INHERITANCE OF RROODINESS 3 



than in non-broody lines. 



Broodiness affects the physiological state of the individual bird, accord- 

 ing to unpublished data collected on Rhode Island Reds at the Massachu- 

 setts Station by Dr. H. D. Goodale. In a study including 21 hens, the 

 daily body temperatures were recorded throughout the period to discover 

 possible changes during broody cycles. As a rule there was a temper- 

 ature drop from the mean of about 106.5 degrees to about 105 degrees for 

 from three to five days following the cessation of laying associated with 

 a broody period. The mean daily body temperature of six non-broody 

 laying hens from December 8 to February 6 was slightly above 106 de- 

 grees. Daily temperature records were taken on five sitting hens from 

 September 8 to October 5. Here the range in temperature was from 

 103 to 107.5 degrees, with a mean of about 105.5 degrees. 



Scope of This Report 



The present study includes the birds hatched from 1929 to 1938, in- 

 clusive, in our non-broody and high fecundity projects. The data include 

 72 sires and 210 dams, with a breeding performance record based on 1767 

 daughters. 



These data are considered from three standpoints relative to the inher- 

 itance of the broody instinct: first, inherited degrees of ])roodiness; 

 second, deferred broodiness; and finally, ])ossil)le sex-linked iniieritance 

 of the broody instinct. 



INHERITED DEGREES OF BROODINESS 



It is a well-known fact that the number of broody periods varies widely 

 among individuals, and may range from one to eight or more in the first 

 laying year. Hays (1939) pointed out that, in a flock of Rhode Island 

 Reds bred to reduce broodiness, the mean number of broody periods in 

 each individual fell from 3.5 to 1.1 in the 18-year period from 1916 through 

 1933. In the same period, the percentage of broody individuals fell from 

 86.31 to 5.19. Since the mean length of the non-productive period asso- 

 ciated with each broody period has remained constant at almost fifteen 

 days, it is obvious that any quantitative measure of degree of broodiness 

 must be based on the number of broody periods. 



The behavior of daughters from dams showing different degrees of 

 broodiness is recorded in table 1. All daughter records include only the 

 first laying year. 



Group 1 dams were kept for but one laying year and had but one broody 

 period. Of the daughters of such dams, 12 percent were non-broody, 10 

 percent were broody once, 7 percent were broody twice, and 11 percent 

 were broody three or more times. Based on their own behavior and on 

 the behavior of their daughters, the group 1 dams appear to represent a 

 low degree of broodiness. 



Group 2 dams had been broody twice in their first year of laying. Only 

 28.26 percent of their daughters were non-broody and more than 39 per- 

 cent had three or more broody periods. These dams were decidedly in- 

 ferior to the group 1 dams. 



Group 3 dams belong \o a more intensely broody group, as they had 

 shown three or more broody periods in their first year. Only 9.76 per- 



