FACTORS THAT AFFECT COMPOSITION OF MILK 47 



VARIATION OF PERCENTAGE OF FAT IN MILK WITH ADVANCE OF 

 LACTATION 



In studying this table, we notice that the percentage of fat 

 decreases in the second month, as compared with the first, 

 and then begins to increase, continuing to increase from month 

 to month during the entire period of lactation. The rate of 

 increase is more rapid during the last two or three months than 

 previously. Such behavior appears to be the general rule. 

 Variation from the comparative degree of regularity observed 

 in the foregoing table may, of course, appear in the case of 

 individuals. 



Van Slyke also shows " the influence of advancing lactation 

 upon the percentage of fat as observed in the case of milk used 

 at cheese-factories. In general, dairymen have their cows 

 begin the period of lactation in March and April, so that milk 

 taken to a cheese-factory represents, during the season, stages 

 of the lactation period extending from about the second to the 

 eighth months. Cows kept under ordinary farm conditions 

 are subject to greater variations of external influences than those 

 used in the investigation represented by the figures in the pre- 



