A large proportion of broiler chickens suffer from lameness euphemistically called ‘leg weakness’. In a survey of commercial, intensively reared broilers, 90% had a detectable gait abnormality and 26% suffered an abnormality of sufficient severity for their welfare to be compromised (Kestin et al., 1992). It is assumed that leg weakness is painful but there is little direct evidence of this. Chickens have been shown to be able to select an adequate protein diet from a choice of two or three foods which are individually inadequate (Forbes and Shariatmadari, 1994). Broiler chickens showed a significant preference for food of the colour which was paired with ascorbic acid supplementation when the requirement for ascorbic acid was increased by heat stress (Kutlu and Forbes, 1993).
Regulation of essential fatty acid intake in the rat: Self-selection of corn oil.