178 THE CHEMISTRY OF CATTLE FEEDING 



Farm for each period of four weeks throughout the time of 

 lactation. It will be seen that the yield diminishes steadily, 

 almost from the first, until about the middle of April, when she 

 was turned out to grass. The effect of this change of food 

 was to produce a sudden and considerable increase in the 

 yield. The maximum increase was attained in the period 

 ending June 10, after which it again declined owing to the 

 gradual advance in the stage of lactation. 



It is, of course, impossible to base any general inferences 

 on the record of a single cow. The following figures relating 

 to a herd of twenty-three cows, which were turned out to grass 

 on May i, are perhaps more convincing, if not quite so striking. 



TOTAL DAILY YIELD OF TWENTY-THREE Cows. 



Date April 29. April 30. May I. May 2. May 3. 



Yield (gals.) ... 48* 48* 45f S* 5'i 



The influence of the food on the quality of the milk is less 

 certain. The evidence is somewhat conflicting; but there 

 appears to be no doubt that liberal feeding, when it does not 

 increase the total yield, tends to raise the percentage of solids 

 in the milk. On the other hand, when the rations are not 

 adequate to the quantity of milk produced especially if they 

 are deficient in protein the percentage of solids is generally 

 diminished. The variation in the quality of milk which can 

 be effected in this way is, however, confined within very narrow 

 limits. 



The majority of practical men seem to believe that the 

 food has no effect at all* upon the ratio of fat to non-fatty 

 solids ; and the physiological evidence regarding the processes 

 by which milk is formed (p. 286) tends to confirm this view. 

 Still it is found that liberal feeding, i.e. rations which tend to 

 increase the total yield of milk, or the percentage of solids in 

 it, tends also to increase the ratio of fat to non-fatty solids. 

 According to Fleischmann, 1 "animals whose milk is abso- 

 lutely richer in fat, at the same time yield milk relatively richer 



1 "The Book of the Dairy." 



