INFLUENCE OF THE PLANE OF NUTRITION UPON MILK 61 
beginning of lactation does not appear to be able to consume 
sufficient feed to supply the heavy demands upon her body. 
Our attention was first attracted to this factor by the 
results of an experiment carried out for another purpose. 
A Jersey cow was fed very liberally with grain for several 
months before calving in order to have her excessively fat. 
Immediately after parturition she was put upon a ration, 
estimated from feeding standards to be sufficient to maintain 
her body weight allowing nothing for milk production. The 
surprising part of the result was that the cow continued to 
give practically the same amount of milk, 18-24 lbs. a day 
for the thirty days she was kept on this ration. The con- 
tinued production of milk on a ration sufficient only for 
maintaining the body strongly supports the theory now 
generally accepted that milk secretion, at least in the early 
stages of lactation, is the result of the action of a hormone 
which stimulates the udder into activity. The nutrients 
necessary for the milk production unquestionably were taken 
from her body as evidenced by a decline in weight of nearly 
four pounds daily. 
The point that especially attracted our attention, however, 
was the fact that the fat percentage in the milk during this 
period of underfeeding was abnormally high and that it 
declined within twenty-four hours after the ration of the cow. 
was increased to a point where sufficient nutrients were 
supplied for both maintenance and milk production. These 
data are shown in Table I. 
It will be noted that the average fat content for the thirty 
days of underfeeding was 6.01 per cent while the average 
for the entire year, which was normal for the animal, was 4.8 
per cent. The experiment was repeated with similar results 
with a Holstein cow. The average fat percentage for the 
year with this animal was 2.99 and during a period of under- 
feeding seven days after calving the fat content was 4.47 per 
cent. 
In order to secure further data on this subject an experi- 
ment was conducted with another Holstein cow. This animal 
was fed a very heavy grain ration for over a year resulting 
