RAPID FEATHERING IN RHODE ISLAND REDS 23 



Types of matings made in line 1 for 1942 may be briefly considered. Two 

 sires, both graded slsl 4, were used for breeding. These males were mated to 

 five dams graded si 3. The type of mating must have been slslXX sire and 

 slXX dam. From these matings 32 sons and 41 daughters were recorded. All 

 sons were graded slsl 4 as would be expected. All daughters were graded si 3, 

 except two which were graded si 2. It is very evident that these sires and dams 

 bred true for rapid back feathering as well as for the sex-linked gene si. 



Types of matings in line 2 may also be examined. A single sire was mated to 

 a number of different dams. Mating the SlSlXx sire to SI 1 females gave 9 51 

 sons and no other types. There were 4 SI 1 daughters and 4 SI 2 daughters 

 from this mating. The dams were probably SlXx in genetic makeup. The 

 slow feathering sire of line 2 was mated to one dam graded SI 2. All sons pro- 

 duced were SI in grade. Out of 4 daughters, 3 were medium in back feather- 

 ing and 1 graded 0. All lacked the sex- linked gene si. 



The mode of inheritance of rapid back feathering appears to be somewhat 

 involved. The sex-linked recessive gene si appears to play an important role 

 in relation to the degree of back feathering. Specific matings made in 1942 to 

 test the relation between the sex-linked gene for rapid feathering and possible 

 autosomal genes for rapid back feathering point definitely to the sex-linked gene 

 si as essential to secure complete back feathering at 8 weeks of age. This reces- 

 sive gene si need not be in homozygous condition to produce complete back 

 leathering in an individual male, but from the standpoint of his breeding ability 

 it is highly desirable that he be homozygous for gene si. 



Evidence seems to point to a single dominant autosomal gene X which has a 

 cumulative effect and must be supplemented by recessive gene si to give complete 

 rapid back feathering. Sexual dimorphism in the rate of back feathering in 

 Rhode Island Reds renders the grading of females for back feathering an un- 

 certain procedure. On the basis of these studies, it seems evident that in breed- 

 ing for rapid back feathering two procedures will quickly accomplish the desired 

 end. (1) Both breeding males and females should be selected at 10 to 12 days 

 of age for the presence of the recessive sex-linked gene si. (2) The same birds that 

 showed tail development on the first examination should be graded for back 

 feathering at 8 weeks of age, and only those with complete back feathering should 

 be placed in the breeding pens. 



Males of different grades with respect to back feathering at 8 weeks appear 

 to have the genetic composition indicated below: 



Representative photographs of the 1942 generation are shown in Plates I, 

 II, and III. 



Summary 



This report covers the period from 1931 to 1942 during which a study was 

 made on the mode of inheritance of rapid feathering in Rhode Island Red chicks. 

 Some of the more important deductions are: 



1. Rhode Island Reds are normally sexually dimorphic with respect to rate 

 of feathering in chicks. Under continued selection for rapid feathering, this sex- 

 dimorphism almost completely disappears. 



