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Circadian incubation™ Next generation design for the future-focused hatchery

Pas Reform Hatchery Technologies

The ultimate goal of the modern hatchery is to produce large ­numbers of uniform, r­ obust day old chicks: traits that originate in the embryo and correlate directly with the performance and ­resistance of chicks on the farm. The following two articles discuss ­progress in the development of modular single-stage equipment for Circadian ­Incubation™, i.e. equipment that supports the use of thermal stimulation for the ­production of uniform batches of robust, high quality chicks in the future-focused h ­ atchery.

Circadian Incubation™

Circadian incubation™ The next generation of modular, single-stage technology

Introduction Modern poultry production requires birds that grow uniformly and efficiently, which means that most of the bird’s nutrition is directed to production. Efficient birds are resistant to stressful conditions and use only small amounts of nutrients for the maintenance of basic physiological systems. Geneticists have introduced the concept of robustness to describe these efficient, modern birds in more biological terms, so that today, robustness also defines an important trait for selection, related to animal health and welfare (Star et al., 2008 J. of agricultural and ­environmental ethics; McKay, 2009, In: Biology of Breeding Poultry. Ed. P. Hocking). Robustness is a health criterion that originates in embryonic life and correlates with growth and the resistance of the individual chicks under different farm conditions. We define a robust day old chick as a first class chick that delivers predictable growth and production under different farm designs and fluctuating conditions, such as high and low temperatures. Batches of robust day old chicks show low mortality, need less medication and have the potential for optimum growth even under adverse farm conditions. To support the development of robust day old chicks, Pas Reform has introduced Circadian Incubation™ as a natural and progressive development of single stage incubation. Circadian incubation™ is based on observations that embryonic ‘training’ – or the imprinting of body functions – stimulates robustness on the farm. This ‘imprinting’ is achieved by exposing the embryo to


environmental triggers during critical periods of the maturation of physiological control systems - and has been shown to cause long-lasting alterations in the perinatal epigenetic programming of body functions (Tzschentke and Plageman, 2006). In poultry, the best understood physiological system is the maturation of thermoregulation and its dependence on incubator temperatures. Study shows that embryos exposed to short periods of heat or cold develop an improved capacity to control body temperature during periods of heat or cold in the farm (Decuypere, 1984; Janke t al. 2002). Consequently, these birds retain most of their feed for growth – and use much less for the maintenance of body functions. Circadian incubation™ is a single-stage protocol that includes periodic stimulation, by increasing temperature during certain sensitive periods of embryonic development. The term ‘circadian’ literally means ‘about a day’ as it derives from the latin (‘circa’= about and ‘dies’= day). Circadian thus refers to daily biological rhythms observed in most organisms, such as the day-night rhythm in body temperature. The biological rhythms, also called the circadian or biological clock, are essential for regulating the daily metabolic rhythm and other physiological functions. In contrast to nature, embryos hatched in a convential incubator are not exposed to a daily rhythm. This changes when the Circadian Incubation™ technique is implemented.

Circadian Incubation™

The development of a robust day old chick To understand day old chick robustness, we need first to understand the development and maturation of physiological systems in the embryo (Tzschentke and Plagemann, 2006; Gilbert and Epel, 2009). Embryonic development comprises a number of complex ­physio­­logical interactions between cells and groups of cells, ­ best understood by simply observing the development that takes place in different phases. The first phase of development is called the Differentiation Phase. This is when the different embryonic structures and premature organ fields are determined and differentiated. The second phase – the Growth Phase – is so called because this is when the different organs and tissue grow to their final s­ tructure and size. Not only do the organs develop their final form, they also acquire the capability to function physiologically, although at this point they are not yet integrated into a physiological control system. The third and final phase of embryonic development is known as the Maturation Phase, characterized by the maturation of physiological functions and the development of integrated ­physiological and endocrinal controlling systems.

Embryonic development is a continuous process. Each embryonic phase overlaps, while the embryo moves gradually from an embryonic state to that of a hatchling. Normal post-natal ­performance is only possible when functional maturation of the organs and fine-tuning of the integrated physiological circuits have taken place, during the final days of incubation. A good example of an ‘integrated physiological circuit’ is the thermoregulatory system, which controls body temperature in the late-stage embryo and the chicken. Organs involved in ­thermoregulation – such as the hypothalamus, thyroid and ­pituitary gland – develop and grow during the mid-period, or Growth Phase, of incubation. Final maturation of the thermoregulatory systems, however, occurs during the last days of the Maturation Phase in the embryo and the first days post-hatch. To further understand the route to achieving a robust day old chick that can cope with varying farm conditions, we need to look at a lower level of embryonic development: that of cell-tocell interaction and differential gene expression. Each phase of embryonic development described above is recognized by specific cellular interactions and the expression of genes. As the embryo develops after fertilization, the number of cells increase – and these cells become differentiated as each adopts the characteristics of its ultimate restricted fate. Some cells grow to form muscle tissue, while others become part of the skeleton. The differentiation of cells is the result of differential gene expression: muscle cells express genes for contractive proteins while bone cells produce proteins that can bind calcium, for example. Thus differential gene expression is the fundament of

Circadian Incubation™


the three phases of embryonic development – and the differential activation and expression of genes has formed a key focus for research and publication in the field of developmental biology (eg. Gilbert, 2006). It is now generally understood that minute variations in the environment of embryonic cells will induce variations in the expression of genes. Embryos derived from the same parents, having inherited basically the same genetic potential, develop to different phenotypes when exposed to different environmental inducing agents: the agents that prepare and adapt the embryo to cope with varying conditions after birth. A term often used to explain embryo-environment interaction is epigenetic adaptation: the study of how changes in gene expression patterns mediated by the environment can cause variations in phenotypes (Gilbert and Epel, 2009). Today’s discussions on the embryonic origin of human health and heart failure in later life, for example, refers to epigenitic affects during the embryonic and foetal development of the baby. In poultry research, the idea that the embryo can be acclimatised to a certain trigger for better performance later in life is becoming more widely accepted (Decuypere, 1984, Minne and Decuypere, 1984; Nichelmann and Tzschentke, 2002; Yahav et al, 2004). Currently, the most studied trigger for epigenetic adaptation is the exposure of the embryo to brief periods of high or low temperature. Critical periods, when the embryo is prone to thermal adaptation, have been found during the early phase of development, when the differentiation of specific structures is being induced – and again in the later phase of development, when the organs and physiological systems mature. A four-day thermal-manipulation during the differentiation phase has been shown to influence the proliferation of muscletype cells in turkey embryos, to subsequently and positively affect post-hatch muscle development (Maltby et al., 2004). In the chicken, short periods of increased temperature from embryonic days 4 - 7 encouraged embryonic movement and activity, promoting leg and muscle growth in the embryo (Hammond, et al., 2007). Broiler embryos can be thermally ­conditioned during their final days in the setter, such that they achieve tolerance to heat challenge at an early age in the farm (Moraes et al, 2003; Collin et al., 2007), thus altering postnatal growth (Collin et al., 2005; Halevy et al., 2006a,b). Short periods of cold exposure (60 min at 15 ºC) at days 18 and 19 of embryonic development shows an improved performance at 38 days of age (Shinder, et al, 2009). Long lasting adaptation occurs when periodic thermal ­manipulation is applied during the last part of the Maturation Phase, when the integrated circuits for the thermoregulatory system are well developed - and therefore most responsive to ‘training’ (Tzschentke, 2007; Tzschentke , 2008; Tzschentke and Halle, 2009). Thermal manipulation during this late phase in the setter and hatcher shows an improvement of 1.5 % on hatcha­ bility, a 2.9 % improvement in male growth and improved feed conversion (Tzschentke and Halle, 2009): all indications of enhanced robustness in the day old chick. (See table 1 on page 5)


More research will decipher specific, sensitive embryonic phases and conditions, to engender the further use of thermal stimulation in commercial incubators, to induce enhanced robustness in day old chicks from different flock ages and commercial breeds. In the meantime, promising scientific results already ratify the development and introduction of Circadian Incubation™.

From single-stage incubation to Circadian Incubation™ If the goal of the modern hatchery is to produce uniform, robust day old chicks, the multi-stage system does not deliver the degree of control required – and single-stage incubation requires further development. Single-stage incubators can of course be adjusted and set such that climate conditions match the needs of modern embryos, to improve day old chick quality and uniformity (Boerjan, 2002). Today, the basic assumption for the design of single-stage incubation programs is that optimal embryonic development occurs under constant conditions, without fluctuation. However, the idea that the embryo can be adapted to certain stress factors (high or low temperatures, for example) to improve robustness and deliver better performance later in life is gaining significant acceptance. In the poultry sector, where substantial growth is indicated over the next two to three decades, Circadian Incubation™ signals an important bridge to meeting next generation demands and opportunities in commercial hatcheries. The majority of thermal conditioning investigations have been performed under controlled experimental conditions, in small incubators. In collaboration with a commercial broiler hatchery and Wageningen University Research Centre, Pas Reform has undertaken trials on a commercial scale with four flocks of 35, 42, 48 and 56 weeks respectively. In each experiment, Ross 308 eggs from three different suppliers were incubated in a modular, single-stage incubator, adapted to enable the Circadian principle with a capacity of 115,200 hen eggs. For each batch of eggs, a thermal conditioning period of three hours was applied by increasing temperature set points from 36.7 ºC (98 ºF) to 38.1 ºC (100.6 ºF) for three hours on days 16.5, 17.5 and 18.5 in the setter. (See figure 1 on page 5) In all four experiments, the egg shell temperatures raised ­immediately after increasing the set point. At the end of the thermal conditioning period, average egg shell temperature was measured at 39.8 - 40.1 ºC (103.6 - 104.2 ºF). On each experimental day, egg shell temperatures returned to normal and were comparable with egg shell temperatures in the control incubator 1.5 hours after completing the period of thermo-conditioning, by returning set points to normal (36.7 °C / 98 °F) temperature. Each batch demonstrated positive influences on hatching results, as a result of thermal conditioning. A clear, positive trend on growth performance was observed, with 1 to 2 points improvement in feed conversion ratios.

Circadian Incubation™


Figure 1

Temperature stimulation in a

average eggshall temperatures (ºF)


modular, single-stage incubator, adapted to enable the Circadian


Incubation™ principle. A thermal

conditioning period of three hours was applied by increasing


temperature set points from 98 ºF to 100.6 ºF for three hours on day 16.5, 17.5 and 18.5. Eggshell


temperatures were measured

automatically by means of contact

99,00 16,0







day of incubation

Table 1 Overall (females +

Male: weight gain

Male: final body

Male: Feed ­conversion

males) hatchability of

g/broiler/day 1 - 35

weight (35 d)

rate (1 - 35d)

62.2 ± 2.9

2270 ± 203

1.50 ± 0.04

fertile eggs (%) Control


Temperature stimulation Eggs (337) exposed for 2 hr/day

at 38.5 ºC during the last 4 days of incubation (days 18 - 21).

(Tzschentke B. and Halle I (2009).


Influence of temperature Temperature


64.6* ± 2.0

2336* ± 191

1.47* ± 0.02

stimulation during the last 4 days of incubation on secondary sex


ratio and later performance in

male and female broiler chicks.

*(P< 0.05)

Br. Poultry Sci 50(5): 634 - 640)

Further studies will improve the protocols for thermal conditioning in practice for different commercial breeds and flock ages. For this reason, Pas Reform has initiated a collaborative research project with dr. B. Tzschentke from Institute of Biology, Working Group Perinatal Adaptation at the Humbold University of Berlin (HU) and dr I. Halle from Friedrich-Loeffler-Institut (FLI), Federal Research Institute for Animal Health, Institute of Animal Nutrition, Braunschweig. We know, however, that thermal conditioning is only beneficial when applied in a clear, controlled manner, for specific time points and duration. A Circadian Incubation™ program can only be applied in commercial practice, if the hatchery’s single-stage incubation system contains individually controlled sections for accurate climate control and (thereby) delivers homogeneous eggshell temperature. The system must also be equipped with sufficient, cooling and heating devices – to deliver short, highly accurate cold or heat stimuli for the incubating embryos to result in uniformly robust day old chicks. Used correctly, Circadian Incubation™ opens the door for the hatchery manager to produce uniform, highly robust day old chicks that will go on to deliver robust, improved performance at farm level.

Conclusions The ultimate goal of modern hatchery management is to produce uniform, robust day old chicks. Robustness is a health criterion that originates in the embryonic lifestage of the chicken and correlates directly with the performance and ­resistance of individual chicks under differing farm conditions. Robustness requires a specific incubation trigger during so-called critical periods, eg. stimulation by heat or cold, to ­physiologically imprint the embryo such that the chicken thrives in its farm environment. Short-term thermo-conditioning using Circadian Incubation™ improves hatching results and produces long-lasting effects, with 1 - 2 % increase in final body weight and 1 - 2 points better feed conversion rates. Batches of uniform, robust day old chicks improve uniformity at slaughter age and thereby improve efficiency and performance throughout the entire production chain. However, to support the use of Circadian Incubation™, the incubator should provide accurate climate control, to promote tight temperature uniformity. Each egg must receive a consistent flow of conditioned air for optimum thermal conditioning.

Circadian Incubation™


Next generation design for the modern hatchery Creating an adaptive environment


1 The challenge of temperature homogeneity

In the previous article titled ‘Circadian Incubation™’, Pas Reform discussed the effects of thermal stimulation on subsequent post hatch performance. Research shows a positive and sustained effect on hatchability, robustness, final bodyweight and feed conversion ratios, when periodic temperature increases are administered during the last days of incubation (maturation phase).

Thermal stimulation can only be applied in practice when ­incubation equipment delivers a homogeneous climate for uniform embryonic development. Only the smallest variations in temperature and therefore in heat transfer can be tolerated, which is largely determined by air temperature and velocity around the eggs.

This article discusses progress in the development of modular single-stage equipment for Circadian Incubation™, i.e. equipment that supports the use of thermal stimulation for the production of uniform batches of robust, high quality chicks in the modern hatchery.

For incubator manufacturers, the challenge today is to design incubators capable of supporting uniform, optimised embryonic development for each egg at every stage of its development. This means providing every one of a very large number of eggs in a closely packed environment with an optimal airflow for uniform temperature distribution. Air must move freely around the eggs at all times. This challenge is complicated by the trend towards larger capacity incubators. Because of increased heat production by modern embryos, it is more difficult to maintain homogeneity in egg shell temperature and air movement rates for each egg in such large incubators. Further complications can arise as a result of airflow obstruction in the incubator. The even distribution of temperature and humidity within the incubator depends on the ease with which air can pass through the setter trays and over the surface of the eggshells. Poorly designed trolleys and trays can result in air passing around the mass of eggs, rather than passing evenly between them, which leads to non-homogeneous temperature distribution.


Next generation design for the modern hatchery

Figure 1

Building a 3D simulation model of a separately controlled incubator section.

There are three additional sources of non-uniform air temperature in incubators: 1 The ambient temperature and relative humidity of inlet air usually differs from average temperature and relative humidity inside the machine, resulting in localised temperature and humidity variation at the point of intake. 2 Both cooling and heating in the incubator generate localised temperature variations. 3 The evaporation of water to control humidity levels for optimum egg weight loss can lead to temperature differences. The challenge of modern incubator design is to exchange energy, CO2/O2 and moisture without affecting homogeneous temperature around the eggs. The following chapters demonstrate how a redesign of the ­incubator can improve homogeneous temperature distribution, creating the ability to operate within the strict parameters required to successfully apply Circadian Incubation™. Chapter 2 introduces the application of Computational Fluid Dynamics (CFD) simulations, to gain valuable insights into the incubator’s air flow pattern and temperature distribution. Chapter 3 ­presents the aerodynamics of a fully optimised airflow and air redistribution system for Circadian Incubation™. Finally, chapter 4 shows how the homogeneous temperature achieved with an optimised airflow system is further improved by the use of a system newly developed by Pas Reform and known as ‘Adaptive Metabolic Feedback™’.

2 Computational Fluid Dynamics: a first in the hatchery sector Traditionally, new developments in the design of airflow systems have relied upon the actual, physical development of a prototype and in-practice testing: a lengthy and expensive process, limited by the number of practical situations and product alternatives that can be physically tested. While looking at ways to optimise temperature uniformity, Pas Reform started to implement Computational Fluid Dynamics (CFD) to simulate the airflow and the heat transfer inside the incubator. CFD is a scientific discipline, in which the flow and the heat transfer of any gaseous or liquid medium can be simulated within a virtual environment. It uses numerical algorithms to calculate airflow and temperature distribution, thereby allowing deeper insights into the internal physics of the incubator and other environmental factors. CFD was first applied in Aerospace development about 30 years ago, followed by the automotive industry, which now routinely uses CFD in new product development and testing. Despite its proven accuracy and dependability in these highly specific and demanding arenas, Pas Reform is the first to apply CFD for new product development in the hatchery sector. In its application of CFD for incubator design, the company worked in collaboration with FlowMotion, an engineering company that specialises in fluid dynamics for industrial applications, with a proven track record in food technology.

Next generation design for the modern hatchery


Figure 2

The most effective method of

exchanging energy, CO2/O2 and moisture in the incubator, is to generate as many vortices as

possible of a specific dimension

and intensity in the wake of the

air pump blade. (Colours indicate difference of airspeed)

The application of CFD in product development can be separated into three phases: pre-processing, solving and post-processing: 1 In the first phase, Pre-processing, a 3D model of an incubator section is created. With a completed 3D model, the calculation region is divided into millions of small cells, for which the governing equations need to be solved numerically. (See figure 1) Boundary conditions are prescribed for all incubator surfaces, inlets, outlets, fans, etc. – ie. all the areas that are instrumental in generating airflow and producing heat transfer, including the hatching eggs. The design of the calculation grid and the definition of all boundary conditions are the most critical processes in CFD, because they have the largest influence on the viability and accuracy of results. This phase requires sophisticated expertise and experience in fluid dynamics. 2 In the second phase of CFD, Solving, the computer calculates governing equations for each grid cell. And there are millions of cells. This process can take anything from a couple of hours for a small number of cells, to a number of days for complex flows.


3 The final phase of CFD is Post-processing – where the data produced in the previous two phases is visualized. Crucially, this is where the expertise of Pas Reform Academy’s R&D team, with its detailed understanding of the needs of the growing embryo – joined forces with the expertise of FlowMotion to fulfil these needs in terms of aerodynamics, to analyse the huge amount of simulation data produced against the real world air flow requirements of modern incubators.

3 Aerodynamics of a new airflow principle From conception, Pas Reform’s Smart modular single-stage ­incubators were designed to overcome the drawbacks of ­conventional incubation described in the first paragraph of this article. Smart’s modular single-stage design creates sectional environments, each with the capacity for up to 19,200 hen eggs. During incubation, each section climate can be individually controlled – the only way to guarantee homogeneous incubation temperature in incubators containing more than 100,000 eggs. Separate temperature, heating, cooling, humidification and ventilation systems in each section of the incubator provide a homogeneous environment around the incubating eggs.

Next generation design for the modern hatchery

Figure 3

Figure 4

amount of fresh air from the

eggs along the side of the setter

The Vortex™ draws in an optimum setter room and circulates it

through each separate section of the incubator. (Colours indicate difference of airspeed)

Smart is a trusted system in hatcheries around the world. And as an innovator in the hatchery industry, it was logical for Pas Reform to look for ways in which this established platform could be further improved, to fully maximise the benefits of homogeneous climate control for Circadian Incubation™. The application of CFD made it possible to gain valuable further insights into the airflow pattern and temperature distribution produced in each separate section of an incubator. With this data, the detailed investigation of various incubator designs became viable – and Pas Reform has focused its attention on a number of variations, including the number and shape of air pump blades, air inlet principles, section partitions, size of mixing zone, air pushing or pulling principles, trolley and tray design, heating, cooling and humidifying principles, air tightness and footprints. After three years of intensive and varied flow simulation, Pas Reform has developed a fully optimised airflow and air ­redistribution system – with the following aerodynamics: Air pump blade principle The basis of the new airflow and air redistribution system is Pas Reform’s ‘Vortex™’, a newly designed air pump named after the vortical movement of airflow it produces. (See figure 2) With the intensive analysis of many different, simulated air pump blade shapes, it is clear that the most effective method of exchanging energy, CO2/O2 and moisture in the incubator, is to generate as many vortices as possible of a specific dimension and intensity in the wake of the blade. The shape of the air pump

The inlet air moves around the

trolleys, to avoid ambient air from making contact directly with the

eggs. (Colours indicate difference of airspeed)

blades also positively influences the pumped flow rate of fresh air, the amount of torque required to achieve maximum tempe­ra­ ture uniformity, the electrical power consumption of the system and the flow along the cooling/heating elements of the incubator. Air Preparation principle Through the inlet in the ceiling of each incubator section, the Vortex™ draws fresh air from the setter room, which flows through a vertical channel and through the hub and inner ­structure of the air pump blades, creating a radial pump for the air. (See figure 3) Each separate section of the incubator is equipped with a Vortex™, that circulates the ‘fresh air’ from the tip of its air pump blades to partitions on each side of the incubator section. The partitions direct the air along the side of the setter trolleys, into the so-called ‘mixing zone’ of the incubator. The primary advantage of this flow pattern is that ambient air never makes contact with the eggs directly, so avoiding significant, localised changes in egg temperature. (See figure 4)

Next generation design for the modern hatchery


Figure 5

Figure 6

remaining variations in air

the Vortex™ pulls the mixed air in

The mixing zone minimises temperature. (Colours indicate difference of airspeed)

Air Mixing principle Once the air has passed the trolleys, it reaches the ‘mixing zone’, where remaining variations in air temperature are minimised by mixing the air before it is drawn over the eggs. The size of this mixing zone is crucial for its impact on egg temperature homogeneity within each separate incubator section. (See figure 5) Exchange Principle The Vortex™ pulls the mixed air in vortical spirals through the egg trays and over the eggs, back towards the centre of the air pump. (See figure 6) This has two significant advantages over conventional airflow systems. By pulling (instead of pushing) vortices over the eggs, the surface of the hatching egg is exposed for an optimum exchange of heat and humidity. The specific flow direction along the eggs changes constantly, ensuring that uniform egg shell temperature is created and maintained for each egg throughout incubation. Additionally, the vortices move in parallel with the turning direction of the setter trolleys, managing airflow such that it reaches the entire surface of the eggshells. This prevents the development of ‘dead spots’ where there is little air movement, to provide unique, homogeneous air distribution within each incubator section.


Principle drawing showing how

vortices through the setter trays and over the eggs.

To further reduce obstruction by the setter trays, new tray design incorporates an open, spacious grid that prevents the development of dead spots and allows the free movement of air vortices through the trays, to reach each individual hatching egg. (See figure 7) When the vortices finally flow out of the trays, they reach the ‘Exchange zone’ of the incubator section. Here the primary target of the air pump is to exchange energy, CO2/O2 levels and moisture, to condition the air before recirculation throughout the incubator section, for homogeneous egg temperature distribution. The shape of the Vortex™ has explicitly been optimised to mix ‘old’ air coming from the incubator section with ‘fresh’ air from the tip of the Vortex™ and the integrated heating/cooling of the incubator, by its specific vortices in the wake of the blade. (See figure 8)

Next generation design for the modern hatchery

Figure 7

Figure 8

the free movement of air vortices,

air before recirculating throughout

The redesigned setter tray allows

to reach every individual hatching egg.

The Exchange zone conditions the the incubator section, for

homogeneous egg temperature distribution. (Colours indicate difference of airspeed)

4 Maximising uniformity by Adaptive Metabolic Feedback™ The advancements in airflow design described in chapter 3 of this article produce an environment that can be precisely controlled: a prerequisite for thermal stimulation – or the deployment of Circadian Incubation™. In this chapter, we show how temperature homogeneity, achieved by optimising airflow, can be further maximised using so-called ‘Adaptive Metabolic Feedback™’. Adaptive Metabolic Feedback™ (AMF™) enables the control parameters of the incubation process to be adapted, according to the time-varying metabolism of a specific batch of embryos in the incubator. Ultimately AMF™ maximizes uniformity, by optimising airflow and air redistribution such that Circadian Incubation™ can be applied. Incubators must ventilate, to allow enough oxygen to come in and to allow the gases produced during the process of incubation to escape. The ventilation system controls the rate of air refreshment and, consequently, the level of carbon dioxide and relative humidity in the incubator. Carbon dioxide percentages and relative humidity increase when the valves are closed and ventilation is zero. Levels of carbon dioxide and relative humidity are strongly associated and should ideally be controlled simultaneously, with equal sensitivity.

The aspect of increased humidity is often neglected – despite the fact that increased levels of relative humidity in the incubator limit the evaporation of water from the eggs, decreasing egg weight loss and the effects of evaporative cooling. High levels of relative humidity have physical as well as physiological influences on embryo development. The evaporation of water is a physical process that uses heat – and therefore the eggs lose heat during that process, also known as evaporative cooling. The continuous evaporation of water from the eggs during all stages of the ­incubation process – measured as egg weight loss – is essential for maintaining mineral balance in the different embryonic compartments at a physiological level. In non-ventilated incubators, actual relative humidity rises above set points and as the incubator humidifiers are not in operation, cold spots are avoided. Embryo temperatures increase because evaporative cooling is limited as a result of increased moisture content in the incubator air. However, increased moisture content in the non-ventilated incubator limits egg weight loss, affecting embryo development to finally increase the risk of poor chick quality, bad navels and large yolk sacs. The control of the moisture-carbon dioxide couple in commercial incubators must therefore follow physical as well as physiological rules. It is important that the modern incubator has the ability to operate according to varied moisture-carbon dioxide profiles, suited to local circumstances.

Next generation design for the modern hatchery


This knowledge formed the essential background for the deve­ lopment of Pas Reform’s ‘Adaptive Metabolic Feedback™’ system for ventilation. Based on the actual metabolism of the incubating eggs in a commercial incubator, the uniquely adapted moisture – CO2 couple determines the ventilation rate of the incubator, in line with the rate of development of the incubating eggs. Because both moisture and CO2 are monitored continuously against specific setpoints, AMF™ optimises incubation by ­minimizing cold spots from ventilation and humidifiers, while simultaneously avoiding the excessive build-up of CO2. The fine control delivered by AMF™ ensures that the natural evaporation of water from the eggs is unaffected, while the incubator meets the time-varying needs of the growing embryo in its different stages throughout the cycle. Adaptive Metabolic Feedback™ achieves this continuous control over both recirculated and fresh air by listening to the embryo’s metabolism, as reflected in the production of moisture and carbon dioxide. In this way energy, CO2/O2 and moisture are exchanged without affecting the incubator’s homogeneous temperature.


Conclusions Since the Circadian Incubation™ principle greatly challenges the incubator’s homogeneity, new design concepts are needed to further improve homogeneous temperature distribution. Three years of intensive (flow) simulations and empirical field studies have shown that the combination of (1) a modular ­incubator design, (2) a new airflow principle based on the creation of vortices and (3) Adaptive Metabolic Feedback™, produce the highly precise environmental controls that are a prerequisite to the successful use of thermal stimulation. The combined use of these three components1 makes it possible to exchange energy, CO2/O2 and humidity without affecting homogeneous temperature around the eggs. This delivers ­significant advantages for the modern hatchery, including homogeneous egg temperature distribution in the maturation phase of incubation. Short, accurate increases in temperature for each of the embryos is possible, to deliver the benefits of Circadian Incubation™ on hatchability, robustness, final bodyweight and feed conversion ratios. 1

Patent Pending with Worldwide Intellectual Property Rights

Next generation design for the modern hatchery

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• Minne, B. and Decuypere, E. (1984) Archiv für Experimentelle Veterinär­ medizin, 38: 374-383.

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Pas Reform Hatchery Technologies Pas Reform is an international company, which has specialised in the development of innovative hatchery technologies for the poultry sector since 1919. The company has earned its position as one of the world’s leading hatchery e ­ quipment manufacturers, through decades of research into the bio­­logical and physiological aspects of embryo development, combined with a thorough understanding of all aspects of the poultry production chain – and a dedicated focus on the future.

Pas Reform Hatchery Technologies Pas Reform is an international company, which has specialised in the development of innovative hatchery Technologies for the poultry sector since 1919. The company has earned its position as one of the world’s leading hatchery e ­ quipment manufacturers, through decades of research into the biological and ­physiological aspects of embryo development, combined with a complete u ­ nderstanding of all

Pas Reform Hatchery Technologies Pas Reform P.O. Box 2 7038 ZG Zeddam The Netherlands Phone +31 314 659 111 Fax +31 314 652 575 E-mail Internet

aspects of the poultry production chain - and a dedicated focus on the future.

Circadian Incubation™  

Circadian Incubation™