Broilers are currently reared under nearly continuous lighting (CL) schedules. However, the suitability of such lighting regimens may be questioned in terms of performance and welfare. This paper reviews the literature concerning the effects of intermittent lighting (IL) schedules on these issues. Final body weights at market age of broilers reared under IL schedules are equal to, or even higher than, those of broilers reared under CL schedules. However, endogenous (genotype and sex) and exogenous (dietary composition, feeder space, etc.) factors may interact with the lighting schedule. In contrast, feed conversion is consistently improved with IL, partly as a consequence of a more concave growth curve (initial growth depression followed by compensatory growth). Inconsistencies in the literature concerning the effect of IL on (abdominal) fat content and dressing yield are caused by interactions with other factors. However, it is clearly demonstrated that IL reduces leg abnormalities, in particular the incidence of twisted legs. Additional welfare benefits of IL are found in reduced physiological stress and improved eye condition. An increase in the amount of catching damage has been observed with IL, but this may be avoided by modifying light management before commencement of the catching operation. The importance of light is not restricted to the lighting schedule; aspects of the light quality are also important. Although the data related to light intensity are conflicting, it is generally recommended that an intensity of 51ux should be provided. Whilst fluorescent light does not affect broiler performance adversely, its lower use of electricity compared with incandescent lighting does reduce input costs. More research is needed to evaluate the impact of these qualitative aspects of lighting on poultry welfare.

Fear is now widely regarded as an undesirable state of suffering by many members of the public, the scientific community, welfare and policy groups, as well as by a growing number of farmers. At first glance this view appears to be inconsistent with one based on biological significance, in which fear is regarded as an adaptive state with fear behaviour functioning to protect the animal from injury. Fear is often adaptive in ideal circumstances but neither we nor the animals in our care live in an ideal world. In reality, many farming systems prevent the animals from responding in an adaptive fashion to potentially threatening stimuli. In these circumstances, fear can be a powerful and potentially damaging stressor, particularly if it is intense or persistent. Both acute and chronic fear can seriously harm the welfare and performance of poultry. Certain fear responses, such as violent escape or panic, are inap-propriate in intensive systems and can cause injury, pain or even the death of birds. High levels of underlying fearfulness have also been negatively associated with plumage condition, egg production, egg shell quality, growth, and food conversion efficiency. Furthermore, because fear inhibits all other motivational systems, its elicitation is likely to impair the ability of birds to adapt to environmental change, to interact successfully with each other or with the stock person, and to utilize new resources. Therefore, high fear is clearly undesirable from the bird's and the farmer's viewpoint and its reduction is of major importance. This objective had been hampered because of the complex-ity of the concept of fear and the controversy over its measurement. However, operational definitions of fear and its components are given in this review and a number of tests which have been used to measure fear in poultry are described. Strong intra-individual correlations found between the fear scores afforded in many of these tests suggested that they are measuring the same intervening variable, presumably underlying fearfulness, rather than purely stimulus-specific responses. Two of the commonest and potentially most frightening events encountered by poultry are sudden changes in their physical or social environment and exposure to humans. Other more specific types of alarming stimuli are also listed. Hitherto, the most promising ways of reducing underlying fearfulness and increasing adaptability, at least in the laboratory, involve one or more of the following approaches: environmental enrichment, regular handling or related treatments, vitamin C supplementation of the diet or drinking water, and genetic selection. The potential benefits and short-comings of these remedial measures are discussed, with attention to their practical relevance as well as to their more fundamental implications. Other measures to mask and/or minimize the incidence of frightening events are also briefly mentioned. Our objective should be not only to achieve a balance between maintaining an emotional state that facilitates the avoidance of danger while reducing the likelihood of overreaction and the expression of inap-propriate responses, but also to provide a stimulating, safe but economically viable environment. Continued investigation should enable recommendations to be made concerning the most effective programme, in terms of environmental modification, human-animal interaction, nutritive manipulation, and selective breeding, in order to achieve the optimal levels of fear in poultry, whatever the future trends in the industry.

Several successful methods of inducing moulting have been used to recycle laying hens, the majority of which require an optimum weight loss of 25–30% to achieve maximum egg production during the post-moulting period. The conventional feed restriction procedure is most often used in the egg industry because it is a simple, practical and economical technique that can be used in combination with light and/or water restriction. Mineral-induced moulting procedures, such as the use of high levels of either aluminium in the form of a soluble salt or dietary zinc, have also been used successfully. In addition, low levels of dietary zinc combined with a low calcium diet have also induced moulting in laying hens. The use of low sodium diets has been equally as successful as the conventional feed restriction technique as a means of inducing a moult. Although mineral-induced moulting procedures produce similar results to the conventional feed restriction techniques in post-moulting egg production, but with lower mortality rates, some of these procedures may not yet be practical for use in the egg industry. Hormone-induced moulting is another method and involves the use of the gonadotropin-releasing hormone (Gn-RH) agonist. It has an advantage over the conventional feed restriction procedure in that it does not require severe initial body weight loss to attain maximum egg production in the post-moulting period.

The phenomenon of compensatory growth in broiler chickens subjected to early life undernutrition is reviewed. Increased interest in this concept is attributed to problems associated with early life fast growth rate, especially in broilers fed ad libitum. These problems include high body fat deposition, and a high incidence of skeletal and metabolic disorders. Factors that influence compensatory growth in the broiler chicken include the nature, severity and duration of undernutrition, as well as the age at the commencement of undernutrition and the degree and pattern of realimentation. Many studies have reported improvement in feed efficiency during compensatory growth in restricted-refed broilers. Broiler chickens undergoing compensatory growth also exhibit greater than normal feed intake relative to body weight and some associated digestive adaptation. The use of this concept to address problems associated with early life fast growth rate requires more studies of the nutrition of the broiler chicken during the period of growth compensation.

The physicochemical properties of non-starch polysaccharides (NSPs) are responsible for their antinutritive activities in the broiler chicken. In particular, soluble viscous NSPs depress the digestibilities of protein, starch and fat. On the other hand, insoluble and non-viscous NSPs may have a beneficial effect. Fat digestion is used here to illustrate how the physicochemical properties of NSP may interfere with digestion and absorption. It is suggested that the gut microflora can mediate the antinutritive effects of soluble and viscous NSP. It is concluded that the determinations of crude fibre and/or acid detergent fibre and neutral detergent fibre in feedstuffs are not appropriate for predicting and understanding the physiological action of NSPs in broilers. The determination of the in vitro solubility of NSP and the viscosity of the feed ingredient could become of major importance for ‘antinutritional’ evaluation. More research needs to be conducted to study the interactions of NSPs with the microbial activity in the intestinal tract of the broiler chicken.