ANNUAL PERSISTENCY IN RELATION TO 

 WINTER AND ANNUAL EGG PRODUCTION 



By F. A. HAYS and RUBY SANBORN 



Annual persistency, as terminated by the onset of complete molt, has been 

 emphasized for more than the past three decades as of marked significance in 

 the selection of breeding females for egg production. The cessation of egg 

 production in summer or fall is generally accompanied liy a complete change 

 of plumage and this period of non-production may continue for 30 to 120 

 days. The exceptional hen may lay a considerable number of eggs while 

 molting, but such individuals are of infrequent occurrence. 



Hurst (1925) classifies laying hens into complete and partial-molt classes 

 and states that there is complete cessation of laying in the first class while 

 the second class sheds its feathers gradually and continues to lay for 13 or 14 

 months after the first pullet egg. According to Hurst, complete early molt 

 depends upon the inheritance of a dominant Mendelian gene. 



Goodale and Sanborn (1922) note that cessation of production in the summer 

 or fall at the end of the pullet laying year has a genetic foundation as indi- 

 cated by the beliavior of families in this respect. Data collected on the 

 Massachusetts Agricultviral Experiment Station flock of Rhode Island Reds 

 show that the biological laying year may extend to 14 or 1.5 months as a 

 maximum with 6 or 7 months as the minimum for normal birds. A study of 

 all factors affecting the duration of the pullet laying year in the flock in 

 question has not yet been completed. 



A flock bred for egg production should theoretically consist of two general 

 classes of birds with respect to persistency, namely, a high persistent class 

 and a low persistent class. In reality these two classes do not stand out 

 distinctly to form a bimodal curve when all the birds with annual records for 

 the nine-year period are tabulated in persistency classes using 1.5-day class 

 intervals. (See chart 1.) The proliability exists, however, that environmental 

 forces largely obscure these expected classes. A tabulation of the 2179 birds 

 with annual persistency records does give a frequency distribution that is 

 indistinctly bimodal and furnishes the basis for classification of those birds 

 laying for a shorter period than 315 days as low in persistency and those 

 laying for 315 days or longer as high in persistency. Such a classification is 

 largely arbitrary', however, and is used in these studies only as a working 

 basis until tlie true genetic point of division may be discovered. 



Scope of This Rkpokt 



This study was undertaken for a three-fold purpose, namely, to show (a) 

 tiie relation between controllable environmental conditions and persistency, 

 (I)) tlie relation between inherited characteristics concerned with fecundity 

 and persistency, and (c) the relation between persistency and fecundity. 

 From the practical breeding standpoint these considerations are of great im- 



