Avian eggshells are natural composite bioceramics containing organic and inorganic phases. The occurrence and role of particular collagens and proteoglycans in the eggshell and their pattern of secretion by the oviduct is discussed. While type X collagen, the main constituent of the shell membranes, functions to inhibit their mineralisation, mammillan, a mammillary keratan sulphate proteoglycan, is involved in nucleation of the first calcite crystals of the shell and ovoglycan, a unique dermatan sulphate proteoglycan, is involved in the growth of the crystalline palisade. Eggshell biomineralisation is effected by specialised oviduct cell populations in a defined topographically and temporally regulated process.

This paper describes the patterns of embryonic mortality in poultry species and summarises the various causes of mortality. Descriptions of the morphological stages of development at each of these time periods are given. Data are presented describing factors affecting development at oviposition, egg storage and incubation.

Drug and pesticide residues in edible poultry tissues and eggs are a human food safety concern. Quantifying and predicting the concentrations of residues in eggs is a particular challenge because of the unique aspects of egg development and compartmentalisation of the yolk and white. For a number of years, research efforts have been directed at examining residue incorporation nto eggs and developing models to predict residue incursion. This paper will review the physiology of egg yolk formation as it relates to residue incursion, the models developed to understand and quantify residue patterns, and the use of magnetic resonance imaging to detect residue incorporation into eggs.

The main advantages of battery cages for laying hens over alternative husbandry systems are (1) increased hygiene resulting in a much lower incidence of diseases in which the infectious agent is spread through the droppings, (2) small group size resulting in a low incidence of social friction, (3) ease of management, (4) absence of litter problems, (5) better working conditions, and (6) a much lower cost of production. The disadvantages are (1) lack of physical and psychological space for the hens, (2) lack of exercise resulting in a higher incidence of metabolic disorders, (3) lack of nesting opportunities resulting in severe frustration for many birds each time an egg is laid, (4) lack of dust bathing opportunities which, although not a severe disadvantage, should still be charged to cages, (5) lack of other behavioural opportunities which again seem not to be a severe disadvantage and which await further elucidation, and (6) a higher incidence of foot lesions.

Genetic engineering holds out great promise for the development of improved poultry vaccines. Engineered microbes containing foreign genes from several pathogens provide the basis for multivalent vaccines. The vaccine vector should be non-pathogenic and capable of incorporating and expressing foreigngenes. Subunit proteins expressed by non-avian vectors, such as baculoviruses, can be used to evaluate the nature of their antigenic and protective properties and could find use as subunit or virus-like particle based vaccines. Live recombinant viruses can also be used as vaccines. While RNA viruses such as picornaviruses have been used as vectors, DNA viruses are more easily engineered. Avian poxviruses expressing the Newcastle disease virus (NDV) haemagglutin neuraminidase (HN) and fusion (F) proteins protect against Newcastle disease. Because of their ease of administration through the feed or water, their ability to establish mucosal immunity, and recent advances in genome manipulation, avian adenoviruses are now being developed as recombinant avian vaccines. A recombinant fowl adenovirus expresses a green fluorescent protein reporter gene cloned into a non essential TR-2 region of viral DNA and is also immunogenic. Current efforts are directed at incorporating genes, such as HN from NDV, from avian pathogens into this vector. Genetic engineering can also improve diagnostics. For example, recombinant HN can be used in enzyme-linked immunosorbent assay (ELISA) based NDV diagnostic kits. Baculovirus expressed NDV nucleoprotein (NP) used in a differential ELISA can differentiate between birds immunised with a fowl pox virus expressing NP and NDV infected birds. Polymerase chain reaction (PCR) also has an impact on avian health. PCR can be used in diagnostics and, because of its extreme specificity, in epidemiological studies. Rapid and accurate identification and emerging or re-emerging microbial diseases are some challenges that can be more readily addressed by the application of molecular approaches including genetic engineering. Similarly, the development of multivalent and multi-pathogen vaccines through genetic engineering is certainly a realistic objective. Such vaccines would provide multiple protection in a cost effective manner.

The eggshell of the hen is a highly ordered, mineralised structure deposited within an acellular milieu – the uterine fluid secreted by the distal oviduct. Spherulitic crystal growth is initiated by deposition of calcium carbonate on aggregates of organic material present on the outer surface of the eggshell membranes. Gel electrophoresis reveals a complex array of proteins in uterine fluid and eggshell extracts. The eggshell matrix proteins can be classified as egg white proteins (lysozyme, ovalbumin, ovotransferrin, clusterin), bone protein (osteopontin), or proteins specific to the uterus and eggshell (ovocleidins-17 and –116; ovocalyxins-32 and –36). Eggshell extracts, uterine fluid and purified fractions are able to modify the morphology of calcite crystals in vitro. In young hens the breaking strength of the eggshell is inversely related to the degree of calcite orientation. Conversely, reduced strength in eggshell from aged hens coincides with a high variability in crystallographic texture. In guinea fowl the exceptional mechanical properties of the eggshell are explained by an increase in the amount of eggshell produced and particular features of the crystallographic texture. These observations suggest that the eggshell matrix influences the process of crystal growth by controlling size, shape and orientation of calcite crystals. This structural control probably contributes in a substantial manner to the mechanical properties of eggshell.

Hatching birds which have been dependent on the yolk for their energy supply during much of the embryonic period must undergo a rapid transition to utilising carbohydrate rich exogenous feed. This change is accompanied by the preferential growth of the small intestine and activation of digestive enzymes and absorption pathways. The ontogeny of these processes is described and includes the intense development immediately after hatching. The effect of delayed access to feed on intestinal development is also discussed.

Agricultural commodity group scholarships are viewed as recruitment tools. Career choices of poultry scholarship recipients on the west coast of the USA were analysed. Responses of recipients who entered non-poultry careers included reports of how they use information from mandated poultry courses, how they informally educate others about poultry, and how they volunteer with poultry youth programmes. Teachers told of using poultry examples in class. Other professionals gave accounts of disseminating positive poultry information in the course of their work. Poultry and other agricultural trade associations realise many unforeseen benefits by supporting worthy students, even when the students do not enter an agricultural career.