NUTRIENT REQUIREMENTS 109 
OBSERVATIONS. 
It has long since been recognized that because of the dif- 
ference in composition of the various kinds of feed stuffs no 
single standard of composition for all feeds would be prac- 
tical, and yet, while there is as great a difference in the com- 
position of milks as there is in feed stuffs, there has been no 
adjustment of the nutrients in the ration to the quantity and 
character of the solids contained in the milk yielded, though, 
as has been shown, such an adjustment appears to be quite 
simple and practicable. If in formulating a ration it is 
deemed necessary in economic milk production, to take note 
of the fact that one feed stuff contains 12 per cent of protein 
and another 20 per cent, is it not equally important in our 
attempt to adjust the ration to the needs of the cow in milk 
production to also take into account the fact that one cow 
may give milk containing 3 per cent fat while that of anoth- 
er may contain twice as much? It would seem quite as con- 
sistent to feed an animal food regardless of its composition 
as to feed an assumed balanced ration regardless of thecom- 
position of the product which is to be elaborated from the 
nutrients in the food. 
Great stress has been placed upon the fact that the nu- 
trients in milk have a nutritive ratio of approximately one 
to five, and that therefore the ration for a milch cow should 
have a similar nutritive ratio; apparently overlooking the 
fact that only about fifty per cent ot the ration is used in 
milk production and the balance for maintenance of body. 
If note is taken of the fact that about half the ration is used 
for maintenance and that the maintenance ration has a nu- 
tritive ratio of one to ten, it becomes apparent that for the 
production of milk of average quality by an animal of aver- 
age milk producing powers the nutritive ratio of the ration 
should be approximately 1:7.5. But since animals vary in 
productive powers, and since this variation is not in pro- 
portion to weight of body, it follows that if rations are ad- 
" justed to the actual requirements of animals the nutritive 
ratio of the rations will also vary, as will beshown. 
The author has used tables XXVI and XXIX for two 
years in class work with highly satisfactory results. The 
tables of nutrients required to a pound of milk ranging in 
