An analysis of data for domestic pullets, turkeys, partridges and quail (Coturnix) indicates that, once all birds within a flock have become sexually photoresponsive but before spontaneous sexual development commences, mean age at first egg, egg production in a given period, mean body weight at first egg and mean egg weight increase linearly with age at photostimulation. These relationships are steeper for age at first egg in turkeys, partridges and quail, for egg production in turkeys and partridges and for egg weight and body weight in turkeys than those seen in domestic pullets. This may indicate differential responses by seasonal and non-seasonal breeding birds, species-specific factors such as geographical origins, or may reflect differing periods of artificial selection in the four species. Egg weight in domestic pullets and turkeys is significantly correlated with body weight at first egg.

Many decades of selection for increased egg output per bird and for efficient feed conversion have resulted in stocks capable of remarkable levels of performance. In the search for new ways to achieve further improvements in egg production efficiency, residual feed intake is seen as a parameter that merits the serious attention of breeders. This review examines relevant research relating to feed conversion efficiency since 1972 – including some results obtained by the author from commercial populations – and offers guidelines on the ways in which datd on individual feed intake could be applied within modern selection programmes.

More energy efficient and longer lasting lamps are being used to replace incandescent lighting in poultry houses. This paper reviews the response of domestic fowl, turkeys and geese to various sources of illumination. It concludes that there is no evidence that fluorescent or high pressure sodium lighting, irrespective of intensity or spectral distribution, has any consistent detrimental effect on growth, food utilization, reproductive performance, mortality, behaviour or live bird quality in either domestic fowl or turkeys, nor in the egg production of geese. There are limited data to suggest that the use of fluorescent lighting may be beneficial in the reduction of leg problems in meat chickens. Notwithstanding that poultry may perceive low frequency fluorescent light as discontinuous (at least in Europe), it does not appear to compromise the welfare of poultry, and has been shown in one study with laying fowl to be preferred to incansdescent lighting.

The lipids of the yolk represent the primary nutrient source for the chick embryo, providing over 90% of the energy required for development as well as supplying a range of structural components for membrane biogenesis. Since the energy needs and the requirements for particular fatty acids differ greatly among the various embryonic tissues and between successive developmental stages, the regulated distribution of lipid components from the yolk to the different body sites forms a central feature of this system. As a consequence, the various tissues of the newly hatched chick display a range of highly characteristic lipid and fatty acid compositions in accordance with their functions but which, in many cases, also reflect the intensity and complexity of the lipid transfer process in the embryo. For example, the liver of the chick contains very high levels of cholesteryl ester as a result of the mechanism of lipid transfer. Moreover, the triacylglycerol fraction of the liver is highly enriched in docosahexaenoic acid, possibly reflecting hepatic involvement in the transfer of this fatty acid to the brain. The accretion of large amounts of both docosahexaenoic and arachidonic acids in the phospholipids of the brain and retina is a key feature of chick embryo development, the importance of which is underlined by the expression of a series of mechanisms, possibly mediated by the liver and adipose tissue, designed to promote the transfer of these fatty acids to the neural tissues.

Phytic acid or phytate is a naturally occurring organic complex found in plants. As a reactive anion, it forms a wide variety of insoluble salts with divalent and trivalent cations. Phytic acid is also known to complex with proteins and consequently reduce their availability. Recent studies indicate that phytic acid reduces the activity of pepsin, trypsin and αamylase. Because of a lack of endogenous phytase, which hydrolyses phytic acid, phytate phosphorus is biologically less available to poultry. Because of the complex factors influencing phytate hydrolysis, such as dietary calcium content, inorganic phosphorus and vitamin D3, and the age and genotype of birds, there is wide disagreement concerning the ability of poultry to utilize phytate phosphorus. Data suggest that the amount of endogenous phytase is extremely low in young birds but that it increases with age. Cereal based poultry diets supplemented with microbial phytase result in increased digestibility and availability of phytate bound phosphorus, calcium, zinc and copper. Microbial phytase supplementation has also been shown to increase ileal digestibility of crude protein and amino acids in female broiler chickens and in female turkeys, but curiously not in male chickens. There is no report to date of such a study in male turkeys. While the efficacy of supplemental microbial phytase depends on its rate of inclusion, on the calcium and phytate phosphorus contents and on the dietary ca1cium:phosphorus ratio, clear benefits have been shown in terms of increased availability of phytate-bound minerals and crude protein, and reduced environmental pollution through lower levels of phosphorus and nitrogen excretion. To maximize the benefit from the addition of microbial phytase, future research should focus on determining the optimum dietary conditions for it to work.

Aerial emissions from poultry production may affect bird performance, cause respiratory ill health in stockmen and are a source of environmental pollutants. Recent measurements of the concentrations in, and emissions from, poultry houses are presented. Control of aerial emissions must be integrated with other environmental parameters that determine the profitability and sustainability of poultry production.

This review presents findings on the influence of natural raffinose series oligosaccharides and synthetic (industrial) products on the productivity of broiler chicken. There is evidence of negative effects on animal health and productivity from the use of raffinose series oligosaccharides, but beneficial effects from synthetic oligosaccharides. Part of this contradiction may be due to differences in the chemical nature of the supplements, the level of supplementation or the duration of feeding. The future for synthetic oligosaccharides is bright, but further adoption of natural sources requires a greater understanding of their chemistry to facilitate the production of beneficial compounds and the elimination of detrimental fractions. Most current literature favours the inclusion of various oligosaccharides in the diet. The cost of production could be minimised by the use of natural ingredients which contain oligosaccharides, or by cheap synthetic products, sources of which are highlighted in this review.

The gastrointestinal tract of the newly hatched chick is in a process of development and maturation. In the chicks of domestic fowl and turkeys considerable evidence suggests that, from hatching, the rate of development of the gastrointestinal tract exceeds the rate of body weight gain both physically (relative weight) and morphologically (villus height and perimeter, and villus volume). Rapid development is especially evident in the duodenum, jejunum and pancreas. Once hatched, the time at which maximum specific activities of digestive enzymes has been observed in the pancreas and intestinal brush border vary somewhat, but most often it occurs at or shortly after hatch. Subsequently, specific activities of these enzymes frequently decrease with age. Nevertheless, total digestive enzyme activity tends to increase during the early post-hatch period because of the rapid increase in the weight of the pancreas and intestines. In some instances the increases in total enzyme activity may be too small to keep up with increases in feed intake. For example, a lag in lipase secretion in relation to feed intake may contribute to the relatively poor utilization of some dietary lipids during the first 10 days or so after hatch. Although research findings on digestion and nutrient utilization have varied, there are numerous indications that, in addition to certain lipids, the utilization of some carbohydrates and protein is less efficient during the first week or two after hatch than in older chickens and turkeys. Overall, these observations suggest that additional research is warranted to obtain more definitive information on the development of gastrointestinal function in young poultry.

Haemorrhagic enteritis (HE) of turkeys is an economically important viral disease of turkeys, not only because it causes high mortality and immunosuppression, but also due to increased slaughterhouse condemnations. The disease is characterized by haemorrhagic enteritis and necrosis of lymphoid cells and a proliferation of reticuloendothelial cells in the spleen. In marble spleen disease (MSD), in addition to splenic changes, pulmonary congestion and oedema are also seen. Whereas splenomegaly in chickens (SMC) is characterized by lesions in the spleen similar to those of HE and the pulmonary lesions of MSD. The causative agents of HE of turkeys, MSD of pheasants and SMC are serologically indistinguishable group II Aviadenoviruses. All the three viruses can be propagated in lymphoblastoid cell lines derived from Marek's disease virus induced lymphoma in turkeys viz. MDTC-RP-16 and MDTC-RP19. The infection can be diagnosed by isolation and characterization of aetiological agents, serological tests such as the agar gel precipitation test, enzyme linked immunosorbent assay and the use of immunoperoxidase to demonstrate intranuclear adenovirus-like particles in infected cells shown by electron microscopy. The control of HE is possible by vaccination using avirulent MSD virus of pheasants as well as avirulent or attenuated strains of turkey HE virus.

In recent years it has been shown that Campylobacter jejuni is the most common cause of gastroenteritis or enterocolitis in man, especially in developed countries. Numerous studies have demonstrated a high prevalence of C. jejuni in chickens and it is evident that chicken meat is a significant source of human gastroenteritis due to lack of care in handling raw products and inadequate cooking. Campylobacter spp. are frequently found in the intestinal tract of poultry where colonization leads to contamination of carcasses during processing, especially at the defeathering and evisceration stages. This paper reviews the occurrence of C. jejuni in poultry, particularly in the live bird and on processed carcasses. It also considers possible factors in the introduction and spread of C. jejuni on farms and discusses progress in developing measures for controlling Campylobacter spp. in the production chain.

Avian infectious bronchitis (IB) is a major cause of economic loss to the poultry industry. The disease, which has been identified in many areas of the world, primarily affects the respiratory tract of – usually young – domestic fowl. However, in addition to their common affinity for the respiratory tract, IB virus strains differ in their tropism for such other target organs as the female reproductive system or the alimentary tract and kidneys. The names now normally given to the disease are ‘infectious bronchitis nephritis’, ‘IB nephritis’ and ‘NIB’. These reflect its inflammatory nature and the organ primarily affected. The pathogenicity of IB virus strains varies and the severity of a disease outbreak is also influenced by the age of the birds and by environmental/management factors. In young broilers, which appear to be the type of stock most affected, the main symptoms of nephritis IB are generally the sudden occurrence of mild respiratory signs which tend to decline within a week. This is followed by a rapid rise in mortality causing the loss of 5–25% of the birds over the ensuing 10 days or so. The birds tend to die abruptly. Gross lesions are mainly confined to the kidneys. The kidney parenchyma of affected chickens is pale, swollen and mottled; tubules and urethras are distended with uric acid crystals. In pullets IB nephritis occurs principally in modern hybrid laying stocks shortly after the onset of egg production when, for several weeks, mortality is typically around 0.4% per week. Post mortem lesions resemble those found in broilers but usually visceral urate deposits are also present. Diagnosis of nephritis IB needs to include detection of IB viral antigen using immunofluorescence on frozen kidney sections and/or viral isolation and identification of IBV following standard techniques. Vaccination with the commonly used IB vaccines such as the H120 strain affords only limited protection against nephritis IB. Attention is drawn to the need for further research.

Because evaporative cooling is the principal avenue of heat loss at high ambient temperatures, high humidity superimposed on high temperature presents poultry with an additional thermal challenge. Whenever body temperature exceeds ambient temperature, sensible heat loss (radiation, conduction, and convection) to the environment will occur. The generally accepted model of heat balance, which states that when ambient temperature increases homeotherms will endeavour to maximize sensible heat loss before resorting to evaporative heat loss, was recently challenged. However, several factors that can influence heat balance were not considered in the reasoning pursued in that challenge. In this paper the theory behind heat balance models is discussed and the data that were used to challenge the model are reanalysed. The question of whether poultry are capable of physiologically increasing sensible heat loss under hot, humid conditions remains unanswered and presents an area worthy of future study.

Changes in broiler production parameters occur through a combination of genetic progress in the stock, improvements in management practices and flock health. Data from a comparative test conducted by Ross Breeders Ltd in 1994 involving commercial broiler stock and a control line established by them in 1976 showed that considerable improvement had been made in the rate of growth, feed conversion efficiency, yield and breast meat percentage during the 18 year period. Manipulations of lighting regimens have indicated that, under research conditions, it is possible to reduce the incidence of leg problems and total mortality, and on-farm experiments have demonstrated that profitability can be increased and flock health improved by the use of controlled feeding programmes and whole wheat feeding. In the future it is likely that feeding programmes, growth and the environment within large commercial broiler houses will be closely monitored by computers to produce optimum performance. It is vital, therefore, that trials in the future are conducted in facilities which allow the control group of birds to express their genetic potential to ensure that research findings are relevant to the broiler industry. The future of the broiler industry is difficult to predict but the use of in ovo vaccinations and novel feed ingredients, including targeted feed enzymes, is expected to increase whilst a better understanding of variability in wheat and the nutrient requirements of fast growing birds need investigation.

This review examines the avian heterophil leucocyte and provides a morphological and cytochemical profile drawn from light and electron microscopy studies of these cells and their characteristic cytoplasmic granules. Other aspects covered include relative and absolute heterophil counts in different avian species and the response of heterophils to stress and to acute inflammation. Heterophils are round cells and, with Romanowsky stains, their primary fusiform granules appear brick-red in colour. A secondary type of round granule, less dense in the electron microscope and smaller than the primary granule, can be seen in most avian species. The primary granules frequently display a ‘central body’ that may be proteinaceous in nature. Unlike mammalian neutrophils, avian heterophils are devoid of myeloperoxidase. However, their cytoplasmic granules contain several lysosomal and non-lysosomal enzymes including acid phosphatase, arylsulphatase, β-glucuronidase, phosphorylase, uridine diphosphate glucose-glucogen glycosyltrans-ferase, neutral and acid α-glucosidases, acid trimetaphosphatase and lysozyme. In the majority of birds heterophils are the second most numerous cell in circulation, the exceptions being several species of the Psittacine and Anseriformes orders, ostrich, ring-necked pheasant, pigeon and rosy flamingo. Heterophils generally outnumber lymphocytes in chicks between hatch and one week of age. Their numbers increase during mildly or moderately stressful conditions and consequently the heterophil/ymphocyte ratio can be used to detect the presence of physiological stress for most stressors. A heteropenia can occur, however, during severe stress. Heterophils respond to a stimulus (chemotactic agent) within about 30 minutes during the early inflammatory phase and they may also have sensitive and selective phagocytosing properties. By seven days heterophils become unrecognizable and, with macrophage recruitment, the characteristic heterophilic granuloma develops.

Due to a belief in the special healthy characteristics of their meat, ratites (ostriches, emus, rheas) are receiving more and more attention as meat producers for developed markets. All three kinds of ratites can be slaughtered by the same technique. At the scientific level, avian nomenclature is applied to the muscles used in meat production, while a variety of trade names is being used commercially. Dressing percentage, meat production on a live and carcass weight basis, as well as proportional weight of individual muscles are of the same order for all three species. Ratite meat is characterized by a high final pH value which may result in a limited shelf life. Nutritional information, especially about emu and rhea meat, is rarely found.