1911.] PUBLIC DOCUMENT — No. ;il. 87 



THE EFFECT OF PROTEIN UPON THE PRO- 

 DUCTION AND COMPOSITION OF MILK. 



BY J. B. LINDSEY. 



Investigations and observations indicate that milk is not a 

 simple rinid secreted directly by the blood, but a complex sub- 

 stance resulting from the activity of the milk cells. The cells 

 and milk glands take from the blood and lymph vessels materials 

 suited to their purpose, and by chemical and physiological pro- 

 cesses convert them into a ditt'erent substance, namely, milk. 

 ]\Iilk, therefore, consists for the most part of reconstructed 

 cell substance, and it is not possible, by any system of feeding, 

 to produce very great modification in its composition. The 

 composition of milk depends principally upon the breed and 

 individuality of the cow. stage of lactation, and development 

 of the ndlk cells. 



German investigators, during the years 18G8 to 1876, studied 

 the additions to the different basal rations of increasing amounts 

 of protein upon the composition of the milk, and noted only 

 very slight variations. Danish observers^ as a result of experi- 

 ments by the group method with 1,152 cows, concluded that 

 the protein was practically without influence in varying the 

 proportions of the several milk ingredients. American experi- 

 menters report similar conclusions. 



This station, from time to time, has conducted a number of 

 experiments to observe the influence of different amounts of 

 protein in increasing the quantity of milk, to note the protein 

 requirements of dairy animals, and also to study its influence 

 in modifying the proportions of the several milk ingredients. 

 Some of these results have been published in reports of the 

 station, and they have been recently summarized in detail in 

 Part T. of this report. The following are the principal con- 

 clusions : — 



