Electrical waterbath stunning is the most common method used to stun poultry under commercial conditions. The voltage supplied to a multiple bird waterbath stunner must be adequate to deliver the required minimum current to each bird. High frequency (> 300 Hz) electrical waterbath stunning needs further investigation to determine its efficiency. It should always be followed by a prompt neck cutting procedure where all the major blood vessels in the neck are severed. Irrespective of the waveform or frequency of the currents employed, constant current stunners should be installed under commercial conditions to ensure that the minimum currents are delivered to individual birds in waterbath stunners. Head only electrical stunning of poultry is being investigated in detail and there is scope for commercial development. Important features include (a) a constant current capable of delivering a preset current, (b) a bird restraining conveyor and head presentation devices enabling the stunning tongs to be accurately placed, (c) more effective electrical stunning tongs in terms of delivering necessary currents while using low voltages, and (d) induction of cardiac arrest immediately after stunning to eliminate wing flapping. Stunning/killing of poultry still in their transport containers using gas mixtures would appear to be the best future option as far as bird welfare is concerned. However, birds can also be stunned/killed on a conveyor using gas mixtures, thereby eliminating the stress associated with the shackling of live birds before electrical stunning. Under the conveyor system birds should be presented to the gas mixtures in a single layer. Within gas mixtures a minimum of 90% argon in air would appear to be the first choice. A mixture of 30% carbon dioxide and 60% argon in air is better than using a high concentration of carbon dioxide in air, and is therefore considered to be the second choice. A two stage system that involves firstly stunning broilers with a low concentration of carbon dioxide and then killing them with a high concentration of carbon dioxide can be used by those who wish to use this gas for economic reasons. The two stages should be distinctly separated so that the birds are stunned well before exposure to a high concentration of carbon dioxide in air. In comparison with carbon dioxide alone, a mixture of 30% oxygen and 40% carbon dioxide in air prolongs the induction of anaesthesia and the exposure time required to kill the birds. The addition of oxygen to carbon dioxide may therefore not have any benefit to bird welfare or the processors. Mechanical stunning of poultry using penetrating captive bolts or non-penetrating mushroom headed bolts has been developed. However, stunning with these devices results in very severe wing flapping and further research is necessary to find ways of alleviating this problem.

Immunological control is recognised as the only major practical alternative to chemotherapy for the control of coccidiosis. Initial hopes that it would be possible to develop a genetically engineered vaccine against Eimeria species have not yet been realised, and there is therefore renewed interest in the development and application of vaccines based upon live parasites. Recognition that existing drugs are not as effective as in the past, that few new drugs are currently under investigation, and that the inclusion of drugs in the feed may be restricted in the future has focused attention on the need for new vaccines. Although considerable research has been undertaken on the basic mechanisms involved in the acquisition of immunity, very little attention has been given to the practical aspects of vaccination. In order for an anticoccidial drug to be successful, it is necessary to generate considerable information on efficacy and safety. With few exceptions, little information is available to support the use of coccidiosis vaccines. Hopefully, the introduction of new vaccines and improved application methods will encourage manufacturers to generate more information concerning their products. In future, coccidiosis should be controlled by adopting an integrated approach where drugs and vaccines are both used to prevent this disease. In addition to immunisation, a possible advantage to the application of certain vaccines is that their use could repopulate a poultry house with drug-sensitive organisms. Theoretical rotation programmes, in which the use of drugs is alternated with that of vaccines, are described.

Haemorrhages in the muscles of broiler chickens are major quality defects which occur in all types of muscles and muscle parts. They are closely related to muscle injury and can be the result of trauma, strenuous muscle activity, exposure to extreme environmental conditions, restraining and electrical stunning. In this review the different types of haemorrhages are classified. A brief introduction on muscle morphology and blood supply is given to discuss the mechanisms that may cause haemorrhages and a survey of these mechanisms is presented. Some of the mechanisms, together with factors likely to affect the susceptibility of chickens to haemorrhages, are discussed in relation to rearing, transport, slaughter and processing of broiler chickens.

Poultry have four types of cone in the retina of the eye, and this means that they probably see colour differently from trichromatic humans. Notwith- standing the fact that humans and birds have maximum sensitivity in a similar part of the spectrum (545–575nm), poultry are likely to perceive light from various types of lamp at a different intensity from humans because they are more sensitive to the blue and red parts of the spectrum. Although colour has been confounded with illuminance in many trials, wavelength has an unquestionable effect on poultry production and behaviour. Growth and behaviour responses depend principally on retinal photoreception, whereas photosexual responses are mainly influenced by hypothalamic light reception. In turkeys and chickens growth under red illumination is inferior to that under blue or green light, and this may be a result of birds exposed to red light being more active and showing more aggression than birds exposed to shorter wavelength radiation. In contrast, the easier penetration of longer wavelength radiation to the hypothalamus makes red light more sexually stimulatory than blue or green, although the hypothalamic photo- receptors are more sensitive to blue/green light when illuminated directly. Egg production traits, however, appear to be minimally affected by wavelength.

Wheat is a major raw material included, often at high rates, in diets for poultry in many countries throughout the world. Although traditionally regarded as having moderately uniform nutritional value, evidence is accumulating that there is considerable variablility in apparent metabolisable energy (AME) values, particularly eith young birds. Considerable effort has been expended in attemting to explain why this should be so, and to develop laboratory procedures whereby it may be predicted. Much attention has been focused on the non-strach polysaccharide (NSP) fraction. The major constituent of wheat is strach which is consequently the principal energy yielding component. Any factors which influence starch digestibility will therefore exert an impact on AME. Strong positive relationships between starch digestibility and AME have been established. An in vitro system has been developed which demonstrates that extrinsic rather than intrinsic factors are responsible for variations in the digestibility of starch in vitro as it has been shown that straches isolated from wheats with low AME values are hydrolysed to a similar extent in vitro as straches from wheats with high AME values. Differences in starch hydrolysis in wheat meals in vitro (i.e. strach in situ) were observed between high and low AME wheats, suggesting that, following subsequent validation, the system may offer considerable potential as a means of characterising wheat for broilers.

As a consequence of selection and improvement in rearing and nutrition management, the characteristics of poultry production have changed dramatically over the last decades. Decreasing the age of birds at slaughter has altered the intrinsic sensory attributes of meat. Selection has also provided birds with increased muscle yield, altered muscle structure and metabolism. In broilers there are examples to suggest that such selection has had no detrimental effect per se on meat quality. Results in turkeys are more equivocal and suggest that increased performance may alter meat quality. Pre- and post-slaughter processes affect the ante-mortem physiology of the birds and the post-mortem metabolism of muscle, and can cause irreversible defects in subsequent meat quality. Production of optimal quality poultry meat depends on controlling both farming and slaughter-related parameters and understanding the complex interactions between them.

In Switzerland eggs have not been produced in battery cages since January 1992. During the 10 year period from 1981 farmers replaced their battery cages with deep litter, aviary and grid-floor systems and modified cages. However, the cages used to replace the conventional battery cages and most of the grid– floor systems did not fulfil the requirements of the Swiss Welfare Act and they were not permitted to be advertised or sold thereafter. Sixteen years after the ban on battery cages, the Federal Veterinary Office has undertaken a survey to determine how laying hens are kept in Switzerland and how the alternative systems have fared. The survey was carried out on 96 randomly chosen farms with at least 500 hen places to find out more about the housing conditions, management processes, status and performance of hens. The results show that aviaries are very common in Switzerland (65% of the laying hens) and that the laying performance in these systems is significantly higher than that in grid– floor systems and similar to that in battery cages. Provision of a protected outdoor area is a valuable benefit. To be successful with aviary systems it is necessary for pullets to spend the rearing period under similar housing conditions.

Modern fowl breeder production has resulted in a wide disparity between the environment, mating behaviour and morphology of modern breeds in comparison with progenitor species. The environment is strictly controlled in most respects and dim lighting is maintained with luminaires that were originally designed for humans and that differ substantially in terms of intensity and colour balance from natural daylight. The elaborate mating displays observed in feral poultry and red jungle fowl rarely, if ever, occur in breeder houses. In most avian species females choose the males, whereas cockerels in breeder houses often appear to mate forcibly and aggressively with hens in the absence of any assessment by the hen. Cockerel and hen breeder fowl also differ morphologically from their progenitor species through genetic selection (larger and heavier) or mutilations (dubbing, etc). Given the apparently large differences between the subtle, gradually evolved mating ‘ecology’ found naturally and the production environments found commercially, it is perhaps surprising that little consideration has been given to this disparity in modern breeder production environments. An understanding of the factors governing choice of mate in commercial breeder houses and the influence of the visual environment may highlight novel methods whereby efficiency of these enterprises can be improved and elements of the welfare of breeder fowl assessed.

Ostrich chick production is highly management intensive. An artificial production system should be able to provide adequate protection to ostrich chicks up to four weeks of age. Factors influencing the successful growth of chicks include the provision of proper housing, adequate ventilation, exemplary hygiene and correct dietary requirements. Inadequate nutrition is commonly the cause of microbial infections. It is important for the producer to do an accurate on-farm cost management appraisal, the greatest variable production cost being feed. There is need to generate more finance for further research on ostrich chicks, and the development of an integrated system between producers, ostrich producer associations and industry in order to maximise productivity and economies of scale.

An important objective of the least cost formulation of broiler diets is to provide sufficient amounts of the most limiting amino acids to support the needs of tissue maintenance and accretion while minimising any excesses. Threonine is the third most limiting amino acid in broiler diets behind the total sulphur-containing amino acids and lysine. Research into the threonine requirement of broilers is sparse compared with that of methionine and lysine. However, recent work on the threonine needs of growing and finishing broilers has been invaluable in helping commercial nutritionists determine the minimum amount of threonine required in least cost diet formulations. This review summarises this recent research. It also considers threonine needs for optimal immune system functions, feather growth, glycine requirements and gastrointestinal functions, as well as under conditions causing heat stress.

This paper details the post-mortem changes that take place in the muscular tissue of poultry and the consequences of these on the resulting meat quality at the point of consumption. The history of the development if the modern meat type chicken, the form and function of its muscles, the factors that determine muscle growth and their effects on meat quality are all described. Past studies tend to have been concentrated on the processes occuring in mammalian tissue and those mainly on beef, with little attention being directed at the changes taking place in poultry muscle. In this context the view that modern broilers grow “at the edge of what is metabolically possible” is important. This hypothesis owes its origin to the fact that muscle, and thus protein, accretion is accomplished through a dynamic equilibrium between synthesis and degradation. Evidence is provided to show that the muscle cell reaches a certain maximum synthesis capacity, to grow beyond which requires it to decrease its rate of degradation. This property is possibly of considerable influence in meat ageing and forms the basis for the proposition that the breast muscle of poultry is especially suited to study the effects of post-mortem proteolytic degradation on meat ageing and product quality.

The aim of this experiment was to develop an alternative, acceptable and humane method for killing broiler chickens. Our main premise was that euthanasia should preferably take place in two steps. Firstly, the bird should be anaesthetised quickly and completely using appropriate procedures and, secondly, the anaesthetised bird should be killed as quickly as possible. Two gas mixtures were considered for anaesthesia: 40% carbon dioxide with 30% oxygen and 30% nitrogen or 40% carbon dioxide with 15% oxygen and 45% nitrogen. It was found that the birds' behaviour in the high oxygen environment was less disturbed, with less agitation and distress being demonstrated. For this reason, the high oxygen condition is to be preferred and this anaesthetic was used in the second part of the experiment. The bird was exposed for one minute to 40% carbon dioxide, 30% oxygen and 30% nitrogen (anaesthesia) and then to 80% carbon dioxide, 5% oxygen and 15% nitrogen (euthanasia). This condition was compared with the frequently used eutha- nasia condition involving argon. The use of argon is based on the idea that it produces fast suffocation of the birds. The argon condition consisted of 30% carbon dioxide and 60% argon in air with less than 2% oxygen and 8% nitrogen. The chickens died significantly later in the oxygen/carbon dioxide condition than in the argon condition. Judgements of death were based on both the pattern of electrical brain activity and on heart rate. The time taken for the chickens to become unconscious, as judged from the isolectric electroencepha- logram, was also significantly longer in the oxygen/carbon dioxide condition than in the argon condition. However, in the argon condition the birds immediately showed strong signs of agitation and distress, particularly intense and heavy muscle contractions, whereas these signs were less pronounced in the oxygen/carbon dioxide condition. It is concluded that, although the chickens lost consciousness sooner and also died sooner in the argon condition, there are good reasons to prefer the oxygedcarbon dioxide condition because it results in less disturbed behaviour and the birds exhibited milder signs of distress during the period when consciousness cannot be fully excluded. Hence, a milder death, taking somewhat longer, is preferred to a quicker but more distressing death. Finally, the oxygen/carbon dioxide condition was repeated with turkeys when, in general, the results were the same.

A total of 215 indigenous chickens were found in 10 homesteads visited in Oodi, Kgatleng, Botswana from June to July 1999. The mean (SD) flock size was 21.5 (11.6) with a range of 7–47. The chickens were not housed but instead spent the night on top of trees to escape predation. Vaccinations against poultry diseases such as Newcastle disease were not carried out. Instead, traditional herbal remedies were used to treat sick chickens. Only a few adult birds were infested with scaly leg mites and fleas. Worm eggs were not detected in faecal samples examined but some coccidial oocysts were seen. Antibodies to avian infectious bronchitis, infectious bursa1 disease, Mycoplasma gallisepticum and egg drop syndrome were demonstrated in some of these chickens, suggesting previous infections or exposure.

Studies with germ-free chicks and antimicrobial compounds have indicated the significance of the interaction between host nutrition and the intestinal microflora. This interaction has suddenly leapt to prominence as a result of the decision of the European Union to remove several antibacterial agents from use in animal feed. A consequence of this decision has been a loosening of some of the constraints on intestinal bacterial growth rates which will benefit from the use of slowly digested ingredients, because undigested feed is a potential substrate for bacterial fermentation. The use of poorly digestible ingredients runs the risk not only of poor performance, which has always been the case, but now there is an additional danger from bacterial overgrowth and subsequent disease/intestinal disorders. Variations in the nutritional quality of the ingredients are therefore of increased relevance, and any measures that reduce such variations are likely to be of benefit. As a result, the use of enzymes, which are known to reduce variations in the performance of birds fed on barley-, wheat- and maize-based diets, will need to be revisited, particularly with reference to correct dosage. In the past the use of antibiotics effectively reduced the need to consider enzyme use and dose. Coccidiosis control is also of great interest because of its association with necrotic enteritis. Prevention of coccidiosis and limitation of the damage to the intestines associated with this disease is of paramount importance if necrotic enteritis is subsequently to be avoided. As a result, the use of coccidiostats for direct control and betaine and other pronutrients for amelioration of the symptoms is receiving greater attention. Ultimately it is hoped that nutritional control will lead to microbiological control, allowing for more consistent production responses in the absence of antibiotics.

Atmospheric ammonia is a major aerial pollutant of poultry buildings. The current exposure limits for ammonia of 25ppm are set on the basis of human safety rather than animal welfare. This paper reviews the evidence for ammonia exposure affecting various aspects of poultry welfare. The reviewed evidence suggests that ammonia exposure (1) causes irritation to the mucous membranes in the eyes and the respiratory system; (2) can increase the susceptibility to respiratory diseases; and (3) may affect food intake, food conversion efficiency and growth rate. The behavioural effects of ammonia on poultry have recently been investigated and suggest that there may be a threshold for ammonia detection or aversion at or below the current exposure limit. The available evidence for the effects of ammonia on poultry welfare should be considered when setting future guidelines for ammonia exposure in poultry houses.

This paper describes the rural poultry production system and the role of scavenging chickens in the rural household economy of Ethiopia. Past attempts that have been made to improve the production and productivity of local birds through upgrading (distribution of exotic birds) and cross breeding in Ethiopia are assessed. The merits and demerits of the different ecotypes of indigenous chicken and their crosses are discussed. The current significance and future role of indigenous birds in the face of extensive importation of exotic birds are appraised. Finally, future areas for research on indigenous chickens are identified in terms of the development of a sensible conservation programme and the utilisation of local chickens as genetic resources.