Effect of Lighting Systems in the Grower and Adult Periods Upon the Over-All Performance of White Leghorns

THE EFFICACY of the conventional lighting program (natural daylength or 12–14 hours of constant light in the grower period, plus 13–15 hours of constant light in adult period) has been challenged in recent years. The different lighting programs (other than natural daylength) tested since 1955, represented constant, decrease, increase, and intermittent types for both grower and adult periods. Light restriction represented constant light of less than 12 hours per day, or light given in decreased quantitites, and initiated at different ages from hatch through 18 weeks. The decrease and increase types were given either gradually or abruptly. The intermittent type referred to a series of light-dark cycles per day. Pullets given light restriction in the grower period, plus 13–15 hours of constant light in the adult period, outperformed their sisters given the conventional lighting program (Platt, 1955; Marr et al., 1957; Lert et al., 1960). This finding…