MAINE AGRICULTURAL KXPERIMENT STATION IQII 275 



Sninmary of Early Experiments. 



An experiment in which the highest laying hens were used 

 as breeders showed that mass selection for high production on 

 the basis of the trap nest record of the individual alone did 

 not, as a matter of fact, result in a steady continuous improve- 

 ment in average flock production, even though it was continued 

 for a period of ten years. 



A further experiment along the same line showed that the 

 daughters of "200-egg" hens with from six to nine years select- 

 ed ancestry (on the basis of trap nest records) behind them 

 were no better layers, on the average, than birds bred from the 

 general flock. 



There is no evidence that either (a) the method of housing, 

 or (b) of feeding, or (c) the fact that the chicks were through- 

 out the period of the experiment hatched in incubators and 

 reared in brooders, or (d) the fact that some degree of inbreed- 

 ""ng was practiced during the mass selection experiment had 

 anything whatever to do with the outcome of that experiment. 



It has been shown that during the period of selection the 

 adult mortality decreased. Tt has further been shown that at 

 the present time, in spite of the fact that there has been no 

 change in the method of hatching and rearing by artificial 

 means, the records of hatching and of chick mortality are such 

 as to give no indication whatever that the strain of Barred 

 Plymouth Rocks which has been used in all the work in breed- 

 ing for egg production has become in any way deteriorated 

 through the action of environmental or other factors. It has 

 further been specifically shown, by an experiment in out-crossing 

 involving a large number d{ individuals, that the infusion of 

 new blood into this stock failed to produce any change in the 

 egg production of the progeny. Such a result makes it impossi- 

 ble to suppose that the degree of inbreeding practiced during 

 the mass selection experiment can have had an3^thing whatever 

 to do with the results of that experiment. 



Nezi' Plan of Breeding. 



In the laying year 1907-08 a new plan of breeding was 

 adopted as a working hypothesis to be tested by experiment. 

 This plan is based on the employment of individual pedigree 



