Global poultry production has increased rapidly over the last 50 years and is now the most-consumed meat species in the world. The consumption of poultry in Poland accounts for almost 40% of the total meat consumption and averages 30 kg per person. Being the most flourishing sector of agriculture, poultry production faces many challenges from increasing competition (high quality products and lower prices for consumers). The profitability of poultry breeding and rearing is determined by the production of healthy and well-developed chicks, and the value of hatching eggs is closely linked to genetic line, flock age, layer housing conditions and parent flock nutrition, as well as incubation and pre- and post-hatching management. The qualitative assessment of newly hatched chicks must be based on clear and objective methods regarding health status of the flock and performance of the birds. It is essential that modern poultry production pays particular attention to these factors to achieve a high percentage of hatchability and the production of chicks which fully express their genetic potential under intensive production systems.

Stress based on high temperature and humidity reduces the production performance of fast-growing broilers and causes high mortality. Temperatures higher than optimum have been applied to broilers in the embryonic period in order to overcome thermal stress. This study was conducted to investigate the effects of exposure to two long-term high-thermal environments on the developmental stability of embryonic growth, hatchability and chick quality. For this purpose, 600 broiler eggs were incubated. Treatments consisted of eggs incubated at 37.8°C at 55% relative humidity throughout (control), heated to 39.6°C at 60% relative humidity for 6 h daily from 0 to 8th day, and heated to 39.6°C at 60% relative humidity for 6 h daily from the 10 to 18th day. Embryo weights and lengths of face, wing, femur, tibia and metatarsus were measured daily between the 10th and 21st day of the experiment. Daily relative asymmetry values of bilateral traits were estimated. The hatchability, the weight of the 1-day-old chicks and chick quality were determined. In conclusion, no negative effects of the treatments of the long-term high-thermal environment in the early and late stages of incubation for epigenetic adaptation were determined on the embryo morphology, development stability and weight of the chick. Moreover, regressed hatchability of embryos that were exposed to a long-term high-thermal environment was detected. Especially between the 10 and 18th day, the thermal manipulation considerably reduced the quality of the chicks. Acclimation treatments of high temperature on the eggs from cross-breeding flocks should not be made long term; instead, short-term treatments should be made by determining the stage that generates epigenetic adaptation.

Newly hatched chicks may be held longer than 48 h and experience long periods of fasting in commercial hatcheries. Limited information is known about the physiological status of chicks in such situations, due to the difficulty of precisely recording time of hatch. This study investigated the effect of the time from hatch to pulling (holding period) on physiological measures/parameters in 109 broiler chicks. Fertile Ross 308 eggs were incubated in a custom built small-scale incubator. The individual hatching time of each focal chick was determined using eggshell temperature monitoring. At ‘pulling’ (512 h of incubation time), the quality of focal chicks was assessed using the chick scoring method and physiological parameters were measured including BW, organ (heart, liver and stomach) weights, blood values and plasma corticosterone level. The time from hatch to pulling varied from 7.58 to 44.97 h. Egg weight at setting was significantly correlated with chick BW and weight of organs at pulling, but had no effect on chick quality, blood values and plasma corticosterone. Relative BW at pulling was negatively associated with the duration of holding period (P=0.002). However, there was a positive correlation between relative stomach weight and the duration of the holding period (P<0.001). As the holding period duration increased, there was a trend that blood partial pressure of oxygen, haematocrit and haemoglobin also increased, and blood partial pressure of carbon dioxide, total carbon dioxide and bicarbonate decreased (P<0.05). A wide range of plasma corticosterone was observed from chicks that had experienced different durations of holding period. We conclude that shortening the hatch window and minimising the number of chicks that experience a long holding period before pulling may improve chick quality and physiological status, which may be due to unfavourable environmental conditions that include feed and water deprivation.

Like other chick quality parameters, hatchling length is an easy and repeatablequality evaluation parameter for newly hatched chicks. This important trait hasa positive correlation with the size of the egg and the chick's weight. Thehatchling length is the best indicator of pre-incubation and incubationconditions and for the rate of absorption of yolk after hatching in the bodycavity of the chick. Chicks with large lengths have heavier heart weights, liverweights and bursa of Fabricius at hatch. The length at hatch can be measuredfrom the crown to toe and it can be improved by maintaining embryo temperatureuntil internal pipping, proper egg storage conditions, maximum turning of eggs,maintaining the minimum egg weight losses at the 18th day of embryonicdevelopment, maintaining ample O2 supply and removal ofCO2 through gas exchange programs, improved shell quality and betterhealth of the breeder flock.

The yolk does not play any role in the bird's future growth but it can createmany disease problems in the bird's life. A bigger, day-old chick has a largeresidual yolk and a small yolk-free body mass. This characteristic does not playany role in the development and growth during the incubation and post incubationprocesses. In conclusion, hatchling length offers a fast, repeatable, andnon-destructive method to evaluate chick quality.

The zootechnical performances of broilers at the end of the rearing period depend in part on the quality of day-old chicks at placement. The quality of day-old chicks is highly affected by the incubation conditions, by hatch time (which determines the time spent in the hatcher under high temperature and humidity), and by the handling of chicks after hatch. This article first presents an overview of the most relevant pre-incubation factors that affect chick quality: egg size, egg weight, quality of eggs, sex of embryos, age of breeders, and conditions and duration of egg storage. It then reviews the most important incubation factors that affect hatch time, hatchability and hatch window (temperature, humidity, turning, ventilation and concentration of gases). Finally, the effect of early post-hatch handling (including processing and especially transportation of chicks) as a possible source of stress influencing the quality of chicks at placement is discussed.

The quality of day old chicks is crucial for profitable broiler production, but a difficult trait to define. In research, both qualitative and quantitative measures are used with variable predictive value for subsequent performance. In hatchery practice, chick quality is judged on a binomial scale, as chicks are divided into first grade (Q1-saleable) and second grade (Q2) chicks right after hatch. Incidences and reasons for classifying chicks as Q2, and potential of these chicks for survival and post-hatch performance have hardly been investigated, but may provide information for flock performance. We conducted an experiment to investigate (1) the quality of a broiler flock and the relation with post-hatch flock performance based on a qualitative score (Pasgar©score) of Q1 chicks and based on the incidence of Q2 chicks and (2) the reasons for classifying chicks as Q2, and the potential of these chicks for survival and post-hatch growth. The performance was followed of Q1 and Q2 chicks obtained from two breeder flocks that hatched in two different hatching systems (a traditional hatcher or a combined hatching and brooding system, named Patio). Eggs were incubated until embryo day 18, when they were transferred to one of the two hatching systems. At embryo day 21/post-hatch day 0, all chicks from the hatcher (including Q2 chicks) were brought to Patio, where the hatchery manager marked the Q2 chicks from both flocks and hatching systems and registered apparent reasons for classifying these chicks as Q2. Chick quality was assessed of 100 Q1 chicks from each flock and hatching system. Weights of all chicks were determined at days 0, 7, 21 and 42. There were no correlations between mean Pasgar©score and post-hatch growth or mortality, and suboptimal navel quality was the only quality trait associated with lower post-hatch growth. Growth was clearly affected by breeder flock and hatching system, which could not be linked to mean Pasgar©score or incidence of Q2 chicks. Q2 chicks showed lower post-hatch growth compared to Q1 chicks but effects on flock performance at slaughter weight were limited because early mortality in Q2 chicks was high (62.50% at 7 days). We concluded that chick qualitative scores and the incidence of Q2 chicks may be informative for the quality of incubation, but are not predictive for post-hatch flock performance. Culling Q2 chicks after hatch is well-founded in terms of both animal welfare and profitability.

Embryonic development is a dynamic process that requires a fine balance between several factors in order to achieve an optimum hatchability and chick quality. These factors include the background of the embryo, such as genetic line of the breeders, the age of the breeder, egg weight, and factors related to the environment in which the egg is stored and incubated, such as temperature, humidity, gas levels and altitude. Gas exchanges are of fundamental importance for embryonic development during incubation and may affect the livability of the embryo. This paper reviews the roles of the gaseous environment (i.e. O2 and CO2) around hatching eggs during storage and during incubation and the effect it might have on the survival of the developing embryos and the chicks that hatch. The state of the art on the different attempts to establish the optimum requirements of different gases that promote the optimal developmental trajectories at different periods during incubation is presented. The roles and consequences of different levels of O2 and CO2 during storage and incubation on hatchability, incubation duration, hatching process, embryo growth, embryo mortality, organ development and morphology, metabolism, blood acid-base balance, chick quality and chick post-hatch growth are reviewed.

A first product of this European project was a tool for scoring chick quality. A link was established between chick quality and embryonic physiological parameters such as heat production. Eggs from broiler breeders that give rise to rapidly growing broilers have a different embryonic development that may need modified incubation conditions. Within genotypes, better chick quality induces better liveability and faster growth in broiler production. Extensive data on broiler breeder production were generated. Feed restriction was necessary to maintain welfare and reproduction at acceptable levels in standard broiler breeders. The dw-experimental genotype (E) was more tolerant to ad libitum feeding. If an alternative to feed restriction had to be found, the use of a dw genotype with less severe feed restriction could be adopted. Fibre per se, or partial feed restriction during the growing period, only compensated to a small extent for the negative effects of early fast growth on later reproduction. The results of the project on behaviour did not support welfare concerns on feed restriction. They confirmed the hypothesis that environmental pecking is a displacement activity rather than a sign of frustration. Factors other than central control by pituitary hormones seem to be involved in the modulation of the laying rate. The local (intra-ovarian) role of growth factors such as Insulin-like Growth Factors (IGFs), Bone Morphogenetic Proteins (BMPs) and leptin are known to modulate the effect of gonadotrophins on ovarian function. For both BMPs and IGFs, feed restriction enhanced the interaction between growth factors and gonadotrophins as well as the proliferation of granulosa cells in vitro. Future genetic selection of broiler breeder production might aim at uncoupling the control of growth factors in the ovary from the selection for rapid growth to maintain or increase the growth rate of chicks without further penalising the already poor reproductive performance of broiler breeders. Putative quantitative trait loci for ovulation rate were identified in the project and may eventually facilitate selection by breeding companies for birds that could be fed enough feed to optimise their welfare.

The quality of the day-old broiler chick is foremost in the minds of many poultry managers. From fertilised ovum to the placement at the broiler farm, some factors such as the characteristics of the incubating eggs, the egg holding conditions, the incubation conditions and the conditions that exist between hatching and placement at the farm and their interactions may affect chick quality. It may be questioned if maximal hatchability is the best indicator for chick quality and/or post-hatching viability, even if optimal hatchability is considered a prerequisite for successful incubation. The environmental conditions during incubation (e.g. the temperature, humidity and ventilation rate (carbon dioxide concentration)) are not set independently from each other, although each may have its own optimum for hatchability and chick quality. These optima for each incubation factor may alter differentially according to the characteristics of the incubating egg. It is concluded that more independent control as well as more control of the variability of the classical physical conditions in the incubator are required in order to improve hatchability and chick quality.