Enzymatic activity assays, used mainly to show biochemical transformations in humans and mammals, have recently found increasing application in birds. Enzyme activity in birds is affected by numerous factors, including age, sex, species, breed, nutrition, physiological state, and farming techniques. In large-scale poultry breeding, in a flock that may number over ten thousand birds, individual birds may be in different stages of development of a disease process, and may respond differently to stress factors present during rearing. There is also high individual variation among birds, so that results of enzyme activity analyses fall within fairly broad ranges. The aim of this paper is to review experiments on the activity of selected antioxidant, liver and cardiac enzyme profiles in turkey tissues. The results of many years of measurements of the activity of selected enzymes, presented in this study, may be considered physiologically normal for this group of birds. Analyses of the activity of these enzymes are important in determining whether oxidative stress reactions are induced in cells and which cells or organs have been damaged. During oxidative stress, which leads to cell damage or organ dysfunction (of the liver or heart), there is generally an increase in the activity of AST, ALT, ALP, LDH, GGT, SORD, MDH, AC, G6PC, G6PD, Cp, CK and HBDH, and a decrease in that of SOD, GPx, CAT, ACHE, BCHE, SDH, Ca2+ATPase. On the basis of the literature reviewed it can be concluded that the use of feed components and supplements with antioxidant or immunostimulatory properties can mitigate oxidative stress, which is manifested as beneficial changes in the activity of these enzymes.

Confinement housing appears to be at the forefront of concern about farm animal welfare. Although many factors may affect the welfare of commercial laying hens housed in cage and non-cage systems, welfare issues in confinement systems often involve behavioural restrictions, while many welfare issues in more extensive systems involve health and hygiene. Hens require an absolute amount of three-dimensional space in order to be able to perform basic body movements. They may prefer to distance themselves from other birds, but their strength of motivation to do so has not been thoroughly investigated, and preferred inter-individual distances may vary with activity. The relationships between the effects of space and group size on behaviour are not well understood, particularly in large groups where birds may cluster together around resources and at different times of day. There are common risks to hen welfare posed by both cage and non-cage systems such as overcrowding. However, some welfare issues present a greater risk in one system compared to another. When considering space and social environment, the comparison of cage and non-cage systems must take into account the threats to welfare that are specific to each system. Furthermore, this review highlights the importance of the design of the housing system rather than just the housing system per se.

This review discusses the different duck species and their feeding management used in meat production in various countries. The initial review describes the requirements of meat type ducks for energy, proteins and amino acids and minerals, vitamins and trace-elements. Other areas discussed include recommendations regarding feed management (feed presentation, feed restriction, use of enzymes and feedstuffs, fatty acid composition of diets). The main breeds used for meat production in the world are Pekin, Muscovy and mule ducks. As growth rate, efficiency and body composition of these three genotypes are different, the specific features of each type of duck are examined when reared under intensive production systems.

Immune dysfunction can be either at the humoral or cellular levels and is mediated by a myriad of factors including virus-induced immunosuppression. Infectious bursal disease virus (IBDV) affects domesticated poultry and causing health problems mainly due to prolonged immunosuppression. Destruction of the immunoglobulin-producing cells is the principal cause of IBDV-induced immunosuppression, which leads to significant impairment of the primary antibody responses. Due to these effects, IBDV infection not only increases the susceptibility of poultry to other viral infections but predisposes the host to several other bacteria of variable pathologies. The IBDV-induced immune-suppression is well-known phenomenon, however, recently there have been significant advancements in understanding the molecular mechanisms of this immune-suppression. This review discuss current updates regarding the immunotoxic and immunosuppressive nature of IBDV in the poultry and highlights areas requiring future research attentions that may help to establish foundations for effective and improved vaccines against IBDV.

Peroxisome proliferator-activated receptors (PPAR) belong to a family of nuclear hormone receptors that are activated by fatty acids such as polyunsaturated fatty acids (PUFA) and/or their derivatives. Three isoforms of PPAR namely α (alpha), β (beta), and γ (gamma) are found to be highly expressed in tissues relevant to energy homeostasis. The PPAR signalling pathway, which is involved in lipid metabolism and storage, play a role in livestock meat quality. Elucidating the molecular mechanisms of PPAR action of fat metabolism may have extensive implications not only in animal biology for health and feed efficiency improvement, but also in molecular nutrition as a potent nutritional supplement in poultry species.

The housing and management of laying hens and their productivity has gone through enormous developments in the last century. Housing has changed from free-range systems, via battery cages to a variety of loose housing and different types of battery cages, and back to outdoor access systems. Although battery cages are still the main system used worldwide, the number of hens housed in aviaries and free-range systems has increased in Europe, Australasia and some parts of the USA, but aviaries and free-range systems are still considered a niche sector compared to caged housing. The following paper reviews how breeding and selection have responded to changes in housing and management and whether different types of housing require different breeding programmes and, more specifically, whether a dedicated breeding programme should be developed for aviary and free-range systems.

From the available literature it was concluded that broadening the selection goal in existing lines is the best option for breeding programmes to provide genotypes that are suitable for a range of housing systems.

In Pakistan, H9N2 avian influenza viruses were first reported in 1998, and since then, they have been prevalent in chickens and have continuously evolved through reassortment in live bird markets. Poultry carrying H9N2 viruses act as incubators for the evolution of influenza viruses in wild birds. Recent reports have shown that the Pakistani H9N2 viruses have undergone antigenic drift and evolved into novel genotypes posing a potential threat to poultry and human health having genome segments similar to H5N1 and H7N3 viruses. Recent evidence of interspecies transmission suggested that the H9N2 avian virus could be the next human pandemic strain. Continuous monitoring of viral evolution and updates on vaccines are warranted to achieve efficient control and eradication of H9N2 viruses in Pakistan. The following review covers the emergence and evolution of H9N2 viruses and vaccination strategy in Pakistan.

The bone is a mineral reserve for metabolic requirements and eggshell formation as well as providing support to the bodies of birds. Bone weakness in laying hens has caused many problems such as bone deformation, osteoporosis, cage layer fatigue and fractures. These problems result in economic losses and are detrimental to animal welfare. Breaking strength is a good indicator of the health and strength of bone and an increase in breaking strength in laying hens would be important to decrease economic losses and improve the welfare of animals. One of the main factors affecting bone breaking strength is nutrition, as it is closely related to dietary calcium, phosphorus, vitamin D and particle size of the calcium source, particularly when the dietary calcium is insufficient. It has been accepted that the composition of the diet, trace elements, especially boron, vitamins, and feed additives play important roles in maintaining bone health and improving the breaking strength of bone in laying hens. This article reviews the results of studies in laying hens wherein the effect of nutrition on the breaking strength of bone were examined.

Propolis is a resinous hive product collected by honeybees from various sources of plants. Numerous scientific investigations have been focused on the biological activities of propolis and its functions as a health supplement in humans. It could have similar function in other animals, such as in poultry. This review is focused on the recent findings concerning the effects of propolis, as an antioxidant, on performance, carcass characteristics, behaviour, immunity, and physiological homeostasis in domesticated poultry species (broiler chickens, laying hens, quail, and duck); and the needs in future poultry research.

Much of the dark meat from U.S. broilers continues to be exported to other countries because of local consumers’ long-standing and strong preference for white breast meat. In this review we will discuss what causes meat colour differences and how environmental and genetic factors influence the colour of poultry meat. It is well documented that the darker colour of leg/thigh meat is due to the larger amount of myoglobin and haem pigments, as well as a higher pH when compared to breast meat. Slaughtering older birds increases myoglobin content in the meat and selection of breeds for greater breast meat yield may be involved. Using a wheat-based diet tends to lighten the colour of breast meat but has less effect on the thigh meat. Several antimicrobials used in further processing can lead to either bleaching or a reddening of the meat. Changes to colour using chemical or physiological methods are theoretically possible, however may not be great enough to improve consumer acceptability. From a marketing perspective, increased media promotion of dark meat as being equal to white meat in healthiness and superior in flavour may have the greatest effect on increasing sales.

This review article discusses the production results of experiments performed on turkeys, where WG, mainly whole wheat (WW), was incorporated into diets with the use of different methods: i) pre-pelleting inclusion of WG, ii) post-pelleting inclusion of WG with dilution of the daily diet, iii) post-pelleting inclusion of whole grain without dilution of the daily diet and iv) free-choice feeding. The latest experiments conducted between 2012 and 2013 on turkeys fed WW indicated that: (1) pre-pelleting inclusion of 20% WW had no effect on the body weight (BW) of turkeys or feed conversion ratio (FCR), (2) moderate (up to 20% on average) dilution of standard turkey diets with WW had no effect on the final BW of birds or muscle yield, and improved feed utilisation, in particular when WW was fed instead of ground or pelleted grain, (3) post-pelleting inclusion of WG in diets supplemented with protein-mineral-vitamin concentrate allowed to increase the amount of WW up to 25 and 30% in the daily ration in feeding periods of 4-8 and 9-12 weeks, respectively. However, in free-choice feeding, WW can result in poorer growth performance of turkeys due to an inadequate total protein intake.

Avian metapneumovirus (aMPV) infections are an economical issue for the poultry industry worldwide, and have been associated with upper respiratory tract infections and reductions in egg production in various avian species. The aMPV causes turkey rhinotracheitis (TRT) and is associated with swollen head syndrome (SHS) in chickens, which is usually accompanied by secondary infections that increase mortality. It was first reported in 1978 in South Africa and since then, has been seen in most regions of the world. It has been classified into four subgroups called: A, B, C and D. TRT and SHS are characterised by tracheal rales, sneezing, swollen sinuses, swollen head, and nasal and ocular discharge. The aMPV can lead to a drop in egg production and/or an increase in egg abnormalities in both turkeys and hens. Chickens may have antibodies without exhibiting clinical signs. Transmission requires direct contact among birds and its spread over long distances is uncertain, but wild birds are postulated as probable links. The aMPV infections can be diagnosed by serology (ELISA) and molecular methods (PCR). Good biosecurity and immune interventions are effective and necessary aspects of the control program. Live vaccines predominantly control aMPV infection in poultry flocks, but vaccine virus can be found for extended periods after application that may lead to reversion.

The emergence and evolution of viral pathogens cause a major problem in the poultry industry. Mutation and recombination processes are involved in the genetic and phenotypic variations of infectious bronchitis virus (IBV) in chickens, leading to the emergence of new variant strains, and give rise to virus population diversity to be modelled by the host, particularly by the immune system. The consequence is the continuous emergence of new variants with regard to pathotypes, serotypes, and protectotypes. The viral genes encoding the spike, replicase and nucleocapsid proteins can be considered the main genomic regions, which indicate the evolution processes of IBV. Despite the use of vaccination, new IBV variants are evolving and circulating in the field and should be considered as initial candidates for vaccine development. The new generation vaccines developed against locally prevailing IBV strains may be more helpful and avoid the reversion of virulence in live vaccine viruses. Understanding the mechanisms underlying the evolution of IBV has basic relevance and, without doubt, is essential to appropriately control and prevention of the disease.

There is a wide spectrum of techniques available to evaluate the functional aspects of the immune system in both humans and animals, including avian species. Some of the immunological techniques are qualitative and others are quantitative. In this paper, these techniques will be reviewed starting with a description of the nature of the antibody-antigen interaction, followed by the immune techniques that are used to detect immune complexes (i.e. antigen-antibody responses) whether free or associated with cells, then the numerous immune markers or parameters that are used to measure the avian immune responses.

The ultimate goal of poultry hatching is to increase the hatching rate and to produce healthy hatched birds. In the incubation process, temperature is the most important factor for the egg hatching rate, the growth performance and offspring phenotype. This not only affects the early development of the offspring, but also has a continued influence on the physical characteristics of the birds, such as final body weight and meat quality. This article reviews the importance of incubation temperature on offspring phenotype, sex differentiation, organism immunity and the development of muscle fibre in poultry.

The gastrointestinal tract is a large reservoir of both Gram positive and negative bacteria, of which the Gram negative bacteria act as a source of lipopolysaccharide (LPS). Luminal LPS, commonly known as endotoxin, can enter systemic circulation via paracellular and transcellular permeation. It has been shown that endotoxin exposure can increase intestinal paracellular permeability and alter intestinal structure and function, resulting in impaired absorption and utilisation of nutrients with negative impact on both poultry heath and growth. Acute exposure to large amounts of endotoxin suppresses feed intake in chickens and activation of the innate immune system. Substantial evidence suggests that endotoxin is recognised via toll-like receptor (TLR)-4, located on the surface of immune cells, which activates kinases to enhance the transcription of pro-inflammatory cytokines such as tumour necrosis factor alpha (TNF-α) and interleukin (IL)-1 and 6 which mediate the inhibitory effect of endotoxin on the intestinal nutrient absorption. Inflammation can divert energy and nutrients away from growth supp and into supporting the immune system responses, leading to growth suppression and lowered feed efficiency. In addition, sustained exposure to endotoxin may elicit tolerance, which can make animals refractory against secondary Gram-negative infections. In this review, the effects of endotoxin on intestinal barrier functions and the subsequent negative impacts on the production of chickens are summarised. Overall, this review combines the current knowledge of the chicken's intestinal responses to Gram negative bacterial infection, illustrating the importance of gut health in defence against bacterial infections and improving poultry health, growth and welfare.

The importance of gulls as bioindicators, reservoirs and vectors of Escherichia coli strains resistant to the older generation of antibiotics, broad spectrum cephalosporins and fluoroquinolones is reviewed in the following paper. The aim is to highlight the fact that they could be a hot spot for the development of new resistance types. Even though gulls do not naturally come into contact with antibiotics, they are omnivorous and they often eat food in agricultural, rural and urban areas so they can be infected with resistant strains from livestock or human sources which they can spread again into the environment. They may then come into contact with poultry kept under free range conditions. More intensive investigations of this subject are required, as well as the need to find accurate and reliable preventive measures, are demonstrated in the present paper.

Poultry is frequently colonised by and constitutes a natural reservoir for Campylobacter spp., primarily C. jejuni and C. coli. Infection with C. jejuni is a leading cause of food borne gastroenteritis in humans worldwide. Prevalence rates in poultry are variable and can reach as high as 100% on some farms. Campylobacter spp. are commensal organisms that establish persistent infections which produce little or no overt disease in the avian host despite extensive colonisation. Although campylobacteriosis is insignificant for poultry health, contaminated poultry meat is recognised as the main source for human exposure. An alarming recent trend is the rapid emergence of antimicrobial resistant Campylobacter spp. strains all over the world. Colonisation can persist for the lifetime of the animal, consequently leading to carcass contamination at the slaughter facility. Therefore, considerable research efforts have been devoted to the development of interventions to diminish contamination in poultry, with the intention to reduce the burden of food borne illnesses. During the past decade, significant advances have been made in understanding Campylobacter spp. in poultry. This review summarises the currently available information about the infections in poultry. Secondly, it addresses the colonisation, risk factors and current challenges of Campylobacter spp. in poultry. Finally, immune intervention and the future prospects of vaccination for the control of Campylobacter spp. in poultry are discussed.

In the field of animal nutrition, butyrate is used as a zootechnical ingredient and can be used as an unprotected salt or in the form of protected derivatives such as butyrate glycerides or butyrate-loaded matrices. Dietary butyrate supplementation has been shown to improve growth performance and resilience of broiler chickens through distinct mechanisms, operating on both eukaryotic and prokaryotic cells. Firstly, butyrate influences endogenous avian cells in multiple ways: it is an agonist of free-fatty acid receptors, an inhibitor of pro-inflammatory pathways, an epigenetic modulating agent and acts as an energy source. Secondly, butyrate influences the microbiota residing in the avian gastrointestinal tract (GIT) as a result of its bacteriostatic properties. The responses, e.g. changes in growth performance, gut morphology, carcass traits or nutrient digestibility of chickens, to dietary butyrate supplementation are inconsistent with factors such as additive inclusion level, diet composition, age and health status of the bird modulating the effects of butyrate and its derivatives. For many derivatives, the precise GIT segment wherein butyrate is released is unclear. Release location may affect the observed responses to butyrate given the diversity of cell types and pH conditions encountered throughout the gastrointestinal tract of poultry, and the differences in microbiota composition in the different gut segments. As a consequence, our understanding of the mode of action of butyrate is hampered. Characterisation of existing derivatives and development of targeted-release formulations are, therefore, important to gain insight in the different physiological effects butyrate can elicit in broiler chickens.

Avian influenza viruses have become endemic in land-based domestic poultry and have crossed species barriers. Turkeys are an important host in influenza virus ecology because they are susceptible to infection with these viruses and are often involved in inter species transmission. Several previous studies reveal that waterfowl-origin influenza viruses can be more easily transmitted to domestic turkeys than to chickens. Studies indicate turkeys to be better hosts for low pathogenic avian influenza viruses isolated from commercial poultry operations and live bird markets in comparison to chickens. Moreover, turkeys require low, 50% infectious-dose titres from wild bird as well as poultry adapted viruses, suggesting their high susceptibility for infection following a low dose exposure. Additionally, interspecies transmission of swine influenza viruses to turkeys occurs frequently, thus turkeys may be considered as a bridge species between poultry and wildlife. These findings suggest that turkeys can be easily infected with influenza viruses of different origins and highlight the potential role of turkeys in the transmission and maintenance of influenza viruses between premises.