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.

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.

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.

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.

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.

Poultry production systems are outlined under the social and physical environmental conditions of Ethiopia. The results of research on the performance of local domestic fowl and on the performance and adaptability of imported stocks and resulting crosses with native fowl are also assessed. Farmyard/backyard type production, in which native fowl scavenge for most of their food, predominates and is widespread in the rural community. Both state and privately owned commercial farms using imported stocks are beginning to develop around urban centres. The egg production and growth rates of native stocks are low. Under prevailing management conditions it has been found that crosses between native stock and imported White Leghorns, incorporating about 60% White Leghorn blood, perform better than either parent types.

In the UK consumers are becoming more aware of issues related to food quality. Food marketers face the problem of responding to these developments by offering products which are consistent with changing consumer preferences. It is therefore increasingly important for marketers to understand the nature of consumers' preferences. This study focuses on the preferences of egg purchasers and uses conjoint analysis to identify consumer preference segments in the market. The analysis reveals that the preferences of consumers are very heterogeneous, but that it is possible to identify segments with distinct preferences for particular egg attributes.