FORTY-THIRD ANNUAL CONVENTION 213 



Relative Monthly Milk Production 



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 resulting 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 i6o lactation periods, nine grades for 

 twenty-two early lactation periods, and fourteen scrubs for fifty- 

 four lactation periods were used. Records for succeeding thirty- 

 day periods of each lactation to the purebreds, produced con- 

 siderably 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 succeeding month's 

 record 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 comparison in any way as none of the scrub cows have 

 daughters, by more than one purebred sire, in milk. The varia- 

 tion in the production of the dams themselves, and the fact that 

 for this preliminary report the records of such a small number 

 of heifers of purebred sires are available, also renders this im- 

 possible. Furthermore, the sires were not selected with this in 

 view but were the bulls in use in our purebred herds with one 

 exception, which is noted later. 



In the case of the heifers by the Holstein sire it will be 

 noted that when the best record made by each heifer is compared 

 to the best record of her dam, these heifers have produced in 

 quantity, of milk, from 1603.4 to 3714.3 pounds, or 45% to 

 75% more than their dams and 50.33 to 82.08 pounds, or 27% 

 to 41%, more butterfat. When the average records for each 

 are compared, in spite of the fact that mature records of the 

 scrubs are compared with immature records of the heifers, as in 



