Studies in Mjlk Secretion. 103 



Increase required on Equivalent Record ' ' is given the per cent of 

 increase the cow ought to make for the same length of time in order 

 to make good her equivalent record. For the basis of determining 

 what the per cent of gain on the equivalent record should be, 

 there is taken the amount of fat the cow should produce during 

 the time which elapsed between two successive calvings ; this 

 amount is divided by the amount of fat a cow of her age should 

 produce at the time of the first of these two calvings ; for 

 example, No. 2 was 2 3^ears and 27 days old at the time she 

 dropped her first calf, and at such age should produce 7.318 

 pounds of fat. The time intervening between the first and 

 second calf was ten months and 26 day», and she should gain in 

 this time in production of fat 1.447 pounds. This would make a 

 gain over 7.318 pounds of 19.8 per cent, which is her required 

 gain on the basis of equivalent records. Her actual gain was 

 30.5 per cent, so that she did much better than her requirement. 

 On the other hand, this same cow from the ages of three to five 

 actually gained 11. 2 while her required gain was 36.9 per cent. 

 In working out equivalent records no account is taken of age 

 over five 3'ears. 



In the same manner the actual and equivalent gains are made 

 out for those cows in Table VII which were tested at the various 

 ages from two to five and the averages under each head and for 

 each age are given. From these averages it will be seen that 

 among the different ages, three, four and five-year olds, the 

 actual gains were in excess of the gains required on the basis of 

 equivalent records. 



The actual gains from year to 3'ear as determined from the 

 average records of all the cows, and the average gains required 

 on equivalent records present such a wide variation from each 

 other and from the figures determined in Table VII, that we have 

 placed all the averages in tabular form below for ready compari- 

 son. 



From From From 

 2 to 3 3 t04 4 to 5 



years. years. years. 



Per cent. Per cent. Per cent. 



Actual gain as found from average product for 



all cows of different ages (Table I ) 32.7 13.3 7.7 



Average gain required on equivalent record plan. 22.2 18.2 15.4 



Actual gain as found from average gains of cows 



that were tested more than once 34.4 21.7 12.0 



