Process of Power Changes 19 



Cows Over 5 Years of Age Holstein-Friesian Milk 



Production Official Tests for Year 



Ending May 15, 1906. 



Ages of Cows Av. Milk in 7 Days 



5 years to 6 years 433.75 pounds 



$ years to 7 years 449.00 pounds 



7 years to 8 years 449.51 pounds 



8 years to 9 years 458.10 pounds 



9 years to 10 years 468.71 pounds 



10 years to 11 years 490.35 pounds 



11 years and over 446.33 pounds 



By an inspection of the details of which this 

 table is composed, and by making another table 

 which shows the same cows tested in successive 

 years, I find that the actual increase in milk pro- 

 duction from year to year is much more than that 

 given in the above table. Also I find that actual 

 increase extends up to twelve years of age, which 

 is as far as these records reach on cows tested 

 two years in succession. 



A cow may not be full grown when she has 

 her first calf, but she does not continue to grow 

 in size up to the time she has her tenth or elev- 

 enth calf. Under continued exercise which is 

 more than some minimum amount per unit of 

 time, animal powers continue to develop up to 

 some unknown point near the end of life. 



