22 



MASS. EXPERIMENT STATION BULLETIN 429 



the date of completion was December 29 in the first generation, December 1 in 

 the second generation, and December 12 in the third generation. 



In the first generation, the mean number of eggs laid after molting of wing 

 primaries began was greater in line A than in line B. In the second generation, 

 the birds in line A averaged 11.1 fewer eggs after wing molt started than the 

 birds in line B. In the third generation, the line A birds again showed heavier 

 production after the molt started than did line B. Apparently no success was 

 attained in this attempt to breed for increased production during wing molt. 



In the first two generations, the number of eggs laid during the biological 

 year and the number of eggs laid in 365 days were both significantly greater in 

 line A than in line B. In the third generation, production was essentially the 

 same in both lines. 



There is no evidence in table 14 that selective breeding will increase the num- 

 ber of eggs laid while in wing molt. 



T.-VBLE 14. — Breeding For The Ability to Lay .\fter The Onset of 



Wing Molt. 



Line A 



Number 

 of Birds 



Average 



Line B 



Number 

 of Birds 



Average 



1941 Generation of Daughters 



Duration of wing molt, days _ 10 130.2 2 168.0 



Date of completing wing molt 10 Dec. 7 2 Dec. 29 



Number of eggs laid during wing molt 10 25.2 2 16.5 



Production during biological year, eggs.... 10 190.5 2 136.5 



Annual production, eggs 10 187.2 2 136.5 



1942 Generation of Daughters 



Duration of wing molt, days - 4 98.0 11 113.3 



Date of completing wing molt... 4 Dec. 11 11 Dec. 1 



Number of eggs laid during wing molt 4 19.5 11 30.6 



Production during biological year, eggs.... 4 290.0 11 246.7 



Annual production, eggs 4 276.3 11 237.0 



1943 Generation of Daughters 



Duration of wing molt, days 18 122.9 3 93.3 



Date of completing wing molt 18 Nov. 25 3 Dec. 12 



Number of eggs laid during wing molt 18 33.8 3 14.7 



Production during biological 3'ear, eggs.... 18 235.4 3 237.7 



Annual production, eggs 18 228.1 3 229.7 



Relation of Wing Molt to Subsequent Hatchability 



There is a rather widespread belief that very late molting may be inimical to 

 subsequent hatchability. Hays (1943) found no correlation between the length 

 of the biological laying year and subsequent hatchability. In table 15 some data 

 are presented concerning the duration of wing molt, the time of completion of 

 wing molt, and subsequent hatchability. 



The rather fragmentary evidence suggests that if molting of wing primary 

 feathers extends over a greater period than 14 weeks, it may be accompanied 

 by reduced hatchability. There is also some evidence that the completion of 

 molt after November may be associated with lower subsequent hatchabilit},'. 



