EGG PRODUCTION OF CHICKENS IN DARKNESS 



W. O. WILSON and A. E. WOODARD 

 Poultry Husbandry Department, University of California, Davis 



In the course of selection for high egg production, poultry breeders 

 have apparently favored hens with low light requirements. Experi- 

 ments were designed to determine the amount of light per 24 hr neces- 

 sary for an all-or-none response for egg laying in White Leghorns. 

 Since we had obtained 70% egg production with 6 min of light per 24 

 hr (Wilson and Abplanalp, 1956), it seemed desirable to try com- 

 plete darkness. The resuUs of these tests are reported herein. 



The sew Leghorn hens used in the tests were kept in individual 

 cages. They were trained to eat and drink in darkness by exposing 

 them to intermittent light for several days before the start of the test. 

 The room in which the hens were kept was darkened with black poly- 

 ethylene film and ventilated by fans equipped with suitable light traps. 

 Feed and water were constantly available. The eggs were collected 

 daily, the attendant using a miniature flashlight to record eggs. The 

 amount of light inside was approximately 0.0002 ft-c during the mid- 

 day hour. 



The first test was with 60 laying hens kept in three separate pens 

 of 20 hens each. The hens in the second test were a select group of 40 

 hens that laid at a high rate. 



The results of egg production for the five-week test period are 

 shown in Fig. 1. In the first test, egg production dropped from 66 to 

 23% in the fourth week and increased very slightly the last week. At 

 the end of the dark period the hens were moved outside, and egg 

 production increased rapidly. In the second test egg production de- 

 creased less rapidly. It was still 43% in the fourth week of darkness. 

 A respiratory disease caused considerable mortality and a decline in 

 egg production in the fifth week. Thirty-six percent of all hens were 

 laying at the end of the test. The lowered egg-production rate was due 

 to cessation of egg production by individual hens. Production of hens 



787 



