96 MASS. EXPERIMENT STATION BULLETIN 388 



rapid feathering may or may not be present in rapid-feathered stock. There is, 

 however, a definite sex difference in the rate of feathering in the dorsal region. 



The Effectiveness of Selective Breeding in Reducing Mortality in Rhode 

 Island Reds. (F. A. Hays.) This is a cooperative project with the Regional 

 Poultry Research Laboratory, East Lansing, Michigan. In the spring of 1934 a 

 project was begun to test in a small way the effectiveness of selective breeding in 

 reducing mortality in Rhode Island Reds. 



The foundation stock consisted of pedigreed birds that had been bred for 

 characters associated with high fecundity since 1916. During the first five years 

 females alone were kept to the age of 18 months. Beginning with the sixth gen- 

 eration, hatched in 1939, both males and females were retained to the age of 18 

 months. An attempt has been made to establish two lines, one for low mortality 

 and the other for high mortality. Breeding males and females 24 months of age 

 were used as breeders and the sole basis of their selection was the mortality rate of 

 their sisters during their first laying \ear. A check line consisted of birds bred 

 for high fecundity. Inbreeding in both lines was avoided by the constant use of 

 males drawn from the check group but selected on the mortality basis. Limited 

 facilities available permitted the production of about 100 birds in each of the 

 mortality lines, and since 1939 about equal numbers of males and females have 

 been carried to 18 months of age. Complete mortality records have been kept 

 and post-mortem examinations have been performed by the Department of 

 Veterinary Science. 



The limited data now available indicate in general that selective breeding was 

 effective in small groups in reducing the mortality rate from the miscellaneous 

 diseases and disorders appearing under our conditions. 



Genetic Laws Governing the Inheritance of High Fecundity in Domestic FowL 



(F. A. Hays and Ruby Sanborn.) Many phases of this problem have been studied 

 and reported upon. At the present time special attention is being given to the 

 genetics of intensity and winter pause. These two characters have a rather 

 complex inheritance and their interactions with other characters are very sig- 

 nificant. Possible interactions between genes affecting intensity and genes 

 affecting egg size are being given close study. The mortality problem as affected 

 by selective breeding is also being given constant attention. 



Recent findings indicate that chicks emerging early from the shell are likely 

 to be superior from the standpoint of fecundity; that heavy body weight in both 

 males and females at six months of age is a significant criterion of future low 

 mortality; and that selective breeding for characters affecting egg production 

 has not reduced the viability of the stock. Reducing the variability in egg pro- 

 duction is a slow process because of the complex nature of inherited factors and 

 environmental interactions. 



A Study of Fertility Cycles in Males. (F. A. Hays.) Histological studies of 

 testes from males in a wide age range, taken throughout a two-year period, in- 

 dicate that both age and season affect the rate of spermatogenesis. There is 

 definitely a cyclical behavior in males with respect to their fertility. Preliminary 

 breeding tests have not indicated that fertility is governed by inherited factors. 

 This problem of possible inherited factors is being studied further along with 

 environmental factors that may be in operation. 



Physiological Relationships Between Molting Behavior and Fecundity Char- 

 acters. (F. A. Hays.) Bi-weekly individual molt records are being continued 

 on a fourth series of males and females from parents with known molt records. 

 The first breeding stage of this project began in the spring of 1941. Two lines 



