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

Abstract

Point-of-lay pullets were housed in 2 temperature-controlled rooms maintained at a constant 32°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 age×light 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.