24 MASS. EXPERIMENT STATION BULLETIN 307 



These data show that mongrel flocks may be greatl\' improved in egg produc- 

 tion through the use of purebred males from flocks improved for production. 



Extension projects in flock improvement carried on by the Massachusetts 

 Agricultural Extension Service show very definitely that the egg production of 

 ordinary flocks may be greatly increased through the use of outside males from 

 flocks highly improved for egg production. 



A method of breeding within the flock that will raise the mean annual egg pro- 

 duction from 114 eggs to 235 eggs in twenty years without any culling in the 

 laying houses may be considered rather satisfactory. Such a result has been 

 accomplished in the Massachusetts Station flock using the system outlined below. 

 As previously indicated the flock was started by purchasing mature pullets from 

 two different sources, and males that were not closely related to the pullets 

 were obtained from one of these flocks. The foundation stock was not improved 

 for fecundity but represented improved breeding from the exhibition standpoint. 

 These birds were late maturing, low in intensity, high in broodiness, and not 

 persistent la\ers. 



Early in the history of the flock it was decided by Goodale after much study 

 that selective breeding to be effective must be based not upon egg records as a 

 unit but upon inherited characters that directly afTect egg production. 



The first character bred was for early sexual maturity. Female breeders 

 that began to lay at the youngest age were made use of and mated to males whose 

 sisters had laid earlier than the average. The fourth generation, hatched in 

 1916, showed the character of earh- maturity to be rather well established, with 

 a flock mean of 213 days. Since that time only early-maturing females have 

 been used, and the flock mean age has fluctuated between 185 and 210 days. 



Genetically early-maturing birds begin laying at 215 days of age or younger. 

 On account of the advantages of large size so intimately associated with egg size, 

 the selection of extremely earl>-la\ing breeders has been avoided. In recent 

 vears preference has been given to females that began la\ing at from 200 to 

 210 days of age. 



The elimination of broodiness in the flock was undertaken ne.xt, without 

 sacrificing any progress in breeding for early maturity. Progress was made by 

 selecting as many female breeders as possible that were free of broodiness in the 

 pullet year. This was followed by the exclusive use of male breeders from this 

 class of dams. Some males and females tested for non-broodiness were made 

 use of from time to time. Selection has since been based on the greatest freedom 

 from broodiness within the family. As previously indicated, the percentage of 

 individuals broody in the first laying year has fallen from 90 per cent to about 

 1 1 per cent. 



Intensity of laying or the ability to lay a large number of eggs in a specific 

 time interval was the third character to be considered in improving the flock. 

 This character was established largely through one female and her descendants. 

 Since high intensity depends upon dominant genes, it was not necessary to 

 practice close inbreeding to establish the character. In the early part of the 

 experiment breeding females were selected for the ability to lay a large number 

 of eggs up to March 1, or for the ability to lay many eggs (26 or more) in a winter 

 month like December. In recent years intensity has been measured by mean 

 winter clutch size. A clutch represents the number of eggs laid on successive 

 days, and the average size of clutches from first pullet egg up to March 1 gives 



