Excess calcium intake has been shown to reduce growth and feed efficiency and to increase bone ash and bone strength in growing chickens. Source and level of dietary phosphorus have been shown to affect calcium tolerance. The effects of high calcium can be largely explained by its effects on intestinal pH. The proposed mechanism involves excess calcium reducing the soluble fraction of minerals and the proportion of minerals in small complexes. In consequence, their availability for absorption is probably also reduced. The growth depression of chickens fed on diets high in calcium may be partly caused by the decreased availability of other minerals needed for growth. Calcium tolerance of growing chickens may be increased by ensuring that there are higher than normal levels of the other required minerals in the diet.

The paper addresses all feasible applications of long ahemeral light cycles in breeding flocks and reviews the limited published studies. Long cycles are likely to be most beneficial towards the end of the production cycle – when eggshell quality is often poor – and at the beginning of lay to increase the proportion of eggs exceeding the minimum weight for incubation. Published reports show an improvement in both fertility and hatchability of breeding flocks under long cycles.

Many studies have shown that saline drinking water supplied to mature laying hens at concentrations similar to those found in underground bore water has an adverse effect on eggshell quality and on the incidence of eggshell defects. This response can be observed in the absence of any adverse effects on production parameters such as food intake, egg production and egg weight. Strain differences appear to exist, and even within a strain there is considerable variation in the responses of individual hens to saline drinking water. The sensitivity of the hen also increases with age with a greater occurrence of broken and shell-less eggs. The incidence of shell-less eggs also increases with higher concentrations of NaC1 in the water. The use of saline drinking water with breeder flocks significantly reduces the production of day-old chicks through reduced numbers of settable eggs and lower hatchability. The primary metabolic lesion associated with the poor eggshell quality which results from the intake of saline drinking water appears to be related to the supply of bicarbonate rather than calcium to the lumen of the shell gland for eggshell formation. A reduced activity of carbonic anhydrase in the shell gland mucosa is of particular importance. This limits the supply of bicarbonate and the dependent calcium to the lumen of the shell gland. Treatments which have been found to be effective are preventive rather than remedial in nature. The two most promising treatments, apart from desalination of drinking water, appear to be the use of ascorbic acid supplements in the diet or drinking water appear to be the use of ascorbic acid supplements in the diet or drinking water and the use of zinc–methionine supplements in the diet. The mechanism by which ascorbic acid exerts its effect is unknown but the response is dose-dependent. The zinc component of zinc–methionine appears to be the important factor with this treatment, perhaps through its effect on carbonic anhydrase, a zinc-requiring enzyme.

Animal protein supplements are superior to plant protein supplements as sources of essential amino acids and are desirable components in poultry feed formulations. Fish meal and meat meal are widely used animal protein supplements in the Asian and Pacific regions. The nutritive value of these two ingredients and other potentially useful sources of animal protein are examined, with particular emphasis on protein quality. The value of some ‘novel’ animal protein sources is also discussed.

Irradiation offers a potential method for effective microbial control of poultry feed. Birds fed such irradiated diets are not adversely affected and radiation status of the diet is unchanged. While radiation at 25–35 kGy is likely to raise feed temperature by only 5°C during processing, there seems to be loss in potency of certain nutrients. Most reports indicate loss in potency of all fat-soluble vitamins, and there are less consistent reports regarding thiamine and pyridoxine. At 25–35 kGy irradiation there will be around 15% loss of potency of these vitamins. Irradiation also causes increased peroxidation of fats, although this effect can be controlled by appropriate inclusion of antioxidants. There are no consistent reports of irradiation having any effect on protein quality or amino acid status of diets.

Poultry feeds and especially their animal byproduct components are a primary source of microbes to poultry. Current methods of microbial feed control do not consistently achieve eradication of organisms such as salmonella. Irradiation of poultry feed at predetermined doses results in complete destruction of salmonellae, enterobacteria, moulds, fungi and insects. Effective doses range from 10 to 40 kGy. There are no reported instances of adverse performance from birds eating irradiated feed, and radiation status of feed in unaffected.

The food intake and growth rate of broilers kept at high temperatures can be improved by supplementing the diet or the drinking water with sodium bicarbonate. The response appears to be due to the bicarbonate ion and is associated with an increase in water consumption. Measurements of dietary or retained values for cation–anion balance or dietary electrolyte balance were unsatisfactory for predicting the growth and/or feed conversion responses of broilers at high temperatures. Improvements in body weight do not appear to be associated with increased body water retention.

The major histocompatibility complex (MHC) is a group of genes present in all vertebrates. The chicken MHC is broken into three distinct regions, each of which codes for certain gene products. These antigens are known to influence a variety of biological functions including fowl cholera, Marek's disease, Rous sarcoma virus, lymphoid leukosis and coccidiosis. Fertility, embryonic mortality, hatchability, and egg production are some of the production parameters linked to this gene complex. Blood groups serve as markers for these regions, offering a means of genetic screening.

This review on avian blood leucocyte responses to stress covers the literature from the early 1980s. It considers only non-infectious hormonal responses of leucocytes to stress mediated either by nutritional, parenteral, climatic/environmental (physical or social) or psychological stressors. The heterophil/lymphocyte (H/L) ratio after the administration of ACTH either in the diet or by injection and during food restriction studies has been studied. The ratio was found to be inadequate during severe food restriction studies, as some stressed birds responded with a heteropenia, lymphocytosis and a significant basophilia. Climatic and environmental stressors such as road transportation and heat stress produced significantly raised H/L ratios and basophilias, respectively. Psychological stressors such as fasting, frustration or noise showed different leucocytic responses and the times in which cells were mobilized also varied. Although the H/L ratio is a less variable indicator of avian stress than individual cell numbers and more reliable than corticosteroid levels in plasma, this rule applies only when mild to moderate stress exists. During extreme stress, as in life-threatening situations, a heteropenia and basophilia develop so the H/L ratio cannot always be accepted as an accurate measurement of stress in poultry. Thus, in some avian stress a two-phase cellular reaction may be present. This biphasic leucocytic response to stress may be unique to Aves.

The avian kidney has shown a remarkable ability to maintain adequate and even normal function in the face of a mycotoxin challenge. Full evaluation of the nephrotoxicity of a substance must therefore go beyond pathological and ultrastructural documentation and include a complete functional evaluation. To date, only three nephrogenic mycotoxins, citrinin, ochratoxin A, and aflatoxin B1 have been assessed for their ability to alter avian renal function. At non-lethal doses, citrinin appears to have acute reversible effects on the distal portion of the nephron, possibly acting to inhibit water absorption. Ochratoxin A is more potent and less acute than citrinin but less site-specific in that both proximal and distal tubules are damaged, resulting in severe loss of both fluids and electrolytes. Aflatoxin B1 at a dosage and duration which induced hepatotoxicity, concurrently exerted nephrogenic effects such as increased urinary calcium excretion and decreased inorganic phosphate excretion. In commercial broilers aflatoxin B1 has been shown to decrease plasma levels of 25-hydroxy vitamin D, 1,25-dihydroxy vitamin D and may also decrease endogenous parathyroid hormone synthesis and the renal sensitivity to parathyroid hormone. Furthermore, exposure to aflatoxin B1 may cause prolonged alteration in renal function such as reduced glomerular filtration rate. This review summarizes the studies which have been conducted to evaluate avian renal function during both acute and chronic exposure to these three mycotoxins.

Abstract Handling, in the context of this review, is the process whereby birds are removed from a building to a truck and, after transportation, from a truck to a building. The procedure includes collection, carrying to the transport vehicle, containerization (i.e. usually placing in crates) and loading onto the transporter. In general, most of these processes are carried out manually. Handling of poultry has been shown to be a potential cause of injury and, in addition, birds find human contact aversive. If mechanical devices could be developed that handled birds gently, close human contact could be reduced and there would be a potential to improve bird welfare. Several patented devices are discussed. The use of physiological and stress indicators in the evaluation of mechanical systems being developed can help to ensure that when brought into commercial use, bird welfare is not compromised during handling.

The sources and factors by which poultry house dust and gases are generated, the levels encountered and their effect on the respiratory health of stockmen are reviewed. Although exposure to aerial pollutants in intensive housing can lead to respiratory disease, the mechanisms involved in this process are poorly understood. These mechanisms and the dynamics of the micro-environment involved in the generation of dust and gases from poultry litter are discussed. From the limited knowledge available, only partially effective methods of dust and gas control are possible.

Although still in the experimental phase, the technique of freezing domestic fowl semen may prove of interest and value to the industry. Various stages of the application of this method of preservation still need to be improved. One of the most critical aspects is the choice of cryoprotectant and its use during the process of freezing and thawing. While glycerol has a better cryopreservative action than other cryoprotectants in domestic fowl semen, it exerts a widely demonstrated contraceptive action, the mechanism of which has not yet been clarified. Thus the use of glycerol as a cryoprotectant must be accompanied by its complete removal before insemination.

The fertilizing capacity of semen preserved by freezing is notably less than that of fresh (non-preserved) material and has been evaluated as 1.6% and 19.7%. Genetic influences appear to affect spermatozoan response and tolerance to thermal treatments resulting in differences in subsequent fertility. Most studies using fowl semen report final freezing temperatures between –79°C and –196°C, a cooling rate of 1–10°C/minute and a thawing rate of 50–70°C/minute.

Straws have been found to be more satisfactory containers than glass vials or ampoules for preserving semen from domestic fowl.

Consumer demand for food products of superior health quality has renewed interest in modifying the lipid composition of poultry meat and eggs. While work involving the reduction of the cholesterol content of poultry products has met with little success, dietary fatty acid modification has proved to be a viable method of adding value to poultry products for the health conscious consumer. Because of the association with a decreased risk of coronary heart disease, recent dietary fat studies have centred on the manipulation of specific fatty acids, i.e. 20-carbon omega-3 fatty acids (eicosapentaenoic acid 20:5n3, decosahexaenoic acid 22:6n3) found in marine sources. Seasonal availability, affordability and consumer preference often limit fish consumption, thereby excluding the primary source of 20-carbon omega-3 fatty acids. Enrichment of poultry meat and eggs with these fatty acids might provide an excellent alternative source. The omega-3 fatty acid content of both poultry meat and eggs can be readily increased by the inclusion of marine oils/meals in the diet. However, off-flavours associated with carcass and egg samples enriched in this way have prompted investigations into the use of terrestrial sources of omega-3 fatty acids. While effective in enriching meat and egg products with linoleic acid (18:3n3), plant sources result in only minor changes in the content of 20-carbon omega-3 fatty acids. Various methods of oil refinement and extraction, as well as alterations in production practices and the use of dietary antioxidants have been examined as ways to improve flavour quality and storage stability of omega-3 fatty acid enriched products. Continued investigation in the areas of sensory evaluation and product stability are needed if significant improvements in the health quality of foods available to the consumer are to be made.

Survey data collected by the University of California have quantified some current systems of commercial egg production in the USA as a whole and in the state of California. Specific comparisons are made. Respondents were asked to estimate certain changes in the egg production sector between the present time and the year 2000. These projections suggest: a continuing trend for contract production to decline in favour of company owned sites; some further increase in cage rearing; more attention to improved methods of handling manure and disposing of dead birds; and a continuing growth in the number of large scale in-line egg production complexes. The projection that the size of the USA layer population will increase by over 20% by the end of the decade is considered unlikely to happen.

The first quail chicks imported into Estonia were hatched in 1967 and the first quail farm was built in 1976. Commercial quail production began in 1980 and 10 years later annual egg production had reached 7.1 million and annual production of meat birds was about 10 tonnes. The development of quail farming in Estonia has depended on several factors, particularly the development through selection of improved egg-meat strains and successful research into incubation, brooding, nutrition and the husbandry and management of both broiler and egg production stocks. Current levels of performance under commercial conditions are for egg production of up to 86% or 315 (per bird housed) from 35 to 400 days of age. Average feed consumption levels as low as 2.62 kg/kg egg mass are achieved. Estonian broiler quail males average about 140 g and females 150 g live weight at 35 days and are considerably heavier than the original Japanese stock. Average feed conversion (males and females) is as low as 2.83 kg/kg live weight.

In the UK the poultry industry has a good record with regard to surface water contamination and has been responsible for only a small proportion of the total pollution incidents attributable to agriculture. Guidance is provided to farmers by a Code of Good Agricultural Practice for the Protection of Water. Because poultry manures have high concentrations of total nitrogen, with much of this in soluble form, the pollution of ground water with nitrates is a more serious problem. A voluntary Pilot Nitrate Scheme has been introduced in some parts of the UK which controls the quantities of animal waste applied to the land and also the timing of waste application. Linked to the scheme is a comprehensive programme of scientific monitoring. The broad requirements of the European Community Nitrate Directive are described. In the case of air pollution due to odours, poultry farms were reported to be responsible for 17% of complaints attributed to agriculture. Where appropriate, legislative means exist to reduce the nuisance and a Code of Good Agricultural Practice for the Protection of Air has been published. Some implications for poultry production in the future are considered.