142 POULTRY PRODUCTION 



a certain limit, increased egg production is obtained only at 

 the expense of hatching power. 



On the other hand, with the hen that produces an unusually 

 small number of eggs, lack of vitality is likely to be the limit- 

 ing factor which affects the hatching power as well as the 

 production. 



Bearing on this same point, Pearl and Surface^ reached 

 the conclusion that "there is a distinct correlation between 

 winter (November to March) egg production and the per- 

 centage of fertile eggs hatched during the subsequent breed- 

 ing season. This correlation is of such sort as to indicate 

 that in general the higher the winter egg production of a 

 particular bird the lower will the percentage of that bird's 

 fertile eggs hatched probably be, and vice versa." 



Rate of Production and Hatching Power. — There seems 

 also to be a relation between the rate of egg production 

 during the incubating season and hatching power. As 

 shown by Table XVI, hens laying 11 eggs or less during the 

 same period that other hens were laying 19 or more, were 

 credited with a 17.3 per cent greater hatch, considering 

 all eggs that were set. 



High Egg Production.— High egg production, the supreme 

 object of productive breeding for which ^'igor and hatching 

 power are the foundation, is the point of selection which is 

 tlie least unrlerstood. Egg production is an exceedingly 

 com])lex character, easily affected by such en^'i^omnental 

 conditions as the date of hatching, feeding, housing, hygiene, 



' Maine Bulletin No. 168. 



' Rogers, Cornell Countryman, vol. ix, No. 3. 



