Physiological and environmental factors affecting egg quality

Abstract

Egg quality is greatly influenced by hen physiology, including age, moult and by environmental conditions (temperature, lighting cycle and rearing system). Egg weight increases with hen age, partly due to the increased yolk proportion. Eggshell quality and functional properties of eggs are progressively impaired with hen age. Moult restores, for a shorter production cycle, the progressive degradation in egg production and quality observed at the end of the laying period. High ambient temperature (> 30°C) elicits in hens changes in acido-basic balance and in feed consumption. These changes reduce egg production, egg weight and eggshell strength. Lighting programs applied during the rearing and production periods of hens influence egg production. Ahemeral (> 24 h) and symmetrical cycle programs increase egg weight and eggshell thickness but recent EU directives banned their use. The production system has limited and inconsistent effects on sensorial, nutritional or functional properties of eggs. Furnished cages initially resulted in higher percentages of downgraded eggs but progressive improvements in cage design, of equipments distribution and changes in hen group size allow similar performance to conventional cages if hens are beak trimmed.