Dec. 17, 1917 
Influence of Age of Cow on Milk and Milk Fat 
657 
SUMMARY 
The percentage of fat in the milk of Jersey cows attains its maximum 
with respect to the average for the entire lactation period during any 
one of the first three periods, but the chances appear to be greater that 
this will be attained in the second or third period rather than the first. 
Holstein cows almost invariably show the highest average percentage 
of fat for the lactation period during the first period. 
Ayrshire cows more frequently show a higher average lactation test 
during the first than during subsequent periods, but less frequently than 
in the case of Holstein cows. 
The variations in the average percentage of fat among the first few 
lactation periods are not sufficiently great to be of much practical im¬ 
portance, but the gradual decline in average test accumulates to a figure 
of considerable importance as the number of periods of lactation becomes 
greater. 
A low plane of nutrition during growth and prior to the first lactation 
period probably contributes materially to a decrease in the average 
percentage of fat for the first lactation period from that which it would 
be if the period of growth is supported by a more liberal plane of nutri¬ 
tion. 
Neither the percentage composition of the milk nor the physical 
and chemical constants of the milk fat of aged cows show any abnor¬ 
malities attributable to old age. 
Butter made from the milk of a cow 19 years old and in her thirteenth 
lactation period was pronounced to be of excellent quality, and kept 
for a period of three months at a temperature of 8° to io° C., without 
showing any marked deterioration. 
LITERATURE CITED 
(1) Eckles, C. H. 
1915. the: ration and age of calving as factors influencing the growth 
AND DAIRY QUALITIES OF COWS. Mo. AgT. Exp. Sta. Bui. 135, 91 p., 
26 fig. 
(2) Haas. 
1898. EINFLUSS DES ALTERS DER KtJHE AUF DIE MENGE UND GttTE DER MILCH. 
In Milch Ztg., Jahrg. 27, No. 53, p. 841. 
(3) Hills, J. L. 
1907. THE EFFECT OF AGE ON THE YIELD AND QUALITY OF MILK. In Vt. Agr. Exp. 
Sta., 19th Ann. Rpt., 1905/06, p. 339-350. 
(4) HogstrOm, K. A. 
1906. komjOlkens fetthalt, dess normala vaxlingar och arftlighet. 
In K. Landtbr. Akad. Handl. och Tidskr., Arg. 45, No. 3/4, p. 137-176, 
18 diagr. 
(5) Hooper, J. J. 
1915. fat content of milk from heifers and cows. In Breeder's Gaz., v. 
68, no. 19, p. 808. 
