STATISTICAL WEIGHTING FOR AGE OF 

 ADVANCED REGISTRY COWS 



C. W. HOLD A WAY 

 Virginia Agricultural Experiment Station, Blacksburg, Va. 



Any study of milk production that is made from a 

 statistical standpoint must necessarily be complicated, for 

 the reason that advancing age in a cow up to the time she 

 is mature enables her to produce more milk and butter 

 fat. A further difficulty lies in the fact that after ma- 

 turity the effect of age on production has not been de- 

 termined with any degree of certainty. Whether or not 

 the increase in capacity is directly in proportion to the 

 advance in age ; at what age is the maximum of produc- 

 tion reached ; what relation is there between age and per 

 cent, of fat in milk, and at what age is a cow past the 

 power of full productiveness, are all questions that need 

 investigation in a broad way. 



Necessarily, the various breed associations must have 

 made some comprehensive investigations to enable them 

 to fix standards for milk and fat production, and since the 

 only extensive authenticated records that we have are 

 records of these associations, this study was made for 

 the purpose of determining if their records were con- 

 sistent with their standards, and if these standards could 

 be used as a basis for weighting cows of different ages. 



Method of Collecting Data 

 Seven-day records only were used, these being secured 

 from the Holstein-Friesian Blue Book, Vol. 24. For the 

 purpose of future investigation all the animals in two 

 direct lines of descent were tabulated, one from a female, 

 the other from a male, both animals being noted ones in 

 the breed. The names, herd book numbers, ages at time 

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