INHERITANCE OF RROODINESS 7 



EVIDENCE REGARDING SEX-LINKED INHERITANCE 

 OF BROODINESS 



Although no evidence has been presented from this Station to indicate 

 sex-linked inheritance for broodiness, it is desirable to test these data for 

 possible sex-linkage. 



Dams that were not broody themselves and that had produced no 

 broody daughters during their first breeding year were considered to be 

 partially tested dams. Seventeen males were mated to these tested dams. 

 Eight of the males or about 47 percent produced some broody daughters. 

 In the total of 210 dams in table 1 that were given a breeding test, 108 

 or 51.43 percent had some broody daughters. These facts indicate that 

 essentially the same percentage of sires and dams transmitted the broody 

 character to their daughters. 



Selection of Breeding Males and Females on the 

 Broody Behavior of Their Sisters 



Breeding males are often selected on the basis of the broody behavior 

 of their sisters. Breeding females, on the other hand, may be selected on 

 both their individual broody behavior and the behavior of their sisters. 

 Table 3 supplies evidence on the effectiveness of selections based on 

 sisters' behavior as far as the broody instinct is concerned, and compares 

 the transmissibility of the broody trait by males and by females selected 

 on the same basis. 



Table 3. — Breeding Behavio« of Sires and Dams. 



The 38 sires with broody sisters had families with an average of 32.06 

 percent of broodiness. The 34 sires with non-broody sisters had families 

 with an average of 10.90 percent of broodiness. 



There were 111 breeding females with broody sisters. The daughters 

 of this group showed a mean family broodiness of 28.66 percent. From 

 95 dams that had no broody sisters, the mean family broodiness in the 

 daughters was 12.36 percent. 



These figures indicate that selection on the family basis to eliminate 

 broodiness is effective, and that sires and dams selected on the same 

 basis transmit the broody instinct equally. 



