Another busy year in the poultry science world – with several major conferences being held – notably the Norwegian meeting in June. Many thanks to the organisers there who were very helpful in letting authors know about publishing suitable reviews in the Journal from the topics they presented. This issue has several papers that touch on the same topics – which sometimes happens in publishing. When papers are unsolicited and are submitted unselectively, it is interesting that similar topics crop up – albeit with a different focus depending on the authors. We have more papers regarding disease and manure in this issue – both important topics. Necrotic enteritis, for example, seems to remain a major issue for poultry producers, albeit one which is better understood and rectified nowadays. As I write, we are preparing for our annual board meeting in Korea in October. There are many new developments in the world of publishing – open access to papers, changes in online publishing and so on – and it is my responsibility to update the Board regarding such issues. In addition, we move from strength to strength in terms of submission of unsolicited papers from around the world, and greater volumes of papers require higher degrees of management and selection. As such, we are currently reviewing methods for speeding up publication times for authors, whilst balancing the extra papers coming through. Watch this space! Hopefully I will have caught up with many colleagues and friends at Korea’s APPC – if not I wish you all well and trust that 2014 has been a good year for you.

Best wishes to all

Dr Lucy Waldron

Editor

The cuticle is the outermost layer, deposited on the palisade layer of the eggshell during the last 1.5-2 hr of eggshell formation in utero. It is a non-calcified, thin, water-insoluble layer composed mainly of glycoproteins with some carbohydrate and fat constituents. The cuticle functions as a protective layer which regulates gaseous exchange across the shell, acts as a first line of defence against microbial penetration across the eggshell and is associated with termination of calcite crystal growth during shell formation. The extent of cuticle deposition is influenced by hen age and strain. The physiological and microbiological characteristics of the hen eggshell cuticle are reviewed in relation to its protective functions.

There are many challenges and opportunities in composting poultry litter removed from broiler houses. These include reducing operational costs and managing compost moisture, NH3-N losses, and odours. This review paper reports on systems for composting broiler litter that require little or no amendment, while controlling N emissions. Poultry litter, as removed from broiler houses, has a moisture range of 22-50%, N content of 3-5.9%, and a carbon to nitrogen ratio of 9-12. Recommendations, based on field studies and economic analysis, have concluded that composting broiler litter is most economically done with little or no amendment and at starting moisture levels around 40% or less. Pilot and field studies using various composting methods, some of which employ continuous or intermittent aeration regimes as well as static windrows or piles, have been reported. Related studies based on composting un-amended caged layer manure are discussed along with their application to broiler litter. Results suggest the most applicable system for broiler litter for producing a low moisture, high N product would be an in-vessel system with forced aeration, mechanical turning, and a high NH3 level (>160 ppm) in the ambient environment surrounding the compost. Such a system would not produce a mature compost, but would lead to a stabilised (10-18.6% dry matter loss), dry product (10-18% moisture), with high nitrogen content (12-15% total N loss) that could be marketed to nurserymen and gardeners, as well as general farmers.

Telomeres are specialised nucleoprotein end structures of eukaryotic chromosomes and protect and maintain genome integrity from recombination, exonuclease degradation and end-to-end fusion. Because of the end replication problem, telomere length in somatic cells tends to decrease with organismal age. Telomere shortening is known to occur in chicken somatic tissues and correlates with advanced developmental age. However, age is not the only determinant of telomere length in an individual. Several factors at the genetic and epigenetic levels are known to affect telomere length in different ways. Herein, we review several factors that affect telomere length in the chicken. Genetic factors include breed and sex, while the epigenetic factors include environmental and stochastic influences. Age, stocking density and living or housing systems were reviewed as environmental factors pertaining to the habitat of the organism. Factors such as oxidative stress, antioxidants in feed and restriction feeding were the stochastic factors that we reviewed.

This review examines methods for culling small numbers of poultry on farm, considering both common techniques and methods that are yet to be tested on poultry. The aim of this review is to inform the design of experiments that will assess the pros and cons of culling techniques. The methods reviewed include manual and mechanical cervical dislocation, crushing methods (such as burdizzos or pliers), percussive devices, blunt force trauma and a brain-stem piercing device. Previous work on these approaches, of which there is a limited dataset, has relied on behavioural and brain activity as proxy measures of unconsciousness (insensibility) and death, however there remains some uncertainty as to when birds can be considered unequivocally insensible. These factors will be considered when deciding which of the methods will be recommended to be taken forward for further assessment.

Immunosuppressive viral diseases have become a major cause of mortality and economic losses in poultry industry mainly because of increased susceptibility of second bacterial infections and low response to vaccination. Nowadays chicken infectious anaemia is a great threat to poultry industry due to the large number of deaths and immuno-suppression it causes. Chicken anaemia virus replicates in erythroid and lymphoid progenitor cells, causing an apparent, sub-clinical infection that leads to depletion of these cells with consequent immunosuppressive effects. This review will summarise the currently available information about the chicken infectious anaemia virus and subsequent disease. Secondly, it will address the possible immune-pathogenic and immune-suppressive effects of chicken infectious anaemia in birds, including commercial poultry. Finally, the future prospects of vaccination against chicken infectious anaemia and other possible novel methods for the control of chicken anaemia virus are discussed.

This review examines the emergence of drift variants of low pathogenic avian influenza (LPAI) viruses, with particular focus on their occurrence in India. Influenza viruses are dynamic and continuously evolving, and variants emerge from the instability of these viruses due to their constant mutations through antigenic drift. The drift variants emerging from the LPAI viruses gradually acquire higher virulence, inflicting heavy mortality and severe economic losses. Different aspects covered in reference to the Indian observations include mortality, clinical signs, post mortem lesions, and differential diagnosis. In addition, the cause of death based on the typical lesions encountered, and the limitations of any vaccination programme to control the variants are discussed in a global context.

A gravity model was used to determine the impact of exchange rate volatility on turkey trade flows. Previous analyses of aggregate agricultural sectors or products have assumed the effect of exchange rate volatility is uniform, that is, it impacts the individual components of the aggregates in the same way. This is highly unlikely, given the differences in biological and marketing factors across commodities and sectors. In order to address this issue, we examined how exchange rate volatility affects international turkey trade rather than the more commonly analysed ‘poultry’ trade. Findings revealed that the effects of short- and long-run exchange rate volatility on bilateral turkey trade are positive and statistically significant. Increasing distance between importing and exporting countries has a negative effect on turkey trade flows, while being a member of NAFTA and EU-27 has positive impacts on those flows.

In developed countries, small farmer entrepreneurs contemplating poultry production are becoming more interested in assessing mobile poultry processing units (MPPU) to add additional value to the birds they sell in urban or farmers’ markets. However, there continues to be a lack of viable poultry processing options for small flocks as evidenced by the recent United States Department of Agriculture map, which depicts the locations of both small farms and processing facilities, county by county, across the United States. This map substantiates the need for more affordable poultry processing options to serve small-scale farmers. Many small-scale farmers operate MPPUs under federal exemptions that exclude them from continuous inspections by the USDA's Food Safety and Inspection Service, but they are still required to meet all sanitation and wholesomeness requirements. Costs associated with processing are somewhat less under this exemption, but one is unable to sell poultry as having been inspected in the open market. The USDA-FSIS has also created a mobile slaughter unit compliance guide for those who wish to be USDA regulated. Either way, regulated or unregulated, the MPPU may be an affordable and efficient solution to add value to small flock production. Small-scale poultry farmers, both organic and pastured, may benefit from the opportunities associated with mobile processing.

Sub-clinical necrotic enteritis (NE) is a major economic cost to the broiler production industry due to poor growth and feed conversion efficiency of broiler chicken flocks, higher condemnation of livers or rarely the whole carcasses at the slaughter house and an increased risk of microbial contamination of poultry meat. Sub-clinical NE is a multifactorial disease although Clostridium perfringens plays a major role in its pathogenesis. Its diagnosis and confirmation are quite different from those of general infectious diseases. Disease confirmation is from the presence of necrotic or ulcerative lesions on the small intestinal mucosa with identifiable aggregates of pathogenic C. perfringens. C. perfringens numbers in the small intestinal digesta or the mucosal scrapings are not correlated with disease severity, whereas counts above 106 cfu/g in the caecal contents indicate an increased probability of NE-specific gut lesions. Not only does the presence and counts of C. perfringens strains capable of producing related toxins affect the incidence of the disease but also a number of predisposing factors are important in the aetiology of NE. The major factors that predispose growing chickens to sub-clinical NE are diet variables, diseases that cause mucosal damage of the intestine and environmental factors that either alter the development of gut associated lymphoid tissue or change litter quality within the production house. Dietary variables may be a major cause of variation in sub-clinical NE in commercial broiler production; differences in polysaccharides, lipids, protein sources, protein digestibility and the presence of antinutritive factors have been identified as variables affecting the incidence of the disease.

This review covers the egg production models used in poultry. Similarities and discrepancies among the models are illustrated using a real data obtained from a layer breeder flock. Egg laying in poultry begins at sexual maturity and quickly reaches peak production, and then declines with hen age. For many years, egg production studies have been carried out for the purpose of modelling. Some of the functions were developed for this purpose, such as nonlinear regression equations (Gamma, McNally, McMillan, Adams-Bell, Compartmental, Modified Compartmental, logistic-curvilinear, Gloor, Lokhorst, Narushin-Takma) and some Multiphasic (Segmented Polynomial, Persistency, Individual). Almost all of these functions have been developed to allow modelling on the basis of flock averages. Most models having empirical structure and a small number of parameters are considered biologically meaningful. New models are currently required to be useful for both individual egg yields and to contain biologically relevant parameters.

Newcastle Disease (ND) is regarded as one of the major diseases of poultry because of the devastating losses that the virulent form of the ND virus can impose on both commercial and domestic chickens. However, the disease can be controlled through the administration of effective vaccines. Almost all the commercially available ND vaccines require refrigeration and begin to deteriorate rapidly after 1-2 hours if left at room temperature (around 25°C). Subsequently, because maintaining an adequate supply of refrigerated facilities may be a difficult task in many countries with unreliable electrical supplies, the development and large scale production of an effective thermostable ND vaccine seems imperative to support the poultry industry. Such vaccines should be resilient to damage associated with either very cold or hot environments so there are no concerns about the viability of the vaccine in response to temperatures fluctuations that can occur in extreme environments when the difference in temperature during cold and warm seasons can vary greatly. In the following review paper, the development of such a vaccine is discussed, including molecular characterisation, organ tropism of vaccine strains, production, as well as administration methods and their efficacy. It addition, the potential payback has been calculated alongside opportunities provided by removing vaccines from cold chain storage.

Ammonia (NH3) emissions from poultry farming operations have become a crucial concern due to their potential adverse effects on performance, birds and human health, and the environment. Due to genetic improvements, current commercial poultry require high quality balanced nutrition to maintain their rapid growth and production. Amino acids are components of protein nutrition that greatly influence the growth of the birds, and methionine is the first limiting essential amino acid in the high protein diets of poultry. However, excess or misuse of amino acid supplementation to poultry diets increases nitrogen (N) excretion and emissions to the environment. Currently, there are limited numbers of research publications regarding NH3 emissions from poultry manure, and few of them address manure enhancement by microbial nitrification. Therefore, the aim of this review is to evaluate the potential of soil nitrifying bacteria to reduce NH3 volatilisation and enhance N retention in poultry manure. This review presents the current status of knowledge regarding soil nitrifying bacteria, NH3 nitrification, and summarises the strategies to enhance microbial nitrification of poultry manure, and the environmental ramifications when using different techniques to control NH3 emissions. In spite of the fact that there are few research studies on reducing NH3 volatilisation through nitrification, it has been concluded that nitrification would be a sustainable method for mitigating N excretion and NH3 emission from poultry; however, further research is needed to identify the proper nitrifying bacteria to enhance microbial nitrification.

Since January 2006, the use of antibiotics for domestic animals as feed additives has been banned within the European Union, influenced by the consumers’ demands for products free of antimicrobial residues. As an alternative, probiotics in animal nutrition have attracted attention for their potential roles as growth promoters as well as antibiotics. Recently, much research data has been gathered and suggests a potential role for probiotics from fungi as natural growth promoters in broiler nutrition. One such fungi, Aspergillus awamori, has been shown to improve the growth performance and meat quality of broiler chickens. This review examines the current scientific data on the use of A. awamori as a probiotic in broiler nutrition. From the available literature, it can be concluded that A. awamori may provide an effective alternative to antibiotics in the production of broilers.

Necrotic enteritis (NE) caused by Clostridium spp. is an economically significant bacterial disease of poultry worldwide. Traditionally the disease has been prevented through feed supplementation with antibiotics sub-therapeutically as antimicrobial growth promoters (AGPs). However this practice has led to the emergence of resistant pathogenic microbes and drug residues, potentially threatening animal and public health. Therefore the marketing and incorporation of AGPs into poultry feed has been banned in Europe which has exacerbated the incidence of NE, bringing about huge economic losses to poultry farmers. Poultry researchers, exporters and consumers have emphasised AGP-free poultry rearing and have been searching for non-antibiotic and cost effective alternatives to control NE. Strategies suggested include vaccination, coccidiosis control, probiotics, competitive exclusion products, prebiotics, egg yolk immunoglobulins, bacteriophages (or phage gene products), organic acids, feed enzymes, plants and plants extracts/essential oils and nutritional changes.

There are many predisposing as well as virulence factors for NE induction and pathogenesis and more are expected to be discovered in the future. The ambiguous pathogenesis trend of the disease is still hindering the development of a potent active vaccine against NE. The choice of a single and fully effective approach is difficult. However, probiotics and specific egg yolk immunoglobulins (IgYs) alone or in combination could serve as promising strategies for controlling NE in broilers in the absence of AGPs.

The World’s Poultry Science Journal is indebted to Prof J.A. Castello, Prof D.K. Flock, Dr D. Grastilleur, Dr S. Cherepanov and Prof N. Yang for the translations of these summaries.