INFLUENCE OF THE AGE OF THE COW ON THE COMPO¬ 
SITION AND PROPERTIES OF MILK AND MILK FAT 
By C. H. EcklES, Dairy Husbandman, and L. S. Palmer, Chemist , Department of 
Dairy Husbandry, Missouri Agricultural Experiment Station 
INTRODUCTION 
The question of the changes in the composition of milk with successive 
lactation periods has been one which has from time to time attracted 
the attention of chemists and physiologists. That phase of the question 
relative to the percentage of fat in the milk has been of great practical 
importance to the dairyman, who is interested in knowing whether the 
percentage of fat in the milk of the heifer can be used as an index of 
what may be expected of the mature animal. Data bearing on this 
question have been compiled by several investigators, but the conclu¬ 
sions drawn from these data have not been entirely uniform. These 
data have been gathered in most cases from dairy herds located at various 
experiment stations, both abroad and in this country. 
It is the purpose of the present paper to offer data on this question 
taken from the records of the University of Missouri dairy herd. It is 
believed that the data have an added value because of the fact that this 
herd has always been composed of pure-bred animals only, comprising 
the Jersey, Holstein, Ayrshire, and Shorthorn breeds, and also because 
of the fact that all of the animals were born and raised at the Station, 
with the exception, of course, of the individuals of each breed which 
were purchased when the herd was started. 
Another phase of the question of the influence of age on the composi¬ 
tion of milk is that of the effect of old age. Whether or not very old 
cows, which are not infrequently found in long-established herds or in 
private families, continue to give normal milk has never, to our knowl¬ 
edge, been studied. A very thorough search of the literature has failed 
to disclose any investigations of this character. The authors have had 
an opportunity to study the composition of the milk of one aged cow in 
the University herd and also of two other cows in the same herd which 
were advanced in years. The data secured from these animals will also 
form a part of the present paper. 
HISTORICAL REVIEW 
The principal investigations of the influence of age upon the percentage 
of fat in the milk have been by La Cour and by Haas and Hogstrom in 
Europe and by Wing and by Hills and Hooper in this country. 
La Cour (7) 1 reported the results of five years' observations of the per¬ 
centage of cream in the milk of a large number of cows, using the Fjord 
1 Reference is made by number (italic) to Literature cited,” p. 657-658. 
Journal of Agricultural Research, 
Washington, D. C. 
le 
(64s) 
Vol. XI. No. 12 
Dec. 17,1917 
Key No. Mo.—4 
