EFFECTS OF INBREEDING ON FECUNDITY 

 IN RHODE ISLAND REDS 



By F. A. Hays, Research Professor of Poultry Husbandry 



INTRODUCTION 



Two experiments previously reported by Hays (1924 and 1929) have shown 

 that inbreeding reduces egg production. The birds in these experiments failed 

 to exhibit many of the characters that make high production possible. In 

 view of these results it is conceivable that the standards for selecting the founda- 

 tion stock as well as for the selection of breeders each year were not so rigid but 

 that many undesirable characters became intensified through inbreeding. In 

 order to overcome these possible defects, a new experiment was started in the 

 spring of 1929 using very rigid standards of selection. 



The new project was made up of three lines of essentially unrelated birds. 

 Line A breeding pen consisted of three groups of three full sisters each. These 

 three groups of sisters had the same sire, but their dams were essentially un- 

 related. A check group was made up of three females selected at random from 

 the high fecundity flock but not related to the inbred birds. All females were 

 pullets, and the entire group was mated to the sire of the inbred pullets. Line 

 B and line C breeding pens were made up in the same general way as line A, but 

 the birds used in each line were not related to the birds in either of the other lines. 

 The 1930 matings consisted of pullets from the three lines mated to a cockerel 

 of their own line and three check pullets selected from the general flock. There 

 was one full-brother x sister mating each in lines A and B and two in line C. 

 The other inbred matings were half-brother x sister matings. Daughters were 

 retained from one inbred mating (half-brother x sister) and from one check 

 mating in each of the three lines. 



The 1931 matings consisted in line A of one half-brother x sister mating and 

 five full-brother x sister matings with three check matings. For line B there 

 were four full-brother x sister matings and three check matings. Line C had 

 three full-brother x sister matings and two check matings. 



Matings for 1932 in line A consisted of four full-brother x sister matings, two 

 matings with line C and two check matings. Line B was discontinued with the 

 1931 generation because none of the females in this generation qualified for breed- 

 ing in 1932. In line C there were two full-brother x sister matings, three matings 

 with line A birds and two check matings. 



The matings of 1933 to produce the last generation were as follows: An inbred 

 line A male was mated to one of his full sisters, to two A and C line cross females, 

 to four check females from line C, to five check daughters from the 1932 check 

 matings in line A, and to one female selected from the general flock. In line C 

 a male from a cross of lines A and C was mated to four of his full sisters, to one 

 inbred line C female, to four line C 1932 check females, and to one female from 

 the general flock. 



Standard for Selecting Female Breeders 



A careful studv was made of the flock as a whole to discover those families 



