BREEDING FOR EGG PRODUCTION 15 



egg weight of 24 ounces or more; when genes A and B are present in the same 

 individual, the egg weight in February falls below 24 ounces. There are thus 

 three general classes of birds with respect to egg size. The A class may lay 22- 

 ounce or smaller eggs, the AB class will approximate 23 ounces, and the B class 

 will lay eggs weighing 24 ounces or more. The breeding problem lies in the 

 constant selection of pullet breeders laying 24-ounce or heavier eggs and yearlings 

 laying 25.5- to 26-ounce eggs, and the constant use of males carrying the in- 

 heritance for large egg size. 



The Selection of Superior Males 



Selection of superior males for breeding has always been a troublesome problem. 

 The reason is evident, because there are no measures of the male's performance 

 w^ith respect to the characters affecting egg production. Young males are 

 selected either on the performance of their female ancestors or on the partial 

 records of performance of their sisters. In the light of the many genetic factors 

 concerned, it is evident that either method is very unreliable. Aged males may 

 be selected on the performance records of their daughters, and satisfactory matings 

 should be repeated. Even though progeny-tested males are used as far as possible, 

 the system requires that at least three times as many males be used as cockerels 

 each year as will be required for breeding when three years of age because of high 

 mortality in males. Males must be at least three years of age before the fecundity 

 records of their daughters are known. This fact greatly limits the use of this 

 method with the medium breeds where the reproductive life of males is relatively 

 short. 



Since complete progeny testing has such pronounced limitations, a system 

 of partial progeny testing has been suggested by Warren (1932). He recommends 

 that cockerels for breeding be selected from families where the sisters show such 

 desirable characters as early maturity, high intensity, etc., early in the season. 

 This method is of some value in selection but falls far short of being an accurate 

 method. 



Unpublished data from the Massachusetts Experiment Station flock of Rhode 

 Island Reds show that during the past five \ears only 3 (5 per cent) of the 60 

 males used have raised the mean egg production of the daughters over their 

 dams. These males were mated to females laying from 226 to 250 eggs during 

 their pullet year. Since the average egg production of birds in this experiment 

 is 235 eggs, such dams are truly representative. 



The method of evaluating males for breeding purposes which the authors 

 believe to be genetically sound is based on the relative proportions of early- 

 maturing, non-pause, highly intense, non-broody, and highly persistent daughters 

 produced by the males compared when mated to females carrying these charac- 

 ters. Thus individual males may be directly compared in their abilit>' to transmit 

 any or all of these five characters which are so vitally related to high production. 

 By this method it is possible to use partially tested males with considerable con- 

 fidence when they are two years of age rather than to wait until the male is 

 three years of age. This method of selection has proved superior to any other 

 method used to fix the five high fecundity characters in the flock. Under all 

 conditions males can be compared on the progeny test only when each is mated 

 to the same character of females. 



