Excluding disease, the single most important factor affecting the albumen quality of the freshly laid egg is the age of the bird that laid it. With advancing flock age, Haugh unit scores decrease and the variability of the scores increases. An induced pause in egg production is beneficial in largely restoring albumen quality in aging hens. Both strain differences and strain/age interaction effects in Haugh unit scores of fresh eggs have often been observed, but these are normally small and have little practical significance. Albumen quality of the egg is not greatly influenced by bird nutrition. Environment and housing, even heat stress, appear to have almost no direct effect on the albumen quality of the egg at oviposition.

When ambient temperatures are high, delays in egg collection and/or cooling increase the rate of Haugh unit score decline. The maintenance of albumen quality during egg storage is dependent on the eggs being cooled quickly following lay and subsequently being held at low temperatures, preferably down to, but not below, 0°C. Oiling of eggs within 24 h of lay is very effective in retarding deterioration of the albumen but does not replace the need for cool storage. Information on genetic effects on the albumen quality of stored eggs is equivocal, although there is general agreement that any effects are small and of little commercial significance. Of greater importance is the finding that within strains there can be great variation in Haugh unit scores and that strains laying white-shelled eggs are much less variable than those producing brown-shelled eggs.

The availability of soyabean meal for animal feed use in Asia and the Pacific is low. The potential usefulness of a wide variety of protein-rich plant materials which could replace soyabean meal in poultry feed formulations is examined in this review. These materials are classified into four groups: oilseed meals; grain legumes; green meals and miscellaneous. Their nutritional values are discussed with reference to amino acid profiles. The presence of anti-nutritional factors and the resulting constraints on their use are also considered.

Concern about the cholesterol content of the human diet has led to many attempts to reduce the cholesterol content of eggs. Although this has involved a number of different approaches, including genetic selection and nutritional or pharmacological manipulation, the overwhelming evidence is that egg yolk cholesterol level is very resistant to change. The present review argues that this is because of the particular mechanisms involved in yolk formation. Yolk precursors are synthesized in the liver of the laying hen and transported in the plasma to the ovary where they are taken up into the developing follicles by receptor-mediated endocytosis. As a consequence, the cholesterol content of the yolk is primarily dependent on the cholesterol content of triglyceride-rich lipoproteins. Studies in mammals have shown that inhibition of cholesterol synthesis can reduce the rate of synthesis and secretion of lipoproteins by the liver, but has little effect on the composition of the lipoproteins that are secreted. This response, and the key role of cholesterol in the synthesis of steroid hormones, would seem to preclude the possibility of any substantial reductions in egg yolk cholesterol levels through manipulation of cholesterol metabolism. Possible alternative approaches are briefly discussed.

A literature search was carried out for papers which described the intermittent lighting of laying hens and included information on mortality and behavioural responses. A review of 36 sets of mortality data indicated that intermittent lighting generally improved bird liveability, compared with that under conventional lighting. Biomittent lighting, which involved low total daily amounts of illumination, gave the greatest improvement. This brings into question welfare recommendations for a minimum of 8 h illumination per 24-h cycle. Asymmetrical and Biomittent intermittent lighting generally reduced vices, obesity and heat stress. Hens submitted to asymmetrical and Biomittent intermittent lighting had similar endocrine periodicities and patterns of activity to conventionally illuminated birds.

Some new scientific developments are reviewed with respect to commercial application in poultry breeding. In the case of conventional breeding, ‘Best Linear Unbiased Prediction’ (BLUP) of breeding values and ‘juvenile selection’ schemes are evaluated. In the area of molecular genetic technology, ‘DNA fingerprinting’ and certain aspects of ‘gene transfer’ are considered.

The forceful arguments for the use of BLUP in dairy cattle breeding are not relevant to poultry. Its application is determined mainly by the balance between the additional cost of data processing and the value of the increase in genetic progress. The advantages of juvenile selection schemes for pure breeding are more obvious than for crossbreeding. The way in which the emphasis on crossbred records depends on the genetic correlation between purebred and crossbred information is also shown.

The prospects for DNA fingerprinting as an aid to selection will depend much on the identification of linked ‘trait genes’ having a marked influence on performance. In the case of gene transfer between species with the objective of influencing performance, viability appears to be a major obstacle to application in animal breeding. Such problems may be less serious when transferring genes for disease resistance. The application of these new developments is complicated by the fact that the aim of poultry breeding is to produce crossbreds. The new developments that have been assessed have to compete in terms of economic efficiency with the particularly favourable conditions which poultry provide for the application of conventional breeding procedures.

Amino acid availability values of feedstuffs are likely to form the basis of poultry feed formulation in the future. Already many nutritionists employ digestible amino acid values, but there is a lack of information from a single source derived from the application of accepted measurement procedures. The present paper reviews the basis of amino acid digestibility in poultry, examines the essential elements of measurement procedures, discusses recently published information and considers briefly how digestibility relates to availability. Finally, the use of digestible amino acids in practical feed formulation is considered.

Semen diluents are presently being used both for short- and long-term storage of domestic fowl semen. They are being developed to improve the reproductive efficiency of males and to lower the cost of artificial insemination. The development of semen diluents began with the use of simple NaCl solutions. Now, more complex diluents containing different osmotic regulators, energy sources, buffers and chelating agents are on the market. The discovery of cryoprotectants, such as glycerol and dimethylsulphoxide, has facilitated the preservation of chicken semen indefinitely at −196°C. The diluents which have been developed for short-term storage of semen are currently being used commercially wherever the technique of artificial insemination is being used seriously, especially in the turkey industry. Even though diluents for long-term semen storage are now available, their commercial application is not yet feasible.

This paper reviews the development of the various diluents which has resulted in the ability to preserve domestic fowl semen for short and long periods. Also discussed are some of the research data that have been collected on the viscosity of semen and semen diluents and what effects this has on semen quality.

Temperature as one of the most important single physical factors determining or influencing embryo development and hatchability is reviewed and possible temperature manipulations are discussed as a management tool.

Pre-incubation egg holding temperature is reviewed as a factor acting on variability in developmental stage at oviposition. A mathematical approach for determining the temperature threshold or physiological zero for embryonic development is outlined. Temperature requirements during incubation are discussed, taking into account the ultimate aims and objectives of the incubation process, i.e. hatchability and chick quality for survival, growth and reproduction, challenging at the same time the idea that the best hatchability is synonymous with the highest chick quality.

Factors affecting limits of variation in incubation temperature, with particular reference to strain or line differences, are discussed.

Clinical and pathological descriptions of inclusion body hepatitis–anaemia syndrome (IBH–AS) and hydropericardium syndrome (HpS) are presented and their causation and control are discussed. IBH–AS is a disease which has generally been thought to have a multiple aetiology, including infectious bursal disease virus, avian adenovirus and probably chicken anaemia virus. However, there is new evidence which suggests that avian adenoviruses are primary pathogens in IBH–AS. HpS is a new broiler disease which has spread throughout Pakistan. It has a number of similarities with IBH–AS. Recently, outbreaks of a disease exhibiting features of IBH–AS and HpS have been observed in North and South America. Mortality has been reported to be higher than is usual for IBH–AS and some hydropericardium has been observed.

Reports and observations relating to the skeleton and bone biology of the domestic fowl from the mid 16th century onwards have been assembled. Reference is made to early observations on osteology, pneumatic bones, bone growth, vital staining, bone cell microscopy, vitamin D in relation to rickets, genetics, archaeology and the folklore associated with the clavicle.

Although spent hens are economically important, they are considered a by-product of the egg industry and efforts are therefore needed if better quality meat and higher returns are to be achieved. This review has compiled information on various aspects of spent hen processing and utilization. Meat and fat yields depend on age and weight of the birds with heavy hens producing better yields and better quality products than light weight birds. Except for muscle tissue removed almost intact by filleting machines, hand deboned meat is superior to mechanically deboned meat. Toughness of spent hen meat is no obstacle to the production of a variety of comminuted products. Such by-products as skin, gizzard, heart, ova yolk and fat can be utilized in emulsion-based chicken and other meat products. The use of phosphates to produce better quality spent hen meat products has been demonstrated. Improved deboning techniques and modern methods of meat processing are capable of enhancing the quality and value of meat from spent hens leading to greater demand and better financial returns.

Accessory reproductive fluids and organs of male domestic fowl, turkeys, ducks, quail, guinea fowl and pigeons were examined. Male domestic fowl, turkeys and ducks produced different quantities of accessory reproductive fluids – lymph-like fluid and/or foam – during natural copulation. Quail released a unique foam, which is produced constantly in the cloacal region regardless of the ejection of semen and the time of day. The natural ejaculate of this species is always associated with the release of foam. In contrast, guinea fowl and pigeons released neither lymph-like fluid nor foam at ejaculation when semen was collected using the lumbar massage method. The tissues and organs which are involved in the production of these accessory reproductive fluids are the paracloacal vascular body (PVB), lymphatic folds (LF), dorsal proctodeal glands (DPG), ejaculatory groove region (EGR) and tissues in the vicinity of the papilla of the ductus deferens (TVP). Guinea fowl possessed the PVB, DPG and TVP even though they produce no accessory reproductive fluids. The only exception was the pigeon which has neither the tissues nor the organs listed above. The accessory reproductive fluids have a favourable effect on the function of freshly ejaculated spermatozoa in domestic birds.

The time between a hatching egg being produced and set in an incubator can be divided into a laying house period and a storage period. The period in the laying house affects hatching results by the stage of embryonic development at oviposition as well as by the subsequent environmental conditions. Advanced embryonic development at oviposition or prior to storage seems to improve hatchability, especially when storage is prolonged. Stage of embryonic development at oviposition is influenced by parental age, strain, individual bird variation and clutch length. After oviposition and before storage embryonic development can be influenced by the type of nest, egg collection pattern and temperature.

During storage, hatchability is influenced by the length of the storage period, temperature, humidity, gaseous environment and the orientation of the eggs. A decrease in hatchability can be detected in eggs stored for 2–3 days or more. Storage temperature should be decreased with extended length of storage. Temporary heating before incubation and enclosing eggs in plastic bags during storage improves hatchability, especially when storage is prolonged. A high humidity during storage also improves hatchability, probably due to a reduction in water loss. The changes in albumen pH during storage are discussed in so far as they provide a possible explanation for relationships between environmental conditions during storage and hatching results.

There has been a long and continuing interest among poultry breeders and scientists in relationships of domestic fowl with their jungle fowl ancestor. Recent commercial practices in poultry breeding have greatly changed and improved the meat and egg stocks available for the production of food. There is concern, however, that artificial selection for traits of economic importance has caused a narrowing of the genetic base and subsequent reduction in genetic variability. Because continued progress in the achievement of increased growth or egg production depends heavily on genetic variability, its present status is of interest. Current techniques in molecular biology allow estimations to be made of genetic distance among populations. This paper reviews DNA fingerprinting in poultry using results from this technique to survey genetic diversity among jungle fowl, domestic fowl representative of stocks from several decades ago and today's commercial broilers and layers. The genetic distance between wild jungle fowl and layers has been found to be similar to that between wild jungle fowl and broilers. Within the two types of modern commercial fowl there is less genetic diversity among broiler than layer stocks.

A brief discussion is presented of the indirect effects (particularly through litter condition and leg problems) and the direct effects on carcase composition and quality of variation in protein:energy ratio, nutrient density, type and quality of added fat, fish oils, enzyme addition to the feed, mineral and vitamin levels and the use of certain drugs.

The possible influence of age at change in cycle length and differences in effective photoperiod (Δp) on the response of layers to ahemeral light cycles have been examined. A brief account of the physiology of pattern of lay in the hen is given.

When an ahemeral light cycle is applied, mean rate of lay in relation to a normal 24-h cycle changes. The change in mean rate of lay depends upon the rate of ovarian follicular maturation of the individuals in the flock at the time of change to an ahemeral cycle. Early in lay, when rate of follicular maturation is rapid, changing to a long light cycle reduces rate of lay, whereas changing to a short cycle could increase rate of lay. As rate of follicular maturation declines with age, changing to a long cycle late in lay leads to an improvement in rate of lay. Based on published reports, a theoretical curve of the response to a 28-h cycle is given showing the significance of age at which application is made. From the available literature it appears that, provided Δp ≥ 0, response to ahemeral light cycles is not affected.