DAIRY AND SEED IMPROVEMENT MEETINGS. 221 



I. THE STUDY AND ANALYSIS OF MILK RECORDS. 



A large amount of work has been done along this line during 

 the past year. The most notable achievement in this direction 

 has been the completion of the studies directed towards finding 

 out the law which relates milk flow to age in dairy cattle. 



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 lac- 

 tation, under normal circumstances. Furthermore, it is well 

 known that after a cow passes a certain age her milk flow begins 

 to fall off with further increase in age. Before any accurate 

 study can be made of the inheritance of milk production, upon 

 which any scheme of breeding for improved milk production 

 must be based, it is necessary to have accurate corrections 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 bulle- 

 tin form for the dift'erent dairy breeds. The work on Holstein- 

 Friesian and Jersey cattle is now practically completed. 



An interesting point about this change of milk flow with age 

 is that the increase as the cow grows older after her first lacta- 

 tion is not regular. Instead it follows what is known in mathe- 

 matics 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 her age. This law may be stated verbally in the 

 following way : Milk flow increases with increasing age but at 

 a constantly diminishing rate (the increas,e 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 maxi- 

 mum 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 



