DAIRYING 27 



176. A cow was milked dry ; the milk obtained was divided 

 into three portions, the per cent of fat in these three portions was :* 



ist, 1.04; 2nd, 3.57; 3rd, 8.61. The average of the three por- 

 tions of mixed milk of this milking was 3.6% fat. A second 

 milking of the cow after 15 minutes gave a small quantity of milk 

 which contained 7.8% fat; a third milking after another period of 

 15 minutes contained 6.0% fat, and a fourth after 15 minutes con- 

 tained 4.4% fat ; showing that the difference in the richness of the 

 milk is not due to a change in the milk secretions or the creaming 

 of milk in the udder, but that some of the fat of the milk is 

 mechanically held in the fine ducts of the cow's udder and when 

 these are rinsed out, the milk returns to about its normal richness 

 or fat content as in this case from 3.6 to 4.4%, the latter figure 

 representing the newly formed milk in the last 15 minute period 

 after the ducts had been rinsed out by the milk secreted during 

 the two preceding 15 minute periods ; the newly formed milk having 

 about the normal per cent of fat. 



177. Many analyses have shown, however, that the difference 

 between the first and the last milk is confined almost wholly to the 

 per cent of fat and that the other constituents, casein, milk sugar, 

 etc., are present in about the same amounts in the milk from the 

 beginning to the end of a milking. It has also been noticed that 

 other things besides milking, that give the udder extra manipula- 

 tion such as the butting of a calf, moving around through the day, 

 and the extra manipulations given by milking on the right side of 

 the cow have a tendency to increase the fat per cent, in the milk, 

 as the night milk is richer than the morning milk when the interval 

 of time between the milkings is the same and the milk from the 

 right side of the udder is richer than that from the left side because 

 of the extra manipulations on the milking side of the cow. 



D. Intervals Between Milking. 



178. The question is often asked, "Which is the richer, the 

 morning's or the night's milk?" The answer to this question is 

 another question, "What time are the cows milked in the morning 

 and at night?" If the milkings are at five o'clock and there is 

 just 12 hours between them, there will be'very little difference, if 



* Kirchner Milchwirtschaft. 



