Shkehy — Average Percentage of Fat in a Cow's Milk. 547 

 The following table contains relevant information regarding these cows: — 



The cows were milked twice a day, at 5 a.m. and 2 p.m. The milk was 

 weighed, duplicate samples drawn at each milking and tested by the Gerber 

 method. The cows were milked throughout by the same milkers. In no 

 case were the duplicate samples found to differ from each other, in fat 

 content, by more than 1 per cent., which is the limit in the Gerber method. 



Table 1 gives the morning and evening yields and fat percentages for 

 each cow throughout the investigation. 



From the table the following general results may be noted : — 



(1) The milk yields are generally much higher in the morning than in the 

 evening. 



(2) The fat percentage is generally much lower in the morning than in 

 the evening ; the morning milk of each cow frequently contains less than 

 3 per cent, of butter-fat. 



(3) The percentage fat for successive evenings or successive mornings 

 fluctuates considerably ; the milk yield fluctuates to a less extent. 



The fat percentages for two cows (128 and 97) are represented graphically 

 in diagram 1. 97 is the most variable of the experimental cows, while 128 

 represents an average type, that is, neither the greatest nor the least 

 variable. It is obvious that general conclusions regarding a method of 

 estimating the butter-fat value of a cow can be arrived at only after con- 

 sidering the most variable of the experimental groups, because of the 

 possibility of any untested cow showing similar variation. 



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