FARM CONDITIONS 153 



should be made at intervals for a whole period of lac- 

 tation. 



Frequency of testing. It is not practicable to test 

 the milk of every milking for fat and it is not neces- 

 sary. On the other hand, the testing of a single milk- 

 ing or of a day's milk or even of a week's milk is in- 

 sufficient, since, for many reasons, the percentage of 

 fat may vary greatly from one time to another. The 

 following plan combines a high degree of accuracy 

 with the least amount of labor: Make the first fat- 

 test in about two weeks after the cow calves and then 

 repeat it regularly once in two weeks during the period 

 of lactation. Even a monthly testing will, however, 

 give fairly accurate results. 



Method of sampling. When a single cow's milk 

 is to be tested, the following precautions should be 

 observed in taking the sample: 



( i ) The cow must be milked dry at the milking pre- 

 vious to the one to be tested. (2) On the day of milk- 

 ing for the test, the cow is milked as completely as 

 possible each time. (3) After the morning's milk- 

 ing, the milk is well mixed by pouring from one pail 

 to another or by stirring with a dipper, and about a 

 gill is at once dipped out and poured into a pint fruit- 

 jar, which has been thoroughly cleaned and scalded. 

 The sample is kept in a cool place. Repeat the samp- 

 ling with the evening's milk or with each milking, if 

 the cow is milked more than twice a day, adding a sam- 

 ple of each to the jar containing the morning's milk. 

 (4) Make a test before the milk can sour, mixing well 

 before taking samples for the test by pouring back 

 and forth a few times from one vessel to another. If 



