Genetic engineering holds out great promise for the development of improved poultry vaccines. Engineered microbes containing foreign genes from several pathogens provide the basis for multivalent vaccines. The vaccine vector should be non-pathogenic and capable of incorporating and expressing foreigngenes. Subunit proteins expressed by non-avian vectors, such as baculoviruses, can be used to evaluate the nature of their antigenic and protective properties and could find use as subunit or virus-like particle based vaccines. Live recombinant viruses can also be used as vaccines. While RNA viruses such as picornaviruses have been used as vectors, DNA viruses are more easily engineered. Avian poxviruses expressing the Newcastle disease virus (NDV) haemagglutin neuraminidase (HN) and fusion (F) proteins protect against Newcastle disease. Because of their ease of administration through the feed or water, their ability to establish mucosal immunity, and recent advances in genome manipulation, avian adenoviruses are now being developed as recombinant avian vaccines. A recombinant fowl adenovirus expresses a green fluorescent protein reporter gene cloned into a non essential TR-2 region of viral DNA and is also immunogenic. Current efforts are directed at incorporating genes, such as HN from NDV, from avian pathogens into this vector. Genetic engineering can also improve diagnostics. For example, recombinant HN can be used in enzyme-linked immunosorbent assay (ELISA) based NDV diagnostic kits. Baculovirus expressed NDV nucleoprotein (NP) used in a differential ELISA can differentiate between birds immunised with a fowl pox virus expressing NP and NDV infected birds. Polymerase chain reaction (PCR) also has an impact on avian health. PCR can be used in diagnostics and, because of its extreme specificity, in epidemiological studies. Rapid and accurate identification and emerging or re-emerging microbial diseases are some challenges that can be more readily addressed by the application of molecular approaches including genetic engineering. Similarly, the development of multivalent and multi-pathogen vaccines through genetic engineering is certainly a realistic objective. Such vaccines would provide multiple protection in a cost effective manner.

The purpose of this study was to examine the prevalence and the extent of leg problems in broiler chicks reared in conventional production systems in Denmark. The survey, which was designed as a cross-sectional study, included 28 broiler flocks (8% of the total number of flocks in Denmark); 2800 chicks in total (100 chicks per flock) were investigated for the occurrence of leg disorders in relation to animal welfare. The leg disorders included impaired walking ability, tibial dyschondroplasia (TD), varus/valgus deformations, crooked toes, foot pad burns, and asymmetrical development of the tarsometatarsus. The mean prevalence of impaired walking ability (gait score > O), tibial dyschondroplasia (TD score > 0), varus/valgus deformations, crooked toes and foot pad burns was 75.0%, 57.1%, 37.0%, 32.6% and 42.0%, respectively. The risks of the occurrence of these leg problems were significantly influenced by body weight and sex of the chicks. For birds with impaired walking ability (corresponding to gait scores > 0 and >2), significant interactions were found between body weight and sex. Positive correlations (r > 0.20) were found between gait score and TD score, gait score and varus/valgus deformations, TD score and varus/valgus deformations, varus/valgus deformations and body weight, crooked toes and body weight, and between varus/valgus deformations and body weight. Only weak correlations were found between the relative asymmetry in the length, thickness and diameter of the tarsometatarsus and the other leg problems measured. It was concluded that the prevalence of leg problems in broilers in conventional production systems is very high and compromises the welfare of the birds. One of the main factors responsible is their high growth rate.

This paper discusses the village chicken upgrading programme in Malawi. It looks at the objectives of the programme, its implementation, the problems faced and how it can be improved. The village chicken upgrading programme started in the early 1950s. Its main aim is to improve egg and meat production from indigenous chickens through crossbreeding using the Black Australorp. The programme is hampered by many problems such as ill defined objectives and implementation strategies, lack of proper poultry husbandry skills, inconsistent and poor supply of birds, lack of cheap feed of reliable quality, prevalence of diseases, poor livestock extension services and lack of easily accessible veterinary services. Potential solutions and recommendations for improving the project are suggested.

Chicken genetic resources comprise a wide range of breeds and populations including red jungle fowl (the assumed progenitor of all domestic breeds), native and fancy breeds, middle level food producers, industrial stocks and specialised lines. Based on the suggestion that the more distant a breed or population is the more likely it is to carry unique genetic features, the assessment of genetic distances by means of molecular marker information may provide useful information for initial evaluation of chicken genetic resources. During the last two decades several molecular marker classes have become available. Variable numbers of tandem repeat loci, in particular microsatellites, have been successfully used in chicken diversity studies. Genetic diversity measures using the highly polymorphic variable number of tandem repeat lociyield reliable and accurate information for the study of genetic relationships between chicken populations. First results of the European project on chicken biodiversity (AVIANDIV) obtained from microsatellite typing in DNA pools of 51 diverse chicken breeds showed that jungle fowl populations, traditional unselected breeds and broiler lines appear to be widely heterogeneous populations that may include a large portion of the genetic diversity of the tested breeds. In contrast, highly selected strains (layers and experimental lines) are characterised by a lower polymorphism. They behave as outliers from the set of breeds sampled. Single nucleotide polymorphism is a new and very promising molecular marker system which offers opportunities to assess the genetic diversity in farm animal species differently by investigating the mode and extent of changes in certain positions in the genome.

Pulmonary hypertension syndrome (PHS, ascites) in broiler chickens provides an outstanding example of the pathophysiological interplay between the lungs and heart. Recent research has confirmed the hypothesis that PHS susceptible broilers have an inherent potential to outgrow their pulmonary vascular capacity. Definitive proof that pulmonary hypertension (PH) is initiated as a consequence of an excessive pulmonary arterial resistance was obtained through measurements of pulmonary wedge pressures. Definitive proof that a pulmonary diffusion limitation causes the hypoxaemia characteristic of susceptible broilers was demonstrated by the rapid return to full arterial blood oxygenation in pre-ascitic broilers when they were provided with 100% oxygen to breathe. Experiments involving acute and chronic unilateral pulmonary occlusion provided definitive proof that the entire pathogenesis of PHS can be replicated by reducing the pulmonary vascular capacity. These experiments conclusively demonstrate that the resistance of broilers to PHS depends upon the capacity of their pulmonary vasculature to accept the requisite cardiac output at blood flow rates and pressures sufficiently low to avoid triggering PH and systemic hypoxaemia. The chronic unilateral pulmonary artery occlusion technique was successfully applied to develop a broiler line that is highly resistant to PHS induced by fast growth and exposure to rigorous cool temperatures, demonstrating for the first time that a dominant gene codes for a highly significant proportion of the PHS susceptibility. We now possess the knowledge necessary to create broiler lines capable of maintaining extremely rapid growth under rigorous field conditions while retaining very low susceptibility to PHS.

The eggshell of the hen is a highly ordered, mineralised structure deposited within an acellular milieu – the uterine fluid secreted by the distal oviduct. Spherulitic crystal growth is initiated by deposition of calcium carbonate on aggregates of organic material present on the outer surface of the eggshell membranes. Gel electrophoresis reveals a complex array of proteins in uterine fluid and eggshell extracts. The eggshell matrix proteins can be classified as egg white proteins (lysozyme, ovalbumin, ovotransferrin, clusterin), bone protein (osteopontin), or proteins specific to the uterus and eggshell (ovocleidins-17 and –116; ovocalyxins-32 and –36). Eggshell extracts, uterine fluid and purified fractions are able to modify the morphology of calcite crystals in vitro. In young hens the breaking strength of the eggshell is inversely related to the degree of calcite orientation. Conversely, reduced strength in eggshell from aged hens coincides with a high variability in crystallographic texture. In guinea fowl the exceptional mechanical properties of the eggshell are explained by an increase in the amount of eggshell produced and particular features of the crystallographic texture. These observations suggest that the eggshell matrix influences the process of crystal growth by controlling size, shape and orientation of calcite crystals. This structural control probably contributes in a substantial manner to the mechanical properties of eggshell.

Two World Poultry Congresses have beeb held in the United States, in 1939 and 1974. The USA Branch of the World's Poultry Science Association was not formed until after the first of those. In order to recognise the contributors of the many who have been active, this review of the history of the USA Branch was prepared. It gives the objective of the organisation, the officers during the 35 years and a list of some of the more important activities.

Fertility in poultry is generally measured as the “percentage fertile eggs” laid by hens during a period of time following artificial insemination or natural mating. This parameter has presented some problems for the statistical analysis of fertility and its main limitations derive from the binary classification of an egg as fertile or infertile. An alternative measurements of breeding efficiency is the number of soermatozoa that associate with eggs at fertilisation. These can be estimated in laid eggs and present a robust and fundamental measurement of the efficiency of sperm transfer into hens. In several applications they have revealed differences in the efficiency of mating or artificial insenination that were not discernible by traditional estimations of fertility.

Hatching birds which have been dependent on the yolk for their energy supply during much of the embryonic period must undergo a rapid transition to utilising carbohydrate rich exogenous feed. This change is accompanied by the preferential growth of the small intestine and activation of digestive enzymes and absorption pathways. The ontogeny of these processes is described and includes the intense development immediately after hatching. The effect of delayed access to feed on intestinal development is also discussed.

Agricultural commodity group scholarships are viewed as recruitment tools. Career choices of poultry scholarship recipients on the west coast of the USA were analysed. Responses of recipients who entered non-poultry careers included reports of how they use information from mandated poultry courses, how they informally educate others about poultry, and how they volunteer with poultry youth programmes. Teachers told of using poultry examples in class. Other professionals gave accounts of disseminating positive poultry information in the course of their work. Poultry and other agricultural trade associations realise many unforeseen benefits by supporting worthy students, even when the students do not enter an agricultural career.