THIRTEENTH ANNUAL YEAR BOOK— PART X 545 



The variations to be found in testing milk are due to several causes. 

 The fat content of milk varies much more than any other solid found 

 in it. When any appreciable difference occurs in the fat content of the 

 milk of one or more cows, usually some definite reason can be supplied, 

 but once in a while a variation will occur when there seems to be no 

 valid explanation for it. The addition of a fresh cow's milk will often 

 increase or perhaps reduce the average fat content of the whole herd. 

 The different breeds of cows govern the fat content largely, there being 

 quite a decided difference between the Holsteins and Jerseys in that 

 respect. The period of lactation also affects the fat content. For the 

 first couple of months after calving, the fat content of the milk is a 

 little higher than the following two months, due to the fact that the 

 cow is apt to take a quantity of the accumulated fat from her back 

 and place it in the milk. In about two months the cow is usually in 

 a normal condition again and for the following two or three months 

 the fat content is apt to decrease. From this time on to the end of 

 the lactation period the amount of milk will usually decrease and the 

 fat content will slightly increase. The injection of a cow into the herd 

 at any time during her lactation period will usually cause a slight 

 change in the fat content of the milk of the whole herd. These are 

 some of the reasons that form the bone of contention between the 

 producer on the one hand and the city milkman and the creameryman 

 on the other. 



In cream testing we have about the same variations to contend with 

 and then several more. It is next to impossible to run a separator and 

 keep the test the same at all times. The milk may be a little warmer 

 one day than another; the rate of inflow may be a little greater one 

 day than another, perhaps the machine may be turned a little faster 

 or a little slower than usual or perhaps more or less water used to flush 

 out the bowl; all have their effects upon the per cent of butter fat. 



Generally speaking, the cream screw should be turned in a little in the 

 spring as the cows are usually fresh at this season of the year and are 

 eating large quantities of succulent feeds high in per cent of water, 

 which has a tendency to reduce the fat content and if the cream screw 

 is left the same as for winter use, the percentage of butter fat will fall 

 off. We cannot feed fat into milk, but as a general rule the healthy 

 condition of the fresh cow and the stimulus she receives from being 

 put on green grass in the spring, causes her to give a larger quantity 

 of milk, somev/hat less in percentage of fat than she does in the fall 

 toward the end of the lactation period. 



It is far better to send a fairly heavy cream to the creamery, that 

 is, a cream with a fat content of from 30 to 40 per cent. If a much 

 heavier cream is separated there is a loss incurred in handling when 

 pouring from one vessel to another. If a very thin cream is separated 

 the farmer is sending a quantity of skim milk to the creamery that 

 could be well utilized at home and for which he is receiving no remun- 

 eration. Also if this thin cream becomes very sour before a test can 

 be made, the large per cent of the milk contained therein will curdle 



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