Preen gland function in layer fowls: factors affecting preen oil fatty acid composition.

1. Preen oil derived from the preen gland has previously been shown to differ in its composition between birds of different ages, sex and diet. As a part of a larger study on preening behaviour and its components, the relative percentages of fatty acids in preen oil were examined in laying hens that differed in age, beak trimmed status, feather pecking status (pecker and pecked) and method of sampling (either direct from the preen gland or from lipid extracted from feathers). 2. Five experiments are described. Fatty acids extracted from lipid were analysed by gas chromatography (GC). Fatty acid composition was affected by age, by whether or not a bird was feather pecked (but not if it was a feather pecker) and by lipid source. 3. Changes in preen oil composition with age (shown here) may be due to changes in circulating concentrations of hormones. Differences in preen oil composition between feather pecked and non-pecked birds may influence plumage odour and therefore taste, making the plumage of some birds more attractive to pecking than others. 4. The proportions of some fatty acids derived from feathers differed to those extracted from the preen gland. Lipid found on feathers is most likely a combination of that from the preen gland and from sebaceous secretions from the skin.