INTERMITTENT LIGHTING AND DIETARY-SODIUM BICARBONATE SUPPLEMENTATION FOR LAYING HENS AT HIGH-TEMPERATURES

Point-of-lay pullets were housed in 2 temperature-controlled rooms mai ntained at a constant 32 degrees C with either a conventional 16 h lig ht:8 h dark (16L:8D) or an intermittent 3L:1D lighting regimen. They w ere fed either a conventional layer diet (12.0 MJ of ME and 199 g crud e protein/kg) or this diet supplemented with 1% sodium bicarbonate (Na HCO3). Production and egg shell quality measurements were made at 8-we ek intervals from 22 to 62 weeks of age. All measures were influenced by age. The 3L:1D regimen significantly increased feed intake (P < 0.0 01), weight gain (P < 0.01), egg weight (P < 0.001), egg shell breakin g strength (P < 0.001), and shell thickness (P < 0.01). Significant ag exlight interactions were observed for feed intake, egg production, an d egg mass. Hens in the 3L:1D regimen ate significantly (P < 0.001) mo re food and produced significantly (P < 0.01) greater egg mass to 46 w eeks 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 w ith 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.