RAPID FEATHERING IN RHODE ISLAND REDS 7 



Relation Between Feathering at Twelve Days and Degrees of Back 

 Feathering at Eight Weeks 



In the last two generations, hatched in 1941 and 1942, the chicks were all 

 classified for the sex-linked gene at 12 days of age. At 8 weeks of age all chicks 

 were again classified for back feathering into grades to 4. Since there were so 

 few chicks in grade 4, which implies complete feather growth on the back without 

 any pin feathers, this grade is scarcely worth considering in these studies. Males 

 particularly are known to vary widely in the degree of feathering over the back. 

 The data in table 5 show how the presence or absence of the sex-linked gene si 

 for rapid feathering affects the degree of back feathering in Rhode Island Reds 

 in the three lines. 



There appears to be an important relationship between the recessive sex- 

 linked gene si for rapid feathering and the degree of feathering over the back at 

 8 weeks. In the control line males, slightly over 10 percent that carried gene si 

 in homozygous condition had no back feathering at 8 weeks of age. This fact 

 indicates that such males must have lacked the necessary autosomal genes to 

 produce rapid back feathering. In line 1, slsl males all had some back feather- 

 ing at 8 weeks. In line 2, the sex-linked gene was not present in the males. 



Since sex-linked gene si shows its effect in females in the hemizygous or single 

 dose stage, a greater percentage of the females than males in all three lines was 

 observed to have tail growth at 12 days of age. Only one si female produced in 

 two generations, failed to develop some back feathering at 8 weeks. All other 

 females that had tails at 12 days fell into grades 2, 3, or 4 when 8 weeks old. 

 One very significant fact should be noted in this connection; in the control line 

 58 percent of si females were graded 3 or 4 at 8 weeks, while in line 1 , 96 percent 

 were given these two grades. In other words, the si females in line 1 after seven 

 years of selection for early back feathering must have approached a homozygous 

 condition for autosomal genes concerned. 



Males lacking tails at 12 days may be of two genotypes, Slsl or SlSl, as far as 

 the sex-linked gene is concerned. Table 5 shows that about 22 percent of such 

 males lacked back feathering completely at 8 weeks in the control line and that 

 most of the others fell in grades 1 and 2. In line 1 there were no SI males com- 

 pletely lacking in back feathering and about 97 percent fell in grades 2 and 3. 

 The SI males of line 2 were mostly in the grade for back feathering, with about 

 7 percent in grade 1. In line 1, selection on the basis of back feathering had been 

 effective in the absence of the sex-linked gene. It is very probable also that the 

 SI males in line 1 were all heterozygous for gene si. In the control line fewer 

 males were heterozygous for gene si and probably none were heterozygous for 

 this gene in line 2. 



Females that failed to develop tails at 12 days must have completely lacked the 

 recessive sex-linked gene si. In this group, any differences in rate of back feather- 

 ing between the three lines must have been due to the effects of selection on auto- 

 somal genes. The SI females in the control line fell mostly into grades 2 and 3 

 for back feathering at 8 weeks; the SI females of line 1 fell only in grades 2 and 3; 

 and the SI females of line 2 were mostly in grades 1 and 2. Females of line 1 

 were definitely superior to the controls and those of line 2 were decidedly inferior 

 to the controls. 



Breeding Results Concerned with the Sex-Linked Gene and Other 

 Possible Genes Affecting Back Feathering 



Table 6 shows the character of the progeny produced in ten generations from 

 eighteen different types of matings. Progeny where grouped into either -(- or — 

 classes with respect to back feathering at 8 weeks of age. 



