" Protein and Milk Yield. 

 " In order to keep the tissues of the body in proper repair, a thousand- 

 pound cow requires about .7 lbs. of protein daily. The amount she must 

 have in addition to this depends on the amount of milk she gives. Milk, on 

 the average, contains 3.6 per cent, of nitrogenous material. If a pound of 

 protein absorbed into the blood could be converted into a pound of casein 

 and albumen, the nitrogenous constituents of milk, then a cow would require 

 3.6 lbs. of digestible protein in her feed for each hundred pounds of milk she 

 gives, in addition to the .7 lbs. daily required by the tissues of the body. 

 But, as before stated, when the blood contains considerable digested protein, 

 a good deal of the protein is burned before it can be appropriated by the 

 milk glands; so that it is not surprising to learn that both the experience of 

 feeders and the results of experiments at the stations indicate that we should 

 feed considerably more protein than would suffice if there were no loss by 

 burning. The following table will make these statements clearer : — 



" Protein for Cows. 



Daily 



yield of 



Milk. 



Protein re- 

 quired for Cas- 

 ein & Albumen 

 in the Milk. 



Protein 

 required 

 by body 

 tissues. 



Total 



of last two 



columns. 



Estimated 



surplus lost by 



burning. 



Total 



Protein in 



Ration. 



" Concerning this table, it may be said that the fourth column shows the 

 amount of protein certainly needed, even if there were no loss by burning. 

 That there is such loss is practically certain, but just how much we do not 

 yet know. The estimate given in next to the last column of the table is 

 probably not far wrong. The last column shows what is probably the 

 smallest amount of digestible protein it is wise to feed a cow, giving the 

 amount of milk set opposite in the first column. There is no particular 

 objection to feeding more than this (to cows) if protein is cheap. If we feed 

 less, one of two things must happen : If her body continues to appropriate 

 the protein it needs, she will fall off in milk; if she keeps up her milk flow, 

 her body will not be properly nourished, and she will lose flesh. 



" This table and the accompanying discussion is given not so much to 

 show the right amount of protein to feed a cow, but to show why it is so 



