4 MAINE AGRICULTURAL EXPERIMENT STATION. 



age of a cow. It is a fact well known to all dairymen that as 

 a cow grows older, up to full maturity, her milk yield increases 

 at each lactation, under normal circumstances. Furthermore, 

 it is well known that after a cow passes a certain age her milk 

 flow begins to fall ofif with further increase in age. Before 

 any critical study can be made of the inheritance of milk pro- 

 duction, upon which any scheme of breeding for improved milk 

 production must be based, it is necessary to have accurate cor- 

 rections for the effect of age upon milk flow so that cows of 

 different ages may be compared with each other. The work 

 on this problem, which has been very laborious, is now being 

 brought to a close and tables are being prepared by which it 

 will be possible, knowing a heifer's milk record, to read off her 

 probable production as a mature cow. These tables in due time 

 will be published in bulletin form for the different dairy breeds. 

 The work on Holstein-Friesian and Jersey cattle is now prac- 

 tically completed. 



An interesting point about this change of milk flow with 

 age is that the increase as the cow grows older after her first 

 lactation is not regular. Instead it follows what is known 

 in mathematics as a logarithmic curve. In other words, the 

 amount of milk produced by a cow. in a given unit of time is a 

 logarithmic function of the age of the cow. This law may be 

 stated verbally in the following way : Milk flow increases with 

 increasing age but at a constantly diminishing rate (the increase 

 at any given time being inversely proportional to the total 

 amount of flow already attained) until a maximum flow is 

 reached. After the age of maximum flow is passed the flow 

 diminishes with advancing age at an increasing rate. The rate 

 of decrease after the maximum is, on the whole, much slower 

 than the rate of increase preceding the maximum. In general 

 this law applies to the absolute amount of fat produced in a 

 unit of time as well as to the milk. 



In connection with the establishment of this law of relation 

 of milk flow to age it has been necessary to work out in the 

 laboratory a new method of dealing with such figures and a 

 paper is now in press having the title "The. Fitting of Loga- 

 rithmic Curves by the Method of Moments." 



This work furnishes a good example of the fact that a scien- 

 tific study of agricultural problems may wander into fields quite 



