Constitutional Vigor in Poultry 



587 



the strong pens. The Barred Plymouth Rock pens gave a smaller per- 

 centage of chicks to the number of eggs set than did either of the Leghorn 

 pens. The White Leghorn day-old chicks were heavier than the Plym- 

 outh Rock chicks, although the eggs in the strong Plymouth Rock pens 

 were heavier than the eggs in some of the pens- of White Leghorns. This 

 seems to indicate a negative correlation between size of chick and breed, 

 and size of egg. 



Development of the chicks 

 The chickens from all the fowls, weak and strong, were brooded to- 

 gether. This insured similar conditions and an equal chance of develop- 

 ment for all. 



The mortality up to six weeks of age was shghtly greater among the 

 chicks from the strong pens, which could not be accounted for by the 

 appearance of the chickens. Among both weak and strong the mortality 

 was much heavier with the Leghorns than with the Plymouth Rocks. 

 (Table 10.) 



TABLE 10. Chick Record 

 (December 10, 1907, to December 7, 1908) 



The percentage of chicks at the end of six weeks to the total nimiber 

 of eggs set was sUghtly to the advantage of the strong pens. It is also 

 noticeable that, although the mortality among the Plymouth Rocks was 

 much less than among the Leghorns, it still required more; eggs to 

 produce one Plymouth Rock than to produce one Leghorn (2.8 eggs for 

 each Leghorn chicken and 2.9 eggs for each Plymouth Rock chicken at 

 six weeks of age). 



When penned up in the fall the average weight of the pullets from 

 the strong pens (3.53 pounds) greatly exceeded that of the pullets from 

 the weak pens (2.99 pounds). This difference was greatest with the 



