190 ELEMENTARY AGRICULTURAL CHEMISTRY 



4. Influence of Time of and Intervals between Milking. —In 

 most cases cows are milked twice a day, morning and evening. 

 The intervals between the milkings are usually very unequal, 

 the night intervals being generally the longer. Evening's 

 milk is, under these circumstances, much richer in fat than that 

 taken in the morning. With seventeen shorthorn cows, milked 

 at 6 A.M. and 3 p.m., the author found as an average of 1700 

 analyses 3*2 per cent, of fat in morning's milk and 4-5 per 

 cent, in evening's milk, the animals being stall-fed. In summer- 

 time, July to September, the same herd, milked at the same 

 hours, gave an average of 2-69 per cent, of fat in the morning's 

 milk and 4*03 per cent, in the evening. In a third series of 

 experiments the numbers obtained were in the summer 2- 97 per 

 cent, of fat in the morning and 4*31 per cent, in the evening. 



The yield of milk in the morning is considerably greater 

 than in the evening, the ratio of one to the other being in the 

 cases just cited approximately inversely as the ratio of the fat 

 content. 



If, however, cows are milked at equal intervals of twelve 

 hours both the yield and the average fat content become 

 approximately equal at the two milkings. 



The author proved this by experiment with some of the cows 

 of the herd just referred to. 



The results were as follows : 



But it was noticed that when the change from the usual 

 intervals to the 12 J and 11 J intervals was made the proportion 

 of fat in the morning's and evening's milk was at first little 



