Fat Content. 39 



The fat which is contained in milk in the form of very fine 

 globules, causes in part the white color of the milk through the 

 reflection of light. The size of the fat globules varies in the milk of 

 the same cow and depends upon the individual, length of the period 

 of lactation, the race, feeding, and upon whether the first, middle 

 or the last part of the milking is examined. According to Woll, 

 D'Hunt, Schellenberger and Gutzeit the diameter varies between 

 0.8 and 22 n with an average of 2.2:2.5:2.9:3.6 /*. 



Variations in the percentage of fat are caused by change of 

 food, etc. These changes also have an influence on the size of the fat 

 globules, and according to Woll the fat globules become larger with 

 dry feeding, a statement which could not however be confirmed 

 by Schellenberger and Pankowsky. According to the investigations 

 of these authors the feeding of green forage, especially clover, 

 produces large-sized fat globules. 



The length of the period of lactation should be considered since 

 the variations of size at the beginning of lactation are more con- 

 siderable than in ripe milk, in which the milk globules appear more 

 uniform and mostly of medium size. 



In colostrum they vary from the sizes of dust to 20/j. and over. Donne and 

 Schulz found that colostrum contains large, broad oil drops in addition to the small 

 and minute fat globules, which show a less uniform appearance and contour, when 

 compared with the usually spherical fat globules of ripe milk. 



In interrupted milking the size of the milk globules bears a 

 certain relation to the fat content. With the increased quantity 

 of fat which obtain in the milk toward the end of a single milking, 

 the size of the fat globules also become larger (Schellenberger, 

 Woll). 



With the extension of the lactation period the size of the fat 

 globules decreases, but their number increases. 



According to Gutzeit and Schellenberger the following values were obtained in 

 milk from different breeds: 



Si?e in 1/1000 mm. No. per cc. in millions. 

 Gutzeit : Schellenberger : 



Voigtlander 2.73 1944 to 4476.9 



Jersey 3.5 2.95 2064.1 to 4643.3 



East Friesian 2.30 2521.0 to 5911.0 



Angus 2.95 2.20 2886.0 to 6200.0 



Simmenthal 2.56 2995.0 to 5210.3 



Dessau 3070.0 to 6308.6 



Swiss 2.33 4008.0 to 5326.7 



Shorthorn 2.76 



Montavoner 2.62 



Holstein 2.58 



Breitenburger 2.46 



According to Grimmer the number of milk globules fluctuated in 21 tests on 

 three herds of blackish-brown lowland cattle in Pomerania, from 1,330,000 to 3,073,000 

 per cubic millimeter, having an average diameter of 2.6-3.7/u. 



The milk globules retain their form through their surface 

 tension and are not surrounded by special capsules which could be 

 considered as membranes, as has been thought by former authors. 



