THE EFFECT ON THE PERCENTAGE COMPOSITION 

 OF THE MILK OF (a) VARIATIONS IN THE DAILY 

 VOLUME AND {!>) VARIATIONS IN THE NATURE OF 



THE DIET. 



By WILLIAM TAYLOE, M.D., D.P.H. {Carnegie Research Scholar), 

 AND ALFRED D. HUSBAND, A.I.C. 



(From the Rowett Research Institute, Aberdeen.) 



(With 4 Text-figures.) 



The study of lactation has ahiiost always been undertaken from one of 

 two very diverse points of view, the physiological and the commercial. 

 The chief aim of the physiologist has been to determine, either the origin 

 of the various constituents of the milk and the method of their elabora- 

 tion, or the extent to which internal secretions affect the flow of milk 

 by their initiation, inhibition or stimulation of milk secretion. From the 

 commercial or agricultural point of view, on the other hand, the chief 

 interest has centred round the problem of the production of butter fat, 

 and a very large number of experiments have been conducted to deter- 

 mine by what method of feeding a cow could be caused to give the 

 maximum yield of milk with the highest percentage of fat. 



Much of this work is of great value, but in many cases the fat is the 

 only constituent of the milk which has been determined separately, the 

 other constituents having been estimated together as milk solids other 

 than fat. 



With regard to the diets, unless the calorific consumption is stated, 

 a simple addition of extra protein or fat to a ration does not allow of a 

 judgment being formed as to whether the alteration in the daily volume 

 and percentage composition of the milk is due to protein or fat per se, or 

 simply to an increase in the calorific value of the ration. This considera- 

 tion would appear to have been lost sight of in some cases. 



The most complete investigation of the influence on the percentage 

 composition of the milk of feeding with an excess of one of the energy- 

 yielding constituents of the food is that of Voit(i), who worked with a 

 bitch. He found that, while an excess of one constituent in the food 



