100 MASS. EXPERIMENT STATION BULLETIN 378 



acters affecting egg production. One line is bred for early sexual matur- 

 ity while the other is bred for late sexual maturity. This phase of the 

 project is rather recent, but there is some evidence that the extremely 

 dark shade of plumage demanded in exhibition birds is in part associated 

 with the age at which sexual maturity is attained. 



Rate of Feathering in Rhode Island Reds. (F. A. Hays.) The major 

 objective of this experiment is to develop two lines of birds differing with 

 respect to feather development on the back at eight weeks of age. A third 

 line used as a check consists of stock bred for high fecundity with but 

 limited consideration given to rate of chick feathering. Because of a 

 striking sexual dimorphism in the sexes for rate of chick feathering, it is 

 essentially impossible to classify female chicks at any age for rate of 

 feathering on the basis of feather development over the back; therefore, 

 attention has been directed largely to the males. 



Line 1 has been sired exclusively through six generations by males 

 with complete back feathering at eight weeks. Line 1 has been sired 

 through the same period entirely by males having no back feathering at 

 eight weeks. The check line was sired b}- varying proportions of rapid and 

 slow-feathered males. The sixth generation gave the following per- 

 centages of rapid-feathering sons in 1940: Hne 1, 59.0; line 2, 1.1\ and the 

 check line, 28.4. Results to date indicate that rapid chick feathering in 

 Rhode Island Reds depends on a series of recessive genes. xA sex-linked 

 gene for rapid feathering may be present, but many males having com- 

 plete back covering may lack this gene. LTp to the present time no im- 

 portant differences have been observed in the three lines with respect to 

 characters affecting egg production. 



The Effectiveness of Selective Breeding to Reduce Mortality in Rhode 

 Island Reds. (F. A. Hays.) Cooperative project with Regional Poultry 

 Research Laboratory, East Lansing, Michigan. The sixth generation of 

 birds in this project completed their first laying year in the fall of 1940. 

 In the low-mortality line 135 chicks were hatched in this sixth generation 

 and their total mortality to six months of age was 6.6 percent. In the 

 high-mortality line 153 chicks gave a mortality at six months of 10.46 per- 

 cent. No losses from the paralysis complex were observed. 



Forty-four pullets from the low line and forty-six from the high line 

 were placed in the laying houses in September 1939. At the same time 

 all of the brothers of these pullets were housed for the winter. There 

 were 41 males in the low line and 47 males in the high line. Mortality 

 records are complete for 11 months under these conditions. In the low 

 line the mortality in pullets was 47.7 percent and in the high line 21.7 

 percent. The loss of males in the low line was 14.6 percent compared 

 with 51.1 percent for the high line. For the total population, the losses 

 were 31.8 percent in the low line and 36.6 percent in the high line. 



Cannibalism was rather severe in both lines. If the cases of death 

 apparently from cannibalism are omitted, the losses in the high and low 

 lines were: Pullets, 20.4 percent and 13.0 percent; Males, 12.1 percent 

 and 46.8 percent; Sexes combined, 16.4 percent and 30.1 percent. No 

 appearances of diseases of the paralysis complex were observed in either 

 line. The data appear to suggest that the males of the high-mortality 

 line were decidedly less viable than the males of the low-mortality line. 

 Why the losses in the females should fall in reverse order is not clear. 



