480 NUTRITION OF FARM ANIMALS 



solids and of fat, i.e., it is more concentrated than that yielded 

 after the longer interval. The differences in the composition 

 of the night's and morning's milk, which have been the subject 

 of so much discussion, appear explicable upon this basis, the 

 interval between the morning's and night's milking being usually 

 less than that between the night's and morning's. 



575. Completeness of milking. If successive portions of 

 the same milking be analyzed, the percentage of fat in the later 

 portions will be found to be greater than in the earlier ones, 

 while the percentage of solids-not-fat varies comparatively 

 little. The fact of the greater richness of the so-called " strip- 

 pings " is well known. This difference was at one time ex- 

 plained as caused by an actual rising of the cream on the milk 

 contained in the udder. The fact, however, that but a com- 

 paratively small amount of milk is held in the milk cistern, as 

 well as the entire anatomy of the udder, renders this explanation 

 untenable. The difference is probably due to a partial retention 

 or stagnation of the fat globules in the alveoli and canals, they 

 being afterward washed out by the portions of milk secreted 

 during the latter part of the milking. Incomplete milking 

 not only fails to get this fat, thus lowering the quality of the 

 milk actually obtained (compare 566), but it appears that 

 the retention of the fat in the alveoli tends to check the 

 secretion of the milk. In all forms of milking, therefore, it 

 is important that the cow be milked out as completely as 

 practicable. The advantages of various methods of manipulat- 

 ing the udder, such as the Hegelund method, are probably due 

 largely to this influence. Similarly, in the use of milking ma- 

 chines it seems to be necessary with most cows to remove 

 the last portions, or strippings, by hand. 



Muscular exertion exercise, fatigue 



The influence of muscular exertion upon milk secretion has 

 been much discussed upon a comparatively slender experi- 

 mental basis. In the United States the question has usually 

 been as to the desirability of allowing freedom of motion and 

 exercise to dairy cows, while in Europe, especially among 

 small farmers, cows are used for draft to a not inconsiderable 

 extent. 



