102 Maine Agricultural Experiment Station. 1919. 



Method of Distinguishing Superior and Inferior Sires. 



The bull of superior merit seems unquestionably the ani- 

 mal whose progeny are more productive in milk, butter- fat per- 

 centage and butter-fat than the dams from which they came. 

 This has therefore been the criterion used to distinguish the 

 superior and inferior sires of the Jersey breed. In the first lot 

 are included all bulls which have their daughters more produc- 

 tive in both milk and butter-fat percentage than their dams. 

 In the second group are placed those bulls whose daughters 

 were inferior in both of these particulars to their dams. Since 

 in all probability the first set were a great boon to the breed 

 and the second set a distinct drawback to the breed's progress 

 it seems of objective value to study these two groups especially 

 carefully in the hope of throwing some light on the reasons 

 for this difference. For this purpose pedigrees of all the ani- 

 mals in these two groups were made and subjected to analysis. 



Pedigree Methods. 



The factors determined for these pedigrees are, the amount 

 of inbreeding that has taken place, the degree or amount of re- 

 lationship which exists between the parents of the sire under 

 consideration and the absolute and percentage of American and 

 island ancestry contained in the pedigree of these bulls. 



The methods used have been amply discussed in a series of 

 papers from this laboratory (6, 8, 9) and need only be briefly 

 discussed here. 



Inbreeding in these studies is defined as the condition or 

 state in which an organism has in fact fewer different ancestors 

 than the maximum number possible. 



The degree or amount of inbreeding (total) is measured 

 by a series of inbreeding coefficients, one for each ancestral 

 generation, defined by the following equation: 



100 (P n+1 — q n+ i) 

 Z n = 



Pn+1 



where P n+1 denotes the maximum possible number of different 

 individuals involved in the matings of the n-f-i generation, 



