11 Hours of Darkness with Respect to Growing and Laying Performance as Influenced by Age at Housing and Strain

ABSTRACT Two trials in two years, each involving 2 commercial strains of White Leghorns, were conducted to compare the growing of Leghorn pullets on: (1) one hour of light and 11 hours of darkness (1L:11D) from day 4 to housing; vs. (2) a program of 8 hours of light and 16 hours of darkness (8L:16D). Lighting treatment had a significant effect on body weight in trial 1 with birds grown on 8L:16D being heavier at 4 and 8 weeks of age, while those grown on 1L:11D were heavier at 16 weeks of age. Birds grown on 1L:11D did consume less feed to 20 weeks than those grown on 8L:11D in trial 1 (6.24 kg. vs. 6.61 kg.) and in trial 2 (6.75 kg. vs. 7.60 kg.) where the effect was significant (P<0.05). Birds grown on 1L:11D had a greater age at 50 percent production in both trials. In trial 2, it was found that this effect could be modified by housing birds at differ-ent ages. There was no effect of lighting program during the growing period on subsequent percent egg production in trial 1 though in trial 2 the effect was significant (P<0.05) (1L:11D, 77.2 % vs. 8LT6D, 75.8%) as was the interaction of lighting treatment by strain (P<0.05). There was no ef-fect of lighting treatment on kg. of feed per dozen eggs, but in trial 2 birds grown on 1L:11D laid significantly (P<0.05) heavier eggs. Birds grown on 1L:11D showed a greater return over feed and chick costs for one strain in trial 1 and for both strains in trial 2 at an average of 30 cents per bird. In neither case were the differences significant