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 Ibs. 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 Avas 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 



