible the winter yield of milk is not as 

 rich as that of the summer months. 



Attempts at feeding fat into milk by mixing substances rich 

 in fat with the food have not been successful. It is true that 

 Caspari fed iodized fat and recovered iodin from the milk, although 

 he was not able to find iodin in the milk when iodocasein or iodo- 

 albumin was fed. But this proves only that fat in the food is in 

 part the source of milk-fat, and it does not indicate an increase 

 in milk-fat when fed in large quantities. Tallow has been fed 

 with the same object in view, also without success. Furthermore, 

 oils have been emulsified to render them easily digestible and have 

 been mixed with the food. Such excessive rations of fat seem to 

 increase the fat content of milk for a time, but as soon as the ani- 

 mal becomes accustomed to the change in food the normal compo- 

 sition of the milk reappears. 



However, feeding oils and other fats has an influence upon the 

 chemical composition of milk-fat. This has been proved conclu- 

 sively. For example, when cottonseed oil is fed, the butter-fat 

 gives cottonseed reaction, according to Woods. Cottonseed oil 

 produces a hard butter; gluten, a soft butter. The firmness of the 

 fat, the melting-point, the iodin number, the quantity of volatile 

 acids, appearance, taste, and flavor are affected by the kind of 

 fat given in the food. 



Feeding foods rich in fat has been attempted in the expecta- 

 tion that they would increase the richness of the milk. Cotton- 

 seed meal, cocoanut cake, linseed cake meal, palm nut meal, 

 peanut cake meal, malt sprouts, gluten feeds, brewers' grains, 

 molasses feed, and others have increased the fat content for 

 a short period, but the normal composition has gradually re- 

 appeared. 



It must be admitted that the influence of the food given upon 

 quantity of milk produced and on its composition is of far-reach- 

 ing importance, inasmuch as careless feeding, underfeeding, or 

 feeding unbalanced rations reduce the normal productivity of a 

 cow. Judicious feeding, on the other hand, and any factor which 

 preserves the health of the animal will cause her to produce the 

 quantity and quality of milk which she is capable of producing. 

 A careful milk producer will feed rational mixtures and vary them 



