270 ILLINOIS DAIRYMEN'S ASSOCIATION. 



taking a composite sample of each cow's milk for seven consecu- 

 tive days at intervals of nine weeks. The butter fat in this sample 

 was determined by the Babcock test, and the result obtained was 

 used as the average percentage of butter fat in the milk produced 

 during the four weeks preceding and the four weeks following as 

 well as during the test week. That is, the week when samples 

 were taken was made the middle of a nine- week period. Before 

 this work was begun the complete milk and butter fat records of 

 the cows in the University dairy herd was studied to see how 

 closely the annual production of butter fat could be determined 

 by weighing the milk continuously and testing a composite sample 

 taken every ninth week. It was found by using the amounts of 

 milk yielded by the cows during the successive weeks and the test 

 of every ninth week as above indicated, that the yearly production 

 of butter fat could be calculated, on the average, within five per 

 cent of the actual amount. The records about to be discussed 

 were obtained in the way just indicated. Little difficulty was ex- 

 perienced in persuading the men to weigh their milk continuously, 

 which when once started has been quite generally continued even 

 after the immediate influence of the Station has been withdrawn. 

 The samples in all cases were carefully tested by a representative 

 of the University. 



Explanation of Data. 



In order to present the data on these herds in the most com- 

 prehensive manner, the records of the cows in a given herd, to- 

 gether with the value of their products at a uniform price, are 

 combined in one table. This allows the reader to compare the 

 individuals not only as to production, but upon the money basis 

 as well. At the head of each table is given the record and value 

 of the milk and butter fat of the best cow, poorest cow, and the 

 average of the herd. With the breed and age given, it allows one 

 to take in at a glance the range of production, making such allow- 

 ances as necessary for the maturity of the animal and its breed- 

 ing. Unless otherwise stated, the records are for one years dura- 

 tion. In tables 1 and 4, the exact length of the lactation period 

 is not known, so that the average milk and fat per day are not 



