RAPID FEATHERING IN RHODE ISLAND REDS 21 



and complete back feathering at 8 weeks and had been mated exclusively to fe- 

 males having the sex-linked gene at 12 days. 



In line 2 a small percentage of females showing the sex-linked gene si appeared 

 in 1939 and again in 1941. These may have come from sires heterozygous for 

 gene si. The fact is also important that every single male in this line failed to 

 develop a tail at 12 days of age. 



Since females can carry the recessive sex-linked gene si for rapid feathering 

 only on their single sex chromosome, it is easy to discover such females at 12 

 days of age by tail development. Records were taken on a number of females 

 hatched in 1938 and 1939. These females were divided into two groups, si for 

 rapid feathering and SI for slow feathering. Only those individuals that completed 

 a full laying year were included. Table 9 gives the summarized data. 



Table 9. — Relation Between the Sex Linked Gene for Rapid Chick 



Feathering and Characters Affecting Fecundity, Egg 



Production, and Mortality Rate in Females. 



Number of birds 



Age at first egg Days 



Weight at first egg Pounds 



Winter pause Days 



Winter clutch Eggs 



Winter production Eggs 



Egg weight to Jan. 1 Ounces per dozen 



Persistency Days . 



Annual production Eggs. 



Laying house mortality Percent 



si Group SI Group 



The two groups of females were almost identical in such fecundity characters 

 as age at first egg, weight at first egg, winter pause duration, winter clutch, and 

 annual persistency, as well as in winter and annual egg production. The mean 

 egg weights up to January first were not significantly different. Mortality rates 

 for 365 days in the laying houses were essentially the same. In general, these 

 data appear to indicate that the sex-linked gene for rapid chick feathering is 

 independent of genes associated with high fecundity in Rhode Island Reds. 



Relation of Chick Feathering to Body Weight and Mortality Rate in Males 



All males on which the feathering record was taken at 12 days were divided 

 into rapid and slow groups. All other males had their feathering record taken 

 at 8 weeks of age and are grouped as + or — for back feathering. The body 

 weight was taken on each individual at 5 months of age and the mortality rates 

 up to 5 months were recorded for each of the four groups. 



The data on the sex-linked gene SI were secured in 1938, 1939, and 1941 and 

 only a very small number of the slsl cockerels was retained up to 5 months of 

 age. The data on back feathering were collected each year beginning in 1934. 

 In table 10 the records on back feathering for 1938, 1939, and 1941 were omitted 

 because all of these cockerels were included in the slSl classes for those years. 



Unfortunately the number of males in the slsl class that were retained to 5 

 months of age was too small to permit an accurate evaluation of this class as 

 compared with the SI class. The data show, however, that the slsl cockerels 

 were of about the same body weight at 5 months of age as the SI cockerels 



