18 Process of Power Changes 



has her second calf, a still larger amount when 

 she has her third calf, and so on. We can see 

 this a little better by reference to a table which 

 will show the amount of milk produced by cows 

 of different ages. 



Holstein-Friesian Milk Production Official Tests for 



Year Ending June 14, 1913. 



Ages of Cows Av. Milk in 7 Days 

 Under 2 years, 6 months 322.7 pounds 



2 years, 6 months, to 3 years 348.8 pounds 



3 years to 3 years, 6 months 400.3 pounds 



3 years, 6 months, to 4 years 418.2 pounds 



4 years to 4 years, 6 months 446.8 pounds 



4 years, 6 months, to 5 years 459.2 pounds 



Over 5 years (av. 7 years) 473.8 pounds 



There were 5,961 cows in these tests, and the 



average milk produced by them was 3.4 pounds 

 more than that produced by other cows of the 

 same ages the previous year. Considering only 

 the 473.8 pounds produced by the average cow 

 over 5 years of age, this is 19 pounds more than 

 similar cows produced seven years earlier. At 

 the earlier date there were 455 cows over five 

 years of age which were tested officially and are 

 recorded in volume 6 of the Blue Book. I have 

 analyzed these for the purpose of making a table 

 which will show what happens beyond 5 years of 

 age. 



