Chinese natural medicinal products as feed supplements have been used as growth and health promoters in farm animals in China for centuries. A current estimation of the number of Chinese natural medicines ranges between 6,000 and 8,000, of which less than 5% has immuno-active properties. Most of these medicinal products originate from plants. Polysaccharides are considered to be the most important components, which may act as immune enhancers or immuno-modulators. The relationship between polysaccharide structure and bio-activity is, however, not well understood. In this review, immune activities of the polysaccharides from two mushrooms, Lentinus edodes and Tremella fuciformis, and a herb, Astragalus membranaceus radix, are reported, based on studies in chickens, mice, rats and humans. It can be concluded from these studies that polysaccharides derived from these products can play important roles in: (1) stimulating the growth of immune organs such as spleen, thymus and bursa; (2) increasing the number and activities of many interdependent cell types such as T, B lymphocytes, macrophages, natural killer (NK) cells and lymphokine-activated killer (LAK) cells; (3) enhancing T-cell mediated immune response, such as an increased rate of T-lymphocyte transformation and proliferation; (4) enhancing humoral immune response, such as spleen and serum antibody production, the number of haemolytic plague forming cells (PFC) and haemolysin production and (5) inducing secretion and production of cytokines and complements of T-cells and NK cells.

Today's poultry producers are confronted by numerous prophylactic techniques to prevent diseases. The immuno-active polysaccharides from mushrooms and herbs might be good candidates as health promoting feed additives in poultry diets. Further studies are needed to investigate the effects of such bioactive components to improve productive performance in chicken and to elucidate the possible modes of action related to the gut ecosystem and the immune response.

This paper provides a review of research on ascorbic acid as a nutrient in poultry published subsequent to a major review in this journal in 1986. Further experiments have confirmed the effects of a nutritional supply of AA in limiting the metabolic signs of stress and alleviation of the physiological consequences of stress is manifest in the performance, immunological competence and behaviour of birds. Birds under stress can recognise the stress-relieving properties of a diet containing AA and increase their intake of it, though they require a colour association to make the correct diet selection. Practical studies have generally confirmed the experimental findings, though the responses have been more variable, perhaps because of the greater difficulty in establishing the degree of stress experienced by birds under practical conditions. Optimum responses in growth, feed efficiency and/or liveability in broilers under heat stress seem to occur with supplements of about 250 mg AA/kg. Laying hens under stress, particularly climatic stress, have also shown responses to supplemental AA. This has resulted in improvements in liveability, food intake, egg production and egg quality with dietary AA concentrations in the range 250–400 mg/kg. AA can be beneficial in countering the adverse effects on shell quality of drinking water containing a high concentration of salts. The AA concentrations that have been found to be effective lie in the range 1–2 g AA/kg feed or /I drinking water, though it is possible that breed differences or additional stress factors might affect the response. Studies on the role of AA in the growth of poultry bone and connective tissues have suggested possible benefits of dietary supplementation in some stress or disease situations. AA has also been shown to interact with a number of other vitamins and minerals.

This special report is based on the proceedings of a workshop organised by the Federal Ministry of Consumer Protection, Food and Agriculture, the Institute for Animal Science, Mariensee and the Federal Agricultural Research Centre (FAL), on ‘Management of newly hatched male chicks from layers.’

The background was the fact that in Europe each year, about 280 million male chicks from layers are culled immediately after hatching. In Germany and in other countries, this has resulted in some public concern and political discussion. The objective of the workshop was to summarise and exchange current knowledge on sex determination and sex diagnosis in chicken with special emphasis on potential alternatives to culling male layer chicks.

Academic poultry science in the United States had its origins in the early part of the 20th century. It reached its peak with 45 active departments in the 1940's, but then started to decline significantly in the 1960's. Today, there are only 7 active departments. There have been a number of published theories as to why as the industry grew the academic programs disappeared. Declining student numbers and failure to address industry concerns are the primary theories. This paper addresses all of the available published work together to present the situation as it evolved and point to the potential outcome.

Apart from elimination of errors in obtaining exact measurements of feed intake and total faeces output in the traditional total collection method, the use of markers to determine nutrient digestibility of feeds in animal species would fit into animal welfare considerations. The external marker chromic oxide has been the prominent marker in the 1960s to evaluate metabolizable energy content of feeds for poultry. A preliminary feeding period of 5 days and collection of a sample representing day and night excreta over a 24 hour period have been suggested as protocol to get reliable results with the use of chromic oxide as marker. However, difficulty in obtaining repeatability between laboratories because of the analytical assay for chromic oxide, variability in results, incomplete and inconsistent recovery in excreta, and hazardous possibilities, resulted in replacement of the chromic oxide marker technique with the method of total excreta collection. Although titanium dioxide, which can be analysed by an accurate and simple colourimetrical assay, has been used in several studies in poultry, only one study has evaluated this marker for recovery (98%) in excreta. The internal marker, acid-insoluble ash, which also could present an external marker when the internal content is aided with the use of siliceous substances, is gaining popularity in recent times, although most studies presented higher digestibility values with this marker in avian species than those derived through the total excreta collection method. Lack of standardisation of analytical assays could partly explain the latter phenomenon. Although crude fibre has presented recovery rates of near 100% in excreta of laying hens and turkeys, fear of possible digestion of this substance by cecal microflora has prevented the further utilisation of this substance as marker. Lignin, determined by digestion in 72% sulphuric acid, presented recovery rates of 99 and 98% in chickens and ostriches, respectively, and similar (P>0.05) results than the total collection method in partridges. The elimination of the use of markers to determine energy metabolizability and nutrient digestibility with avian species have been based on a small number of studies conducted mainly before 1965, and extrapolation of results obtained with other animal species.

Newcastle disease (ND) is a highly contagious disease. The present paper deals with classification of ND virus (NDV), clinical signs and pathology, virus strain classification and molecular backgrounds for the pathogenicity. Major emphasis is reviewing immunity and vaccination. Clinical forms of the disease vary depending on many factors, but mainly on the virulence of Newcastle disease virus (NDV) strains. Virulent strains are considered List A pathogens by the ‘Office International des Epizooties’ (OIE). The virulence has been traditionally determined using in vivo pathogenicity tests to distinguish between highly, moderately and low virulent isolates. More recently, molecular biological techniques like polymerase chain reaction and sequencing have been described to differentiate virulent from non- virulent strains.

The systemic and mucosal immune systems are considered to function more or less independently. Systemic antibodies are essential elements in protection against ND, whereas the local antibodies limit multiplication of NDV at the site of entry. Cytotoxic T lymphocytes specific against NDV have been detected in the spleen of vaccinated birds, however, their contribution to protection remains to be elucidated.An increase of the number of various leukocyte subsets was noticed in the respiratory tract and the Harderian gland (HG), which favours involvement of local cellular immunity in the defence against NDV infection. It is tempting to speculate that the local lymphoid infiltrates are involved in first defence and that cytolytic cells clear virus by directly lysing infected target cells at the site of NDV inoculation. Secondly, various cell types, mainly T-lymphocytes and macrophages, may be equipped to produce a range of cytokines with antiviral activity and cytokines that stimulate B-lymphocytes to proliferate and differentiate into antibody-forming cells responsible for the local antibody production against NDV.

Birds, reptiles and insects (e.g. Hymenoptera) share fundamental similarities in their reproductive strategies due to the presence, in the female tract, of specialized sites in which spermatozoa may reside for prolonged periods upon a single mating. In avian species, two distinct storage sites are present, one located in the utero-vaginal junction and the other in the lower portion of the infundibulum. At both sites, spermatozoa are stored in sperm storage tubules (SSTs) which are discrete, generally non-branched invaginations of the luminal epithelium (see review by Bakst et al., 1994). The SSTs located in the uterovaginal junction are considered as the main site of residence of spermatozoa upon their deposition in the lower portion of the vagina. The fertilizing potential of females along the reproductive season is at first dependent on their ability to store and maintain adequate populations of spermatozoa in their SST in order to repeatedly provide the site of fertilization with sufficient numbers of “fit” spermatozoa after each ovulation. As a consequence in poultry species, eggs from females with prolonged sperm storage potential have also a natural tendency to maintain optimal fertility rates for prolonged periods. This situation may be highly desirable to sustain high fertility in the case of partial failure of the males during the season.

This review is an attempt to address the main intrinsic and extrinsic factors capable of favouring or altering fertility in poultry species. Unfortunately, most of the information available is obtained from two species, namely the domestic fowl and turkey, which, in certain circumstances, may not reveal enough to pinpoint the controlling factors of fertility in other poultry species.

The major polyunsaturate in phospholipids of chicken spermatozoa is docosatetraenoic acid, 22:4n-6, which is positively correlatable with sperm motility and fertility. The potential for dietary manipulation of sperm fatty acid in order to improve male fertility has been extensively studied in the chicken. The effects of diets enriched in n-3 and n-6 long chain polyunsaturates have been investigated in different trials using different oil sources and levels of oil inclusion.

The 22:6n-3 and 22:5n-3 content of avian spermatozoa is increased by supplementing the feed with fish oil (rich in 22:6n-3) and linseed oil (rich in 18:3n-3) respectively. The 22:4n-6 content is also increased by supplementing the feed with evening primrose oil (rich in 18:3n-6) in association with high level of vitamin E (200 mg/kg) and with arasco oil (rich in 20:4n-6). The effects of these fatty acid manipulations on sperm quality and/or fertility are reviewed. Both n-3 and n-6 rich diets showed a positive effect on sperm movement during the reproductive period and an age-dependent positive effect on fertility. Reported effects of n-6 rich diets on semen production have been variable with 20:4n-6 rich diet having a positive effect on semen volume and thus on total sperm number and 18:3n-6 rich diets having a negative effect on semen concentration. Spermatozoa enriched in 22:5n-3, or 22:6n-3 or 22:4n-6 result in significantly higher fertility values following artificial insemination compared to control spermatozoa; however, such a positive effect is age dependent and observed at 37 to 42 weeks, but not in older birds.

The n-6 fatty acid composition of chicken spermatozoa is recognised as a specie-specific characteristic. The fundamental relation between dietary lipid, spermatozoa fatty acid composition and thus sperm quality and fertility can be seen as having a potential commercial application.

Studies on genetically modified (GM) feedstuffs for poultry (and other livestock species) have not added any substance to public concerns in Europe about their safety for human or bird health. The compositions of maize lines engineered for insect resistance (Bt-maize) or herbicide tolerance (glyphosate) and herbicidetolerant soybean have all proved to be essentially indistinguishable from their conventional counterparts. Consequently, and not surprisingly, comparative feeding studies with broilers and layers in which conventional maize (50 to 78%) or soybeans (27%) were replaced in feeds by transgenic varieties, also have failed to show differences of any significance in production parameters. These data indicate that feeding studies with target livestock species contribute very little to the safety assessment of crops engineered for input traits that have little or no detectable effect on chemical composition. However, comparative growth studies made with broiler chicks, particularly sensitive to any change in nutrient supply or the presence of toxic elements in their feed, can be used to screen for any unintended adverse consequence of the recombinant event not detected by compositional analysis. This does, however, depend on whether the GM plant can be matched to a parental line or another suitable control and its suitability for inclusion in broiler diets. The discovery that DNA fragments from the digestive tract can be found in the tissues of animals evoked interest in the fate of ingested transgenes. Plant DNA derived from feed has been detected in the muscle, liver, spleen and kidneys of broilers and layers, although not in eggs. However, no fragments of transgenic DNA or its expressed protein have been found to date in poultry meat or eggs or in any other animal tissues examined.

Proper estimation of the nitrogen (N) content of poultry manure and proper manure handling are necessary to ensure that application rates minimize emissions from the manure and nitrate leaching into the cropland. Uric acid and undigested proteins are the two main N components in poultry manure that cause ammonia emissions and nitrate leaching in the ground water. The ammonia that is applied to cropland may be 50 to 90% of total N, depending upon the way the manure has been stored or treated. Ammonia and hydrogen sulphide contents have been proven to be useful alternative measures of odour reduction. The order of importance in influencing ammonia formation is : litter pH > temperature > moisture content. Total fixation of ammonia was achieved below pH 4 and temperatures down 10°C are necessary to have a negative effect on degradation and volatilisation. Adsorbants such as sawdust and straw enable the capture some of the readily available N and enable the microbial population to start immobilizing N. The organic fraction of poultry manure had a C/N ratio that varied from 1 to 27:1. Most of the N (approximately 60 – 70%) excreted in poultry manure is in the form of uric acid and urea. Total N, total Kjeldahl N (TKN), organic N, ammonium, nitrate and nitrite are significantly correlated with the amount of N mineralised as well as the fraction of organic N mineralised during incubation. Some useful equations are: Inorganic N (IN) = ammonium + nitrate + nitrite; Total N (TN) = TKN + nitrate + nitrite; Organic N = TKN – ammonium or TN – (ammonium + uric acid) or TN – IN; Available N (AN) = Inorganic N + 0.4 × organic N; Predicted available N (PAN) = 80% Inorganic N + 60% Organic N.

Genetic variations for feed utilization efficiency widely exist in meat-type chickens, even in populations that have undergone selection for the trait. The trait has moderate heritability and is moderately correlated with growth rate. The genetic basis for the trait was thought to be different from that for growth even though they may be related. As a result, the improvement in feed efficient through selection for body weight should be limiting. Fast growing birds require more nutrients and energy for maintenance. When age-fixed measure is used, part of the genetic variation of feed efficiency for growth may be masked. For this reason, adjusted age-fixed feed efficiency should be used in commercial breeding. The combination of restricted maximum likelihood (REML) method with an animal model can greatly account for the effect of selection of breeding population, leading to more accurate estimates of genetic parameters. The identification of quantitative trait loci (QTL) for feed efficiency in chickens has begun. The incorporation QTL in the prediction of breeding value will further improve selection efficiency for feed efficiency. While it was generally assumed that there is little variation in digestibility and metabolizability of feed within and between different strains or breeds, selection for growth rate has resulted in increased digestive enzyme activity. This suggests that the improvement in digestive ability could not be ignored in investigating new approach for increasing feed efficiency in meat-type chickens. Selection for improved FCR makes birds deposit less of the retained energy as fat and convert more energy and nitrogen into body protein. A negative effect of selection for feed efficiency is that, the combination of fast growth and improved FCR is related to increased occurrence of ascites. Index selection based on weight gain and feed intake could be better for improving FCR.

1. A series of experiments was conducted to determine the effects of dietary levels of total digestible amino acids (TDAA) and undigestible crude protein (UCP) on growth performance ofbroilers between 11 and 32 days of age.

2. Increasing TDAA in broiler diets from about 160 to 190 g/kg improved feed conversion ratio (FCR) linearly.

3. Increasing dietary levels of UCP from about 30 to 45 g/kg had negative effects on body weight gain (BWG) and FCR.

4. Thecombination of dietary TDAA and UCP contents provided a better predictor of BWG and FCR in young broilers than diet Crude Protein (CP) content.

5. For formulation of commercial broilerdiets more emphasis should be placed on measuring digestibility of protein in feed ingredients and complete feeds.

6. More research is required to measure, quantify and predict the negative effects of proteolytic fermentation in the intestinal tract of broilers on feed utilization andanimal health.

Broilers are reared in an intensive production system starting with a small initial live weight that increases dramatically by the end of the production cycle. Within the broiler house there are consequent changes in heat, moisture and carbon dioxide production. Microbial decomposition of faeces and litter produces a number of aerial contaminants, particularly ammonia and dust as well as a complex of compounds responsible for the characteristic odour associated with these enterprises. The concentrationof most aerosol particles increases during the production period. Ammonia emissions from livestock buildings have considerable localised environmental effects when deposited on the adjacent land. High levels of inspirable dust can cause respiratory problems in broilers and the particles carry a proportion of the odorous volatile compounds that often attracts adverse comment by neighbouring residents.

To accommodate the rapid transition to external nutrients, the chick's gastrointestinal tract undergoes dramatic changes within the first few days of life. These include a rapid increase in mass, villi number and length, enterocyte number, crypt depth and proliferating cells. Concomitant with the development of digestive structures and functions a rapid development of the gut associated lymphoid tissue (GALT) occurs. This lymphoid system works within and in concert with digestive tract parenchyma, however, there is little information describing the normal development and immunological function of the avian GALT in the immediate post-hatch period. The purpose of this review is to summarize current knowledge on the structure and function of the avian GALT during the early post-hatch period. At hatch, the gut is poorly populated by both innate immune leukocytes and lymphocytes. The basal numbers of lymphocytes are the result of early waves migrating from the thymus and bursa of Fabricius. Further waves of lymphocyte migration occur after 4 days of life and continue intermittently with time. In concert with this pattern of lymphocyte population adaptive immunity develops. Hence, the gut of the hatchling is unprotected by adaptive immunity during the first few days of life. Protection during this critical period might be the result of maternal antibody activity or that of the innate immune system. This system appears to be functional at this time, though much work is needed to establish this possibility. Upon maturity of the immune system, most of the immunological activity within the chick GALT is concentrated in the hindgut, and specifically so in the caeca and bursa of Fabricius. Once immune responses have become established the relevant cells disseminate systemically and to other areas of the small intestines. Finally, observations on the beneficial effects of early feeding on development of gut and GALT are discussed with reference to management of hatchlings.

Chickens, unlike red meat species, do not show grand ma1 epilepsy in the brain following electrical stunning. The underpinning causes of this and the brain mechanisms associated with the induction and maintenance of electrical stunning induced unconsciousness in chickens have not been elucidated. However, the changes occurring in the electroencephalogram (EEG), abolition of somatosensory evoked potentials (SEPs), induction of seizure and loss of muscle tone or physical reflexes following electrical stunning have been used in the past to ascertain the effectiveness of waterbath electrical stunning in chickens.

The purpose of this appraisal is to evaluate scientifically the relative merits of some of the criteria that have been used for ascertaining the effectiveness of electrical stunning in chickens. Scientific literature suggests that, unlike red meat species, the electrical stunning-induced release of monoamines and inhibitory amino acid neurotransmitter(s) in the chicken brain may play prominent roles in the induction and maintenance of unconsciousness following electrical stunning. These mechanisms would also appear to be relevant to the manifestation of a profoundly suppressed EEG and abolition of SEPs following electrical stunning, which are suggested to be meaningful indicators of an effective electrical stunning in chickens.

Bird behaviour, production, physiological measurements of stress, and pain as indicated by neural transmission in, and anatomy of the trimmed beak have been used as criteria to determine if beak trimming compromises bird well being. In addition, the welfare of those hens that are pecked by beak-intact hens has been evaluated. The welfare of a flock is assessed by mortality, incidence of cannibalism, feathering, and flock behaviour such as fearfulness or nervousness. Disadvantages of beak trimming include short-term and perhaps long-term pain, and short-term stress following beak trimming. Because feeding behaviour must adapt to a new beak form, a bird's ability to consume feed is impaired following beak trimming. Welfare advantages include reduced pecking, feather pulling, and cannibalism; better feather condition; less fearfulness and nervousness; less chronic stress; and decreased mortality. It appears that the welfare disadvantages are applicable to individual birds whose beaks are trimmed, while the welfare advantages are more applicable to the interactive flock. Behavioural evidence suggests that primary breeders of egg laying strains can select for more docile birds and minimize the need to beak trim. Therefore, using genetic stocks that require little or no beak trimming is the most desirable approach. However, under certain management systems (e.g., exposure to high intensity natural lighting) and with some genetic stocks, beak trimming is needed to prevent feather pecking and cannibalism. When employed, beak trimming should be conducted at 10 days of age or younger by trained personnel.