ANNUAL REPORT, 1947-48 71 



In the fall of 1947 about 80 females of different ages in the non-broody line 

 were given prolactin injections to test for broody inheritance. Each female was 

 in active laying and received 50 Internatonal units of prolactin intramuscularly. 

 With very few exceptions, egg laying stopped within two days and was not re- 

 sumed for 15 or 20 days. This treatment failed to initiate broody behavior in 

 any of the birds. 



Another lot of prolactin that is believed to be free of other hormone fractions 

 is now being used to test all females in this line as a guide to future breeding 

 operations. 



Genetic Laws Governing the Inheritance of High Fecundity in the Domestic 

 Fowl. (F. A. Hays and D. W. Talmadge.) Several phases of the fecundity prob- 

 lem have been investigated and results published during the year. 



Selective breeding has considerable value in developing high and low viability 

 lines of Rhode Island Reds. Further evidence has been presented on the in- 

 heritance of intensity of laying. Progeny testing emphasizes the scarcity of 

 superior sires and demonstrates their importance in breeding for high fecundity. 

 Rather extensive colorimetric stuaies of feather pigments in Rhode Island Reds 

 suggest that dense feather pigmentation depends on a series of recessive genes. 

 The decline in egg weight in warm weather is definitely associated with decreased 

 body weight and reduced feed consumption. This decline in egg weight is in- 

 significant in this latitude. Hatchability has been shown to decrease with in- 

 creased age of parents and the decline appears to be associated in part with higher 

 embryonic mortality. 



A Study of Fertility Cycles in Males. (F. A. Hays and D. W. Talmadge.) 

 Pregnant mare serum has not been effective in activating old males to high fer- 

 tility in natural matings. Thyroxine gave no positive effects for the same pur- 

 pose. Artificial light appears to offer possibilities and further tests are being 

 made concerning amount and duration. 



An extensive study in females has demonstrated that as viability increases 

 fertility decreases. Apparently high concentration of the female sex hormone 

 concerned with fertility renders the bird more susceptible to diseases such as the 

 paralysis complex. 



Secondary and Adult Sex Ratio in Relation to Hatchability. (F. A. Hays.) 

 High and low hatchability lines started in 1945 have been continued and com- 

 plete hatching records have been secured. The search for lethals has been con- 

 tinued and the first to appear was the type of chondrodystrophy first reported by 

 Hajs in 1944. There is evidence that females are likely to predominate in early 

 embryonic deaths while males are more abundant in dead embryos from the 

 eighteenth day on. 



Considerable success has accompanied the establishment of high and low hatch- 

 ability lines but further selective breeding appears to be necessary. 



Breeding for High and Low Incidence of Internal Defects in Hen's Eggs. 

 (F. P. Jeffrey and C. E. Walker.) Breeding results indicate that the inherited 

 tendency to produce meat spots in fresh laid eggs is largely independent of the 

 inherited tendency to produce blood clots. Egg shell color in the low meat spot 

 line is now considerably lighter than in the high meat spot line. 



Breeding White Plymouth Rocks for Eggs and Meat. (F. P. Jeffrey.) A new 

 sex linkage relaiionship has been discovered in a strain of White heavies. This 

 autosomal dominant plus the factor for silver allows the production of 100 per- 

 cent white offspring when white males are mated with Rhode Island Red females. 



