Preen gland function in layer fowls: factors affecting morphology and feather lipid levels.

The effects of age and external factors on preen gland morphology and feather lipid concentrations in layer fowl (Gallus domesticus) have not previously been described. This work examines how floor substrate, whether a bird is feather pecked or not, and age influence both gross and histological morphology. Furthermore, the effects of age, beak trimming and floor substrate on feather lipid concentration (mg lipid per g feathers) are investigated. Neither absolute nor relative preen gland weight were reliably affected by floor substrate or feather pecked status. However, these parameters were strongly affected by changes in bird age and related body weight changes. The microstructures of the gland also increased consistently with age. Feather lipid concentration generally increased with age. Feather lipid was strongly influenced by the presence or absence of a dustbathing substrate. Of all the parameters tested here, the age and growth of the bird had the greatest effects on preen gland development. Feather lipid concentration is also influenced by age, and by the presence or absence of a dustbathing substrate.