THE FEEDING OF MILCH CATTLE 323 



components of the mammary gland alter. An 

 organ like the mammary gland which is always of 

 the same composition, can, therefore, when it 

 liquefies, only yield products which are characterised 

 by great similarity. So an explanation is afforded 

 of why the proportion which the constituents of 

 milk bear to one another cannot be appreciably 

 altered by the food. 



(b) The effect of the quantity of food on the milk 

 secretion. 



When a change is made from a liberal to a scanty 

 diet the lacteal gland, as a rule, does not immediately 

 accommodate itself to the quantity of food, but 

 remains for a shorter or longer time at the old level. 

 In this case a greater or less portion of the milk is 

 formed from body substance (flesh and fat), and 

 the cow may lose weight to the extent of i cwt. or 

 more without the yield of milk undergoing any 

 noticeable diminution. As a rule, though, there is 

 a rapid fall in the quantity. It was noticed, for 

 example, that a cow on a heavy ration (23 Ibs. clover 

 hay, 3&J Ibs. mangels, and 8 Ibs. coarsely ground 

 barley, per noo Ibs. live weight) gave 30 J Ibs. of 

 milk with 3-46% fat; whereas after being fed for a 

 month on a poor ration (9 Ibs. clover hay, 44 Ibs. 

 mangels, n Ibs. barley straw) the animal only gave 

 20 Ibs. of milk with 3-50% fat. A second cow which 



