The interrelationships of nutrition and feather pecking in the the domestic fowl - A review

It has been shown in numerous experiments that nutrition influences feather pecking and cannibalism in different poultry species. While nutritionists assume that nutritional deficiencies are the main causes of the problem, ethologists consider feather pecking and cannibalism as a result of a fundamental drive related to feeding behaviour. The present paper reviews the influence of nutrition on feather pecking behaviour in different species of domestic fowls on the basis of publications of the last 60 years. Inadequate supply of protein and amino acids, mainly methionine and lysine, stimulate feather pecking and in some cases cannibalism. The effect of dietary arginine on feather pecking is not clearly documented. The beneficiary effect of tryptophane on feather pecking in different species has been attributed to its function as precursor of serotonin. Sodium deficient diets increased feather pecking in many cases. The effect of other minerals and trace elements did not show consistent results. It is generally acknowledged that nutrient deficiencies increase the exploratory behaviour, which can be directed towards the feather cover of group mates. Supplementation of nutrients beyond the requirement was found to reduce feather pecking in the case of arginine only. A wide range of other feed ingredients and antibiotics have been tested with regard to their effect on feather pecking in chickens, quail and pheasants. None of the ingredients did prevent feather pecking. There was a consistent trend of the feed structure with coarse particles, especially pellets and crumbles, producing more feather pecking and cannibalism than finely ground feed. This effect was explained by the influence of feed structure on the time spent feeding. Pelleted or coarsely ground feed reduce the time required to ingest the feed, and thus, may not allow to fullfil the drive of food pecking and exploration. The remaining pecking activity may be directed on the pen mate's feathers. Dilution of the diets with crude fibre, especially with finely ground fibre, reduced feather pecking and pecking-related feather damages in pullets, laying hens and pheasants. The positive effect of dietary fibre on feather pecking can - similarly to the fine feed structure - be attributed to the increase of time spent feeding. A part of the effect of dietary fibre is supposed to be caused by its influence on the passage of the ingesta through the gut. Although adequate levels of all nutrients and high fibre diets fed as fine mash reduce the risk of feather pecking it does not prevent it entirely. Feeding experiments with a chicken line selected for high feather pecking behaviour have shown that these birds show a special preference for feathers. They constantly eat feathers when offered on a sheet of plastic. Raw feathers in the diet show a similar effect on the passage of the digesta through the gut as indigestible fibre. However, the birds of the high feather pecking line prefer feathers over fibre when given the free choice. The cause for this specific preference for feathers remains to be investigated.