884 



Missouri Agricultural Report. 



MilK \^ater Fax Casein flilKSu^irfilbmm flsh 



Showing composition of milk. 



It is seldom that the extreme limits as given above are met 

 with. See figure 27 for comparative composition of average milk. 



FORE-MILK vs. STRIPPINGS. 



The fore-milk, or that obtained with the first stream or two 

 taken from the cow, is usually very poor in butter fat. The last 

 few streams are rich in fat. The writer has tested this point with 

 different cows, and has found that in some cases the strippings 

 tested as high as seventeen times richer than the first, although 

 usually the difference is only about three to four times. Thus the 

 necessity for thorough milking of the cow before taking a sample 

 to test. 



THE SPECIFIC GRAVITY OF MILK. 



If a can holds 100 pounds of water, to fill it with milk would 

 require about 103.2 pounds. This is because milk has a greater 

 specific gravity than water. By a specific gravity of a material, is 

 meant the weight of a given volume compared with the weight of 

 an equal volume of water under the same conditions. Milk has a 

 higher specific gravity than water, because it contains in solution 

 a number of substances, as sugar, ash, casein and albumen, which 

 increase the weight of an equal volume of milk, causing it to have 

 a higher specific gravity. The fat of milk, on the other hand, 

 which is lighter than water, has a tendency to lower the specific 

 gravity. Since the variations in the fat content of milk range 

 between three and six per cent., it follows that the variations in 

 the gravity of milk are due largely to the variations in the fat 

 cpntent. Since the milk fats vary between known limits, the 

 specific gravity of normal milk varies between definite limits. The 

 lowest specific gravity of normal milk is 1.029, while the highest 



