Intermittent lighting and dietary sodium bicarbonate supplementation for laying hens at high temperatures

Point-of-lay pullets were housed in 2 temperature-controlled rooms maintained at a constant 32 degrees C with either a conventional 16 h light:8 h dark (16L:8D) or an intermittent 3L:1D lighting regimen. They were fed either a conventional layer diet (12.0 MJ of ME and 199 g crude protein/kg) or this diet supplemented with 1% sodium bicarbonate (NaHCO3). Production and egg shell quality measurements were made at 8-week intervals from 22 to 62 weeks of age. All measures were influenced by age. The 3L:1D regimen significantly increased feed intake (P < 0.001), weight gain (P < 0.01), egg weight (P < 0.001), egg shell breaking strength (P < 0.001), and shell thickness (P < 0.01). Significant agexlight interactions were observed for feed intake, egg production, and egg mass. Hens in the 3L:1D regimen ate significantly (P < 0.001) more food and produced significantly (P < 0.01) greater egg mass to 46 weeks of age. No significant differences were observed after 46 weeks. Although not significant, NaHCO3 consistently improved shell breaking strength. The response was small in the 16L:8D regimen (3%) compared with the 3L:1D environment (7%), the latter being additional to the 14% improvement resulting from the use of the 3L:1D regimen. The results indicate advantages from the use of intermittent lighting and dietary NaHCO3 supplementation at high temperatures.