MILK PRODUCTION 527 



continued for a time after the feeding of palmnut meal was 

 discontinued. This fact is of particular interest in its bearing 

 upon the interpretation of Hansen's results. 



The evidence of these two series of experiments seems to put 

 the possibility of a " specific/' effect of certain feeding stuffs 

 upon milk production beyond doubt. They open up an inter- 

 esting field for further investigation, both as regards the physio- 

 logical explanation of the fact and as to its practical significance. 



621. Specific effects associated with fats. In view of what 

 is known regarding the significance of certain fats (or of sub- 

 stances associated with them) for growth (498), it is of interest 

 to note that these " specific " effects on milk production seem 

 to be associated to a considerable extent, although not ex- 

 clusively, with the fat consumed. Morgen's investigations 

 (613) show that the addition of fat to his flavorless rations had 

 such a stimulating effect up to a certain limit. Many of the 

 feeding stuffs believed to exert such " specific " effects are 

 relatively rich in fat, notably palmnut meal for which the result 

 seems best established. Moreover in the case of the latter 

 material, as just noted, Hansen finds the influence most marked 

 with samples rich in fat. Whether these effects are due to the 

 fat as such or to associated substances, as is believed to be the 

 case in growth, is a matter for future investigation. 



622. Influence on utilization of energy. In conclusion, 

 it may not be superfluous to point out that the stimulating 

 effects of feed on milk production do not necessarily imply any 

 higher utilization of the feed energy supplied. Certain feeds 

 apparently " speed up " the metabolic processes in the udder, 

 but whether the increased production is effected with an in- 

 creased or a decreased efficiency cannot be determined from 

 experiments of the type thus far made. (Compare Chapter 

 XVII, i, 737, 738.) 



623. Influence of feed on composition of milk. The results 

 outlined in the last few pages have an obvious bearing on the 

 much discussed question of the effect of feeding on the composi- 

 tion of milk. That such an influence exists has long been the 

 belief of practical dairymen, while the tendency of scientific 

 investigation has been on the whole to throw doubt upon it. 

 Some writers have gone so far as to practically deny that the 

 feeding has any significant influence upon the composition of 



