Method of using carbon dioxide in poultry egg incubation to improve poultry characteristics

Abstract

The invention relates to a method of incubating fertilized un-incubated poultry eggs for hatching, the method comprising: incubating the eggs in a gaseous atmosphere in contact with the eggs for an incubation period of 18 to 21 consecutive days, and during which period, carbon dioxide is supplied to the gaseous atmosphere from a source external to the eggs as required, so that the concentration of carbon dioxide in the gaseous atmosphere in contact with the eggs is 7,500 to 20,000 ppm for at least one period of at least 12 hours, thereby enhancing the health and viability of the chicks and, for chickens, reducing the propensity of chicks hatched from the eggs so treated to conditions such as wooden breast.

Description

TECHNICAL FIELD

[0001] The present invention relates to the treatment of embryonic chickens as eggs in an incubator to improve characteristics of the chickens when hatching the eggs and thereafter as the chickens grow to adult chickens. Characteristics that can be improved include increasing the hatchability of the eggs; increasing the hatch weight of the chickens; increasing the survivability of the chickens and decreasing the mortality rate of the chickens; increasing the weight gain of the growing chickens; increasing the final weight; and decreasing or eliminating the incidence of a condition known as wooden breast in the hatched, growing chickens. BACKGROUND

[0002] Modern day chickens raised for meat, particularly chickens raised in the United States, are grown to a relatively large size (over 6 pounds). The large size is considered desirable because it provides a relatively large amount of breast meat per chicken. Chickens grown for their meat are referred to as "broilers." Chickens grown to a large size (over 6 pounds) for their meat are sometimes referred to as "big birds."

[0003] However, these large size chickens, particularly chickens over 6 pounds, are frequently found to have a condition known as "wooden breast" or "wooden breast" (referred to herein as wooden breast or WB). In this condition, the breast muscle (which provides the breast meat) has a very hard texture and lower nutritional value. These characteristics greatly reduce the value of the breast meat. It is estimated that an average of 5-20% of big birds (those weighing 6 pounds or more at slaughter) suffer from wooden breast, resulting in an overall loss to the chicken's grower that is undesirable. Wooden breast is exhibited in the live chicken prior to any processing or cooking of the chicken's meat, and is not prevented or reduced by any processing or cooking of the breast meat. There is no known solution for treating or avoiding the wooden breast condition other than reducing the size of the chicken's growth, which itself reduces their overall value.

[0004] Hatchability of the eggs is an important characteristic because it relates to the ability of a live, healthy chick to emerge from the egg in which it developed as an embryo. Hatch weight (i.e., the weight of the chick when hatched) is important because it relates to the ability of the chick to survive and grow to adult size. Weight gain (the tendency to increase in weight) as the chicken grows is significant because it indicates the total amount of meat that will be harvested and can be sold. Mortality rate is important because it indicates a higher likelihood that the chicken will reach adult size and be in good health when it reaches its adult size. SUMMARY

[0005] The present invention identifies specific treatment protocols for applying carbon dioxide (CO2) concentrations and protocols (or "recipes") to unincubated fertile embryonic poultry eggs while the unincubated fertile embryonic poultry eggs are being incubated, which have been found to be successful in reducing wooden breast in chickens hatched from the treated eggs, and in promoting other characteristics mentioned herein (i.e., increasing hatchability of the eggs; increasing hatch weight of the chickens; increasing livability and decreasing mortality of the chickens; and increasing weight gain of the growing chickens). These effects have been found with the protocols described herein for establishing CO2 concentrations in the incubator for established periods of time. These protocols can all be implemented practically and safely in commercial hatcheries without causing any other deleterious side effects to the hatched chickens, such as decreasing hatchability, increasing mortality, or other disease conditions.

[0006] The present invention features a method of incubating a fertile unincubated chicken or other poultry egg for hatching, comprising incubating for an incubation period of 18 to 21 days of consecutive eggs in a gaseous atmosphere in contact with the eggs, and during this period, injecting carbon dioxide into the gaseous atmosphere from a source external to the eggs as needed, such that the carbon dioxide concentration in the gaseous atmosphere in contact with the eggs is between 7,500 ppm and 20,000 ppm for at least one period of at least 12 hours (alternatively, at least 24 hours).

[0007] The present inventors have identified several protocols, including the following protocols:

[0008] Protocol 1 : Exposing a fertile unincubated chicken or other poultry egg to a gaseous atmosphere in contact with the egg having a set value of an incubation concentration of carbon dioxide between 7,500 ppm CO2 and 20,000 ppm CO2 within 10% and preferably within 5% for at least one day, preferably at least 6 days, more preferably at least 12 days of the first 18 days of the incubation period, and supplying carbon dioxide to the atmosphere as needed during the 18 day period to maintain the CO2 concentration, wherein the egg is incubated at said incubation concentration, and then incubating the egg in an atmosphere without any supply of CO2 from a source external to the egg for 3 consecutive days immediately after the 18 day period, or supplying CO2 from a source external to the egg to the atmosphere as needed to maintain the CO2 concentration of the atmosphere in contact with the egg at a concentration within 10% and preferably within 5% of the set value between 7,500 ppm CO2 and 20,000 ppm CO2.

[0009] In this preferred embodiment of the protocol 1, the set value is constant for all 18 days throughout the first 18 days.

[0010] In a second preferred protocol, a fertile unincubated chicken or other poultry egg is exposed to a gaseous atmosphere in contact with the egg for successive incremental periods, during each of which the carbon dioxide concentration in the gaseous atmosphere is maintained at a value within 10% and preferably within 5% of a set value by supplying carbon dioxide from a source external to the egg into the gaseous atmosphere as needed to maintain the CO2 concentration in the gaseous atmosphere within 10% and preferably within 5% of the set value, the set value being constant throughout the incremental period and being between the CO2 concentration of the ambient atmosphere, which is considered to be about 350 ppm to as high as 420 ppm CO2, and 20,000 ppm CO2, wherein the set value and the CO2 concentration in the gaseous atmosphere are increased from each of the incremental periods to the next, so that in the incremental period at the end of the incubation period, the CO2 concentration in the gaseous atmosphere is within 10% and preferably within 5% of a value between 7,500 ppm CO2 and 20,000 ppm CO2, and then the egg is incubated in an atmosphere, immediately after the first 18 days of the incubation period, for 3 consecutive days without any additional CO2 being supplied from a source external to the egg into the atmosphere, or with CO2 being supplied from a source external to the egg into the atmosphere as needed to maintain the CO2 concentration in the atmosphere in contact with the egg at a concentration within 10% and preferably within 5% of a constant set value between 7,500 ppm CO2 and 20,000 ppm CO2.

[0011] In a preferred embodiment of Protocol 2, each set value is increased linearly from one incremental period to the next, i.e., by equal increments.

[0012] Protocol 3: A third preferred protocol involves alternating, throughout the incubation period,

[0013] (A) exposing the fertile unincubated chicken or other poultry egg to a gaseous atmosphere in contact with the egg for an exposure period, during each of which the carbon dioxide concentration in the gaseous atmosphere is maintained at a value within 10% and preferably within 5% of a set value between 7,500 ppm CO2 and 20,000 ppm CO2 which is constant during each exposure period, by supplying carbon dioxide from a source external to the egg into the gaseous atmosphere as needed to maintain the CO2 concentration in the gaseous atmosphere within 10% and preferably within 5% of the set value, wherein the set value is the same in all exposure periods, and

[0014] (B) exposing the fertile unincubated egg to a gaseous atmosphere for an interval period without carbon dioxide being supplied from outside the egg into the gaseous atmosphere.

[0015] In preferred aspects of this protocol, each exposure period has a duration of 18 hours to 24 hours and each interval period has a duration of 18 hours to 24 hours; and there are 2 to 20 exposure periods and 2 to 20 interval periods.

[0016] Protocol 4: A fourth preferred protocol involves, throughout the incubation cycle, alternately

[0017] (A) exposing the fertilized unincubated chicken or other poultry eggs to a gaseous atmosphere in contact with the eggs for exposure periods, in each of which the carbon dioxide concentration in the gaseous atmosphere is maintained at a value that is within 10% and preferably within 5% of a set value between the CO2 concentration of an ambient atmosphere and 20,000 ppm CO2, the set value increasing from one exposure period to the next, such that in the last incremental period the CO2 concentration in the gaseous atmosphere is within 10% and preferably within 5% of a value between 7,500 ppm CO2 and 20,000 ppm CO2, by supplying carbon dioxide as needed from a source external to the eggs into the gaseous atmosphere to maintain the CO2 concentration in the gaseous atmosphere of the exposure period within 10% and preferably within 5% of the set value, and

[0018] (B) exposing the fertilized unincubated eggs to the gaseous atmosphere for interval periods without carbon dioxide being supplied from outside the eggs into the gaseous atmosphere.

[0019] In preferred aspects of this fourth protocol, each exposure period has a duration of 18 hours to 24 hours and each interval period has a duration of 18 hours to 24 hours.

[0020] As used throughout this specification and claims, "ppm" means parts per million by weight.

[0021] As used throughout this specification and claims, the term "ambient atmosphere" means the atmosphere in the interior of the incubator and the immediate exterior area.

[0022] As used throughout this specification and claims, the term "as needed" means that carbon dioxide is added if the CO2 concentration of the atmosphere to which CO2 is to be added is below the desired range or level, and no CO2 is added if the CO2 concentration in the atmosphere is at a level within the desired range or at the desired level.

[0023] As used throughout this specification and claims, "carbon dioxide from a source external to the eggs" excludes carbon dioxide that has entered the incubator from the natural atmosphere outside the incubator, and excludes carbon dioxide that has exited the egg from the interior of the egg through the shell of the egg.

[0024] As used throughout the specification and claims herein, the "relative humidity" of air or gas refers to the amount of water vapor currently present in the air or gas as a percentage of the maximum amount of water vapor that the air or gas can hold (without causing precipitation) at a given air or gas temperature. When the maximum water vapor capacity of the air or gas is reached or exceeded at a given temperature, i.e., when the relative humidity reaches 100%, the water vapor will precipitate out as liquid water. Many different devices are readily available and used by those skilled in the art to measure the relative humidity in air or gas.

[0025] As used throughout the specification and claims herein, the term "incubation" refers to the period when a fertilized egg is placed in a controlled atmosphere environment at a temperature sufficient to promote embryo growth and development. Typically, the first 18 days of incubation occur in a room or device known as a setter or incubator in a commercial hatchery, and this process is commonly referred to as setting. The developing eggs are then transferred to a separate room or device known as a hatcher, and this process is commonly referred to as hatching. As used throughout the specification and claims herein, the term "incubation" refers to the combination of the setting and hatching stages.

[0026] In most commercial chicken hatcheries, the setting period is typically 18 days, and the hatching period is typically 3 days. In some cases, these periods can be different. If the setting and hatching periods are different than described throughout the specification and claims herein, the present invention is still applicable. For example, if the total period is 25 days instead of 21 days, the present invention is still applicable. In this case, the carbon dioxide is supplied from a source external to the eggs into the gas atmosphere for 18 days, or even proportionally longer to 22 days.

[0027] The present invention is also applicable to the incubation of poultry species other than chickens. As used herein, "poultry" refers to chickens, turkeys, ducks, and geese. For example, the present invention is also applicable to turkey egg incubation. Typically, turkey egg incubation periods are longer than chicken egg incubation periods. As in the preceding paragraph, the CO2regime described in the present invention can remain the same or the time period can be proportionally longer.

[0028] The present invention provides methods, formulations and equipment for incubating un-hatched fertile embryonated eggs of chickens under controlled CO2 concentrations to improve respiratory and vascular system development and respiratory and vascular function of the chicken before and after hatching, all other hatching conditions and controls being comparable. In commercial hatching methods and equipment not practicing the present invention, CO2 concentrations vary naturally or incidentally in an uncontrolled and variable manner due to the restricted air circulation in the hatching cabinet that is otherwise regulated. The present invention finds that controlling CO2 concentrations and specific concentration regimes and timing in the hatching cabinet atmosphere to hatch and grow healthy chickens that exhibit reduced or no incidence of Sirex and exhibit the following other characteristics mentioned herein (increased hatchability; increased hatch weight; increased viability and reduced mortality; and increased weight gain) is key. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a plan view of a hatching cabinet and related apparatus in which the present invention can be practiced.

[0030] Figure 2A Figure 2B Figure 2C Figure 2D are graphs showing several different regimes for establishing a CO2 atmosphere in a hatching cabinet.

[0031] Figure 3A is a bar graph of Sirex scores for an example of Regime 1. Figure 3B Figure 3C Figure 3D Figure 3E are corresponding results for hatchability, hatch weight, final weight and survival rate of birds subjected to Regime 1 compared to control birds.

[0032] Figure 4A is a bar graph of Sirex scores for an example of Regime 2. Figure 4B Figure 4C Figure 4D Figure 4E are corresponding results for hatchability, hatch weight, final weight and survival rate of birds subjected to Regime 2 compared to control birds.

[0033] Figure 5A is a bar graph of Sirex scores for an example of Regime 3. Figure 5B Figure 5C Figure 5D Figure 5E are corresponding results for hatchability, hatch weight, final weight and survival rate of birds subjected to Regime 3 compared to control birds. DETAILED DESCRIPTION

[0034] ​​​​​​​​​​​​Aspects of the invention involving incubation in an atmosphere containing carbon dioxide are advantageously performed with any fertile chicken egg, particularly with a fertile egg that is expected to produce, upon hatching, a chick that can be properly cared for and fed to grow to a weight of at least 6 pounds, preferably at least 6.5 pounds, even at least 8 or 10 pounds, by 42 to 58 days after hatching. Such eggs are preferably obtained from chickens that are genetically predisposed to produce eggs that will hatch to produce chicks of such size.

[0035] Aspects of the invention involving incubation in an atmosphere containing carbon dioxide under specified conditions can be performed in an incubator, which has primarily conventional design and features, and has the ability to supply carbon dioxide into the incubator, and has the ability to measure the concentration of carbon dioxide in the atmosphere in the incubator, and to start and stop the supply of carbon dioxide into the incubator in response to the measured concentration of carbon dioxide in the incubator.

[0036] For example, with reference to Figure 1 An incubator useful in the practice of the invention includes a structure 1 that houses an enclosed space 3, which is defined by walls 2, and by a floor (not shown) and a ceiling (not shown) that are sealed to the walls, and which contains at least one portal 4 through which a person and a cart or shelf of eggs can enter and exit the space 3 to place eggs in the incubator and to remove eggs or hatched chicks from the incubator. In larger structures, which are typically used by commercial scale producers, the vertical distance from the floor to the ceiling is typically about six feet or more, which enables a person to stand inside the incubator, although smaller structures can also be used. Typically, the walls are insulated, and often the floor and ceiling are also insulated, to help retain heat within the space 3, to aid in the incubation of the eggs within the incubator.

[0037] A gas line 11 ending in an outlet 12 in the space 3 delivers gaseous carbon dioxide or a carbon dioxide containing gas composition from a gas source 13, which can be a storage tank, cylinder, vessel or container, or a delivery truck, containing carbon dioxide delivered at a concentration typically of at least 80% CO2 by volume, through a controllable valve 17. One or more probes 15 measure the carbon dioxide concentration in the space 3. By comparing the measured concentration value with a preprogrammed value of the concentration of CO2 to be maintained in the space 3 in a monitor 16, the monitor 16 controls the opening and closing of the valve 17 in the line 11 in response to the value measured by the probe 15. When the measured value of the carbon dioxide concentration is below a predetermined desired value stored in the monitor 16, the monitor opens the valve 17 so that carbon dioxide is fed into the space 3 until the measured value of the CO2 concentration in the gas atmosphere in the space 3 has increased to the desired value. The carbon dioxide can be fed by any of a variety of means, including but not limited to a gas stream of 100% carbon dioxide, or a gas stream of carbon dioxide in combination with one or more other gas species (a mixture), or a liquid or solid carbon dioxide, or a substance that can produce or release carbon dioxide into the gas atmosphere. When the measured carbon dioxide concentration in the space 3 reaches the desired value, as detected by the probe 15 and the monitor 16, the monitor 16 closes the valve 17. An air vent 18 represents any suitable opening that can be opened and closed as needed through which the atmosphere can be vented out of the space 3. The incubator should preferably also include the ability to provide a measure of the amount of fresh or conditioned air flowing into the incubator (from outside the incubator) and / or the flow rate of the atmosphere in the incubator out of the incubator. This measure can then be used to determine the flow rate of CO2 feed required to maintain a certain concentration of CO2.

[0038] To reduce the CO2 concentration in the atmosphere in which the eggs are exposed in the incubator, air or oxygen and / or nitrogen can be fed into the atmosphere while removing the atmosphere from inside the incubator, thereby reducing the amount of CO2 in the atmosphere relative to the other gas components present.

[0039] The incubator is also equipped with an air or gas temperature controller (which can be either or both of a heater and / or a cooler such as an air conditioning unit 21), and with a water vapor source 22 such as a steam line or vaporizer, all of which are known and conventionally available, and each equipped with a suitable controller to start and stop the supply of heat, cooling and humidity, respectively, so that the atmosphere in the space 3 can be controllably maintained at desired values of temperature and relative humidity. The incubator typically includes a plurality of shelves on which the eggs to be incubated are placed.

[0040] Most commercial incubators contain an internal fan 23 that distributes or mixes the air inside the incubator, ensuring uniform temperature and humidity conditions. The location of the carbon dioxide gas outlet 12 in the incubator relative to the location of the fan is important to ensure uniform distribution of the supplied CO2gas. The outlet 12 of the carbon dioxide gas line can consist of a single point or injection nozzle, alternatively it can consist of multiple nozzles or injection points. It is important to position the outlet 12 close to the fan 23. The preferred configuration is a nozzle ring that injects CO2gas very close to the internal fan inside the incubator, either just upstream or downstream of the fan 21. Preferably, the nozzle ring of the outlet 12 has a diameter that matches the diameter of the fan blades and is located 2 to 12 inches upstream or downstream of the fan.

[0041] The location of the probe 15 is also important to ensure uniform and accurate distribution of the supplied CO2gas. Preferably, the probe 15 is located at a distance of at least half the width of the incubator from the outlet 12. The probe 15 should also be located in the center of one of the egg racks, most preferably only 1 to 3 inches from the egg surface at the center of the egg rack. All of this ensures that the probe 15 measures the correct CO2environment in the incubator and does not produce false readings. Multiple CO2probes can be used for large incubation chambers, or for chambers where the gas mixing is not adequate. In these cases, an average reading or some other method of utilizing the spatially distributed CO2readings can be used to control the CO2addition.

[0042] In operation, the gas atmosphere in the incubator should also contain at least 17% by volume of oxygen, more preferably greater than 19% by volume and most preferably greater than 20% by volume of oxygen concentration.

[0043] The required components and the amount of each component can be provided in the incubator by known techniques of adding and measuring the total gas atmosphere.

[0044] The temperature of the gas atmosphere in which the eggs are incubated should be in the range of 92°F to 103°F. The relative humidity level in the gas atmosphere should be 30% to 70% relative humidity.

[0045] Incubated eggs require a warm (typically 100°F) temperature and controlled humidity to achieve optimal growth. However, during the incubation process, the eggs themselves generate heat and expel moisture and produce carbon dioxide. The amount of heat, moisture, and carbon dioxide emitted by a fertilized egg (or developing embryo) varies throughout the incubation process and can also be different from one genetic strain to another. Therefore, the ability to control the amount of fresh air that is allowed to enter the incubator (accompanied by the same amount of air that exits it from within the incubator) varies depending on the strain of the bird, the number of eggs within the incubator, and the time during the incubation process.

[0046] Some previous studies limited fresh air exchange into the incubator (non-ventilated) to increase the amount of carbon dioxide inside the incubator to approximately 7,000 ppm. This is an available method to increase the carbon dioxide level inside the incubator. This method can be implemented by completely closing the fresh air exchange or adjusting the fresh air exchange based on the carbon dioxide concentration of the incubator. However, this non-ventilated method does not allow the operator to independently control the temperature and humidity while also controlling the carbon dioxide level, which can result in negative effects on the hatchability of the eggs, mortality, morbidity, low weight gain, higher food consumption, etc. of the resulting chickens. In most commercial incubators, it is more important to control the temperature and humidity levels inside the incubator. This results in variable and uncontrolled carbon dioxide levels during incubation.

[0047] The present invention provides a method for controlling the carbon dioxide level inside an incubator without limiting or changing the amount of fresh air exchange that is performed in a conventional incubator. This is achieved by feeding carbon dioxide from an external carbon dioxide source into the incubator in a controlled manner based on a measurement of the carbon dioxide level inside the incubator. Thus, the carbon dioxide level can be controlled independently of the temperature and humidity. This provides an optimal temperature, humidity, and carbon dioxide environment for egg incubation.

[0048] The incubation of chicken eggs in typical commercial practice does not use a controlled C02atmosphere according to the present invention, and thus does not add any C02from an external source. Thus, the concentration of C02in the incubator atmosphere varies greatly over the course of the incubation; the C02concentration level can and does vary between widely separated values from 500 ppm to 7,000 ppm over the course of incubation. The C02concentration varies throughout the 18 to 21 day incubation and hatch, and there is no pattern to the variation. Some C02is produced by the eggs / embryos themselves as part of their respiration process, and enters the incubator atmosphere through the eggshells. In summary, in such commercial incubator operations, the concentration of C02in the incubator atmosphere is only affected by the regulated air exchange to control the temperature, oxygen, and humidity levels, and not by the intentional feeding of C02to maintain a desired C02level during incubation. Embryos subjected to these varying C02concentration levels typically exhibit a significant level of keel chest.

[0049] To implement the incubation method according to the present invention, one or more fertilized un-hatched eggs are placed in the incubator, typically on shelves in space 3 (see Fig. 1). The eggs are placed in the incubator in a manner that is known in the art. The eggs are placed in the incubator in a manner that is known in the art. Figure 1). The desired temperature and humidity levels are established in the space 3 by regulating the air entering the incubator, by air exchange between the atmosphere inside and outside the incubator as needed, and by heating, cooling, humidifying and dehumidifying the atmosphere in the incubator using conventional equipment located within or in fluid communication with the incubator to perform each of said functions. Then, a carbon dioxide concentration is established in the gaseous atmosphere in the space 3 to which the incubated eggs are exposed according to any of the protocols described herein.

[0050] Scheme 1 :

[0051] From the time of fertilization until the time point of four weeks post-fertilization, the fertilized un-incubated eggs are placed in and kept in the incubator in contact with the gaseous atmosphere in the incubator containing an incubation concentration of carbon dioxide within 10% and preferably within 5% of a set value between 7,500 ppm CO2and 20,000 ppm CO2for a period of at least 12 of the next 18 consecutive days, preferably for all 18 days. Preferably, the incubation concentration of carbon dioxide is within 10% and preferably within 5% of a set value between 7,500 ppm CO2and 15,000 ppm CO2. More preferably, the incubation concentration is kept within 10% and preferably within 5% of 10,000 ppm CO2. The set value can vary over the 18-day period, but the set value is preferably constant throughout the 18-day period. During the 18-day period, carbon dioxide is supplied to the atmosphere in the incubator as needed to maintain the CO2concentration with the eggs incubated at the desired incubation concentration.

[0052] Figure 2A One embodiment of this protocol is shown in which the concentration of CO2is kept at a constant value of 10,000 ppm throughout the 18-day incubation of the eggs.

[0053] At the end of the 18-day period, the eggs can be removed to a hatcher, or they can be kept in the incubator for an additional 3 days total. During the period of up to the additional 3 days, one can choose between (a) not supplying any additional CO2from any source outside the eggs into the atmosphere to which the eggs are exposed (thus allowing the atmosphere to contain the CO2naturally present in the air and any CO2produced by the embryos and passing through the shell into the incubator atmosphere); and (b) supplying CO2from any source outside the eggs as needed so that the atmosphere to which the eggs are exposed contains carbon dioxide in a concentration up to 10% and preferably within 5% of a set value between 7,500 ppm CO2and 20,000 ppm CO2(preferably between 7,500 ppm CO2and 15,000 ppm CO2, more preferably 10,000 ppm).

[0054] Scheme 2 :

[0055] From the time of fertilization until four weeks after fertilization, the fertilized un-hatched eggs are placed in an incubator in contact with a gaseous atmosphere in the incubator that comprises carbon dioxide at an incubation concentration according to the following pattern:

[0056] For each of up to 18 consecutive periods of 18 to 24 hours (referred to herein as "incremental periods"), the carbon dioxide concentration in the gaseous atmosphere is maintained at a value that is within 10% and preferably within 5% of a set value between 350 ppm CO2 and 20,000 ppm CO2. In each successive incremental period, the set value is increased so that the actual carbon dioxide concentration in the incubator is higher than it was in the immediately preceding incremental period. Preferably, the set value is increased by an equal increment from one incremental period to the next.

[0057] Carbon dioxide is supplied to the space 3 as needed to increase the carbon dioxide concentration in the incubator to the next desired higher value. The carbon dioxide concentration is established and maintained at the desired value by supplying carbon dioxide from a source external to the eggs (such as through the outlet 12) into the gaseous atmosphere as needed to maintain the CO2 concentration in the gaseous atmosphere within 10% and preferably within 5% of the set value. Preferably, in the last incremental period, the carbon dioxide concentration in the atmosphere is within 10% and preferably within 5% of a set value between 7,500 ppm and 20,000 ppm CO2, and more preferably within 10% and preferably within 5% of a set value between 7,500 ppm and 15,000 ppm, or even more preferably within 10% and preferably within 5% of 10,000 ppm CO2. Thus, the set value in the 24 hour period approaching the start of this regimen should not approach 20,000 ppm CO2 or even 15,000 ppm CO2 or even 10,000 ppm or even 7,500 ppm CO2.

[0058] Figure 2B One embodiment of this regimen is shown. The distance between each pair of consecutive numbers on the x-axis (such as 0 to 1, 1 to 2, 2 to 3, etc.) represents the passage of one 24 hour period. In the embodiment shown, the CO2 concentration is held at a constant level during each 24 hour period, and from one 24 hour period to the next, the CO2 concentration in the incubator is increased to a higher level, which is then held constant throughout the next 24 hour period. In this embodiment, the CO2 concentration in the incubator is about 350 ppm during the first 24 hour period, and 10,000 ppm during the eighteenth 24 hour period. Figure 2B Figure 2B ​One embodiment is shown in which the CO2 concentration in the incubator is increased by the same increment from each 24 hour period to the next, although increasing the CO2 concentration in the incubator by equal increments is not essential to the practice of the invention.

[0059] At the end of up to 18 periods of up to 24 hours, the eggs can be removed to a hatching room, or they can be kept in the incubator for a further total of 3 days. During the period of up to a further 3 days, one can choose between (a) not supplying any further CO2 from any source external to the eggs into the atmosphere to which the eggs are exposed (thus allowing the atmosphere to contain the CO2 naturally present in the air and any CO2 produced by the embryos and passing through the shell into the incubator atmosphere); and (b) supplying CO2 as needed from any source external to the eggs so that the atmosphere to which the eggs are exposed contains carbon dioxide in a concentration that is up to 10% and preferably within 5% of a set value that is between 7,500 ppm CO2 and 20,000 ppm CO2 (preferably between 7,500 ppm CO2 and 15,000 ppm CO2, more preferably up to 10,000 ppm).

[0060] Scheme 3 :

[0061] From fertilization until four weeks after fertilization, the fertilized un-hatched eggs are placed in contact with a gaseous atmosphere in an incubator that comprises carbon dioxide at an incubation concentration according to the following pattern:

[0062] The carbon dioxide concentration in the gaseous atmosphere is alternated between a value called an exposure period and a value called an interval period. In the exposure period, the carbon dioxide concentration is maintained at a value that is within 10% and preferably within 5% of a set value that is between 7,500 ppm CO2 and 20,000 ppm (preferably 15,000 ppm or even up to 10,000 ppm) CO2 by supplying carbon dioxide as needed from a source external to the eggs into the gaseous atmosphere to maintain the CO2 concentration in the gaseous atmosphere within 10% and preferably within 5% of the set value. The set value is the same in all of the first 24 hour period of each 48 hour period.

[0063] Alternately, between exposure periods, for an interval period, no carbon dioxide is supplied from outside the eggs into the gas atmosphere of the incubator. The carbon dioxide concentration in the gas atmosphere in space 3 can decrease during this interval period, or it can increase (or have its decrease offset) by carbon dioxide entering space 3 from within the eggs through the intact but naturally microporous shell. However, for the interval period, the C02concentration in the incubator can be reduced to a desired low level as low as the environment by opening the vent holes that allow the atmosphere within the incubator to flow out of the incubator (optionally activating a fan or blower to facilitate the flow of atmosphere out of the incubator) and supplying ambient air at a sufficient level to establish only a low desired C02concentration level within the incubator.

[0064] Figure 2C One embodiment of this scheme is shown. In this embodiment, successive 48 hour periods are represented by intervals from 0 to 2, then by intervals between successive even numbers (i.e., 2 to 4, 4 to 6, etc., up to 16-18). Within each 48 hour period depicted in this way, the first 24 hour period is an interval extending from a lower even number to the right to the next odd number, and the second 24 hour period is an interval extending from that odd number to the right to the next even number. For example, in the 48 hour period depicted as extending from 4 to 6, the first 24 hour period extends from 4 to 5 and the second 24 hour period extends from 5 to 6.

[0065] In Figure 2C In the embodiment shown, sufficient C02is supplied into the incubator atmosphere so that the C02concentration in the incubator is 10,000 ppm for the 24 hour period from 0 to 1, which is an exposure period, and C02is vented out of the incubator so that the C02concentration in the incubator atmosphere is as low as the environment for the 24 hour period from 1 to 2, which is an interval period. Then, sufficient C02is injected into the incubator atmosphere so that the C02concentration in the incubator is 10,000 ppm for the 24 hour exposure period from 2 to 3, after which C02addition to the incubator is stopped, and the C02concentration in the incubator again decreases to as low as the environment for the 24 hour interval period from 3 to 4. This pattern is repeated alternately for the duration of the scheme. The establishment of C02concentration in the incubator that alternates between 10,000 ppm and as low as the environment continues in the same way among successive 24 hour periods throughout the eighteenth 24 hour period. Depending on the number of eggs being incubated simultaneously in the incubator, the C02level for the alternating days can increase above normal ambient values when there is no external or additional C02supply, as the eggs themselves produce C02.

[0066] At the end of the ninth, tenth or eleventh 48 hour period, the eggs can be removed to a hatching room, or they can be left in the incubator for a total of 21 days from the time the eggs were first placed in the incubator. During the period after the end of the ninth 48 hour period, it can be chosen not to add carbon dioxide to the incubator from any source external to the eggs, or it can be chosen to supply carbon dioxide from any source external to the eggs to maintain the concentration in the incubator atmosphere up to 20,000 ppm CO2, preferably up to 15,000 ppm or even 10,000 ppm CO2.

[0067] Scheme 4 :

[0068] From the time of fertilization until four weeks after fertilization, the fertilized un-hatched eggs are placed in an incubator in contact with a gaseous atmosphere in the incubator, the gaseous atmosphere comprising carbon dioxide at an incubation concentration according to the following pattern:

[0069] The carbon dioxide concentration in the gaseous atmosphere is alternated between a value called an exposure period and a value called an interval period. In the exposure period, the carbon dioxide concentration is maintained at a value that is within 10% and preferably within 5% of a set value between the CO2 concentration in the ambient atmosphere and 20,000 ppm of CO2, by supplying carbon dioxide to the gaseous atmosphere from a source external to the eggs as needed to maintain the CO2 in the gaseous atmosphere within 10% and preferably within 5% of the set value. The CO2 concentration and the set value in each exposure period is higher than the set value and the CO2 concentration in the previous exposure period, so that in the last incremental period, the CO2 concentration in the gaseous atmosphere is within 10%, preferably 5%, of a value between 7,500 ppm CO2 and 20,000 ppm CO2.

[0070] Alternately, between the exposure periods, in the interval period, no carbon dioxide is supplied to the gaseous atmosphere of the incubator from outside the eggs. The carbon dioxide concentration in the gaseous atmosphere in the space 3 can decrease during this interval period, or it can increase (or have its decrease compensated for) by carbon dioxide entering the space 3 from inside the eggs through the intact but naturally microporous shell. However, for the interval period, the CO2 concentration in the incubator can be reduced to a desired low level, such as the CO2 concentration in the ambient atmosphere, by opening the vent holes that allow the atmosphere inside the incubator to flow out of the incubator (optionally activating a fan or blower to facilitate the flow of atmosphere out of the incubator) and supplying air at a sufficient level to establish only the lower desired CO2 concentration level inside the incubator.

[0071] Figure 2DOne embodiment of this protocol 4 is shown. In this embodiment, the consecutive 48 hour periods are represented by intervals from 0 to 2, then by intervals between consecutive even numbers (i.e., 2 to 4, 4 to 6, etc., up to 16-18). Within each 48 hour period depicted in this manner, the interval period is the interval extending from zero or from a lower even number to the next odd number, and the exposure period is the interval extending from that odd number to the next even number. For example, in the 48 hour period depicted as extending from 4 to 6, the interval period extends from 4 to 5 and the exposure period extends from 5 to 6.

[0072] In Figure 2D In the embodiment shown, CO2 has been vented from the incubator so that, in the 24 hour period from 0 to 1, which is the interval period, the CO2 concentration in the incubator atmosphere is about 400 ppm. Then sufficient CO2 is fed into the incubator atmosphere so that, in the 24 hour period from 1 to 2, which is the exposure period, the CO2 concentration in the incubator is 10,000 ppm. After venting CO2 from the incubator to establish the interval period from 2 to 3, sufficient CO2 is fed into the incubator atmosphere so that, in the 24 hour exposure period from 3 to 4, the CO2 concentration in the incubator is 10,000 ppm, after which CO2 addition to the incubator is stopped and the CO2 concentration in the incubator again decreases to about 400 ppm in the 24 hour interval period from 4 to 5. This pattern is repeated alternately throughout the duration of this protocol. The establishment of CO2 concentrations in the incubator that alternate between 10,000 ppm and about 400 ppm in consecutive 24 hour periods continues in the same manner throughout the eighteenth 24 hour period. Depending on the number of eggs being incubated simultaneously in the incubator, the CO2 level for the alternate days can increase above the normal atmospheric value of about 400 ppm when there is no external or additional CO2 addition, as the eggs themselves produce CO2.

[0073] At the end of the ninth, tenth, or eleventh 48 hour period, the eggs can be removed to a hatching room, or they can be left in the incubator for a total of 21 days from the time the eggs were first placed in the incubator. During the period after the end of the ninth 48 hour period, the addition of carbon dioxide to the incubator from any source external to the eggs can be selected not to be made, or carbon dioxide can be selected to be fed from any source external to the eggs to maintain the concentration in the incubator atmosphere between 7,500 ppm and 20,000 ppm CO2, preferably between 7,500 ppm and 15,000 ppm, or more preferably 10,000 ppm CO2.

[0074] The establishment of the lower CO2 concentration in any corresponding interval period can be achieved in the same manner as described above for protocol 3.

[0075] In each of the foregoing protocols 1 through 4, where the carbon dioxide concentration is stated to be within 10% of a given value, preferably within 5% of the given value, more preferably the concentration is within 1% of the given value (rather than within 10% or 5% of the given value).

[0076] At the end of any of the foregoing protocols in which the eggs are exposed to an atmosphere containing carbon dioxide as described above, chicks are hatched from the eggs so treated and incubated thereafter. The chicks are then fed water and food and grown into fully grown chickens under conventional practices, fed and allowed to grow into fully grown chickens by conventional practices.

[0077] As shown in the examples below, it has been found that the foregoing protocols of exposing the eggs to an atmosphere containing a specified concentration of carbon dioxide for a specified period of time promote the growth of the chickens to full size, even to sizes in excess of 6 pounds or in excess of 6.5 pounds, while reducing the incidence of or eliminating the incidence of wooden breast in the chickens.

[0078] The foregoing effects, in addition to reducing the incidence of wooden breast, namely, increasing the hatchability of the eggs; increasing the hatch weight of the chickens; increasing the viability of the chickens and reducing the mortality rate of the chickens; increasing the weight gain of the growing chickens; have also been found with the protocols described herein of establishing the CO2concentration in the incubator for a period of time.

[0079] The methods comprising any of these protocols have the additional advantage that they can be practically implemented in commercial hatcheries, while still allowing hatchery personnel to enter the incubators for short periods of time, as they normally do for routine tasks, without endangering the personnel due to excessive or prolonged exposure to atmospheres containing unsafe levels of carbon dioxide. Moreover, these protocols do not cause other deleterious side effects to the chickens throughout their life cycle. Thus, these protocols do not result in a decrease in growth rate, final weight, hatchability %, survival rate %, or susceptibility to other conditions or diseases.

[0080] Example

[0081] It has been found that the foregoing incubation protocols in the presence of increased and controlled CO2concentrations show a reduction in the incidence or severity of wooden breast in the chickens.

[0082] Example - Scheme 1

[0083] Experiment :

[0084] Nine hundred fertilized eggs from a commonly used commercial chicken line, Ross 708, which were less than 1 week old from laying and were laying in the same laying facility in flocks of the same age, were equally divided into three batches of 300 each. One batch (referred to as the control batch) was incubated in an atmosphere in which no additional C02was injected into the atmosphere from any source outside the eggs for 18 days. For this batch, the C02concentration inside the incubator varied between the ambient atmosphere C02concentration (i.e., about 409 ppm) and up to 1,500 ppm (resulting from C02produced by the eggs themselves). A second batch (referred to as the 4,000 ppm test C02batch or 0.4% C02test batch) was incubated for 18 days in which the C02concentration in the incubator was maintained at 4,000 ppm (i.e., 0.4% C02) by injecting C02as needed occasionally from the first day through the end of the eighteenth day. A third batch (referred to as the 10,000 ppm test C02batch or 1% C02test batch) was incubated for 18 days according to Protocol 1 described herein in which the C02concentration in the incubator was maintained at 10,000 ppm (i.e., 1% C02) by injecting C02as needed occasionally from the first day through the end of the eighteenth day. All three batches were incubated at approximately 100 °F and a relative humidity between 30% and 70%. At the end of the eighteenth day of incubation, the eggs from all three batches were transferred to a hatcher device in which the eggs were hatched for the next 3 days. During this 3-day period, no external C02was injected into the hatcher from any source outside the eggs. Thus, the only difference between the conditions in which the three batches were incubated was that no additional C02was injected in the control batch, while for the other two batches, additional external C02was injected to subject the eggs to C02concentrations of 4,000 ppm and 10,000 ppm, respectively. During the incubation period, the oxygen concentration in the control incubator was always above 20%, while in the 4,000 ppm and 10,000 ppm C02-controlled incubators, the oxygen levels were generally above 19%.

[0085] Once the chicks hatched, approximately 150 male chicks from each batch were taken to a rearing cage where they were started on water and feed. From this point, the birds were treated without difference. At 28 days post-hatch, the chickens from each batch were weighed and then stunned. The birds were then scored for wooden breast by a trained panel of experts under single-blind conditions by manual palpation of the pectoral muscle. Each pectoral muscle was given a score of 0, 1, 2, or 3. A score of 0 indicated that no WB was detected. A score of 3 indicated that a very high level of WB was detected, and scores of 1 and 2 indicated that intermediate levels of WB were detected.

[0086] Results : Figure 3A , Figure 3B , Figure 3C , Figure 3D andFigure 3E Various parameters were compared from chickens hatched from eggs incubated under CO2 conditions in which no external CO2 was injected into the incubator (referred to as "control" birds) to chickens hatched from eggs incubated in the incubator under a constant CO2 concentration of 4,000 ppm for 18 days (referred to as "4,000 ppm CO2" or "0.4% CO2" birds) to chickens hatched from eggs incubated in the incubator under a constant CO2 concentration of 10,000 ppm for 18 days (referred to as "10,000 ppm CO2" or "1% CO2" birds).

[0087] Figure 3A The incidence of wood breast in the chickens in the three batches is shown. It can be seen that the 10,000 ppm CO2 treatment according to protocol 1 (1% CO2) significantly reduced the incidence of WB in the chickens compared to the control birds. The percentage of birds scored as 1 was reduced from 24% to 15%. However, for the 0.4% CO2 test batch, the WB scores were higher, indicating an increased incidence of WB. Score 2 increased from 1% for the control to 9% for the 0.4% CO2 batch, which is significant. These results indicate that simply increasing the concentration of CO2 in the incubator is not sufficient. A specific recipe is needed to improve the wood breast scores of the birds.

[0088] Figure 3B The percentage of fertile eggs hatched at the end of 21 days of incubation was compared. At the end of 21 days, 88.1% of the control birds hatched, while 95.6% of the 0.4% CO2 test birds hatched, and 93.5% of the test 1% CO2 eggs hatched. This is important because an increase in hatch rate significantly improves the profitability of the operation.

[0089] Figure 3C The average weight of the chickens just after hatching was compared. The average weight of the birds increased by about 5% due to the 1% CO2 treatment in the incubator.

[0090] Figure 3D The final weight of the birds at 28 days was compared. The average weight of the 1% CO2 birds was about 5% higher than the control chickens.

[0091] Figure 3E The percentage of hatched birds that survived until the end of 28 days was compared. The 1% CO2 birds survived more than about 4% compared to the control birds.

[0092] Example - Scheme 2

[0093] Experiment :

[0094] Six hundred fertilized eggs from a commonly used commercial chicken line, Ross 708, which were less than 1 week old from laying and were laying in the same age cohort in the same laying facility, were equally divided into two batches of 300 each. One batch (referred to as the control batch) was incubated in an atmosphere in which no additional C02was injected into the atmosphere from any source outside the eggs for 18 days. For this batch, the C02concentration inside the incubator varied between ambient atmospheric (i.e., about 409 ppm) and up to 1,500 ppm (resulting from C02produced by the eggs). The other batch (referred to as the test C02gradually increasing batch or 1% C02gradually increasing test batch) was incubated according to Protocol 2 described herein for 18 days in which the C02concentration in the incubator for the first 24 hours was maintained at normal atmospheric conditions (i.e., about 409 ppm) by not injecting any additional external C02, and then was increased equally over the 24 hours every 24 hours as needed by occasionally injecting C02such that the C02concentration was 10,000 ppm (i.e., 1% C02) by the 18th day. Both batches were incubated at about 100 °F and a relative humidity between 30% and 70%. At the end of the eighteenth day of incubation, the eggs from both batches were transferred to a hatcher device in which the eggs were hatched for the next 3 days. For each batch, during this 3-day period, no C02was injected into the hatcher from any source outside the eggs. Thus, the only difference between the conditions under which the two batches were incubated was that one batch was subjected to Protocol 2, reaching a concentration of 10,000 ppm C02concentration by the 18th day. During the incubation period, the oxygen concentration in the control incubator was always above 20%, while in the 1% C02gradually increasing incubator, the oxygen levels were generally above 19%.

[0095] Once the chicks hatched, approximately 150 male chicks from each batch were taken to a brooder cage where they were started on water and feed. From this point, the birds were treated identically. At 28 days post-hatch, the chickens from each batch were weighed and then stunned. The birds were then scored for wooden breast by a trained panel of experts under single-blind conditions by manual palpation of the pectoral muscle. Each pectoral muscle was given a score of 0, 1, 2, or 3. A score of 0 indicated no WB was detected. A score of 3 indicated very high levels of WB were detected, and scores of 1 and 2 indicated intermediate levels of WB were detected.

[0096] Results : Figure 4A 、 Figure 4B 、 Figure 4C 、 Figure 4D and Figure 4EVarious parameters were compared from hatched chickens from eggs incubated under CO2 conditions in which no external CO2 was injected into the incubator (referred to as "control" birds) and from hatched chickens from eggs subjected to a gradual increase in CO2 concentration in the incubator reaching 10,000 ppm CO2 at day 18 (referred to as "10,000 ppm CO2 gradual increase" or "1% CO2 gradual increase" birds).

[0097] Figure 4A The percentage of birds scoring 1 was reduced from 13% to 8% with the CO2 treatment according to protocol 2. It can be seen that the CO2 treatment according to protocol 2 significantly reduced the incidence of WB in the chickens. The percentage of birds scoring 1 was reduced from 13% to 8% with the CO2 treatment according to protocol 2.

[0098] Figure 4B The percentage of fertile eggs hatched at the end of 21 days of incubation was compared. At the end of 21 days, 91% of the control birds hatched, while 94.1% of the test (1% CO2 gradual increase) eggs hatched. This is important because an increase in hatch rate significantly improves the profitability of the operation.

[0099] Figure 4C The average weight of the chickens immediately after hatching was compared. The average weight of the birds at hatching was approximately 6.5% lower for the 1% CO2 gradual increase treatment in the incubator compared to the control batch. However, as shown in Figure 4D , the 1% CO2 gradual increase birds rapidly increased in weight over the next 28 days and ended up slightly heavier than the control birds.

[0100] Figure 4E The percentage of surviving birds was shown to be not statistically different, although the average survival rate was slightly higher in the control birds.

[0101] Example - Scheme 3

[0102] Experiment :

[0103] Six hundred fertilized eggs from a commonly used commercial chicken line, Ross 708, which were less than 1 week old from lay and were laying in the same age cohort in the same laying facility, were equally divided into two batches of 300 each. One batch (referred to as the control batch) was incubated in an atmosphere in which no additional C02was injected into the atmosphere from any source external to the eggs for 18 days. For this batch, the C02concentration inside the incubator varied between normal atmospheric (i.e., about 409 ppm) and up to 1,500 ppm (due to C02production from the eggs). The other batch (referred to as the 7,500 ppm test C02on-off batch or 0.75% C02on-off test batch) was incubated according to Protocol 3 described herein for 18 days in which the C02concentration in the incubator was held constant at 7,500 ppm for the first 24 hours, followed by 24 hours in which no external C02was injected into the incubator (and the only C02in the incubator came from the normal atmosphere and from C02production from the eggs). This 24 hour cycle was then repeated consecutively until the end of day 18. During the C02off period, the C02concentration in the incubator varied between 409 ppm and 1,500 ppm. Both batches were incubated at approximately 100 °F and a relative humidity between 30% and 70%. At the end of the eighteenth day of incubation, both batches of eggs were transferred to a hatcher device in which the eggs were hatched for the next 3 days. During this 3 day period, no C02was injected into the hatcher from any source external to the eggs. Thus, the only difference between the conditions in which the two batches were incubated was that one batch was subjected to Protocol 3, reaching a concentration of 10,000 ppm C02concentration on day 18. During the incubation period, the oxygen concentration in the control incubator was always above 20%, while in the 0.75% C02on-off incubator, the oxygen levels were generally above 19%.

[0104] Once the chicks hatched, approximately 150 male chicks from each batch were taken to a rearing cage where they were started on water and feed. From this point, the birds were treated identically. At 28 days post-hatch, the birds from each batch were weighed and then stunned. The birds were then scored for wooden breast by a trained panel of experts under single blind conditions by manual palpation of the heart. Each breast was given a score of 0, 1, 2, or 3. A score of 0 indicated no WB was detected. A score of 3 indicated very high levels of WB were detected, with scores of 1 and 2 indicating intermediate levels of WB were detected.

[0105] Results : Figure 5A , Figure 5B , Figure 5C , Figure 5D and Figure 5EVarious parameters were compared from hatched chickens from eggs incubated under CO2 conditions where no external CO2 was injected into the incubator (referred to as "control" birds) and from hatched chickens from eggs subjected to an on-off CO2 concentration reaching 7,500 ppm for alternate days until day 18 (referred to as "7,500 ppm CO2 on-off" or "0.75% CO2 on-off" birds).

[0106] Figure 5A The wood breast score was compared for control birds and 0.75% CO2 on-off birds. It can be seen that the CO2 treatment according to protocol 3 significantly reduced the incidence of WB in the chickens. The percentage of birds scoring 1 was reduced on average from 23% to 17%, the percentage of birds scoring 2 was reduced on average from 5% to 1%, while the percentage of birds scoring 0 was increased on average from 73% to 82%.

[0107] Figure 5B The percentage of fertile eggs hatched at the end of 21 days of incubation was compared. At the end of 21 days, 88.7% of control birds hatched, while 96% of the test (0.75% CO2 on-off) eggs hatched. This is important because an increase in hatch rate significantly improves the profitability of the operation.

[0108] Figure 5C The average weight of the chickens just after hatching was compared. The average weight of the birds at hatching was approximately 1.5% lower due to the 0.75% CO2 on-off treatment in the incubator compared to the control batch. However, as shown in Figure 5D , the 0.75% CO2 on-off birds rapidly increased in weight during the next 28 days, eventually weighing 11% more than the control birds.

[0109] Finally, Figure 4E The percentage of surviving birds was shown to have no statistical difference.

Claims

1. A method of incubating a fertile unincubated poultry egg for hatching, the method comprising incubating the egg in a gaseous atmosphere in contact with the egg for an incubation period of 18 to 21 consecutive days, and during this period, supplying carbon dioxide as needed from a source external to the egg into the gaseous atmosphere, such that the carbon dioxide concentration in the gaseous atmosphere in contact with the egg is 7,500 ppm to 20,000 ppm for at least one period of at least 12 hours, wherein the fertile unincubated poultry egg is a fertile unincubated chicken egg or turkey egg.

2. The method of claim 1, the method comprising incubating the egg in a gaseous atmosphere in contact with the egg for an incubation period of 18 to 21 consecutive days, and during this period, supplying carbon dioxide as needed from a source external to the egg into the gaseous atmosphere, such that the carbon dioxide concentration in the gaseous atmosphere in contact with the egg is 7,500 ppm to 20,000 ppm for at least one period of at least 24 hours.

3. The method of claim 1, the method comprising incubating the egg in a gaseous atmosphere in contact with the egg for an incubation period of 18 to 21 consecutive days, and during this period, supplying carbon dioxide as needed from a source external to the egg into the gaseous atmosphere, such that the carbon dioxide concentration in the gaseous atmosphere in contact with the egg is 7,500 ppm to 20,000 ppm for at least six periods of at least 12 hours.

4. The method of claim 1, the method comprising exposing the fertile unincubated poultry egg to a gaseous atmosphere in contact with the egg for at least 1 day in the first 18 days of the incubation period, the gaseous atmosphere containing carbon dioxide at an incubation concentration of a set value between 7,500 ppm CO2 and 20,000 ppm CO2, and within ±10% of the set value, and during the 18 day period, supplying carbon dioxide as needed into the atmosphere to maintain the CO2 concentration, wherein the egg is incubated at the incubation concentration, and then immediately after the 18 day period, incubating the egg for 3 consecutive days in an atmosphere without any additional CO2 supplied into the atmosphere from a source external to the egg, or supplying CO2 as needed from a source external to the egg into the atmosphere to maintain the CO2 concentration of the atmosphere in contact with the egg at a concentration within ±10% of a set value between 7,500 ppm CO2 and 20,000 ppm CO2.

5. The method of claim 4, the method comprising exposing the fertile unincubated poultry egg to a gaseous atmosphere in contact with the egg for at least 6 days of the first 18 days of the incubation cycle, the gaseous atmosphere containing carbon dioxide at an incubation concentration within ±10% of a set value between 7,500 ppm CO2and 20,000 ppm CO2, and during the 18 day period, carbon dioxide is supplied to the atmosphere as needed to maintain the CO2concentration, wherein the egg is incubated at the incubation concentration, and then for the 3 consecutive days immediately following the 18 day period, the egg is incubated in an atmosphere to which no additional CO2is supplied from any source external to the egg, or CO2is supplied from a source external to the egg to the atmosphere as needed to maintain the CO2concentration of the atmosphere in contact with the egg at a concentration within ±10% of a set value between 7,500 ppm CO2and 20,000 ppm CO2.

6. The method of claim 4, wherein the fertile unincubated poultry egg is a chicken egg.

7. The method of claim 6, comprising exposing the fertile unincubated poultry egg to a gaseous atmosphere in contact with the egg for at least 6 days of the first 18 days of the incubation cycle, the gaseous atmosphere containing carbon dioxide at an incubation concentration within ±10% of a set value between 7,500 ppm CO2and 20,000 ppm CO2, and during the 18 day period, carbon dioxide is supplied to the atmosphere as needed to maintain the CO2concentration, wherein the egg is incubated at the incubation concentration, and then for the 3 consecutive days immediately following the 18 day period, the egg is incubated in an atmosphere to which no additional CO2is supplied from any source external to the egg, or CO2is supplied from a source external to the egg to the atmosphere as needed to maintain the CO2concentration of the atmosphere in contact with the egg at a concentration within ±10% of a set value between 7,500 ppm CO2and 20,000 ppm CO2.

8. The method of claim 6, comprising The fertilized unincubated chicken eggs are exposed to a gas atmosphere in contact with the eggs for the first 18 days of the entire incubation period, the gas atmosphere containing carbon dioxide at an incubation concentration within ±10% of a set value between 7,500 ppm CO2 and 20,000 ppm CO2, and during the 18 day period, carbon dioxide is supplied to the atmosphere as needed to maintain the CO2 concentration, wherein the eggs are incubated at the incubation concentration, and then for the 3 consecutive days immediately after the 18 day period, the eggs are incubated in an atmosphere to which no additional CO2 is supplied from any source external to the eggs, or CO2 is supplied from a source external to the eggs to the atmosphere as needed to maintain the CO2 concentration of the atmosphere in contact with the eggs at a concentration within ±10% of a set value between 7,500 ppm CO2 and 20,000 ppm CO2.

9. The method of claim 8, wherein the set value for the entire first 18 days is constant for all 18 days.

10. The method of claim 8, wherein the eggs are incubated in a gas atmosphere in contact with the eggs and containing carbon dioxide at an incubation concentration within ±5% of a set value between 7,500 ppm CO2 and 15,000 ppm CO2 for a period of 18 consecutive days.

11. The method of claim 8, wherein the eggs are incubated in a gas atmosphere in contact with the eggs and containing carbon dioxide at an incubation concentration within ±10% of a set value of 10,000 ppm CO2 for a period of 18 consecutive days.

12. The method of claim 8, wherein the eggs are incubated in a gas atmosphere in contact with the eggs and containing carbon dioxide at an incubation concentration within ±5% of a set value of 10,000 ppm CO2 for a period of 18 consecutive days.

13. The method of claim 8, wherein for the 3 consecutive days immediately after the 18 day period, the eggs are incubated in an atmosphere to which CO2 is supplied from a source external to the eggs as needed to maintain the CO2 concentration of the atmosphere in contact with the eggs at a concentration within ±5% of a set value between 7,500 ppm CO2 and 15,000 ppm CO2.

14. The method of claim 8, wherein for the 3 consecutive days immediately after the 18 day period, the eggs are incubated in an atmosphere to which CO2 is supplied from a source external to the eggs as needed to maintain the CO2 concentration of the atmosphere in contact with the eggs at a concentration within ±10% of a set value of 10,000 ppm CO2.

15. The method of claim 8, wherein the eggs are incubated in an atmosphere, to which carbon dioxide is supplied from a source external to the eggs as needed to maintain the carbon dioxide concentration of the atmosphere in contact with the eggs at a concentration within ±5% of a set value of 10,000 ppm CO2, for 3 consecutive days immediately after the 18-day period.

16. The method of claim 1, comprising exposing the fertile unincubated poultry eggs to a gaseous atmosphere in contact with the eggs for successive incremental periods, during each of which the carbon dioxide concentration of the gaseous atmosphere is maintained at a value within ±10% of a set value by supplying carbon dioxide to the gaseous atmosphere from a source external to the eggs as needed to maintain the CO2 concentration of the gaseous atmosphere within ±10% of the set value, the set value being constant throughout the incremental period and being between the ambient atmospheric CO2 concentration and 20,000 ppm CO2, wherein the set value and the CO2 concentration of the gaseous atmosphere are increased from each of the incremental periods to the next, such that in the incremental period at the end of the incubation period the CO2 concentration of the gaseous atmosphere is within ±10% of a value between 7,500 ppm CO2 and 20,000 ppm CO2, then immediately after the first 18 days of the incubation period the eggs are incubated in an atmosphere, to which carbon dioxide is supplied from a source external to the eggs as needed to maintain the carbon dioxide concentration of the atmosphere in contact with the eggs at a concentration within ±10% of a constant set value between 7,500 ppm CO2 and 20,000 ppm CO2, or no additional CO2 is supplied to the atmosphere from any source external to the eggs for 3 consecutive days.

17. The method of claim 16, wherein each of the incremental periods is 18 to 24 hours in duration and there are 2 to 20 incremental periods.

18. The method of claim 16, wherein each set value is increased from one incremental period to the next by equal increments.

19. The method of claim 16, wherein the fertile unincubated poultry eggs are chicken eggs.

20. The method of claim 19, wherein each of the incremental periods is 18 to 24 hours in duration and there are 2 to 20 incremental periods.

21. The method of claim 19, wherein each set value is increased from one incremental period to the next by equal increments.

22. The method of claim 19, wherein the set value is increased from one incremental period to the next by equal increments.

22. The method of claim 19, wherein the eggs are incubated in a gaseous atmosphere in contact with the eggs for 18 consecutive 24-hour increments, and in each of the periods, the carbon dioxide concentration in the gaseous atmosphere is maintained at a value within ±5% of a set value by supplying carbon dioxide to the gaseous atmosphere from a source external to the eggs as needed to maintain the CO2 concentration in the gaseous atmosphere within ±5% of the set value, the set value being constant throughout the period and between the CO2 concentration of an ambient atmosphere and 15,000 ppm CO2.

23. The method of claim 22, wherein the set value and the CO2 concentration in the gaseous atmosphere is increased from each 24-hour period to the next 24-hour period, such that in the eighteenth 24-hour period, the CO2 concentration in the gaseous atmosphere is within ±5% of a value between 7,500 ppm CO2 and 15,000 ppm CO2.

24. The method of claim 22, wherein the set value and the CO2 concentration in the gaseous atmosphere is increased from each 24-hour period to the next 24-hour period, such that in the eighteenth 24-hour period, the CO2 concentration in the gaseous atmosphere is within ±10% of 10,000 ppm CO2.

25. The method of claim 22, wherein the set value and the CO2 concentration in the gaseous atmosphere is increased from each 24-hour period to the next 24-hour period, such that in the eighteenth 24-hour period, the CO2 concentration in the gaseous atmosphere is within ±5% of 10,000 ppm CO2.

26. The method of claim 22, wherein immediately after the 18-day period, the eggs are incubated in an atmosphere in contact with the eggs for 3 consecutive days without additional CO2 being supplied to the atmosphere from any source external to the eggs, or CO2 is supplied to the atmosphere from a source external to the eggs as needed to maintain the CO2 concentration of the atmosphere in contact with the eggs at a concentration within ±5% of a constant set value between 7,500 ppm CO2 and 15,000 ppm CO2.

27. The method of claim 22, wherein immediately after the 18-day period, the eggs are incubated in an atmosphere in contact with the eggs for 3 consecutive days without additional CO2 being supplied to the atmosphere from any source external to the eggs, or CO2 is supplied to the atmosphere from a source external to the eggs as needed to maintain the CO2 concentration of the atmosphere in contact with the eggs at a concentration within ±10% of 10,000 ppm CO2.

28. The method of claim 22, wherein the eggs are incubated in an atmosphere immediately following the 18-day period for 3 consecutive days, without additional CO2 being supplied to the atmosphere from any source external to the eggs, or as needed to maintain the CO2 concentration of the atmosphere in contact with the eggs at a concentration within ± 5% of 10,000 ppm CO2.

29. The method of claim 1, comprising, throughout the incubation period, alternately (A) exposing the fertile unincubated poultry egg to a gaseous atmosphere in contact with the egg for an exposure period, the carbon dioxide concentration in the gaseous atmosphere being maintained at a value within ± 10% of a set value that is constant throughout each exposure period, by supplying carbon dioxide to the gaseous atmosphere from a source external to the egg as needed to maintain the CO2 concentration in the gaseous atmosphere during the exposure period within ± 10% of the set value, wherein the set value is the same throughout all of the exposure periods, and (B) exposing the fertile unincubated poultry egg to a gaseous atmosphere for an interval period, without carbon dioxide being supplied to the gaseous atmosphere from outside of the egg.

30. The method of claim 29, wherein each exposure period has a duration of 18 to 24 hours, and each interval period has a duration of 18 to 24 hours.

31. The method of claim 29, wherein there are 2 to 20 exposure periods and 2 to 20 interval periods.

32. The method of claim 29, wherein the fertile unincubated poultry egg is a chicken egg.

33. The method of claim 32, wherein each exposure period has a duration of 18 to 24 hours, and each interval period has a duration of 18 to 24 hours.

34. The method of claim 32, wherein there are 2 to 20 exposure periods and 2 to 20 interval periods.

35. The method of claim 32, wherein the egg is incubated in a gaseous atmosphere in contact with the egg for 9 to 11 exposure periods and 9 to 11 interval periods, wherein the carbon dioxide concentration in the gaseous atmosphere is maintained in each exposure period at a value within ± 5% of a set value that is constant throughout each exposure period, by supplying carbon dioxide to the gaseous atmosphere from a source external to the egg as needed to maintain the CO2 concentration in the gaseous atmosphere within ± 5% of the set value, between 7,500 ppm CO2 and 15,000 ppm CO2. ​ 36. The method of claim 32, wherein the eggs are incubated in a gaseous atmosphere in contact with the eggs for 9 to 11 exposure periods and 9 to 11 interval periods, wherein in each exposure period the carbon dioxide concentration in the gaseous atmosphere is maintained at a value within ±10% of a set value that is constant throughout each exposure period by supplying carbon dioxide as needed from a source external to the eggs into the gaseous atmosphere to maintain the C02 concentration in the gaseous atmosphere within ±10% of the set value.

37. The method of claim 32, wherein the eggs are incubated in a gaseous atmosphere in contact with the eggs for 9 to 11 exposure periods and 9 to 11 interval periods, wherein in each exposure period the carbon dioxide concentration in the gaseous atmosphere is maintained at a value within ±5% of a set value that is constant throughout each exposure period by supplying carbon dioxide as needed from a source external to the eggs into the gaseous atmosphere to maintain the C02 concentration in the gaseous atmosphere within ±5% of the set value.

38. The method of claim 1, comprising, throughout the incubation period, alternately (A) exposing the fertile unincubated poultry eggs to a gaseous atmosphere in contact with the eggs for an exposure period, in each of which the carbon dioxide concentration in the gaseous atmosphere is maintained at a value within ±10% of a set value that is between the C02 concentration of an ambient atmosphere and 20,000 ppm C02 by supplying carbon dioxide as needed from a source external to the eggs into the gaseous atmosphere to maintain the C02 concentration in the gaseous atmosphere in the exposure period within ±10% of the set value, the set value increasing from one exposure period to the next such that in the last incremental period the C02 concentration in the gaseous atmosphere is within ±10% of a value between 7,500 ppm C02 and 20,000 ppm C02, and (B) exposing the fertile unincubated poultry eggs to a gaseous atmosphere for an interval period without carbon dioxide being supplied from outside the eggs into the gaseous atmosphere.

39. The method of claim 38, wherein each exposure period has a duration of 18 to 24 hours and each interval period has a duration of 18 to 24 hours.

40. The method of claim 38, wherein each first set value increases by equal increments from one exposure period to the next.

41. The method of claim 38, wherein the fertile unincubated poultry eggs are chicken eggs.

42. The method of claim 41, wherein each exposure period has a duration of 18 to 24 hours and each interval period has a duration of 18 to 24 hours.

43. The method of claim 41, wherein each first setpoint is increased by equal increments from one exposure period to the next.

44. The method of claim 41, wherein the eggs are incubated in a gaseous atmosphere in contact with the eggs for 9 to 11 exposure periods and 9 to 11 interval periods, wherein in each exposure period the carbon dioxide concentration in the gaseous atmosphere is maintained at a value that is within ±5% of the first setpoint by supplying carbon dioxide as needed from a source external to the eggs into the gaseous atmosphere to maintain the CO2 concentration in the gaseous atmosphere to within ±5% of the first setpoint between the CO2 concentration of an ambient atmosphere and 20,000 ppm CO2.

45. The method of claim 41, wherein the eggs are incubated in a gaseous atmosphere in contact with the eggs for 9 to 11 exposure periods and 9 to 11 interval periods, wherein in each exposure period the carbon dioxide concentration in the gaseous atmosphere is maintained at a value that is within ±10% of the first setpoint by supplying carbon dioxide as needed from a source external to the eggs into the gaseous atmosphere to maintain the CO2 concentration in the gaseous atmosphere to within ±10% of the first setpoint between the CO2 concentration of an ambient atmosphere and 20,000 ppm CO2.

46. The method of claim 41, wherein the eggs are incubated in a gaseous atmosphere in contact with the eggs for 9 to 11 exposure periods and 9 to 11 interval periods, wherein in each exposure period the carbon dioxide concentration in the gaseous atmosphere is maintained at a value that is within ±5% of the first setpoint by supplying carbon dioxide as needed from a source external to the eggs into the gaseous atmosphere to maintain the CO2 concentration in the gaseous atmosphere to within ±5% of the first setpoint between the CO2 concentration of an ambient atmosphere and 15,000 ppm CO2.

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