Testing Milk on the Farm. 145 



definable causes like those given above, the quality of 

 some cows' milk will often change considerably without 

 any apparent cause. The dairyman who is in the habit 

 of making tests of the milk of his individual cows at 

 regular intervals will have abundant material for study 

 in the results obtained, and he will soon be able to tell 

 from the tests made, if these are continued for several 

 days, whether or not the cows are in a normal healthy 

 condition or have been subjected to excitement or abuse 

 in any way. 



165. Number of tests required during a period of 

 lactation in testing cows. The daily records of the 

 six cows referred to on page 142 furnish data for com- 

 paring their total production of milk and butter fat dur- 

 ing one period of lactation, as found from the daily 

 weights and tests of their milk, with the total amount 

 calculated from weights and tests made at intervals of 

 7, 10, 15 or 30 days. The averages of all results ob- 

 tained with each of the six cows show that weighing and 

 testing the milk of a cow every seventh day gave 98 per 

 cent, of the total milk and butter fat, which according 

 to her daily record was the total product. Tests made 

 once in two weeks gave 97.6 per cent, of the total milk, 

 and 98.5 per cent, of the total butter fat, and tests made 

 once a month, or only ten times during the period of 

 lactation, gave 96.4 per cent, of the total milk, and 97 

 per cent, of the total production of butter fat. 



166. The record of one of the cows will show how 

 these calculations are made: It was found from the 

 daily weights and tests that cow No. 1, in one lactation 



period of 307 days, gave 5,044 Ibs. of milk which con- 

 10 



