DURATION OF ANNUAL MOLT IN RELATION TO 

 EGG PRODUCTION 



By F. A. Hays, Research Professor of Poultry Husbandry, and 

 Ruby Sanborn, Research Assistant in Poultry Husbandry 



Introduction 



The time of onset of complete molt at the end of the pullet laying year has 

 long been recognized as affecting pul'let year egg production in a very signi- 

 ficant manner. In flocks bred for egg production female breeders are selected 

 with nmch emphasis on time of molting. Since the onset of complete molt 

 generally marks the termination of egg production, it is evident that early 

 molting may greatly reduce the length of the laying year. Hays and San- 

 born (1927b) found the net correlation between length of the pullet laying 

 year and annual egg production to be +.7501 ±.0063. Hays (1927) showed 

 that late molting (high persistency) depends in inheritance upon a dominant 

 gene P. 



The duration of complete molt has also received considerable attention. 

 The ideal has been a hen showing the ability to shed her feathers and to grow 

 a new coat in the shortest time interval. Moreover, in heavy laying flocks a 

 few individuals appear to exhibit no complete molt, and such birds generally 

 lay continuously for two or more years. The percentage of these non-molt- 

 ing hens is very small, however, and there is no evidence that they are a 

 superior group. Such individuals are separated from the normal birds in the 

 studies reported below. 



In this report consideration is given to a number of conditions which may 

 influence duration of molt, as follows: environmental factors, such as hatch- 

 ing date; (2) hereditary characteristics, such as age at first egg, intensity, 

 winter pause, broodiness, and persistency; and (3) physiological activities, 

 such as previous egg production, 365-day production, and gain in body weight 

 during the laying year. Finally, the relation of duration of molt to vigor and 

 to second-year production is considered. 



Character of Birds Us^ed 

 This study includes all Rhode Island Red females hatched from 1917 to 

 1928 and kept for two full laying years. In general, they were superior to 

 the average of the flock as judged by their pullet-year performance. The 

 greater portion of these birds were bred for high fecundity and the remain- 

 der came froin experiments designed to study broodiness, hatchability, in- 

 breeding, and color. 



The Coefjiclent of Correlation 

 The simple coefficient of correlation is used to measure the degree in which 

 two characteristics tend to vary together. This information is valuable to 

 poultry breeders in the selection of breeding stock and furnishes clues to 

 possible flock improvement. 



