The biological function of the egg shell is as a chamber for embryonic development and from which the chick is able to emerge at the appropriate time. The characteristics which serve this purpose in an optimum way are quite different from the requirements of the table egg industry. Among the challenges imposed by commercial egg production and marketing is the ability to resist fracture damage. The industry sustains economic loss from cracked eggs and at least some of the cracking can be attributed to deficiencies in shell structure. While early research concentrated on the thickness of the shell, more recently there has been an increased emphasis on its fine structure and shape. Egg shell strength has been the subject of much research, but relatively little attention has been paid to the relationship of strength and other shell parameters to breakage under commercial conditions. Where this has been studied, the power of shell measurements to predict breakage has been found to be low. The ultrastructure of the shell has been studied during the past 25 years and this has led to extensive gains in understanding. In the case of the mammillary layer, knowledge has been advanced following the use of plasma etching and scanning electron microscopy. Several structural anomalies have been described which significantly affect shell strength and resistance to breakage. The use of finite element analysis has made possible a definitive description of shell shape and led in turn to useful work on crack generation and shell failure. Studies of the protein content of the shell, which may be an important factor in its crystal growth and structure, are also contributing to our understanding of egg shell architecture.

Research findings on indigenous guinea fowl in Nigeria and the constraints on the local production are discussed. The most pressing problems include low hatchability, high mortality up to eight weeks, lack of reliable advice on veterinary and other problems and a shortage of sources of hatching eggs and young stock. In addition to early mortality, which may be as high as 60%, the characteristic timid, but very active, flighty and noisy temperament probably contributes to poor feed conversion efficiency through high energy output and feed wastage. Nigerian guinea fowl tend to be slow growing, weighing less than 1 kg at 8 weeks of age, and do not come into lay until about 1 year of age. Although monogamous in the wild, a sex ratio of 1:4 can give good fertility. Egg production is confined to the rainy season from April to October. Sex identification presents an enormous problem for most guinea fowl farmers. The nutrient requirements of native guinea fowl have not been established, making it impossible to be sure that balanced diets needed for optimum production are fed. The most important intestinal parasites are Eimeria sp., Ascaridia galli, Heterakis sp. and Capillaria caudiflata. The main external parasites are lice (Damalina sp. and Argas persicus).

Four consistent stock brand names of white egg shell laying fowl were compared with four such stocks laying brown shelled eggs. Data were derived from the Combined Summaries of European Random Sample Egg Production Tests (ERSEPT) 1979-1992 and from the North Carolina Layer Performance and Management Test (NCLPMT) 1984-1992. In the former, laying performance was recorded from 141 to 500 days of age and the data were based on annual means derived from about six testing stations, while the latter involved one testing station with recording over two cycles of production from 140 to 434 days and from 435 to 728 days (which included a moult). Although identical stocks were not available in both continents, results for egg mass show a similar initial superiority for the white egg shell stocks. This advantage decreased over the years and changed to an advantage for the brown egg stocks of about 0.5 kg in the ERSEPT and 1.1 and 0.7 kg, respectively, in the first and second cycles of the NCLPMT. In the ERSEPT the white egg stock advantage in terms of feed to egg mass ratio decreased. This can be attributed to greater genetic gains by the brown egg stocks whose final body weight declined (from 510 g to 270 g above that of the white egg stocks); increased mean egg weight (with the gap between the stock types widening from 2.3 to 3.3 g); and to some extent, earlier sexual maturity, as indicated by decreased age at 50% production. Results of the NCLPMT also show that the improved egg mass for the brown egg stocks was achieved by closing the gap in hen-housed production (20 eggs per bird) while maintaining an egg weight superiority of 3.4 g. The improvement in performance was particularly evident in the first production cycle. In the second cycle the brown egg stocks showed higher mortality rates, together with increased food consumption and a smaller egg size advantage. In both production cycles the brown egg stocks were characterized by much higher levels of meat spots.

The advantages of offering poultry a choice between compound feed and whole cereals are generating considerable interest. This review summarizes studies which have been conducted to evaluate the ability of birds to select a diet in which one feed consists of a cereal. Both growing and laying birds need a period of learning or adjustment before becoming proficient when given a choice of foods. Previous experience and social interactions influence the way in which they adapt to choice feeding. The production performance of birds is not affected by the type or form of the grain or protein concentrate used in free choice feeding. However, these may affect intake and the efficiency of utilization of some nutrients. Practical feeding systems in which feeds are given separately, in one through, or sequentially are presented. Theoretically, there is every reason to believe that feeding whole grain has great potential, but practical evidence is still scarce. The advantages and disadvantages of choice feeding using whole wheat and the economic consequences of feeding wheat were investigated. Some progress has been made in the last decade but continued investigation is needed if significant improvements in economic efficiency and bird welfare are to be made. Such questions as to whether to feed a high-protein food or a conventional food in a choice with whole grain, and whether these should be fed separately or mixed together, have yet to be fully answered. Until then, feeding a conventional food diluted progressively with cereal grains to a maximum of about 35% is beneficial for both poultry producers and individual birds.

In most European countries barley (Hordeum vulgare L.) is an important feedstuff for poultry, and its use could increase with changes in economic circumstances. Compared with wheat, barley contains more fibre and less energy. The nutritive value and suitability of this grain as a feedstuff for growing poultry are more or less affected by varying β-glucan concentrations. The anti-nutritive effects of β-glucan in the gastrointestinal tract of young chicks can be avoided by adding β-glucanase of microbial origin to barley-containing or barley-based diets, thus making this grain crop acceptable for broiler fattening diets. Feed mixtures for layers may contain a higher proportion of barley without negative effects on egg production. When formulating diets, the low content of linoleic acid has to be considered.

The paper reviews the literature on vaccines against infectious coryza of chickens. Our knowledge of natural immunity, antigens involved in protection and the degree of cross-serovar protection provided by vaccines is summarized. The effect of variables such as antigen dose, inactivating agent and adjuvant type on vaccine efficacy is reviewed. The protective ability of a new generation infectious coryza vaccine based on a live attenuated strain of Haemophilus paragallinarum is discussed.

Small-scale oil expelling is a natural component of agricultural systems in the poorer African and Asian countries. This paper relates to the work of the Natural Resources Institute and the assistance it has given to the installation and operation of small-scale oilseed expellers in a number of countries including Zambia, Gambia and Sudan. A concept of integrated agricultural development is outlined comprising oilseed cultivation, small-scale expelling and poultry production. Consideration is given to differences in nutritive value of the oilseed meals produced, oilseed processing technology and the need for interdisciplinary research, coupled with co-ordinated strategies, in order to maximize the impact on farming communities which have desperately few resources.

At the Central Industries' laboratory in Mississippi, USA a total of 15 689 cases were diagnosed as positive for poultry diseases between 1970 and 1990. The average number of cases diagnosed per year was 784, ranging from 319 in 1974 to 1319 in 1989. A total of 52 diseases or conditions is included in the results of this survey. Each case was categorized into one of seven aetiological groups. The principal diagnosis over the 20-year period was bacterial diseases (6979 cases), followed by diseases of unknown aetiology (3660 cases), parasitic diseases (2515 cases), viral diseases (1121 cases), management errors (771 cases), nutritional deficiencies (339 cases) and fungal diseases (304 cases). Although the total incidence of disease did not appear to vary from one season to another, hot weather resulted in more skeletal diseases being diagnosed while fowl pox and ‘brooder pneumonia’ were most prevalent in cold weather. Tapeworm infestations were highest in the autumn.

Gizzerosine [2-amino-9-(4-imidazoyl)-7-azanonanoic acid] was isolated from a fish meal which caused black vomit in broiler chicks. Those given a diet containing fish meal which caused black vomit or synthetic DL-gizzerosine secreted excess gastric juice. The excess juice resulted in gizzard erosion and black vomit. In all the experiments, amongst chicks that died, those without gizzard perforation were greater in number than those with such lesions. It is considered that gizzard perforation by excess gastric juice is not the most serious lethal effect of gizzerosine. Chicks have been found to exhibit wide variation in sensitivity to gizzerosine. In a 4-week feeding trial of a fish meal that caused black vomit, 25 out of 100 died but nine grew normally. It should therefore be possible to estimate the maximum permissible concentration of gizzerosine in practical broiler diets. In the case of manufacturing facilities in which vapour is used to dry the fish meal indirectly, the conditions which avoid gizzerosine formation are known. It is desirable to determine safe conditions for fish meal drying when the process uses hot air heated by a flame.

Beak trimming remains a controversial subject. It has undoubted economic advantages for the producer, in particular by reducing the incidence of cannibalism and feather pecking, but the procedure is traumatic for the bird and deprives it of important sensory feedback from its beak. It can have harmful neuroanatomical consequences: although the tissue damage is repaired the sensory receptors are not replaced, neuromas may form and become a source of chronic pain. The danger of neuroma formation is reduced and may be absent if the procedure is performed only in young birds. Beak trimming results in both immediate and more persistent effects on behaviour, food intake and body weight. Trimmed birds are generally less active, show less behaviour involving pecking, eat less and grow more slowly than controls. These changes are primarily a consequence of the sensory deprivation. In caged medium hybrid layers and growing broilers beak trimming is difficult to justify, whereas the incidence of pecking damage is so high in light hybrids in multi-bird cages at high stocking densities that beak trimming is universal. A case can also be made for its continuation, on welfare as well as on production grounds, in floor-housed flocks of laying fowl and breeding turkeys. In these contexts it reduces mortality by inhibiting feather pecking, cannibalism and, possibly, aggressive pecking. In the long term beak trimming should be phased out and undesirable behaviour controlled by environmental means and by increased effort being devoted to the genetic selection of commercial stocks which do not engage in damaging pecking, either in cages or when floor-housed in large flocks.

Since the recognition of mycotoxicosis about 30 years ago, various research projects have been undertaken to develop measures to prevent or reduce the serious financial losses it causes. Although inhibitors which prevent mould growth and the production of toxic substances have been developed, several factors still limit their effectiveness and practical use by the feed industry. Various kinds of sorbent materials have also been assessed for their ability to remove or diminish the adverse effects of mycotoxins in animal feeds. Even though it does not bind all the mycotoxin and allows partial absorption of toxin in the gastrointestinal tract, hydrated sodium calcium aluminosilicate (HSCAS) is considered to be an outstandingly effective additive. Several new possibilities have emerged involving the use of the sulphur-containing amino acids, antioxidants, vitamins, trace mineral and other nutrients in building detoxicants. Research into methods of preventing mycotoxicosis in poultry needs to be carried out against the background of the underlying levels of mycotoxins found under the normal storage conditions for feed used in the industry.

This paper reviews the current state of knowledge of the avian basophilic leukocyte. It includes a description of the general morphology of the cell derived from light and electron microscopy. The relative and absolute counts of basophils in different species are described, including the current status of the cytochemical constituents in their characteristic granules. The role of the basophil during the acute inflammatory response following exposure to non-infectious and infectious agents is examined. In birds basophils appear to play an important role in early inflammatory and immediate hypersensitivity reactions, but differ from those in mammals by not contributing to delayed hypersensitivity. They are crucial participants in cutaneous basophilic hyper-sensitivity reactions and in passive cutaneous and systemic anaphylaxis. The role of the basophil in the stress response in birds is discussed. When some birds are exposed to severe stress a basophilia develops – a physiological response that may be unique to birds.

There are several empirical formulae that describe input and output relationships in egg production, but their applicability is restricted to specific genetic, nutritional and environmental conditions. Simplistic regression relationships are not an adequate basis for the optimization of complex, dynamic and highly interactive production systems. Mechanistic and dynamic models that describe causes and interactions between input and output relations are required. In order to evaluate nutritional requirements and to predict bird responses to the concomitant influences of the internal and external factors, the development of such models seems currently to be the most profound challenge in poultry science. This paper reviews current empirical systems for predicting nutrient requirements for egg production and discusses the advantages of incorporating mechanistic and dynamic elements.

From earliest times up to the present day, the anatomy of poultry has been depicted by artists whose work has been acclaimed for its scientific accuracy and for its artistic qualities. Six examples are presented that illustrate the lymphatic system, reproductive organs, skeleton, respiration, embryonic blood circulation and plumage.

Although it is generally assumed that stress is detrimental to the well-being of poultry, there are positive aspects which are often overlooked. In the context of evolution, stressors such as infectious agents, climatic extremes, and domestication processes play important roles in inter-population and intra-population genetic variability. Pathological, immunological and behavioural studies in both avian and mammalian species indicate that too much or too little stress is undesirable, and that a certain degree of stress is essential for maintaining normal biological functions. Prior stressful experiences, particularly during the neonatal stage, may have long-term benefits in helping an individual to cope with subsequent stressors. Reliability of stress indicators and their variability at both population and individual levels is a major factor in attempting to quantify ‘optimum stress’.

The problems of predicting the growth, body conformation and feed intake of a flock of growing chickens are analysed in order to identify the key components needed to produce an effective model. Distinctions are made between the problems of a bird at one time, a bird over time, and a group of birds at a time. When considering a bird at a time a series of sub-problems is identified, including the prediction of the potential for growth and the way in which body composition should be taken into account. Given solutions to these problems, those of predicting the requirement of the bird for the resources of energy and nutrients for maintenance, growth and fattening then arise. For a bird fed ad libitum the rate of feed intake needs to be accurately predicted by the model if it is to be successful in predicting growth rate and efficiency. An approach to this problem is outlined, together with an initial approach to the problems raised when attempting to model populations of birds.