Selection experiment for increased egg production under 23 H and 24 H light‐dark cycles in the domestic fowl

Abstract

1. A selection experiment was conducted for increased rate of lay under 23‐h (23HS line) and 24‐h (24HS line) light‐dark cycles over 5 generations.

2. In generation 5, rate of lay was higher in the 23HS line than in the 24HS line, and the proportion of hens with mean intra‐sequence intervals of less than 24 h in the 23HS line increased to 88% in generation 5 from 15% in the base generation.

3. The realised heritability for rate of lay was 0.25 ± 0.04 in the 23HS line and 0.15±0.05 in the 24HS line.

4. Egg weight and shell weight decreased in both lines, and the decrease in the proportion of shell was larger in the 23HS line than in the 24HS line.

5. It is suggested that a regimen of 23 h light and dark may be an effective environment for selection to improve the laying performance of a population approaching a plateau for egg production.

Notes

Present address: Tohoku National Agricultural Experiment Station, Morioka, Iwate 020–01, Japan.