INBREEDING IN RELATION TO EGG PRODUCTION 259 



respect in the second and third year over the first. These changes run almost 

 parallel with hatchabiUty records as will be noted under "Character of Female 

 Breeders." When the check birds were inbred during the last three years of the 

 experiment, practically all of the matings were successful. The former inbreds 

 which were intercrossed during this period fell below the checks, yet they showed 

 improvement over the initial three-year period when they were inbred. 



The last two columns of the table indicate the number of famihes kept to be 

 tested for egg production and from which to select future breeders, as well as the 

 percentage of matings eliminated. Matings were eliminated by lack of progeny, 

 very small numbers of progeny or for pronounced inferiority in desirable fedundity 

 traits. This fact should be observed, however: that during the first three 

 years of the experiment, all check famiUes with offspring were retained and 12 

 out of 15 inbred families were kept. During the last three years of the experi- 

 ment more culhng was possible because more families were available. In 1926 

 two of the three check families with progenj^ were kept and 7 out of the 1 1 inbred 

 famiUes were kept. In 1927, 5 out of 9 check families were retained and only 

 9 out of 25 inbred famiUes were kept. For 1928, 3 out of 7 check famihes were 

 kept and 8 out of 14 inbred families were retained. These data, therefore, 

 indicate that family culhng for undesirable qualities was only possible during the 

 last two years reported. 



Ehmination of famihes for all causes is shown in the last column of the table. 

 The check group suffered less from ehmination during the first three years when 

 they were cross-bred and when no selection was practiced. The inbred group 

 during the same period without selection lost 75 per cent of its possible families 

 the first year, none the second year and 56 per cent the third year. In the last 

 three-year period family losses in the checks were 33, 44, and 63 per cent, respec- 

 tively, as compared with 46, 68 and 67 per cent for the inbreds. In general, these 

 data indicate that losses of families were not greatly increased by inbreeding 

 either in the original inbred groups or later in the check groups. 



In the selection of breeders each year only the best available were utilized 

 from the standpoint of fecundity traits. Theoretically such a procedure should 

 make for progress, provided the standard for breeders was raised each year. The 

 character of available material, however, often made raising the standard for 

 breeders from year to year impossible as will be shown under "Character of Female 

 Breeders." 



Purpose of This Report 



In the field of pedigree breeding there is a demand for specific information 

 regarding the behavior of fecundity traits under inbreeding. These individual 

 traits concerned in egg production have already been discussed in numerous 

 publications from this Station. The outstanding purpose of this report is there- 

 fore to furnish specific information on the question of how inbreeding actually 

 affects egg production by its influence upon known fecundity traits such as age 

 at first egg, intensity, winter pause, etc. Since these fecundity traits are known 

 to be inherited, it is necessary to consider each breecUng female as a unit and 

 each of her daughters as a unit to discover any possible effects of inbreeding on 

 egg production. A general summary of results would be of little value in con- 

 structive breeding where attention must be focused upon individual traits or 

 characteristics. This report therefore presents the necessary data on the char- 

 acteristics being studied and will furnish a guide in pedigree breeding. 



Method of Presenting Data 



The data obtained in this experiment are presented in detail each year as the 

 experiment processed. The year's results are given under the following sections : 



