INHERITANCE OF BROODINESS 5 



Dams that are not broody until the second laying year (group 7) may 

 be considered to be less intensely broody than those going broody in the 

 first laying year. Group 7 dams may be compared with group 1 dams 

 for indications of possible genetic diflferences. The only evidence to 

 indicate a possible genetic difiference in the two groups of dams lies in 

 the fact that 11.00 percent of the daughters from group 1 dams were 

 broody three or more times, compared with 5.47 percent of the daughters 

 from group 7 dams. 



There were four dams (group 8) that did not exhibit the broody in- 

 stinct until their third laying year. These dams had the same percentage 

 of non-broody daughters as the group 1 dams; and among the broody 

 daughters, the proportions broody once, twice, or three or more times 

 were essentially the same. From the standpoint of the number of broody 

 periods in their daughters, the two groups of dams do not appear to differ. 



In general, the data in table 1 indicate that degree of broodiness as 

 measured by the number of broody periods depends upon heritable fac- 

 tors. Rather conclusive evidence on this point is the fact that, as the 

 number of broody periods in dams increased, the percentage of daughters 

 showing three or more broody periods increased for dams of groups 1, 

 2, and 3. Dams that were broody once in their pullet laying year (group 

 1), dams that were broody first in their second laying year (group 7), and 

 dams that were broody first in their third laying year (group 8) showed 

 about the same breeding behavior with respect to the number of broody 

 periods in their daughters; indicating that the time of onset of the broody 

 instinct during the life of the individual may not aflfect the intensity as 

 measured by number of periods. Dams that are phenotypically non- 

 broody may be selected with a good degree of accuracy at the end of 

 two laying years, as indicated by groups 4, 5, and 6. These data serve 

 to emphasize the importance of first reducing the degree of broodiness 

 and following this by selective breeding to eliminate the instinct from 

 the flock through the use of aged tested breeding stock. 



Breeding Behavior of Broody Hens 



There were 7 dams with only a first-year production record that ex- 

 hibited the broody instinct. Each of these dams produced some broody 

 daughters in a total of 56, indicating dominant inheritance. There were 

 15 broody dams that had two complete production records and 133 daugh- 

 ters. Thirteen or 86.67 percent of these dams produced some daughters 

 with the broody instinct, and two had no daughters going broody in their 

 first laying year. A total of 19 broody dams was kept for three full lay- 

 ing years and had 203 daughters that completed one year of laying. 

 Sixteen or 84.21 percent of these dams produced some broody daughters 

 and three had no broody daughters. 



This group of 41 broody dams includes only individuals that had at 

 least three daughters that completed the first laying year. There was a 

 total of 392 daughters tested. More than 85 percent of these tested dams 

 had some broody daughters; and those with no broody daughters may 

 not have had an adequate test because of too few daughters or because 

 of deferred broodiness in daughters. 



