The constant economic pressure on poultry producers to lower their costs and increase the quality of their products has been a big challenge in today's competitive world. Moreover, the confirment of turkeys has been linked with several kinds of breast skin lesions, mainly enlarged sternal bursa (ESB), or breast blister, and focal ulcerative dermatitis (FUD), or breast button. Both of these conditions (particularly ESB) are believed to cost the turkey industry large amounts of money each year because of the need to trim the breast and the consequent downgrading of the carcass. In addition, they cost the processing plant time by slowing down the production line beacuse of the need to employ more personnel to carry out the work of breast trimming. This paper reviews investigations into the possible causes of the lesions and concludes that many factors (strain, early body weight, photoperiod, stress, litter and floor type) influence their development.

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.

Exogenous enzyme supplements are used widely in poultry diets in an attempt to improve nutrient utilisation, the health and welfare of the birds, product quality and to reduce pollution as well as to increase the choice and content of ingredients which are acceptable for inclusion in diets. Considerable advances have been made during the last decade in the manufacture, activity, quality, thermostability and specificity of supplemental enzymes for use in poultry diets. This paper attempts to give an overview of the advantages and disadvantages, as well as the interesting difficulties and variable effects observed when enzymes are added to poultry diets.

Phytate is a molecule rich in phosphorus (P). However, the P in phytate is of low availability to monogastric animals because they lack the proper enzyme system to hydrolyse phytate. Consequently, there is a high P concentration in the manure from animals fed on diets containing phytate, and this can lead to pollution of the environment. Because phytate can complex with minerals, starch, proteins and digestive enzymes, it also has anti-nutritional properties. Limiting the P output by monogastric animals, by increasing the digestibility (availability) of the P in the diet by hydrolysing phosphate from phytate, was the original reason for developing the microbial phytase, Natuphos®. It has been shown in many studies that P excretion by pigs and poultry can be reduced by 30% by including phytase in their diets. The digestibility of other nutrients bound to phytate can also be increased considerably by hydrolysis of the phytate molecule by phytase. A number of studies have been performed in poultry and pigs to determine the effect on amino acid digestibility of adding microbial phytase to the feed. In general, an increase of 1-3% has been reported. It was shown by meta-analysis that these improvements were significant for most amino acids at a phytase supplementation rate of 500 FTU/kg diet. In piglets and broilers an improvement in performance of 1.5-3.0% was often observed when phytase was included in the diet, even if the diet met the digestible/available P requirement. This improvement in performance cannot be explained by improvements in amino acid digestibility alone. It has been suggested that there is an effect on energy utilisation as well, and this has now been confirmed in studies with poultry. To apply this information in feed compounding, matrix values are proposed for use by the industry in linear programming. Depending on many factors, feed costs can be decreased by up to EUR 3.50 (US$ 3.00)/tonne by the addition of phytase to diets that are not limiting in P. Limiting the total P content in the diet to a lower concentration can increase the economic advantage of adding phytase. Processing of feed, especially pelleting, can reduce the activity of phytase. It is therefore necessary to protect the enzyme and this can be very difficult, especially when it is important that the enzyme should also become rapidly available to the animal. The product Natuphos® 10000 G fulfils these requirements. The broadness of the impact of this enzyme on the nutritional value of feed makes it a really remarkable enzyme.

The quality of the day-old broiler chick is foremost in the minds of many poultry managers. From fertilised ovum to the placement at the broiler farm, some factors such as the characteristics of the incubating eggs, the egg holding conditions, the incubation conditions and the conditions that exist between hatching and placement at the farm and their interactions may affect chick quality. It may be questioned if maximal hatchability is the best indicator for chick quality and/or post-hatching viability, even if optimal hatchability is considered a prerequisite for successful incubation. The environmental conditions during incubation (e.g. the temperature, humidity and ventilation rate (carbon dioxide concentration)) are not set independently from each other, although each may have its own optimum for hatchability and chick quality. These optima for each incubation factor may alter differentially according to the characteristics of the incubating egg. It is concluded that more independent control as well as more control of the variability of the classical physical conditions in the incubator are required in order to improve hatchability and chick quality.

The egg yolk contains several substances of potential therapeutic value, some of which are already used in commercial products. A number of scientific papers dealing with their properties and applications have been published. In this review we present some current and possible applications for egg yolk lipids, lipoprotein, phosvitin, sialic acid and antibodies (IgY). Moreover, we discuss the possibilities of increasing the yield of yolk and simultaneously the yield of these substances by both management and breeding approaches.

The use of non-starch polysaccharide (NSP) degrading enzymes as feed additives has consolidated around their application to barley- and wheat-based diets for broiler chicks. Only with this application has a good understanding of their mode of action been developed and reasons for their effectiveness established. Most of the effect of NSP degrading enzymes can be ascribed to reversing the increase in digesta viscosity caused by polysaccharides leached from grain cell walls. Because digesta viscosity is greatest in the youngest birds and decreases with age, the value of supplementary enzymes for older birds is limited to secondary and less well defined effects. These include the release of nutrients otherwise entrapped in the cellular matrix of the feed. Maize alone amongst the commonly used cereals does not appear to release soluble NSPs in amounts sufficient to produce a detectable depression in performance. However, maize is not a homogeneous commodity and for some samples this may not be the case. Use of NSP degrading enzymes with legume seeds can improve nitrogen retention but effects are generally small. The structures of the soyabean NSPs, particularly the pectic polysaccharides, appear unique and existing commercial formulations are not recognised to contain enzymes capable of their degradation. With the present knowledge of soyabean polysaccharide structure, more informed formulation of enzyme products for use with soyabean should enable better responses to be achieved. When coupled with the lesser response from maize, this could allow the effective use of enzyme additives with maize-soyabean diets.

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.

Infrared (IR) spectroscopy is based on the principle that the chemical bonds in organic molecules absorb or emit infrared light when their vibrational state changes. In the near IR part of the spectrum, large changes in vibrational state are observed (overtones), while in the mid IR region, primary vibrations are produced. The latter yields sharper, more clearly defined peaks that are better suited for quantitative purposes. Raman spectroscopy, in which the decay of the vibration is observed after strong excitation of the sample, is a variant on mid IR spectroscopy. A major challenge in applying IR spectroscopy to animal production is sample presentation. Transmission is the most powerful method well suited to liquids and gases but is inappropriate for undiluted solids. Although reflection offers an alternative for solids, it is less than ideal for quantitative purposes as the path length is not known. For pastes and opaque liquids, attenuated total reflectance offers good possibilities for the future as it acts like a transmission device but sample application is simple. A novel method is photo-acoustics in which the heating of a sample (as it absorbs the IR light) is measured using a microphone. IR spectroscopy is typically fast and easy to use. In feedmills it allows the quality (e.g. proximate and nutritionally relevant parameters such as metabolisable energy) of feed ingredients and complete feeds to be monitored. In meat processing IR spectroscopy offers the opportunity to assess meat and fat quality, and perhaps even palatability (texture and flavour). New developments in IR spectroscopy will expand its applications further. These include hand-held instruments that may find use in determining digestive disorders among birds in the field, fibreoptics that will allow instantaneous measurements to be made in almost any part of a plant, tunable lasers (with their much stronger signals) that will make IR spectroscopy much more powerful, and imaging IR spectroscopy which may be used to determine the homogeneity of meat (e.g. colour). IR spectroscopy, with its speed, ease of use and versatility, could be about to become one of the most powerful analytical techniques available to the animal production industries. It promises to allow for improved quality control in virtually every aspect of production, from feed manufacture to final product evaluation.

The genetic basis and dominance relationships of the Naked neck gene and its geographical distribution in local populations is described. The effects on growth, feed efficiency, body composition and meat yield of broilers and the effects on egg laying and egg traits, reproduction and liveability in broiler breeding and laying birds are reviewed. On the whole, the results are encouraging for the future use of these genotypes at high ambient temperatures, either for meat or egg production. The results revealed that the autosomal Naked neck (Na) gene reduces feather mass by about 20% in heterozygous (Ndna) and by about 40% in homozygous (Na/Na) birds. The reduction in feather mass improves heat dissipation through the naked area, leading to a relatively higher tolerance to heat and a higher productivity under high ambient temperatures. It is concluded that heterozygous Naked neck broilers gain about 3% more weight than their normally feathered siblings under commercial conditions during the spring and summer months, and that this advantage is almost tripled at a constant high ambient temperature of about 32°C. Thus, the higher the capacity of broilers to gain weight, the more they benefit from the reduction in plumage as a result of the Naked neck gene.

A series of factors have contributed to the progressive diversification of reproduction strategies to produce day-old chicks in distinct geographical locations. Some of these strategies are adaptable by simple technology transfer and education (e.g. darkout housing to control photoperiod, appropriate feeding and management of breeder flocks) while others require continued efforts from geneticists and physiologists to develop new genetic lines and tools (eg. selection of breeds adapted for hot climates and gene banking). Reproduction strategies in broiler breeders will also probably continue to diversify depending on economic and social components, including labour and feed costs as well as local regulations. As a consequence, the final choice between natural mating or artificial insemination (for caged or floored breeders) is itself multifactorial and may lead to the selection of parent stock lines optimised for one or the other strategy, according to country and living standards. Finally, the diversity in consumer demand for poultry will itself favour the emergence of specialised birds and management techniques directly adapted to local needs.

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.

Although in the western world there has been a long term decline in the consumption of eggs, Asian egg consumption is on an upward trend, even in developed Asian nations like Japan. However, the latter part of the 1990s has seen a slower rate of growth in consumption. This study represents an attempt to analyse the present state of affairs by estimating the income elasticity of demand for eggs in selected countries. The annual increase in the consumption of eggs is high because of the very low consumption in developing countries. Production is also on the increase as a result of improvements in local breeds and the ready availability of high yielding birds even in rural areas. Based on estimates, countries were categorised into three groups – those of high income elasticity (Malaysia, China), medium elasticity (Sri Lanka, Pakistan) and low elasticity (Japan, Korea). Increasing disposable household income will continue to result in an expansion in the production and consumption of eggs in Asia. By the year 2010 over 60% of the world's population will live in Asia; furthermore, the growth in disposable income and purchasing power coupled with rapidly changing food habits will make eggs one of the more popular protein-rich foods with both the rural and urban populations in Asia.

New strains of avian leukosis virus (ALV) and new threats to the poultry industry such as the appearance of subgroup J ALV arise as a result of virus mutation. Avian retroviruses are classified as exogenous (transmitted as infectious virus) and endogenous (transmitted genetically). Exogenous species are the avian leukosis-sarcoma viruses, reticuloendotheliosis virus, and lymphoproliferative disease virus of turkeys. Endogenous virus families include the ev loci, EAV, ART-CH and CR 1. Evolutionary relationships between different species of retrovirus are determined from their nucleotide sequences and construction of phylogenetic trees. Similar analyses are conducted to determine the relationships between endogenous and exogenous retroviruses and the various retroelements from which retroviruses are believed to have evolved. Retroviruses are subject to several types of mutation. Point mutations are the most common and occur mainly because of errors during reverse transcription. The frequency of point mutations is of the order of one mutation per virion per replicative cycle. Point mutations occur most frequently in the env gene of ALVs resulting in changes in antigenicity and host range. Antigenic variation enables mutant viruses to avoid the host immune response. Mutation also occurs from genetic recombination among exogenous and endogenous ALVs, and between exogenous ALVs and non-retroviral host genes such as cellular oncogenes, giving rise to acute avian leukaemia and sarcoma viruses. Thus, continuing viral mutation will result in the appearance of ALVs with new disease producing properties.

Ostrich skin when tanned forms distinctive and exclusive leather which is much sought after in the fashion industry. Promotion and marketing are focused on its distinctive quill pattern, durability and suppleness. The leather commands a high price by comparison with other livestock leather. The industry in southern Africa is currently export focused with the highest number of tanned skins being exported from South Africa principally to Japan. There are currently many debates on the optimum age for slaughter, skin size being dependent on buyer demand. Skins are subjected to strict grading criteria. Many factors need to be considered to maximise skin yield and quality including adequate nutrition, preventing on-farm scarring and bruising during transport, preventing feather pecking and treating birds for parasitic and arthropod infestations. Stringent conditions during the processing of the skins at the abattoirs and tanneries are crucial in preventing damage and subsequent downgrading. Environmental impacts of tanning are crucial and harmful by- products, including trivalent chromium, must be extracted from the effluent. The establishment of a strategy that ensures improvements in both the local ostrich and skin industry, and in the export market is necessary if southern Africa is to become a global player.

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.