392 



% of M 



Rdatii, 



Ik Pn duct, 01 



aey 



Chart 1. 



Showing relative monthly milk production of 

 College herd 



EELATIVE MONTHLY MILK PEODUCTION 



Chart I shows the relative monthly milk production of the 

 college herd of purebred cows, representing the four leading 



dairy breeds ; the first 

 generation grades re- 

 sulting from the use 

 of purebred sires on 

 the scrub cows ; and 

 the scrub cows. 



In making this 

 chart the records of 

 seventy-one purebred 

 cows of various ages 

 for 160 lactation peri- 

 ods, nine grades for 

 twenty-two early lac- 

 tation periods, and 

 fourteen scrubs for 

 fifty-four lactation 

 periods were used. 

 Records for succeed- 

 ing thirty day periods of each lactation to the purebreds, pro- 

 duced consderably more milk than did the scrubs and did not 

 decrease so rapidly between the fifth and ninth months. This 

 last point of relative persistency is more clearly shown in chart 

 II which is made from the same records. 



This chart shows the 

 relation of each suc- 

 ceeding month's rec- 

 ord of the first month 's 

 production of that 

 group. In this chart 

 it will be noted that 

 the purebred cows are 

 much more persistent, 

 especially from the 

 sixth month on, than 

 the grades. The 

 grades, however, do 

 not decline nearly as 

 rapidly from the fifth 

 month on as do the 

 scrubs. 



In table IV comparison is made between a number of the scrub 

 cows and their daughters by purebred sires. This is not a breed 



