INBREEDING IN RELATION TO EGG PRODUCTION 297 



the foundation was less restricted, as in the check groups used, progress could 

 be made by inbreeding with selection for high intensity. 



1^23 



- ISBRED DAUGHTERS 



- CHECK DAUGHTERS 



1924 



1S25 1926 



HATIKG TEAH8 

 CHART 5. — Effect of Inbreeding on Broodiness 



1527 



1928 



From chart 5 it will be noted that the one inbred mother in 1923 which had 

 daughters with complete records was broody, while the mothers mated in 1924 

 show but 17 per cent broodiness, and the mothers in 1925 were 100 per cent free 

 from broodiness. On the other hand, the initial group of check mothers was 

 made up entirely of non-broody birds. The check mothers of 1924 showed 

 75 per cent non-broody, and the check mothers of 1926 were all broody during 

 their pullet year. 



The daughters' broody records for these three years are rather enlightening. 

 The three inbred daughters of 1923 exhibited no broodiness during their pullet 

 year. One of these daughters was non-broody for two years, one died early the 

 second summer, and the third became broody during her second year. Since 

 broodiness is a dominant trait (Ha\'s, 1924), the mother of these daughters 

 might be expected to transmit the broody trait to about one-fourth of her daugh- 

 ters, even though mated to a male lacking the broody genes. This is an illustra- 

 tion of the fact pointed out by Hays and Sanborn (1926) that many genetically 

 broodj- birds do not exhibit the trait during the first laying year. The per- 

 centage of non-broody inbred daughters was 60 in 1924, and all were non-broody 

 in 1925. There were but two daughters concerned in 1925, however. The check 

 daughters of 1923 showed 45 per cent non-broody; those of 1924, 100 per cent 

 non-broody; and those of 1925, 67 per cent non-broody. There are indications 

 that broodiness was fast disappearing in the check birds as well as in the inbreds. 



Concerning the last three years of the experiment when the plan of matings 

 was changed, the data on the daughters are complete for onlj- two years. The 

 inbred mothers used were practically free from broodiness, while the check 

 mothers were inferior to those user* from 1923 to 1925. On the whole the degree 

 of non-broodiness in the inbred daughters has changed but little in the five-year 

 period, while broodiness has decreased for the checks. 



