Dec. 15, 1924 
Feed Oost of Milk Production 
595 
Haecker’s (4) standard and Morri¬ 
son’s (5) standard (mean of his range 
values) are included in the graph. It 
will be observed that Haecker’s stand¬ 
ard does not correspond as closely to 
his own observations as does Morrison’s 
standard. Morrison’s standard pre¬ 
sumably represents his summary of all 
the available evidence on the relation. 
The relation between the composi¬ 
tion of the milk and the nutrients re¬ 
quired for lactation, under comparable 
conditions of feeding, may be stated 
thus: The nutrients required for lac¬ 
tation are directly 'proportional to the 
energy value of the milk solids. This re¬ 
lation should be known as Haecker’s 
law. 
maintenance estimate strictly upon the 
weight of the cow. This is common 
scientific practice of the present time 
and we may assume that it is justified 
in the case of the milk cow. 
One of the first questions to answer 
is, is there any correlation between size 
(maintenance requirements) of the cow 
and percentage fat content of the milk? 
Eckles (2, p. 408) is authority for the 
statement that “ there is no relation 
within the breed between the size of the 
animal and the richness of the milk.” 
Statistical evidence on this point is 
summarized in Table III. This table 
gives the mathematical constants of the 
correlations between certain size 
measurements (largely weight) of the 
PERCENTAGE pAT CONTENT Of M/LH 
Fig. 1.—Lactation requirements per pound of milk as affected by percentage fat content of milk. 
In the equation, A t l= 0.049 (2.66+f) > to the solid line curve, Nl =pounds of nutrients per pound of 
milk, and £=per cent of fat in the milk. 
Coming back to the present view¬ 
point, it may be concluded, at least so 
far as commercial milk production is 
concerned, that the lactation require¬ 
ments, N l , may be expressed as a 
function of the fat percentage of the 
milk, t, by the equation: 
Nl=K l (2.66 + f) 
in which Kl is a constant so far as 
affected by fat percentage. 
THE MAINTENANCE REQUIRE¬ 
MENTS 
We have next to consider the main¬ 
tenance requirements per unit of milk 
in relation to the percentage fat con¬ 
tent of the milk. Haecker based his 
cow and the percentage fat content of 
the milk as derived from published 
records indicated in connection with 
the table. 
From Table III it is plain that 
weight and fat percentage are entirely 
independent within any one of the 
breeds represented. Therefore (with¬ 
in the same breed) the maintenance 
requirements are independent of fat 
percentage, and, so far as affected by 
fat percentage , the maintenance require¬ 
ments are a constant, K m . The 
maintenance requirements per pound 
of milk are, therefore, 
K m _ 
milk yield in pounds 
