BREEDING FOR EGG PRODUCTION 



255 



of breed or strain (Fig. 128). Breeding and selection will make it 

 possible to reduce the number of weak ones to a minimum. 



Lack of Vigor. The following are some of the common causes 

 of loss or lack of vigor as determined by Rice and Rogers:* 



1. Increased Productiveness. In its wild life the ancestor of 

 the domestic hen laid but few eggs a year, perhaps a dozen. The 

 modern hen is expected by good care and management to lay 

 from 120 to 160 a year, and, at the same time, these eggs, or some 



FIG. 128. Strong and weak males. Contrast the bright protruding eye, erect carriage, 

 and short heavy spur in the one and the low tail, sunken eye, long slender spur, and drooping 

 carriage in the other. 



of them, must be hatched into chicks with as much strength and 

 vigor as the parent. It is evident that any increase in the produc- 

 tion of eggs must be accomplished by a proportionate increase in 

 the physical strength of the bird, to enable her to assimilate the 

 increased amount of feed required for this increased production. 



2. In-and-in Breeding Without Regard to Vigor. Inbreeding 

 is often resorted to in order that the high producing qualities may 

 be better and more quickly fixed ; but, where due consideration is 

 not at the same time given to vigor, loss of vitality is bound to follow. 



* Cornell Reading Course ("Constitutional Vigor in Poultry Breeding"). 



