8 TESTING AND HANDLING OF MILK AND CREAM 
for whole milk, about 20 c. c. instead of 17.5 c. c. The speed of the 
tester should be increased 10 per cent and the tester kept as warm as 
possible. Skim milk always contains some butter fat, and should a test 
fail to reveal the presence of butter fat, it is an indication that the 
testing was poorly done and should be repeated. 
Milk test bottle 
Skim milk test bottle Dairy thermometer 
Dividers 
Variation of Fat in Milk. 
The percentage of fat in normal milk varies a great deal. However, 
the fat content seldom falls below 2 per cent or rises above 7 per cent. 
The fat content of milk from a whole herd of cows varies only within 
comparatively narrow limits. The following are the chief factors 
which cause the fat conetent of milk to vary: 
1. Individuality of cows. 
2. Breed of cows. 
3. Time between milkings. 
4. Manner of milking. 
5. Whether the milk is fore or after milk. 
6. Age of cow. 
7. Lactation period. 
8. Surrounding conditions. 
9. Condition of cow. 
