i^IATIONS OF MILK CONSTITUENTS 



159 



figures presented in the table on page 158 represent 

 the monthly averages of nearly 100 different lactation 

 periods. 



In studying this table, we notice that the per- 

 centage of fat decreases in the second month, as 

 compared with the first, and then begins to in- 

 crease, 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 com- 

 parative degree of regularity observed in the fore- 

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

 individuals. 



It will be a matter of more immediate interest to 

 consider 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 



VARIATION OF FAT IN CHEESE-FACTORY MILK V^ITH 



ADVANCE OF LACTATION 



Month 



April 



May 



June 



July 



August. . . 

 September 

 October. . . 



Per cent of fat 

 in milk 



New York 

 3.43 

 3.58 

 3.64 

 3.62 

 3.84 

 3.98 

 4.23 



Wisconsin 

 3.48 

 3.49 

 3.50 

 3.55 

 3.63 

 3.84 

 4.08 



Percentages in com- 

 parison with first nionth 



