486 Scientific Proceedings, Royal Dublin Society. 



2. By adding butter fat, soya fat, wheaten starch, or casein to a 

 "milk and body maintenance" ration the total fat in the daily milk is 

 increased. In all the tests recorded in this investigation the milk ilow 

 remains unaffected by the addition of these single food substances ; but the 

 percentage of fat in the milk is increased. That is to say, the percentage of 

 fat in the milk is raised, not only by the addition of fat to the food, but also 

 by the addition of carbohydrate or protein. Obviously, if an increase in the 

 milk flow occurs proportionate to the increase in the total fat, the percentage 

 of fat in the milk is unchanged. 



3. In the production of butter fat in milk, starch, casein, and fat (both 

 butter and soya) replace one another; but the quantities which replace each 

 other cannot yet be definitely stated. In the early part of lactation 0'45 lb. 

 of soya fat produced an increase of O'OSo lb. of fat in the milk of goat 1 ; 

 1'06 lb. starch (that is about two and a quarter times more starch than fat) 

 produced an increase of O'OS lb. milk fat in goat 2 ; and 0'45 lb. butter fat 

 produced an increase of 0'04 lb. milk fat in goat 3. In the second half of 

 lactation 0'5 lb. soya fat produced an increase in the total milk fat of O'Ofi lb. 

 in goat 1, 1'13 lb. starch (about two and a quarter times the weight of fat), 

 an increase of 0-02 lb. milk fat in goat 2, and I'lo lb. casein an increase of 

 0'025 lb. milk fat in goat 3. In one case soya fat was just slightly better and 

 in another it was twice as good as two and a quarter times its weight of starch. 

 Butter fat was slightly better than soya fat for milk fat production, but the 

 test was too limited to draw a general conclusion. It was thought that 

 butter fat would be much superior for this purpose to soya fat, because of 

 its content of vitamin A ; but perhaps sufficient vitamin A was already 

 supplied in the remainder of the ration to prevent a possible difference 

 between the effects of the two fats becoming apparent. 



In goat 2 the substitution of fat for starch in ration Fj had a peculiar 

 result. Possibly this is temporary, and the duration of this test was too 

 short to allow of a general conclusion. When, however, casein replaces the 

 fat (ration G, goat 2), the total fat in the milk is similar to that produced 

 by an ec[ual weight of starch. Thus right through the experiment casein and 

 starch replace one another in equal proportions. Evidently this can only 

 hold where sufficient protein is already supplied in the " milk and body 

 maintenance" ration to contribute to the production of the protein moiety 

 of the milk yielded, and otherwise maintain nitrogenous equilibrium. 

 Further work remains to be done on the quantitative replacement of fats 

 and carbohydrates in food for the purpose of milk fat production. 



4, While an addition to the " milk and body maintenance " ration 



