ANNUAL REPORT. 1940 101 



Genetic Laws Covering the Inheritance of High Fecundity in Domestic 

 Fowl. (F. A. Hays and Ruby Sanborn.) Progress is observed in selec- 

 tive breeding of Rhode Island Reds for characters affecting high fecundity. 

 Most of these characters are of rather complex genetic makeup. Early 

 sexual maturity has been well established at a mean of about 190 days 

 when birds are hatched in March and April. Intensity is still variable and 

 the object is to attain a minimum of 3 eggs for winter clutch size. Win- 

 ter pause has been reduced in duration, and the percentage of birds ex- 

 hibiting pause has fallen as low as 27 percent. The percentage of broody 

 birds and the degree of broodiness in broody birds have both gone to a 

 low level. Persistency has improved so that the mean is not far below 

 365 days. 



Beginning in 1929, comparisons have been made between the birds in 

 this experiment and four strains from outside sources. From the stand- 

 points of fecundity and of viability no outside strain has proved superior 

 to our experimental strain. Crosses between the high fecundity line and 

 these four strains did not produce superior birds. 



Attention is also being given to fertility, hatchability, chick feathering, 

 body weight, egg weight, plumage color, comb type, shank feathering, 

 and inherited factors affecting mortality rate. Progress is being made 

 without sacrificing desirable characters. 



A Study of Fertility Cycles in Males. (F. A. Hays.) Records are being 

 collected on the spermatogenesis of males of different ages through the 

 fall, winter, and spring periods. Testicular tissue is being prepared for 

 cytological study to develop some standard for comparing the reproduc- 

 tivity of different males. Particular attention is also being given to pos- 

 sible inherited factors affecting fertility in males. Preliminary data indi- 

 cate notable differences in the histology of the testis as related to season. 



Physiological Relationships Between Molting Behavior and Fecundity 

 Characters. (F. A. Hays.) Bi-weekly records are still being made on 

 the molting behavior of production-bred and exhibition-bred Rhode Island 

 Red males and females. The third series of observations began July 25, 

 1940, and will be concluded December 26, 1940. The first breeding phase 

 was begun during the spring of 1940 and data will be secured on the 

 molting behavior of this first generation. The stocks available show wide 

 variability in molting behavior, and several important relationships be- 

 tween molting behavior and fecundity are suggested. 



Miscellaneous Studies. ( F. A. Hays.) Several studies are being carried 

 on under this heading. Rhode Island Reds are being studied for possible 

 linkage relations between genes for shank feathering, genes for comb 

 form, and genes for mottled ear lobe. Differences between Rhode Island 

 Red plumage color and buff plumage color are being studied by hybridiza- 

 tion. A method of separating sexes at hatching on the basis of down color 

 is being studied in Rhode Island Reds. For auto-sexing, a type of gold 

 barred bird is being developed. 



Manganese Requirement of Rhode Island Reds to Prevent Perosis. 



(Marie S. Gutowska and Raymond T. Parkhurst.) To determine the 

 threshold level of manganese necessary for the prevention of perosis in 

 Rhode Island Reds, an experiment was conducted with four lots of chicks 

 fed the standard perotic ration, supplemented with commercial ground 

 calcites with and without manganese sulfate, so that the manganese levels 



