FERTILIZER CONTROL STATION. 347 



(4) The substitution of cotton-seed or linseed meal for a portion 

 of the corn meal of a moderate ration diminished the cost of pro- 

 duction. During the first period steers 3 and 4 were fed daily 3 J 

 pounds of corn meal, while steers 5 and 6 received 2 pounds corn 

 meal and Ij pounds linseed meal, this being the same weight of 

 grain in each case. Steers 3 and 4 gained onh' 85 pounds in the 

 same time that steers 5 and 6 gained 154 pounds. In the second 

 period the rations were changed and steers 3 and 4 received the mix- 

 ture of corn meal and cotton-seed meal, and gained 15y pounds in 

 the same number of days that they required to gain 85 pounds in 

 the previous period, when the grain ration was equally large but 

 wholly corn meal. 



Comparison of Rations. 



In tlie preceding experiments with milch cows and steers the ra- 

 tions have differed widely in quantit}' or in composition, and as a 

 result corresponding variations in production and growth have been 

 observed. A close study of these rations is necessary in order to 

 see clearlv in what wav and to what extent they differ. It is not 

 enough to simply know the name and quantitj' of the food consumed, 

 we must know of what it is composed and what part of its ingredi- 

 ents is appropriated to the uses of the animal body in order to under- 

 stand why two rations similar in weight may be so dissimilar in effect. 

 "What we wish to learn concerning these rations is the quantities of 

 digestible ingredients which each contained. These quantities can be 

 calculated, as we know the composition of the foods and their di- 

 gestibility. The method of calculation is simple. If corn meal con- 

 tains 10 per cent of protein, 80 per cent of which is digestible, then 

 each 100 pounds of the meal furnishes 8 pounds of digestible 

 protein. 



Milk rations. The rations given the milch cows are first con- 

 sidered. 



23 



