CONDITIONS AFFECTING THE CHURNABILITY OF CREAM 243 



containing a larger proportion of the softer fats than do those of 

 any of the other breeds. 



3. The period of lactation also affects the mel ting-point _of 

 butter-fat. When a cow is fresh she yields a larger proportion 

 of the soft fats than she does 



later on in the lactation period. 

 Just how much this change in 

 the hardness of the fat is due / 

 to advance in the lactation *' > 

 period and how much to 



change from succulent to dry ^^ t , , 



feeds is not definitely known, V^^cssa ml 



since the two parallel each 

 other so closely, it being the 

 common practice in this coun- 

 try to have the cows freshen 



FIG. 89. Sectional view of Disbrow. 



in the spring. According to 



investigations conducted at the Purdue Station, 1 the melting 

 point of the fat lowers as a cow advances in her lactation period, 

 provided she is fed the same feeds throughout the year. If 

 these findings be correct, they mean that the influence of the 

 feed is much greater than that of the stage of lactation, since the 

 broad truth still remains, that under our conditions the propor- 

 tion of hard fats increases as the lactation period advances. 

 Witn this increase in the proportion of the hard fats in the 

 advancement of the lactation period, the fat-globules become 

 smaller. This, together with the increased hardness of the fat, 

 causes difficult churning at times. It readily can be seen that 

 the larger the fat-globules are the greater are the chances for 

 these globules to strike each other during agitation in the churn- 

 ing process. 



4. The nature of the food fed affects the melting-point of 

 butter to a considerable extent. Cotton-seed and its by-products 

 have been demonstrated thoroughly by several investigators to 

 cause butter to become hard. When a large amount of cotton- 

 seed is fed, the butter assumes a crumbly, tallowy, hard condi- 



1 Purdue Bulletin 159. 



