42 SCIENCE AND PRACTICE OF DAIRYING. 



tended cows, to introduce feeding rations containing distinctly more 

 digestible nutrients than are at present usually regarded as most 

 favourable. Good milk cows, whose full capacity for giving milk 

 it is desired to develop, require, above all things, food which is not 

 only absolutely but also relatively rich in digestible protein, by 

 means of which the quantity of circulatory protein in the blood 

 may be increased. There can be no doubt that in the case of cows 

 yielding a large amount of milk, the fat derived from the food is 

 utilized for the formation of milk-fat. It seems advisable to the 

 author, therefore, that in the fodder of good milk cows, the per- 

 centage of digestible fat might likewise be somewhat increased over 

 what has, so far, been regarded as desirable. The old doctrine that 

 the composition of the solids of milk is little influenced by the 

 nature of the feeding; and that it is impossible to increase the per- 

 centage in milk, of any one constituent, by special feeding, has, up 

 to the present time, invariably proved itself correct. It has been 

 asserted, indeed, that an increase in the relative percentage of fat in 

 milk may be obtained by feeding with palm-nut meal and malt 

 combs, but this statement is based on isolated observations, and has 

 not been confirmed in dairy practice. 



It cannot be regarded as correct that with increased percentage 

 of the dry substance of milk all the separate constituents are raised 

 in the same proportion. Nor is it true that the percentage composi- 

 tion of solids for one animal and one lactation period is approxi- 

 mately constant. It is similarly incorrect to suppose that with an 

 improvement in feeding an increase in the yield of milk is obtained, 

 which never affects one or other of the separate constituents. This, 

 at any rate, does not hold good for the fat, since the percentage 

 quantity of fat is subject from day to day, and in the course of 

 a lactation period, to far greater variation than the other less vari- 

 able milk constituents. The percentage of fat in milk is without 

 doubt most sensitive to all the external influences that affect the 

 yield of milk. Very often it is observed that the cow, when the 

 activity of the milk-glands is temporarily increased in course of 

 lactation, yields not only more milk, but a milk richer in fat, the 

 fat being increased more than the non-fatty solids. For example, 

 this is often seen at the beginning of pasturing in summer. Fur- 

 ther, accurate observations on the yield of milk from well-tended 

 and well-fed cows have shown that the average composition of the 

 solids of the milk of single cows is generally proportional to the 



