118 POULTRY PRODUCTION 



pullets, purchased from nearby farms. The average first- 

 year production of these pullets was 75.2 eggs. The average 

 first-year production of their daughters, by the standard- 

 bred male, was 157.5 eggs, or more than double the production 

 of their mothers. The poorest results secured in a series 

 of tests of this sort with three breeds showed 'an increased 

 average production of the daughters of 2.25 dozen eggs, as 

 compared with their mothers, the mothers in this case giving 

 an average pullet production of 103.2 eggs. 



If an average value of twenty cents per dozen for eggs is 

 assumed throughout the year, the productive value of each 

 daughter for her first laying year was $1.37 greater than that 

 of her mother. Assuming that the sons did not increase in 

 value at all, and that there were as many males as females, 

 the per chick increase in value was in the first case about 

 68 cents for the first year. In the second case the increase 

 in the productive value of the daughters for the first year as 

 compared with their mothers was 45 cents, or an average 

 increased value per chick, if both sexes are considered, of 

 about 22 cents. On the basis of fifty chicks raised from eaCh 

 mating the productive value of the first male was §34.00, 

 while that of the male giving the poorest results was $11.00. 



Inbreeding and Line Breeding. — Authorities differ on the 

 distinction between these terms. In the most recent exhaus- 

 tive study of inbreeding PearP suggests that most definitions 

 of inbreeding have been based on practical expediency rather 

 than on careful analysis of the problem. He defines inbreed- 

 ing as the reduction of the number of possible different ances- 

 tors in any generation or generations. This is, of course 

 accomplished through the mating of individuals more or 

 less closely related. 



Line breeding is a special form of inbreeding in which the 

 number of possible different ancestors of a given bird is 

 reduced in such a way as to increase the number of appear- 

 ances of a certain ancestor in its pedigree. 



The difference between line breeding and inbreeding is 

 shown in figures 56 and 57. 



' American Naturalist, vol. xlvii, No. 562. 



