WO2007120973A2

WO2007120973A2 - Process and apparatus for depopulating groups of animals

Info

Publication number: WO2007120973A2
Application number: PCT/US2007/061923
Authority: WO
Inventors: Sarah Kathryn Coulter; Neil Hannay; George Matthew Harriott
Original assignee: Air Products And Chemicals, Inc.
Priority date: 2006-02-10
Filing date: 2007-02-09
Publication date: 2007-10-25
Also published as: WO2007120973A3

Abstract

An apparatus and method for depopulating animals in the event of a contagious outbreak comprises a euthanizing gas distribution and delivery system. This invention uses C02 N2 and/or Ar from a cylinder, a liquid bulk tank or a generated gas from a pressure swing adsorption gas separation apparatus or a selective semi permeable membrane gas separation apparatus (10), delivered to the animal containment structure (16) via a series of tubings (18) which may be inexpensive and disposable. The tubing system is designed to maximize the distribution of the gas without the need to use sheeting wrap to enclose a subsection of the animals and to limit the interactions between humans and the animals. After use, the tubing system can be disposed of through either incineration or through in-house composting.

Description

TITLE OF THE INVENTION: PROCESS AND APPARATUS FOR DEPOPULATING GROUPS OF ANIMALS

[0001] This patent application claims priority to provisionally filed US Patent 60/771 ,982 having the same title and filed on February 10, 2006, which is fully incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] News articles suggest that if Avian influenza mutates into a human flu virus, this highly infectious disease could potentially kill up to 3% of the world's population. One of the primary control mechanisms to limit the spread of contagious and potentially zoonitic diseases is to depopulate infected flocks at a very early stage in a potential outbreak. [0003] The use of gases, such as Ar, N₂ and CO₂ (and blends there of) in lethal gas compositions are well-known for bird flock depopulation and have been approved and promoted by the United States Department of Agriculture ("USDA") and American Veterinary Medical Association ("AVMA") as humane methods for euthanasia of bird flocks. Humaneness is determined based on whether an animal experiences distress between the time it begins to inhale the euthanizing agent and the time it loses consciousness. Recommendations indicate that if CO₂ is used, its ultimate concentration should be between 30-70% shortly after initial administration. If N₂ or Ar are used as asphyxiants, it should lower the oxygen concentration to <6% and preferably <2% shortly after administration. [0004] Flock containment structures or coops, such as chicken houses, houses, coops, ranches, huts, farm-raised, industrial farming, grow-houses, grower-raised structures, are typically 40-60 feet in width, 500 ft long and can be between 8 and 22 feet high. It would be difficult to create an oxygen-deficient environment of <6% O₂ in such a large space in a reasonable amount of time. Presently the poultry agri-business uses large plastic sheets which are partially laid out on the floor, the chickens are assembled thereon, and then the sheet is folded over onto itself to create a volume containing the chickens, and an open gas cylinder is placed into the volume with the chickens. The use of the plastic sheet decreases the volume of gas necessary to achieve the asphyxiant environment, and contains the gas jetting from the open cylinder.

[0005] Alternatively, fowl, such as chickens and/or turkeys, can be moved to one side of the house and plastic sheets can be installed or moved horizontally (perpendicular to floor to form a false wall) and/or lowered vertically (parallel to the floor to form a false ceiling), again with the intention of limiting the volume of space required to achieve the optimal atmosphere for depopulation and one or more cylinders are moved into and opened in that smaller volume. [0006] Another method involves assembly of large containers within the coop; the fowl are moved or placed by humans in the container and the container is filled with any of the above mentioned gases or a combination of the gases.

[0007] Each of these methods requires close human contact with the fowl before the depopulation begins. The technology that is currently used to deliver gas to the coop in the field to reach these ultimate concentrations requires a great deal of human labor, and the potential for virus exposure is high using such technology.

[0008] Carbon dioxide is the most widely used gas for euthanasia of small animals and is on the list of acceptable agents recommended by the American Veterinary Medical Association (AVMA) as described in J. Am. Vet. Med. 218(5): 659-695 (2001 ). Nitrogen and argon are also cited as appropriate gases. [0009] Gas stunning and gas culling in laboratory environments and in slaughterhouse production is also well known. [0010] Patent number EP 1495678 describes the use of a gas mixture for slaughterhouse, containing an anesthetic gas for stabilization of the animal before slaughter.

[0011] Patent number US 5653629 teaches that poultry packed in a crate suitable for the transport of live poultry are passed into a chamber having an oxygen depleted atmosphere and held in the atmosphere for a sufficient period of time for the poultry first to lose consciousness and then to die as a result of the lack of oxygen in the atmosphere. The atmosphere typically comprises nitrogen or argon, containing less than 1% by volume of oxygen. [0012] Patent number US 5152714 teaches that prior to slaughter, poultry are caused to undergo anoxic convulsions by exposure to an atmosphere for a sufficient period of time to lose consciousness.

[0013] Patent number US20060011 143 A1 describes the use of a system for euthanizing laboratory animals within cages and specifically mentions the use of CO₂ as an appropriate gas.

[0014] Patent number JP2005143389 A "Method and System for Euthanizing Animal" describes a chamber system and a gas mixture (N₂O and O₂) delivery system and gas recovery system for euthanizing small animals. [0015] Patent number JP2000050756 A "Mobile Euthanatizing Device for Small Animal" describes the use of a mobile chamber unit, that uses CO₂ at ambient temperatures to euthanize small animals. This patent and all the other patents mentioned in this present application are fully incorporated herein by reference. [0016] Based on the fact that an euthanizing environment must be established quickly and that current methods require close human contact and potential human safety hazards to ensure such quick establishment of the euthanizing environment, there remains a need to provide an euthanasia method and apparatus which is humane, painless and does not induce fear or panic in the animal. An additional need continues to exist to limit the interaction between humans and the animals to prevent the spread of disease, reduce the costs associated with gas delivery materials and reduce or eliminate the need to sterilize the delivery materials for re-use.

BRIEF SUMMARY OF THE INVENTION

[0017] An apparatus and method for depopulating animals, for example, in the event of a contagious outbreak comprises a euthanizing gas distribution and delivery system. The apparatus for delivering euthanizing gas to an animal containment structure to euthanize a plurality of animals, comprising: at least one gas source of euthanizing gas; at least one tubing comprising a plurality of apertures in fluid communication with the at least one gas source to deliver the euthanizing gas from said gas source to the animal containment structure; wherein the euthanizing gas exits said plurality of apertures. The method of euthanizing a plurality of animals comprising the step of: flowing euthanizing gas from at least one gas source of euthanizing gas into at least one tubing comprising a plurality of apertures, and delivering said euthanizing gas into an animal containment structure through said apertures for a sufficient time to euthanize animals in said animal containment structure. The flow through said plurality of apertures may establish a blanket or a quiescent blanket of euthanizing gas. The blanket of euthanizing gas may be maintained in the animal containment structure, because the movement of gases within the animal containment structure when considered as a whole is substantially non- turbulent.

[0018] This invention uses any euthanizing gas composition. The euthanizing gas composition may comprise a euthanizing amount of CO₂, N₂ and/or Ar from a cylinder (liquid or gas form), a liquid bulk tank (liquid or gas form) or a generated gas from a pressure swing adsorption gas separation apparatus or a selective semi-permeable membrane gas separation apparatus, delivered to the animal containment structure via a series of tubings that may be disposable and inexpensive. The tubing system or tubings are designed to maximize the distribution of the gas in the region in which the euthanizing would be most effective without the need to use sheeting wrap to enclose a subsection of the animals and to limit the interactions between humans and the animals. After use, the tubing system can be disposed of through either incineration or through in- house composting.

[0019] If a gas generator is used as the gas source, it could be delivered on a self- contained fuel powered skid requiring no access to utilities infrastructure. In extreme situations, this could even be air-lifted into a site. If cylinders are available and/or access to liquid bulk supply and the infrastructure (such as roads) are available, either of these modes of supply would be acceptable.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS [0020] Figure 1 is an overhead schematic view of one embodiment of a euthanizing gas apparatus of this invention in an animal containment structure comprising a gas source, its connecting manifold and the further connecting apertured tubing arranged across the length of the rectangular shaped animal containment structure. The apparatus distributes the euthanizing gas to the animal containment structure. [0021] Figure 2 is an alternate overhead schematic view of another embodiment of the apparatus of the invention in an animal containment structure. The apparatus comprises euthanizing gas sources and connecting apertured tubings; the gas sources being in a spaced arrangement along the opposite lengths of the animal containment structure with the tubing in parallel spaced arrangement across the width of the interior of a rectangular shaped structure for distributing the euthanizing gas to the animal containment structure. [0022] Figure 3 is a depiction of a section of the porous tubing showing an array of apertures of varying aperture sizes along the length of the tubing. [0023] Figure 4 is a depiction of a section of tubing over the length of which the diameter changes that may be useful in some embodiments of this invention. [0024] Figure 5 is an overhead schematic view of an alternate embodiment of the apparatus of this invention in an animal containment structure. The apparatus comprises a gas source and an array of tubing showing the tubing occupying only a portion of the animal containment structure with barrier tubing forming at least a partial perimeter around the volume where the euthanizing gas will be delivered. [0025] Figure 6A and 6B are vertical cross-sectionals of an animal containment structure along the length and the width, respectively, showing the layering of euthanizing gas and ambient atmosphere during the depopulation method.

DETAILED DESCRIPTION OF THE INVENTION [0026] It is necessary at times in the raising of various small animals for commercial use to dispose of animals during harvest or during occurrences of disease infestation. Such small animals can include: mink, laboratory supply mice and rats, pet sources, gerbils, guinea pigs, various fowl such as: chickens, turkeys, broiler chickens, hens, ducks, geese, poultry, palmipeds, birds and similar small animals raised in large groups or flocks. At such times, such commercially raised groups of small animals can be euthanized with appropriate gases delivered to the animal containment structures where the animals are raised or temporarily housed. The animal containment structure may be referred to herein as an animal housing or coop. The use of the term coop is not meant to be limiting, and the term animal containment structure can be substituted for it any where coop is used. [0027] In this invention, tubing, which may be flexible, is used to deliver euthanizing gas containing lethal amounts of Ar, N₂ and/or CO₂ to an animal containment structure in such a way that it may limit the amount of human-animal interaction during the euthanizing process. The apparatus and method of this invention is designed to provide a blanket of gas near the floor of the coop, such that an anoxic environment is quickly established without the need to enclose the volume of the gassed space through chamber and/or tenting apparatuses, for example, by using plastic sheets. The gas delivery tubing as described herein is inexpensive and can be disposed of, either by composting or incineration after use which eliminates the need for re-use, or sterilization and reuse, and therefore decreases human contact with the potentially infectious tubing. [0028] The present invention centers on the use of gas from one or more gas sources for depopulation, delivered to an animal containment structure, such as chicken houses, using tubing that may be inexpensive, and/or flexible, and/or disposable. The tubing could be cylindrical (or of any cross-sectional shape) plastic sheeting, fabric, cardboard, paper, etc.. The tubing could be initially placed within the coop in a rolled-up fashion, or folded like an accordion, or deflated like a balloon, or the like. For these embodiments, as the gas enters the tubing, the force of the gas would expand, such as unroll, inflate or extend, the tubing inside the coop, such that the need for humans to fully lay out the tubing inside the coop is eliminated. The diameter of the tubing may be sized to act as a "surge tank" for the gas, meaning that it is filled with the euthanizing gas as the euthanizing gas exits the apertures in the tubing. The tubing would comprise apertures. The apertures in the tubing could be provided by constructing the tubing using a semipermeable (porous) material, and/or a semi-permeable panel attached to an otherwise impermeable material, for example down the length of the tubing, and/or the tubing could be constructed using a material through which multiple holes have been added therein. The apertures (for example, holes, or pores) in the tubing allow for the gas to flow out of it much like the gas would through a distributor, silencer or a frit. By the use of one or more tubings having multipleapertures, the long-range jetting of the euthanizing gas (which may be an asphyxiant gas: e.g. having less than 6 --% O₂ therein) through the ambient air is diminished, thereby creating a blanket of euthanizing gas near the floor of the animal containment structure. In some embodiments, temperature differentials (from expansion cooling or from a cooled gas source) between the euthanizing gas and the ambient temperature would allow the euthanizing gas to blanket or layer on the floor of the coop more efficiently. In this way, the euthanizing environment (for example, O₂ of approximately 0-6%) near the floor could be established quickly and maintained during the depopulation duration even though the total average concentration of oxygen within the entire coop would be higher.

[0029] To decrease flapping and/or whipping of the tubings, the end of the tubing(s) may be sealed or partially sealed, to provide a flow restriction in the tubing. Experimental work has shown that at flow rates of 20,000-50,000 scfh in a 10" diameter tubing that there is no whipping action of the tubing if there is a (slight) flow restriction at the end of the tubing.

[0030] In some embodiments of this invention, depending on the size and shape of the animal containment structure, tubing could be laid or rolled out typically on the floor of the animal containment structure horizontally parallel to the width of the house or parallel along the length of the house, or both. A manifold may be positioned parallel to the length or width of the animal containment structure, or down the center of the structure, or both. If the manifold comprises outlets to which the tubing(s) may be attached and the outlets are located on one side and/or at least one tubing is attached to at least one outlet, the side of the manifold without outlets and/or without the attached tubing may be located near or next to a wall. A manifold without outlets and/or tubings on one side may act as a barrier tubing (which will be described in more detail below) to keep the euthanizing gas within the volume in which the tubing is located. A manifold with at least one outlet on both sides of the manifold and at least one tubing attached to at least one of the outlets on each side, or a plurality of outlets on both sides of the manifold and a plurality of tubings attached to the outlets on both sides of the manifold may be installed down the center of the animal containment structure. If more than one gas source is available or a single gas source can be divided into a plurality of gas streams, more than one manifold could be used in the animal containment structure. The manifolds could be arranged on opposite sides (length or width) of the animal containment structure with the tubings on each installed or rolled out toward the center of the animal containment structure. Alternatively, the one or more manifolds and one or more tubings could be in a non-parallel arrangement (diagonal, circular, zigzag , spiral), or any arrangement, for example, rectangular (adjacent to the walls around the inside perimeter of the coop) or any combination of arrangements as long as enough gas is delivered through the apertures in a suitably quiescent fashion, to create an euthanizing gas layer near the floor of the animal containment structure.

[0031] In some cases, the volume within the coop is too large to create an asphyxiant environment within a reasonable amount of time given the mode of gas delivery. For example, a single cylinder could not provide enough gas for an entire coop, for example one that is 60 ft X 200 ft or greater, or a 20,000 scfh gas generator would take too long to deliver enough gas (too low of a gas flow rate) to create the optimal environment for the same size coop. (AVMA guidelines recommend that an euthanizing environment be created in under 10 minutes). In these and other cases, it may be necessary to decrease the total necessary volume required to fill with gas. Because this invention provides a blanket of gas adjacent to and just above the floor of the coop, it is possible in a coop or other housing to decrease the necessary volume for depopulation by using an euthanizing gas filled tubing (with no holes or holes only on one side) to define the perimeter, e.g. length and/or width, of one side of a portion that is smaller than the floor area of the entire housing. In this embodiment, the tubing itself acts as a barrier tubing and defines a smaller area or portion, and therefore defines a smaller volume for the euthanizing gas layer. The tubing used to define the area to receive the euthanizing gas, may be made large enough to act as a barrier not only for the gas but also to prevent the animals to be euthanized from getting over it. If the tubing (or manifold) defines a perimeter of the volume to receive the euthanizing gas, it shall be referred to as barrier tubing. In an alternative embodiment, gas-tight barrier tubing, without any apertures or any leakage of gas into the coop or the portion of the coop with the euthanizing (for example, asphyxiant) environment, could be separately inflated using a separate pressurized gas source, such as a fan. Alternatively, any gas impermeable structure may be used to contain the gas in the portion of the animal containment structure. [0032] For large coops with a limited single gas supply, an embodiment using at least one barrier tubing could be used multiple times in different portions of the coop sequentially until all of the animals are euthanized. (If there are more than one gas sources, this embodiment and/or other apparatuses of the invention could be run simultaneously in different or adjacent areas of the coop.) For sequential uses of one apparatus of the invention comprising a reusable gas source, the conduit, and/or manifold and/or tubings could be disconnected from the gas source, the gas source may or may not be moved to a new location inside or outside of the animal containment structure, the gas source may be connected to a new or unused (for this purpose) set of conduit(s) and/or manifold(s) and/or tubing(s), and restarted, and the process could be repeated until all of the animals in the animal containment structure are euthanized. [0033] Gas delivered from the embodiments of this invention will seep out radially from the tubing(s). Spacing of the tubings in the animal containment structure will be determined by the amount of gas flow from the tubing (given the aperture size(s), size of the animal containment structure or portion of the animal containment structure in which the apparatus of this invention is to be used, the layout of the tubings and the gas flow from the source) such that the ideal anoxic environment can be established within given time requirements. The tubing and the apertures in the tubing may be provided to deliver the euthanizing gas with a substantially smooth and/or slow flow rate (relative to the gas flow rate exiting the gas source) of the euthanizing gas out of the apertures in the tubing. The flow may be radially out from the tubing. In some embodiments, this may be accomplished by using subtantially uniform distribution of the apertures on the tubing which may be provided for by using a fabric or by using tubing with apertures of uniform size and distribution over the length of the tubing. In some embodiments to provide uniform non-turbulent flow over the length of the tubing, the aperture sizes will have to be varied over the length of the tubing. Tubing with apertures distributed over the majority of the length or over substantially the entire length of the tubing may be used. [0034] In one embodiment, a tubing measuring 40 feet long and 9" in diameter and possessing a permeability of approximately 2.7 ft³/min per ft² of material, may use 400 standard cubic feet per minute (scfm) (680 m³/hour) of euthanizing gas to achieve a gas seepage rate radially from the tubing of 4 ft/min (0.02 m/s) at an internal gauge pressure of 0.027 psig (186 Pa) within the tubing. Given this gas seepage rate, an asphyxiant environment approximately 5 ft from the ground may be established between 8-12 minutes if 45 of these tubings are equally spaced 10 feet apart in an enclosure space measuring 40 feet by 500 feet, each tubing receiving an inlet gas feed of 400 scfm. The depth of the gas blanket and the process time are reduced if the tubes are placed closer together. [0035] In a second embodiment, gas may be delivered to a coop through 500 foot long tubings. Because of the length of the tubing, a single, continuous tubing with graduated diameters may be needed to achieve the appropriate pressure and seepage rate out of the tubing. In one example of this embodiment, the tubing may have diameters varying as follows: for the first section comprising the first 165 feet (50 meters): a 24 inch ( 610 mm) diameter; the second section comprising the next 82 feet (25 meters): a 20 inch (500 mm) diameter; the third section comprising the next 165 feet (50 meters): a 16 inch (400 mm) diameter; and the last section comprising the next 82 feet (25 meters): a 10 inch (250 mm) diameter. Gas may be introduced through the largest diameter end while the smallest diameter end may be sealed or partially sealed. Using a gas flow rate of 4000 scfm (6800 m³/hour), the gas velocity within the tubing may be ~ 0-1181 ft/min (-0- 6 m/s) while the gas seepage rate radially out of the tubing may be 2 scfm (0.01 m/s) with an internal gauge pressure of 0.01 psig (69 Pa) within the tubing. Alternatively the tubing may have a continuously decreasing diameter as shown in Figure 4. [0036] Gas monitors may be used to determine gas concentrations within the coop and may be used to determine the time the optimal environment is established to ensure exposure to the euthanizing gas is sufficient to result the animals' humane death. The gas monitors, if used, could measure O₂ levels; CO₂ levels; or other gases for the purpose of confirming that the gas levels are appropriate and within USDA guidelines for euthanization (for example, asphyxiation). Electochemical cells are frequently used to measure O₂ levels, and non-dispersive infra-red (NDIR) devices are frequently used for CO₂ monitoring. Monitors useful in this invention are commercially available.

[0037] Once the depopulation is completed, in-coop fans could be used to mix up the euthanizing gas and/or to remove the euthanizing gas from the coop. Oxygen and/or CO₂ monitors would determine when the ambient gas levels were safe for humans to enter to begin disposal, if desired. (However, the levels of infectious microorganisms may not be safe for humans and should be checked prior to entry into the animal containment structure.) Because the asphyxiant environment is created near the floor of the animal containment structure rather than within the entire space of the enclosure, the time to enter the coop after depopulation is significantly reduced through this new method as compared to filling the entire enclosure with euthanizing gas. As an example, if an asphyxiant environment with O₂ levels between 0-2% is created 12" from the floor of a coop measuring 500 ft x 40 ft x 22 ft, with proper mixing through the use of in-coop fans post-depopulation, the O₂ concentration within the entire coop may be within the safe limit for entry of 19.5-20% within 1-10 minutes or less. Alternatively, or in addition to fans already present in the housing, the asphyxiant gas could be dispersed or mixed into the ambient air and/or removed by: opening the windows or doors, or both the windows and doors, of the animal housing; using external fans through the windows and/or doors; by using an air compressor sourced motive air (such as in a gas generator when feed air to the gas separation is not needed), or using any other method or means to move and mix the air and the euthanizing gas in the housing. [0038] The equipment used during depopulation may be disposable. If plastic tubing is used, the material could be incinerated with other equipment used (body suits, masks, etc.) If paper, fabric, cardboard, or biodegradable polymer, etc is used, it could be composted in the coop along with the protein. Again, this decreases the amount of interaction between humans and potentially infectious materials (limited sterilization required) and decreases the potential costs associated with the supplies/equipment. [0039] The euthanizing environment may comprise any lethal mixture of gases and/or poisonous gases. An asphyxiant gas mixture displaces the oxygen in the ambient atmosphere so that level of oxygen in the environment decreases from about 21 %, to below about 6%. Examples of gases that could be introduced via the gas source include one or more of:CO₂; N₂;Ar; Xe; He; and Ne. Any of the just-listed gases, in any combination, could be used with an anesthetic gas added, such as N₂O, or any poisonous gas, such as CO, added. Alternatively, gas having a low oxygen content (less than 21 wt%) could be administered initially to stun the animals, followed by the euthanizing (for example, asphyxiant) gas.

[0040] In the present invention the source of euthanizing gas into a housing can be one or more cylinder(s), liquid bulk storage tank(s) (portable or stationary), and/or on-site gas generator(s), such as, semi permeable membrane air separator(s), vacuum swing air separator(s) ("vsa"), pressure swing air separator(s) ("psa") and other typical apparatus for separating a reasonable concentration of nitrogen to create an euthanizing nitrogen- containing gas, or other euthanizing gas composition, e.g. a Cθ₂-containing gas from ambient air. The gas generators have the ability to be mobile (e.g. self-contained, fuel powered gas sources that can be moved to a site by truck or air lifted). In the methods and apparatuses of this invention, one or more gas sources or combinations of the types of gas sources can be used to create the asphyxiant environment in an animal housing. [0041] The gas flow rate from a liquid bulk gas source from a vaporizer on the liquid bulk gas delivery truck may vary from 2,000 to 10,000 standard cubic feet per hour (scfh). The gas flow rate from a liquid bulk supply in liquid form using the ambient temperature to vaporize liquid to a gas may vary from between 1 ,000 and 10,000 scfh. The gas flow rate from a gas generator could be up to or exceed 175,000 scfh, or 1 ,000 to 170,000 scfh, but will vary based on the purity of the gas if generated by vsa, psa or membrane. For example a vsa will generate 40,000 scfh of N₂-containing gas having 97% N₂, or 20,000 scfh of N₂-containing gas at 99% N₂. The gas flow rate from a liquid cylinder or dewar delivery can vary depending upon the size of the cylinder or dewar. A gaseous cylinder or dewar discharges at a declining rate. The flow rate will decline as a function of remaining pressure of N₂, or Ar in the cylinder (e.g. 2000 psig). In a CO₂ cylinder, the CO₂ is stored as a gas over liquid so the flow must be limited to prevent significant cooling and freezing of the nozzle. The apparatus should be designed to provide enough euthanizing gas to the animal containment structure or portion of the animal containment structure at a rate that is high enough to be effective and humane, for example effective within less than 10 minutes. If the animal containment structure is too large either additional gas sources and/or apparatuses of the invention should be used or the embodiment using the barrier tubing should be employed. [0042] The invention will be described in more detail with reference to the embodiments shown in the figures. In the embodiment shown in Figure 1 , a chicken coop 16 is shown with an euthanizing gas source 10, which may be a mobile gas source, positioned adjacent the coop 16. Connected to the source 10 is a supply conduit 12, which in turn is connected to a manifold 14. A plurality of apertured (having holes or woven with spaces between the fibers) tubings 18 are connected to the manifold 14. The apertures dispense the euthanizing gas to the area surrounding the tubing in the animal containment structure 16. The animal containment structure 16 has a length L and a width W. The tubing may be flexible. The tubings have ends 19 away from the end 17 that receives the euthanizing gas from the gas source. [0043] Figure 2 shows an alternate embodiment with gas sources 20, tubings 24 in the housing structure or coop 22, wherein the gas sources 20 are distributed along the length L and the tubings are positioned cross the width W of the rectangular structure 22 with each gas source 20 connected to one tubing 24. In this embodiment, the need for a manifold is eliminated. The gas sources may be industrial gas cylinders placed directly in the animal containment structure with at least one tubing attached to each cylinder. [0044] Figure 3 is an isolated view of a tubing 32 showing the variation in apertures from small apertures 34 close to the end 17 that receives the gas from the gas source 30 to larger apertures 36 close to the terminal or exit end 19 of the tubing where a gas flow reduction 38 (sealed end or partially sealed end) is located. The differential sizes in holes is a function of the distance of the holes from source to balance the flow of the euthanizing gas in the tubing. Alternate arrangements of hole sizes may be useful depending upon the geometry of the coop, the tubings and the gas source or sources used. In alternate embodiments, a variation of porosity can also be achieved by changing the fabric used to construct the tubing along the length of the tubing. [0045] Alternatively, the size and the quantity of holes may vary circumferentially on the tubing to balance or adjust the flow as a function of position around the circumference of the tubing. For example bigger holes may be present in the tubing near the lower portion 55 (closer to the floor) and sides 56 of the tubing, and/or smaller holes may be present on the upper portion 57 of the tubing and/or smaller or no holes may be present on the uppermost portion 58 and/or lowermost portion 59 (contacting the floor) of the tubing. (See Figures 4 and 6 for the labeled portions of the tubing.) Note, depending upon the size of the tubings and the size of the animals to euthanized, alternate locations of the apertures are contemplated.

[0046] The apertures in the tubing are shown as circular in the Figure 3, but can have any shape. The shape of the holes can be triangular, non-distinct, circles, squares, rectangles, trapezoids, rhombizoids, ovals, slits, spaces between fibers of woven fabric and combinations of such shapes. The holes can range in size from micron(s) up to a few inches. Semi-permeable holes can be found in a variety of materials (polymer, fabric, etc.). The seepage rate through fabrics depends on the fiber size and the fabric porosity. [0047] Figure 4 is an isolated side view of a tubing showing a continuous decrease in its circumference over its length. Figure 4 also shows square-shaped apertures 41 located only on the lower portion 55 of the side of the tubing 42.

[0048] Figure 5 shows an embodiment in which the euthanizing gas is delivered to only a rectangular portion 51 of an animal containment structure 50, wherein barrier tubings 46 and 52 are used to define the boundaries (the lengths L1 and L2) for the euthanizing gas delivered from porous tubings 48 located within the portion 51. The other boundaries of the portion 51 are defined by a section W1 of the manifold 44 and a section W2 of the wall of the animal containment structure 50. The euthanizing gas is from source 40. A supply conduit 42 and a manifold 44 are depicted. Also shown on the manifold are outlets 53 to which no tubings are attached. Outlets are also present, although not shown, on the manifold 44 where and to which the tubings 48, and barrier tubings 46, 52 are attached. (In alternative embodiments, the manifold and tubings may manufactured as a single contiguous part.) This invention anticipates the manufacture of standard size manifolds with spaced sealed outlets incorporated therein which can be unsealed and tubings attached thereto if needed depending upon the shape of the animal containment structure or portion of the animal containment structure.

[0049] Figure 6A and 6B show a side view and a front view of a vertical cross-section of the euthanizing atmosphere created by the present invention in an animal containment structure 70 having a floor 61 and a ceiling 63. Flexible porous tubing 60 delivers a blanketing layer 62 of euthanizing gas at the level of the animals (not shown) residing on the floor 61 of the structure. By proper delivery of flow out of the apertures, and/or use of temperature differentials and/or adjustment of specific gravity of the euthanizing gas, the blanketing layer 62 can be maintained substantially discrete from the existing ambient air atmosphere 64. The goal of the invention is to create a blanketing layer of euthanizing gas that will have a height from the floor only slightly greater than the height of the animals. For example the height may be less than 5 feet or less than 3 feet or less than 2 feet or less than 1 foot or less depending upon the animals to be euthanized. [0050] For embodiments using a supply conduit to transport the gas from the gas source to manifold, the supply conduit may comprise one or more of the following materials or connected pipes: polyvinyl chloride ("PVC") or other rigid plastic or polymer piping; polymer tubing; flexible or rigid metal; flexible tubing, dryer vent tubing, flexible exhaust duct (cloth/fabric/tape over wire) or any material known to be useful for transporting a gas from a gas source to a manifold or other gas pipe. The conduit may be substantially impermeable to the gas that flows therein. [0051] For embodiments using a manifold to transport the gas to the tubing, the manifold may comprise polyvinylchloride (PVC) piping; polymer tubing; flexible or rigid metal; flexible tubing, dryer vent tubing, flexible exhaust duct (cloth/fabric/tape over wire); duct work, such as metal wrapped cardboard that may be cut with typical hand tools, such as scissors or a saw, or any material that would be useful for transporting the gas between the gas source to one or more tubings. The manifold may or may not be substantially impermeable to the gas that flows therein. [0052] The tubing that is used to create the blanket of euthanizing gas at the floor of the animal containment structure may comprise one or more of the following: plastic or other polymer pipes or material, fabric (woven and unwoven), fabric ventilation ductwork, biodegradable polymer material, air sock, fabric air duct, flexible air duct, fabric air diffuser, fabri-jet duct, and sock ducts, paper or cardboard, or other semi-permeable material. The permeable or semi-permeable fabrics (some vented and/or porous weaves) may comprise polyethylene (HDPE), polyester twills or other fabrics, and coated polyester fabrics. In some embodiments, the useful tubings may comprise materials having a permeability of less than 12 ft³/min per ft² of material or between 0.1 and 12 ft³/min per ft² of material. Examples of useful fabric ducts that can be used as the tubings, and/or manifolds in the apparatus of this invention are commercially available from DuctSox Corp., Fabric Duct System, Inc., FOF Inc, and other companies. [0053] The tubing diameter may be large enough to deliver gas with limited gas generated sound, limited pressure drop along the tubing and sufficient length to act as surge tank. The tubing may be structured to seal or partially seal the distant non-gas supply end to provide flow restriction 38 (as shown in Figure 3). Gas flow may be controlled to avoid potential "whipping action" of the tubing during the initial gas flow or inflation of the flexible tubing(s), if flexible tubing(s) is (are) used. The flexible tubings may be rearranged from a folded or rolled up position to a fully extended position by the force of the euthanizing gas flowing through the tubing.

[0054] The apparatus of the present invention comprising a flexible and disposable gas tubing connected to the manifold or connected directly to the gas source or its supply conduit can be field assembled or fabricated by unskilled labor by attaching the gas transport sections (e.g., manifold, tubing, and supply conduit) together with duct tape, adhesives, melting (in the case of polymers), solder (in the case of metals), wire clamps, metal cuffs, staples, fasteners, rivets, etc. [0055] The blanket of euthanizing gas is created by the flow from the apertures of tubing into the animal housing. The euthanizing gas may gently flow out of the apertures so as not to cause substantial mixing between the ambient environment in the animal containment structure, except for the air located adjacent to the tubings and to the floor . The creation of the blanket may also be assisted by a temperature differential between the incoming gas and the ambient atmosphere. The cooler the gas is relative to the temperature of the housing atmosphere, the greater the density will be to hold the euthanizing gas layer close to the floor of the housing. The gas can be cooled prior to its entry into the animal housing by adding a cooling device to the apparatus of this invention. The cooling device may be a nozzle or other means to provide for gas expansion from high pressure to low pressure; a refrigerator for the euthanizing gas or gases; or a vaporizer to provide for the vaporization of a cryogenic gas supply (e.g. a liquid bulk supply). Further, the thermal differential between the gas and the atmosphere of the animal housing may be created or increased by closing up the animal containment structure prior to, or simultaneously with the introduction of the euthanizing gas to increase the ambient temperature within the structure so that the incoming euthanizing gas will be relatively cooler than the animal containment structure's ambient air. [0056] Alternatively or additionally, a specific weight differential between the gases in the ambient atmosphere in the animal containment structure and/or the euthanizing gases may be used to assist the creation of the substantially discrete euthanizing layer just above the floor by increasing the average specific gravity of the euthanizing gas. For euthanizing gas compositions that are lighter than the ambient atmosphere, heavier gaseous components may be mixed into the euthanizing gas. For example if an N₂- containing gas is the euthanizing gas, by mixing CO₂ and/or Ar into the N₂-containing gas, the specific gravity of the euthanizing gas will increase. Additionally, if a CO₂- containing gas is the euthanizing gas, then by adding Ar to the CO₂-containing gas, the specific gravity of the euthanizing gas will increase.

[0057] Other ways to assist the creation of the substantially discrete layer of the euthanizing gas is by decreasing the mixing between the euthanizing gas layer and the ambient air in the housing, through the design of the tubing and the tubing holes or porosity of the tubing material; to quickly but smoothly deliver the gas, to decrease the time to allow for air/gas mixing from animal agitation (wing flapping or rapid group movement); and/or to decrease the possibility of shaking, whipping or other movement of the tubing by adding some flow restriction, for example a cap or a seal or a closed end of the tubing. [0058] The geometry of tubing within the animal containment structure will depend on the size of animal containment structure and the volume of available gas supply. Using industrial gas cylinders with attached tubing provides the most flexibility for animal containment structures having complicated geometries. Tubing used in this invention may allow for the generation of a smooth and uniform gas blanket and may be of a length necessary to adequately cover the area of the animal containment structure slated for depopulation. Tubing permeability may be sufficiently small that the pressure drop across the tubing wall is greater or much greater than the axial pressure drop along the tubing to provide a substantially uniform permeation rate for the euthanizing gas through the aperatures along the length of the tubing. In some embodiments, the pressure drop through the wall of the tube (via the aperatures) will be greater than 2 times, or greater than 50 times, or greater than 100 times, or greater than 1000 times the axial pressure drop (pressure drop from the inlet to the closed end of the tube). Each tubing useful in some embodiments of this invention may be from 1 to 500 feet long or longer, or from 10 to 450 feet or from 25 to 400 feet long. The diameter of the tubing useful in some embodiments of this invention may be from 1 to 24 inches or from 2 to 12 inches.. The spacing between tubings is another design parameter: the gas spreads radially outward from the tubing and will eventually fill a semi-circular cross-section of equal depth and width around the tubing if the tubing is porous around its circumference. Reducing the tubing spacing will substantially reduce the time required to create the asphyxiant blanket and the quantity of gas required per tubing to create the euthanizing gas atmosphere. If using generated VSA or PSA gas or liquid bulk gas, the gas source would typically be located outside the animal containment structure. It is conceivable to have an access door cracked slightly for passage of the conduit that connects the gas source to the gas manifold and/or tubings. The present invention contemplates the use of additional material to block air or the euthanizing gas from entering/escaping from the animal containment structure during depopulation. [0059] The present invention has been described with reference to one or more specific embodiments, but the full scope of the present invention should be ascertained from the claims which follow.

Claims

1. Apparatus for delivering euthanizing gas to an animal containment structure to euthanize a plurality of animals, comprising: at least one gas source of euthanizing gas; at least one tubing comprising a plurality of apertures in fluid communication with the at least one gas source to deliver the euthanizing gas from said gas source to the animal containment structure; wherein the euthanizing gas exits said apertures.

2. The apparatus of claim 1 wherein said at least one tubing comprises a wall, a pressure drop across said wall, and an axial pressure drop, wherein said pressure drop across said wall is greater than the axial pressure drop.

3. The apparatus of claim 1 further comprising: at least one supply conduit providing gas flow communication for said euthanizing gas between the at least one gas source and said at least one tubing.

4. The apparatus of claim 1 further comprising: at least one supply conduit and at least one manifold wherein said at least one gas source, said at least one supply conduit, said at least one manifold and said at least one tubing are in gas flow communication.

5. The apparatus of Claim 1 wherein said at least one gas source is a mobile gas source.

6. The apparatus of Claim 1 wherein said at least one tubing is flexible.

7. The apparatus of Claim 1 wherein the at least one tubing is formed from a material selected from the group consisting of plastic, rubber, metal, paper, cardboard, woven fabric, nonwoven fabric and combinations thereof.

8. The apparatus of Claim 1 wherein the apertures have a geometric shape selected from the group consisting of: circles, squares, rectangles, trapezoids, rhombizoids, ovals, slits, spaces between fibers of woven fabric, and combinations of such shapes.

9. The apparatus of Claim 1 wherein the at least one gas source is selected from the group consisting of: industrial cylinder gas, liquid bulk contained gas, vsa gas generator, psa gas generator, membrane gas generator.

10. The apparatus of Claim 4 wherein the at least one manifold is selected from the group consisting of rigid substantially gas impermeable conduit, flexible substantially gas impermeable conduit.

11. The apparatus of Claim 1 wherein the at least one tubing comprises an end furthest from the end that receives said euthanizing gas comprising a flow restriction.

12. The apparatus of Claim 4 wherein the at least one tubing is attached to the at least one manifold by a fastening device selected from the group consisting of: adhesive tape, restriction bands, staples, rivets, screws, solder, nails, clips, cord or combinations thereof.

13. The apparatus of Claim 1 further comprising at least one barrier tubing capable of substantially containing the euthanizing gas in a portion of said animal containment structure.

14. The apparatus of Claim 1 further comprising at least one cooling device capable of lowering the temperature of said euthanizing gas.

15. The apparatus of Claim 1 wherein the euthanizing gas is selected from lethal gas compositions comprising lethal amounts of nitrogen, argon, carbon dioxide, neon, helium, xenon and mixtures thereof in said gas compositions.

16. The apparatus of Claim 1 wherein the euthanizing gas is selected from the group consisting of lethal gas compositions comprising N₂ and CO₂, N₂ and Ar, and Ar and CO₂.

17. The apparatus of Claim 1 wherein the euthanizing gas comprises an anesthetizing gas.

18. The apparatus of Claim 1 wherein the euthanizing gas comprises a poisonous gas.

19. A method of euthanizing a plurality of animals comprising the step of: flowing euthanizing gas from at least one gas source of euthanizing gas into at least one tubing comprising a plurality of apertures, and delivering said euthanizing gas into an animal containment structure through said apertures for a sufficient time to euthanize animals in said animal containment structure.

20. The method of claim 19 wherein said at least one tubing comprises a wall, a pressure drop across said wall, and an axial pressure drop, wherein said pressure drop across said wall is greater than the axial pressure drop..

21. The method of Claim 19 further comprising the step after the delivering step of: dispersing the euthanizing gas.

22. The method of Claim 19, wherein said flowing step causes the additional step of expanding the at least one tubing within the animal containment structure.

23. The method of Claim 19, wherein said flowing step causes the additional step of unrolling the at least one tubing within the animal containment structure.

24. The method of Claim 21 , wherein after said dispersing step said method further comprises the additional step of disconnecting said at least one tubing from said at least one gas source and attaching at least one unused tubing in gas flow communication with said at least one gas source and repeating the flowing step and the delivering step.

25. The method of Claim 19 further comprising the step of locating said at least one tubing on a floor of the animal containment structure prior to said flowing step.

26. The method of Claim 19 further comprising the step of locating at least one barrier tubing on a floor of the animal containment structure to create a portion of said animal containment structure prior to said flowing step, and further wherein during said delivering step said euthanizing gas is delivered to said portion of said animal containment structure.