Due to the increasing throughput of modern egg grading machines, which grade up to 120 000 eggs per hour, the visual inspection of eggs by humans (“candling”), becomes a critical bottleneck in the egg sorting chain. In order to assure a high and consistent egg quality, researchers investigated the use of modern sensor technologies to replace the candling operation. During the last decades, several types of sensors were developed, and it is believed that these sensors will replace human candling in the near future. A first class of sensors is based on mechanical techniques and allows investigation of the physical shell quality, such as the presence of cracks and shell strength. A second class is based upon spectroscopic principles and allows the operator to “see” through the egg shell in order to determine the internal quality of the eggs, such as albumen pH and viscosity and the presence of inclusions such as blood and meat spots. A third class of sensors aims at mimicking the human eye by means of a camera and a software platform (“computer vision”). Besides these types of sensors, some others based on ultrasonic, magnetic resonance and electronic nose principles are investigated and discussed. This paper gives an overview of these modern sensor technologies for egg grading.

This paper reviews and presents new evidence for the role of insoluble fibre (nonstarch polysaccharides and lignin) in poultry nutrition. Insoluble fibre affects gut functions and modulates nutrient digestion. Thus, digestibility of starch is higher and digesta passage rate faster when a moderate level of insoluble fibre is present in the diet. The effect of insoluble fibre on gut functions stems from its ability to accumulate in the gizzard, which seems to regulate digesta passage rate and nutrient digestion in the intestine. Furthermore, there are indications that diets high in insoluble fibre are preventative of cannibalism outbreaks in laying hens. It is hypothesized that with nutrients disappearing from the lumen faster and digesta moving through the gut quicker, birds spend longer time eating and less time pecking each other. However, the ability of insoluble fibre to exert these effects appears to be related, in part, to particle size as fine grinding diminishes its stimulatory influence on the gizzard. More research is underway on the physical and chemical structure of fibre on gut functions, nutrient digestion and bird behaviour.

To more precisely formulate feed and predict animal performance, it is important to base both the recommendations and feed formulations on digestible rather than total amino acid contents. Most published data on the digestibility of amino acids in feed ingredients for poultry are based on excreta digestibility. Ileal digestibility is an alternative and preferred approach to estimate amino acid availability in feed ingredients. Both methodologies are described and assessed. In addition, the differences between apparent and standardised (in which corrections are made for basal endogenous losses) digestible amino acid systems are discussed. The concept of a standardised digestibility system as a mean of overcoming the limitations of apparent digestibility estimates is proposed. In this context, different methodologies for the determination of basal endogenous amino acid losses are discussed. Although each methodology suffers from some limitations and published data on endogenous losses at the ileal level in growing poultry are limited, averaged data from repeated experiments using the ‘enzymatically hydrolysed casein’ method are considered as the best measure of basal losses. Standardised ileal amino acid digestibility values of 17 feed ingredients commonly used in broiler nutrition are presented including grains (barley, corn, sorghum, triticale, wheat), grain by-products (wheat middlings, rice pollard), plant protein sources (soybean meal, canola meal, corn gluten meal, cottonseed meal, lupins, peas/beans, sunflower meal), and animal by-products (feather meal, fish meal, meat and bone meal). This comprehensive set of the ileal amino acid digestibility of feed ingredients in broiler nutrition may serve as a basis for the establishment of the system in broiler feeding and for further research.

When formulating least-cost poultry diets, ME concentration should be optimised by an iterative procedure, not entered as a fixed value. This iteration must calculate profit margins by taking into account the way in which feed intake and saleable outputs vary with ME concentration.

In the case of broilers, adjustment of critical amino acid contents in direct proportion to ME concentration does not result in birds of equal fatness. To avoid an increase in fat deposition at higher energy levels, it is proposed that amino acid specifications should be adjusted in proportion to changes in the net energy supplied by the feed. A model is available which will both interpret responses to amino acids in laying trials and give economically optimal estimates of amino acid inputs for practical feed formulation. Flocks coming into lay and flocks nearing the end of the pullet year have bimodal distributions of rates of lay, with the result that calculations of requirement based on mean output will underestimate the optimal amino acid input for the flock.

Chick diets containing surplus protein can lead to impaired utilisation of the first-limiting amino acid. This difficulty can be avoided by stating amino acid requirements as a proportion of the protein.

Light patterns have less effect on numbers of eggs laid by current stocks than on those of forty years ago, but the principles have not changed. Ovarian activity is stimulated by increasing photoperiods and suppressed by decreasing photoperiods. The light pattern used during rearing can still have large effects on age at 50% lay, even for modern stocks. Early sexual maturity maximises egg numbers but gives smaller eggs. Late maturity maximises egg size at the expense of numbers. The relationship between egg output (g/hen d) and age at first egg is curvilinear, with maximum yield occurring in flocks maturing in about the centre of their potential range. Fancy patterns of increasing daylength after maturity are probably not justified. A flock held on a constant 14h day will lay as many eggs as one given step up lighting.

Intermittent lighting saves about 5% of feed consumption with no loss of output, provided that the feed has adequate amino acid content to allow for the reduced feed intake. Producers with light-proof laying houses should be taking advantage of intermittent lighting.

The recommended light intensity for laying houses is still 10 lx, although the physiological threshold for response to changes in photoperiod is closer to 2 lx. Very dim (0.05 lx) light filtering into blacked out houses will not stimulate the hypothalamic receptors responsible for photo-sexual responses, but may affect the bird's biological clock, which can alter its response to a constant short photoperiod. Feed intake shows a curvilinear dependence on environmental temperature. At temperatures below the panting threshold, performance can be maintained by adjusting the feed so as to maintain an adequate intake of critical amino acids. Above the panting threshold, the hen is unable to take in enough energy to maintain normal output. There is no dietary modification which can effectively offset this problem. Diurnally cycling temperatures result in feed intake and egg production equivalent to that observed under a constant temperature equal to the mean of the cycle. When the poultry house is cooler at night than by day, it helps to provide light so that the birds can feed during the cooler part of the cycle.

Our investigations indicated a possibility to extend the range of lysozyme activity using thermal and chemical – thermal modification. We found that under the adopted conditions of modification a weakly acid environment (pH 5 – 6) promotes an increased polymerisation of lysozyme and makes it possible to obtain approx. 50% of polymers. It was observed that lysozyme concentration in the solution subjected to thermal modification, the pH value of the solution, the temperature and time of modification have a significant effect on the content of the forming polymers. It was found that the application of lysozyme modification leads to an increase in its antibacterial activity in a comparison to the activity of lysozyme monomer. The modified lysozyme did reduce viability of Gram-positive bacteria and Gramnegative bacteria.

Intensive selection based on growth traits in meat-type breeder flocks has resulted in new breeds expressing early sexual precocity but limited persistence of gonad development. This can be in part circumvented by adequate use of specific light regimes. However, these breeds require environmentally controlled housing in which light, temperature and ventilation can be properly balanced, a situation which to date is technically feasible only under relatively mild climatic conditions. In recent years there has been a progressive shift in chicken production to warm geographic regions. As a consequence, increasing numbers of breeder flocks are now raised in open houses in which light regimes are only partly controlled. In most instances, reproductive performance in standard meat-type breeds remains satisfactory if sexual precocity can be delayed until 23–25wks of age. However, the early maturation of flocks stimulated by external photoperiods may result in small eggs during the early parts of the season. Early sexual precocity in breeder males is generally followed by a rapid decline in reproductive performance, resulting in their partial or even total replacement to maintain acceptable fertility rates throughout the season. Such changes, which are currently performed on a large scale, are costly, pose health risks and are only partly effective in maintaining adequate fertility rates. In addition to photoperiod, another common practice to for controlling sexual precocity and reproductive performance in meat-type chickens is based on strict control of feed allowance for each sex. In countries where housing and feed equipment are accessible, techniques such as sex-separate feeding combined with quantitative feed restriction have been of practical value to limit body growth. However, such equipment is costly and requires strict management practices. Severe feed restriction in maturing breeder flocks may be stressful and, which induces heterogeneity in body growth. Another concern is the moderate but constant decline in fertilising potential. A Furthermore a negative correlation between reproductive and growth traits may be responsible for such the decline in fertilising potential of birds selected for rapid growth. This may ultimately favour the emergence of breeds with less intensive growth rates and/or the extension of artificial insemination.

Chicken gene inheritance analysis, started one century ago, had led to the development of the classical genetic map. Efforts and legacy of the previous geneticists' generations are not forgotten and constitute the fundamentals of contemporary genome research progress. Advances in molecular biology, cytogenetics and DNA technologies provided more powerful and sophisticated tools to tackle chicken gene mapping and genome research problems. In the 1990s configurations of chicken molecular and cytogenetic maps had begun standing out. New horizons in chicken genomics are opening with application of BAC libraries, BAC-contig physical maps, ESTs and whole genome sequencing. The chicken has been a notable experimental model for several fundamental and applied biologic disciplines in the last century, and will remain such in the 21st century. The upcoming complete genome sequencing combined with discovering gene functions will facilitate the improvement of traits of economic importance and value in poultry.

Differences in structure between egg constituent proteins influence their ability to interact, upon heating, in gel systems or to compete for space at the interface of oil droplets in oil/water (o/w) emulsions. Phase separation phenomena could be the rule in protein network systems where mixtures of egg yolk with egg white or other protein containing materials are employed. In emulsions, apolipoproteins of LDL micelles appear to play a dominant role in adsorption and interfacial membrane formation around the oil droplets. Yolk granular proteins also have the ability to contribute in the building of the adsorbed layer although their adsorption and stabilizing potential seem to depend on factors as such as NaCl content and pH and also on the extent of granular structure disorganization. Egg white and milk whey proteins are competitively displaced from emulsion oil interfaces by yolk lipoproteins due to the globular and rigid structure of the former. Casein proteins also appear to adsorb less effectively in the presence of yolk apolipoproteins in spite of their rather disorganized molecular structure.

For 16 weeks, turkeys were fed the following feed mixtures: control diet without antibiotic (or inulin), diet with flavomycin (8 mg/kg) and diets with different level of inulin: low (0.1% for 16 weeks), medium (0.4% and 0.2% in the first and second 8-week period, respectively) and high (1 % and 0.4% in the first and the second 8-week period of the experiment). During the first 8 weeks, dietary intake and feed conversion were similar in all groups. A high content of inulin in a diet caused lower body weight gain of turkeys compared to the remaining groups. In this period coefficients of protein digestibility (85.7-86.8%), concentration of dry matter and ammonia in faeces were alike in all groups. Faeces of turkeys fed a diet supplemented with inulin were characterised with a lower pH (5.48-5.56) than these of turkeys from the control group (5.77) as well as with lower activity of microbial β-glucuronidase (0.52-0.79 U/g and 1.01, respectively). The lowest faecal β-glucuronidase activity was in group with flavomycin (0.44). The addition of an antibiotic or inulin did not increase the final body weight of the turkeys; moreover the birds fed with the highest dose of inulin were the lightest. The influence of the experimental diets on ileal parameters was low; they affected however functioning of the caeca. The share of flavomycin in the mixture lowered the activity of microbial α-glucosidase, to some extent enhanced pH of digesta, but did not lower SCFAs concentration. As a result of increased amount of caecal digesta, the total sum of SCFAs produced was higher than in the control group. Higher doses (0.4/0.2% and 1.0/0.4%) of inulin in a diet caused a beneficial pH decrease in digesta (6.84 and 6.92, respectively), compared to lower doses of this preparation (7.12). On the other hand, they evoked a disadvantageous increase in the ammonia concentration in the caeca (1.188 and 1.240 mg/g in digesta of groups Inulin-M and Inulin-H, compared to 1.109 mg/g in digesta of group Inulin-L). Increasing the inulin dose in a diet up to 1% did not increase the activity of microbial enzymes, while increased significantly the concentration and amount of SCFAs in the caeca compared to limited dose (0.1%) of inulin preparation.

Feather growth, structure and patterns of moulting are important characteristics of poultry in commercial environments. As the market age for broilers continues to decline, the “maturity” of feather cover becomes even more important for protection of the skin and underlying tissue. Feather growth begins at around day 5 of incubation while keratinisation is complete 2 – 3 d prior to hatch. Feathers do not grow randomly over the skin surface, but rather in distinct tracts, which cover at most 75% of the skin surface. Broiler chickens will have about 50 g of feathers by market age, although at this early age some feathers will have already been lost by sequential moulting. Although most modern strains of poultry have white or brown feathers, there are various colour schemes that are again dictated during embryo development. In a subsequent paper, we will detail factors affecting feather growth, moulting and the Occurrence of various abnormalities.

Food allergies or food intolerances affect nearly everyone at some point. “Food Allergy” refers to all interactions between molecules derived from the food supply and the immune system. Food allergies can be sub-divided into IgE (Immunoglobulin E) –mediated hypersensitivities and cell mediated hypersensitivities, but in most of the cases is IgE mediated. There has been an increased prevalence of food allergy reactions in the last decade. Approximately 2–3% of adults and 5–7% of children are affected by food allergy. Hen's egg is one of the most common causes of food allergic reactions, particularly in children. The prevalence of egg allergy is about 35% of food allergic children. It usually disappears by age five to seven years, but may sometimes be lifelong. Egg white, which is generally considered more allergenic than egg yolk, has four major allergenic proteins namely, ovomucoid (Gal d 1), ovalbumin (Gal d 2), ovotransferrin (Gal d 3), and lysozyme (Gal d 4) which are defined as immuno dominant proteins of egg white in egg allergic patients. Detailed characterization of the biochemical, immunological and structural properties of the major two allergens of the egg white, the ovalbumin and the ovomucoid have been studied. Studies of the B cell and T cell epitopes of these allergens have been summarized and mechanisms to reduce allergic reactions of these proteins at their molecular level has been evaluated in detail.

Digestion of starch is effected by hydrolysing enzymes in a complex process which depends on many factors; these include the botanical origin of starch, whether the starch is amorphous or crystalline, the source of enzymes, substrate and enzyme concentration, temperature and time, as well as the presence of other substances in the multicomponent matrix in which starch occurs naturally, e.g. cereal grains. Native starch is digested (i.e. hydrolysed) slowly compared with processed (gelatinised) starch whose crystallinity has been lost and where the accessibility of substrate to enzymes is greater and not restricted by α-glucan associations such as double helices (especially in crystallites) or amylose-lipid complexes (in cereal starches). The restriction of starch digestion (primarily in the human digestive system) due to forms which are resistant to hydrolysis has led to the concept of dietary ‘resistant-starch’. Different forms of resistance can be identified which hinder hydrolysis. With regard to digestibility, whether in the human or animal digestive tract, it is important to understand the mechanisms of enzymatic hydrolysis, and the consequence of incomplete digestion i.e. the potential loss of glucose as a valuable source of energy. This review deals with starch hydrolysis by specific amylases in model (in vitro) and more broadly in in vivo systems. The optimisation of starch hydrolysis and digestion is discussed in the light of modern knowledge.

Transmission of food-poisoning salmonellae in the poultry industry is often associated with a contaminated feed supply. Occurrence of food-borne Salmonella spp. continues to be documented on poultry feeds and feed ingredients. This is in part due to the wide variety of environmental origins for Salmonella spp. and its ability to easily cross-contaminate during feed processing and storage. Since Salmonella spp. have been shown to survive for several months under feed storage conditions, they can remain a persistent problem for poultry production. Limiting Salmonella spp. contamination of poultry feeds requires application of surveillance approaches during feed manufacturing and distribution along with the introduction of effective intervention and hurdle technologies. Representative sampling approaches may be needed to achieve consistent contamination reduction.

In commercial production, there is often concern about the quantity and/or quality of feathering in both broilers and layers. For broilers, the concern is adequacy of protective feather cover, while in layers it is usually the necessary degree of feathering needed to optimise feed efficiency. Feather development is under the control of hormones such as thyroxine and oestrogen and indirectly by testosterone. Environmental or nutritional status that influences such hormonal output will indirectly affect feathering. In broilers, rate of feathering is influenced by genetics, since some 20 years ago there was a conscious decision to introduce slow (K) vs. fast (k) feathering as a means of sexing day-old chicks. With the relative “immaturity” of modern broilers, these genes influence feather cover well into the production cycle. In White Leghorn crosses, initial problems with apparent Leukosis susceptibility of the progeny of slow feathering dams had to be overcome by eradication of Leukosis before feather sexing could be generally introduced. Nutrition can influence rate of feathering as well as feather structure, colour and moulting. Amino acid balance and especially deficiencies of TSAA and branched chain amino acids will influence feathering in young birds. Deficiency of vitamins and certain trace minerals also induce characteristic feather abnormalities, as does the presence of dietary mycotoxins. A number of viruses, bacteria and mycoplasma can infect the feather follicle and so influence feather development. Feather pecking and feather licking are behavioural abnormalities, although these conditions can be induced by changes in environmental conditions or nutritional adequacy of the diet.

The risk posed by food borne pathogens in eggs has taken on a high priority for government and consumer. In Europe there has been concern that plans to move from battery cages may increase the risk from eggs. For this reason there is some pressure to demonstrate progress in reducing risk from eggs. At the level of the egg the approach has been to improve resistance of the eggshell to breakage using selection for quasi-static compression or specific gravity. The review will consider phenotypic measurement and developments in genetics and genomics that can place new tools in the hands of poultry breeders, should they want to use them.

New phenotypic measurements that better describe the physical and antibacterial properties of the egg and eggshell need to be developed which accurately measure the egg's natural defence characteristics to complement the developments in chicken genomics. Acoustic resonance analysis to measure the stiffness of the eggshell and ultra-structural measurements using electron microscopy in pedigree populations are methods which have been examined. Also organic matrix measurements, antimicrobial properties and bacterial penetration measurements that have only been of academic interest may be used in test populations. Genetics and genomics can be used with these phenotypic measurements to identify genetic markers that can be used in selection programmes, rather than the measurements themselves, using whole genome scans for quantitative trait loci and association analysis with candidate genes. The availability of the chicken genome sequence and EST resources has made carrying out these analyses easier in pedigree breeding flocks.

The United States (U.S.) poultry industry continues to implement induced moulting to extend egg production in commercial laying flocks. Achieving an optimal moult requires dietary manipulation to cause a complete regression of the reproductive organs and cessation of egg production. This is followed by rejuvenation and initiation of an additional egg laying cycle. Currently feed withdrawal is the primary means to initiate moult and is regarded as an optimal approach for achieving post-moult performance. However, removal of feed can lead to potential physiological stress in laying hens as well as an increased susceptibility to Salmonella enteritidis colonization and invasion. To retain the ecological benefits of induced moult will require development, testing and implementation of alternative dietary approaches that minimizes these problems and increase the egg production and egg quality benefits associated with the additional egg laying cycles. Strategies for accomplishing this are discussed.

The increasing importance of the technological quality of meat, defined as its ability to be stored or further-processed, has highlighted the need for research work on the genetic control of meat characteristics, which has been seldom studied in poultry until now. Both the variabilities of quality indicators between genetic types and within populations in selection are being studied. These complementary approaches aim at defining the possibilities of a genetic improvement of meat quality and the relationships with growth performances of the birds. This implies a better knowledge of the mechanisms involved in meat quality, in order to identify the most relevant criteria of selection. Results obtained up to now in chickens lead to the consensual conclusion that the increased breast mass obtained by genetic selection has mainly been achieved by an increased fibre size, while no changes in the metabolic profile were detected. According to the genetic parameters obtained up to now, the technological quality of the meat could be efficiently improved by the genetic route. Indeed, heritabilities of quality characteristics obtained in the chicken under experimental conditions are high. At the same time, the estimated correlations do not show any genetic antagonism between the birds' performances and the quality of their meat. All these results thus favour selection on the quality of the meat, even if its implementation remains in the hands of the breeders, according to the return in terms of competitiveness. According to the available results, the ultimate pH could be a relevant criterion of selection because of its strong relationship to the colour, the water-holding capacity or the texture of the meat. Much research however remains to be undertaken to optimise the efficiency of selection on the quality of the meat. In particular, interactions with pre-slaughter stresses must be specified, as they can strongly affect meat quality. On the other hand, it is hoped that significant progress in the methods of selection based on the quality of the meat will be brought by the identification of molecular markers of meat quality.