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.

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.

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.

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.

Broiler chickens and laying hens are intensively selected for productive traits. The management of these highly productive animals must be optimal to allow their full genetic potential to be expressed. If this is not done, inefficient production and several metabolic diseases become apparent. The causes of the latter are multifactorial but diet and, particularly, interactions between diet, other environmental and genetic factors play an important role. An imbalance between oxygen supply and the oxygen required to sustain rapid growth rates and high food efficiencies causes ascites in broiler chickens. It is clear that several nutritional factors, the amount of food given, its physical form and the composition of the diet have a major impact on the occurrence of ascites and sudden death syndrome in broiler chickens. Furthermore, the possible involvement of structural endogenous factors such as proportional changes in the respiratory and cardiovascular systems, shifts in the glyco1ytic:oxidative muscle metabolism ratio, and structural changes within the lung capillary system cannot be excluded. In addition, functional causal factors, such as the hypothyroid state associated with decreased maintenance metabolism as a result of the selection for fast growth rate and improved food efficiency, are likely to be involved. Both structural and functional causal mechanisms may already be initiated during the embryonic stage.

Poultry manure and litter have the potential to be either land resources or pollutants of surface and ground water as well as giving rise to unpleasant odours. Provided proper attention is paid to nutrient management, they can be used as fertilisers, soil amendments and feed ingredients. Furthermore, the contents of nitrogen, phosphorus and other minerals in poultry manure and litter can be reduced by paying careful attention to diet composition – for example, by applying the concept of ideal protein, supplementation with synthetic amino acids, the addition of various types of enzymes including phytase, the lowering of the protein and phosphorus contents and the use of highly available sources of supplementary phosphorus and vitamin D. Good nutrient management also depends on obtaining representative samples of feed, manure, litter, water and soil from each handling system and having these analysed on a regular basis in a reliable laboratory. This not only ensures that proper quantities of nutrients are added to the native soil on which the crops that are ultimately to be used as feed sources are to be grown, but also means that lower amounts of nitrogen, phosphorus and other elements are present in the feed. One outcome of the latter effect is that the poultry manure and litter excreted contains fewer potential pollutants and reduces the criticism levelled at the poultry industry that it runs roughshod over environmental concerns. It would be beneficial if all of these analytical procedures were handled in one laboratory specialising in animal agriculture with specialists advising farmers on how best to apply the analytical data.