No. 599] 



ADVANCED REGISTRY COWS 



numbers are ample. First, the means of the classes of 

 this population were plotted. Then their ability to devi- 

 ate in a plus direction, or, in other words, to produce more 

 fat as individual classes was taken into account. The 

 class that had the maximum production and deviation 

 ability was allowed, as a basis for its minimum require- 

 ment, the full average deviation of the population in a 

 minus direction from the mean, and finally the other 

 classes that could not produce as much and had not the 

 ability to deviate as much as this maximum class, were 

 allowed the full minus deviation of the population plus 

 the difference in deviation ability between their particular 



class and the maximum class which forms the apex of the 

 curve. 



If these fundamental allowances are fair, impartial and 

 accurate, the curve is accurate, and the only question that 

 remains is whether or not it should alter the requirements 

 of the Holstein-Friesian Association. If curve 4 touches 

 the Holstein-Friesian Association curve at any point and 

 does not coincide with it throughout, then the latter should 

 be changed. It does touch it at both beginning and end, 

 showing that all classes after the 24 years and up to llf 

 years have an advantage over the others. This advan- 

 tage is greatest for the classes between 5£ and 11 years 

 of age. 



The next consideration in connection with curve 4 is its 

 application, and, when dealing with this, two things 

 should be kept in mind; first, the practical, and secondly, 

 the more concise and mathematical application. The 

 practical application finds its expression in the endeavor 

 of the Holstein-Friesian Association to make a uniform 

 advance per day in the fat requirement for the seven-day 

 test up to the age at which it was considered the maximum 

 production was reached. Table VI compares the increase 

 in the amount of fat required each year over that required 

 in the previous year from two up to six years, with the 

 increase in amount of fat that the year classes are able 

 to produce as calculated from curve 4. 



