The activity of feeding and the metabolism caused by digestion and assimilation of food increase an animal's heat production. This increased heat production has been referred to as specific dynamic effect, specific dynamic action or heat increment (HI). HI is much larger when protein is a source of energy than when carbohydrate or fat are the sources of energy. HI for protein is much greater when the animal's ambient temperature is high than when it is low. Metabolisable energy is used more efficiently, thus having less HI, for maintenance than for production. A suggested explanation is that heat resulting from digestion and assimilation of food can substitute for the heat production in fasting when food provides energy equal to, or less than, maintenance requirements. When energy intake is large enough to support production, HI from anabolic processes becomes a waste product that cannot substitute for a fasting or maintenance function. The same rationale can be applied to the observation that dietary protein has a greater HI when an animal is at high temperatures. At low temperatures protein would be used for maintenance. At high temperatures the same amount of energy from protein would be enough to support production. As a result, HI of the protein would be increased at high temperatures. The high HI of protein or amino acids when at a high level in the diet can be at least partially explained. Protein synthesis requires a large amount of energy. Some energy is required to excrete nitrogenous waste. In addition, dietary protein stimulates protein turnover. Research findings have suggested that HI should be lowered by decreasing dietary protein. For non-ruminant animals this could be accomplished by discovering the essential amino acid requirements for an ideal protein. The ideal protein should result in a minimum HI. Research to date generally fails to document improved feed efficiency as a result of feeding an ideal protein.

Evidence from published trials is reviewed to investigate whether there is any need to change the recommended optimal light intensity for laying fowls from 5 lux. Although some recent trials have recorded excellent performances from birds exposed to light intensities of less than 5 lux, it is concluded that this has more to do with the ability of modern pullets to lay well even without photostimulation than with any change in the threshold of light sensitivity. There is good recent evidence that the stimulation of early sexual maturity a large increment in the photoperiod during the growing stage requires minimal intensity of 2lux, and that 41ux is probably required for maximal response. By combining the results from all available trials, it is possible demonstrate small but significant effects of light intensity on egg size, food intake and mortality. An economic analysis, which takes into account all these responses, indicates that the optimal profit occurs at about .5 lux. Although the prices used in that analysis are both local and ephemeral, the optimum will vary very little within other cost structures, because it is determined almost entirely by the lower outputs predicted at intensities below 51ux and the greater electricity cost in providing very much higher intensities. It recognised that, because maximising profit is not always the sole objective enterprises involving animal production, considerations for the welfare of both the livestock and workers may make it prudent to recommend a slightly higher value such as 1O lux.

Birds live longer than mammals of comparable sizes, contrary to what their metabolic rates, plasma gulcose concentrations and body tempratures, all of which are higher than mammalian norms, would suggest. Although these factors should predispose them to accelerated tissue degeneration, this has been shown not to happen. In this paper the possible mechanism whereby birds limit the accelerated tissue damage that should be associated with the above characteristics are explored. Specifically, this review will focus on the relationship in chickens between the raised concentrations of plasma glucose and the lack of associated tissue complications. We propose that the role of uric acid in birds should be re-examined. Until now uric acid has been considered to be little more than an excretory by-product where its role as an antioxidant can be directly linked to the resistance of birds to glucose-mediated tissue damage. It is suggested that, compared with mammals, the lower rate of generation of reactive oxygen species in birds in association with their stronger antioxidant-defence system contributes to their longevity.

Poultry and poultry products have repeatedly been implicated as a source of foodborne infection for humans. The significant increase in the number of reported foodborne disease outbreaks worldwide has altered opinions on food safety. It has become clear that current legislation alone is inadequate, and that industry must accept a greater share of responsibility for the quality and safety of the food it produces. The fact that processing plants are not able to reduce the incidence of pathogenic bacteria effectively in poultry products means that every effort must be made to reduce infection in and/or contamination of the live birds with foodborne pathogens before dispatch to processing plants. The main control strategy should include the following: cleaning the production pyramid from the top, as in the case of Salmonella enteritidis and Salmonella typhimurium, by destroying infected flocks (with compensation), sanitising hatching eggs and limiting the introduction and spread of pathogens at the farm through Good Animal Husbandry Practices (GAHPs). To achieve GAHPs, effective measures of hygiene should be applied to poultry houses and the feed. Reducing salmonella colonisation by using antimicrobial feed additives, competitive exclusion treatment or vaccines is worth consideration. Fur-thermore, hygienic systems for catching and transporting live poultry must be included. To reduce carcass contamination during processing, thorough schedules for cleaning and disinfection of the equipment and plant are essential. Machine design must permit easy and thorough cleaning. Because the success of any food safety programme on the farm and in the processing plant depends on the hygiene practices of the staff, it is essential to incorporate education programmes for all people involved in the poultry production chain. In the farm-to-fork concept, post-processing food handling is also a very important factor in reducing foodborne infections. Finally, the development and application of acceptable methods for end product decontamination and preservation in the processing plant must be pursued.

The goose is one of the most ancient of domesticated birds now bred commercially. Whereas the greatest concentration of the world's geese is to be found in Asia, there is considerable breed diversity in Europe. Geese enterprises are most successful with highly productive breeds well adapted to local conditions. Economically useful traits, such as body weight, liveability, egg production, hatchability, feather formation and ability to be fed for the production of fat livers, need to be more clearly identified. Knowledge of the genetic differences between and within breeds in reproductive or production traits and of the heritability values of these traits are essential if the artificial selection of geese is to be successful. In the commercial crossing of breeds it is customary and preferable to use dam and male strains selected for reproductive and meat traits, respectively. Implementing modern DNA techniques would facilitate the detection of quantitative trait loci (QTL) and the introduction of marker-assisted selection. Progress with and results from other avian species would help to compensate for the current lack of specific markers and other molecular tools in geese. An important feature of geese is their ability to consume green forages and other cheap components of crops and to maintain productivity on diets with low protein contents; they are also frequently able to make effective use of novel local feed resources. Geese are at present usually raised on deep litter, on free range, in cages or on slats, using short days, diminishing light intensity or fluorescent light, and over one or two cycles of lay. To improve the efficiency of production of geese their biological and economic features need to be more actively studied. There is an urgent need to integrate genetic, nutritional, reproductive and management information and approaches so that present production systems can be adjusted and the genetic potential of geese more fully realised.

The problem of assessing welfare in poultry has been exacerbated by three widespread but erroneous assumptions. These are (1) that there are general indicators of welfare that apply to all situations, (2) that indicators of good welfare and those of reduced welfare are distinct from one another and (3) that any change in a welfare ‘indicator’ reflects a change in the welfare state of the animal. These three assumptions are challenged and replaced with a more evolutionary view of the behavioural and physiological responses of the domestic fowl to its environment. Apart from physical health, which is the Cornerstone of all good welfare, the most important additional component of poultry welfare is psychological health or ‘contentment’, which can be most reliably accessed through the birds' own choice behaviour.