RAPID FEATHERING IN RHODE ISLAND REDS 19 



with rapid back feathering. In line 2 there was a very similar classification of 

 sons and daughters. While mating 17 was more effective than mating 18 in 

 increasing the percentages of sons and daughters with rapid back feathering, it 

 could not be considered to be a very rapid method. 



Progress in Breeding for Rapid Back Feathering — 1934 and 1942 



This project was begun in the spring of 1934 with the primary objective of 

 developing line 1 for complete back feathering at 8 weeks of age and line 2 for 

 complete lack of back feathering at 8 weeks of age. This was the basis used in 

 selecting both sires and dams throughout the experiment. As previously pointed 

 out, a classification of female chicks at 8 weeks of age is difificult and uncertain 

 because of sex-dimorphism in rate of feathering in the general purpose breeds. 



In table 7 the gross data are presented for the three lines and may be used as a 

 measure of progress through this system of breeding. 



The sons and daughters in the control line were rather similar in percentage 

 of rapid back feathering in respective years. In the first generation about 34 

 percent of males and about 50 percent of females exhibited rapid back feather- 

 ing. In the control line there was no significant change through seven genera- 

 tions. In the last two generations, however, there was a very marked increase 

 in the percentage of rapid back feathering in both sexes. This remarkable in- 

 crease appears to have been due to a more extensive use of -\- sires to produce 

 these generations. 



Line 1, bred for complete back feathering at 8 weeks, shows rather consistent 

 though not rapid progress in the desired direction. In the last two generations 

 the desired goal appears to have been reached, with all males and females marked 

 positive at 8 weeks of age. 



In line 2, reproduced entirely by sires lacking back feathering at 8 weeks, a 

 small percentage of males and a greater percentage of females generally showed 

 some back feathering. This fact can be explained only by assuming that some 

 dams must have transmitted rapid back feathering. 



In general, the data in table 7 indicate that the selection of breeding sires on 

 the basis of rapid back feathering is an effective though rather slow method of 

 establishing rapid back feathering as a flock characteristic. 



Breeding Progress with the Sex-Linked Gene for Rapid Feathering 



Records were taken at 12 days of age for the presence of the sex-linked gene si 

 on five generations throughout the experiment. It should be borne in mind that 

 no selective breeding was practiced to establish this gene in the flock. Selective 

 breeding was based solely on back feathering at 8 weeks of age. In table 8 the 

 percentages of males and females of the two possible phenotypes in the three lines 

 are recorded in five generations. 



In the foundation stock 9 percent of the males carried gene si in homozygous 

 condition and 18 percent of the females carried gene si in hemizygous condition. 

 In the control line there was no increase in the percentage of males or females 

 exhibiting this gene in ten generations. 



In line 1 there was a regular and consistent increase in the percentage of males 

 and females showing the sex-linked rapid feathering gene in five generations. 

 In the last generation, hatched in 1942, over 69 percent of the males and about 

 95 percent of the females showed this character. The fact is very evident from 

 these data that males selected for superior back feathering at 8 weeks were males 

 that carried gene si in homozygous condition. It seems very probable that 

 complete rapid back feathering could have been fixed in a very short time if 

 males selected for sires had been required to show the sex-linked gene at 12 days 



