MILK AND ITS PRODUCTS 



175 



ten or eleven months, the fat globules average about one- 

 th rd the size of those in the milk when the cow is fresh. 

 Tl is is one reason why difficulty is often experienced in churn- 

 ing the cream from cows that have been in milk a long time. 



T, BLE 21. EFFECT OF STAGE OF LACTATION ON COMPOSITION 



OF MILK 



163. Individuality of the Animal. The writer has kept 

 complete records for one year or more for 76 Jersey cows. 

 The lowest average fat content for a year was 4.47 and the 

 highest 7.00 per cent. Among 40 Holsteins the lowest was 

 2.6 and the highest 3.81. The records of 25 Shorthorns 

 show a variation from 3.59 to 4.31 in the averages for one 

 year. These give an idea of the extent of variation within 

 a breed. The variation in the other constituents is always 

 less than the variation in fat. 



164. Interval between Milkings. If a cow is milked twice 

 daily at equal intervals, the quantity and quality of milk 



1 U. S. Dept. Agr., Bureau of Animal Industry, Bulletin 155. 



