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.

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.

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.

Over four million tonnes of poultry manure are produced annually in the UK, containing about 100 000 tonnes of nitrogen (N). During the housing, storage and land spreading of poultry manures, ammonia N losses have been estimated at 44 000 tonnes per annum, equivalent to about 19 % of estimated UK ammonia emissions in 1996. Poultry manure applications to agricultural land should supply no more than 250 kg total N/ha per annum to comply with recommendations in the Ministry of Agriculture, Fisheries and Food Water Code and proposed manure loading rates in designated Nitrate Vulnerable Zones in England and Wales. To recycle the annual manure N output from 1000 layers and 1000 broiler places requires 2.6 and 2.0 hectares of land, respectively. To make best use of the readily available N content of poultry manures, applications should be made when there is a crop requirement (generally spring and summer) and should be managed as part of an integrated fertilizer N programme.

As the result of phosphorus being identified as the most harmful pollutant, government regulations introduced in the Netherlands in the 1990s to reduce environmental damage from livestock wastes used phosphorus content as the marker criterion. This subsequently led to reductions in the amounts of phosphorus included in animal feed compounds. Particularly in the case of broiler breeder and broiler grower diets, it was concluded that increased mortality, increased morbidity and other adverse effects on performance were largely the result of insufficient dietary phosphorus. Measures taken have included on-farm addition of supplementary phosphorus and calcium and adjustments by the feed industry. In general, levels of performance have now been restored. However, it is concluded that more research on optimum phosphorus levels is desirable, particularly as producers have to bear the cost of the residual phosphorus in the poultry manure produced.

The recorded history of the turkey spans about 500 years. Turkeys originated in North America, were domesticated in Europe, and are now an important source of food in many parts of the world. This review touches on some major episodes in the history of this valuable and beautiful bird, its discovery, domestication, the fame it achieved, its name and the development of some varieties, including the broad breasted phenomenon and Beltsville Small White.

Few descriptions of traditional duck farming in Vietnam are available. This small study reports on these traditional techniques before they disappear as a consequence of the country's rapid economic and social development. Five production farms and two hatcheries located in South Vitenam were evaluated. The study covered basic questions relating to farm and hatchery management, nutrition, vaccination, pharmaceutical use, costs and priority needs. Questions were translated into Vietnamese for personal interviews. Out of five production farms, three did not use the local veterinary services. However, four used a French duck plague vaccine and not the Vietnamese product. There was little knowledge on the appropriate use of pharmaceuticals. Hatching methods within the two hatcheries were similar to those of South China. The traditional farming systems made efficient use of a scavenging resourcefulness of Vietnamese farmers in their present situation, and identified areas for disease control and research.