20 



THE INHERITANCE OF FERTILITY AND HATCH- 

 ABILITY IN POULTRY. 



Bt F. a. Hays and Ruby Sanborn. 



Introduction'. 



The importance of a thorough understanding of the mode of inheritance of 

 factors affecting fertility of hens' eggs needs no stressing. Neither does the value 

 of a complete understanding of the way hatching power of eggs is inherited require 

 emphasis, for the proper functioning of the factors for high fertility and high hatch- 

 ability is of fundamental and vital importance to ever}"" poultry breeder. 



The purpose of this report is to consider only the question of the inheritance of 

 fertility^ and hatchability- from as many angles as our data will permit. The 

 inheritance of these two characteristics is discussed first from the standpoint of the 

 dams and then from the standpoint of the sires. The fact should be recognized 

 at the outset that numerous variable environmental factors such as weather con- 

 ditions, health of birds, exposure of eggs, variation \\ithin the same and different 

 incubators, etc., are in constant operation. The combined action of these con- 

 stantl}' varAang environmental factors may largelj^ obscure the inherent capacity 

 of the bird to produce fertile eggs that are largely hatchable. A further lack of 

 knowledge of the fundamental factors concerned in breeding for high fertiUty and 

 high hatchabiUt}^, as pointed out by Dunn ('23), makes proper matings impossible. 



Data Available.' 



The data used in this bulletin have been collected each hatching season from 1913 

 to 1923. All records kept represent the pullet year or cockerel year unless otherwise 

 stated. All records were made by pedigreed Rhode Island Red birds. The atten- 

 tion of the reader is called to the fact that stud matings have been used almost 

 exclusively and this will account for a lower degree of fertility than might be 

 obtained from pen matings. Uniform methods of incubation have been used and 

 care has been taken to maintain a definite system of management throughout the 

 eleven-year period. Only females whose daughters were trap-nested are included 

 in this report. 



PART I. 



The Female's Role in the Inheritance of Fertility and Hatchability. 



Fortunately a measure of individual fertiUty and hatchability is possible in the 

 female. The accuracy of such a measure depends very largely upon the number 

 of eggs laid by the pullets in question during the hatching season. Some pullets 

 will lay fifty eggs during a two months' incubation season, while others may lay 

 as few as five or ten eggs. Fertility and hatchabiUty records on the first type would 

 certainly be much more significant than those on the second type. The major 

 portion of the records here reported upon were made between the hatching dates 

 of March 25 and May 15 of the respective .years. In some cases chicks were hatched 

 beyond the above dates, but not as a rule. Since the flock was being bred for egg 

 production, considerable care was exercised to use pullet breeders that would lay 

 a goodly number of eggs during the hatching season. 



Section L Correlation between Fertilihj and Hatchability. 



A hen to be able to produce a large number of chicks must lay highly fertile 

 eggs. Furthermore, her eggs must hatch well. In ordinary usage, good hatching 

 hens are those from which almost all eggs laid give rise to vigorous chicks. Fer- 

 tility and hatchabihty are bound together in the sense that there can be no hatch- 



1 The term fertility as used here refers to the percentage of eggs that are fertile; the test being made on the fifth 

 day of incubation. , 



• The trriii hatchability as used here refers to the percentage of fertile eggs hatched. 



3 The data used in this report icere collected by Dr. H. D. Goodale until 19S1; for the year 1922, by Professor 

 William Sanctuary and the junior author. 



