110 



MILK 



The facts cited show clearly that milk from some breeds con- 

 tains more nourishment than that from others. However, this is 

 not an unquaUfied advantage, since fat consisting chiefly of large 

 globules is not as readily digested as fat composed of small glob- 

 ules. Moreover, when milk is used for infant feeding the dis- 

 advantage of large globules of fat, coupled with the large number, 

 is a decided disadvantage. 



2. Difference in Composition of Milk Due to Individuality. — 

 Milk from individual cows may show considerable difference in 

 composition. It occurs not infrequently that in a herd a cow 

 will produce twice as much milk as another of the same breed, 

 ancestry, age, and receiving the same feed and care. Eckles and 

 Reed think that the difference in quantity produced is due to the 

 amount of food consumed in excess of the quantity necessary for 

 maintenance, and that the ratio between the food available for 

 milk production and the milk produced is practically the same 

 with each cow. A superior dairy cow, therefore, is one that is 

 capable of using food in quantity above that required for main- 

 tenance and using the excess of food for milk production. The 

 authors give figures on the quantity of milk and fat produced from 

 two cows during two lactation periods as follows: 



THE QUANTITY OF MILK AND FAT PRODUCED BY TWO JERSEY COWS 



First lactation period. . . . 

 Second lactation period 

 Number of days in milk . 



Cow 27. 



Lbs. milk. 



4552 

 7174 



Lbs. fat. 



238.8 

 377.0 



Cow 62. 



Lbs. milk. 



878 

 3189 



Lbs. fat. 



232 



44.1 

 114.8 



Reduced to the same number of days, Cow 27 during the first 

 lactation period would have produced 2894 pounds of milk and 

 152 pounds fat; in the second lactation period she would have 

 produced 4560 pounds of milk and 240 pounds fat. The produc- 

 tivity of cow 27 was, therefore, much greater than that of Cow 62. 

 It is further worthy of note that during the second lactation 

 period a larger quantity of milk was produced than during the first. 

 That this is the usual experience has been referred to before. 



Individual differences are made clear by a table given by Eckles 

 and Reed, showing the records of daughters of the same sire: 



