WO2008128027A1

WO2008128027A1 - System and method for stunning hogs with gas

Info

Publication number: WO2008128027A1
Application number: PCT/US2008/060009
Authority: WO
Inventors: Gary Dee Lang; Narsimha R. Nayini
Original assignee: Praxair Technology, Inc.
Priority date: 2007-04-12
Filing date: 2008-04-11
Publication date: 2008-10-23

Abstract

A system and method for controlled atmosphere stunning of hogs is provided. The disclosed method includes the steps of: loading hogs in a stunning chamber and sealably enclosing the stunning chamber to isolate the atmosphere therein. Carbon dioxide is then introduced and forcibly recirculated within the stunning chamber in a series of three or four phases to humanely stun the hogs. The carbon dioxide containing atmosphere is subsequently forcibly exhausted from the stunning chamber and the stunned hogs are advanced to a further processing station.

Description

SYSTEM AND METHOD FOR STUNNING HOGS WITH GAS

Field of the Invention

[0001] The present invention relates to methods and systems useful for controlled atmosphere stunning of hogs or other livestock prior to their slaughter.

Background of the Invention

[0002] There is a need for a humane controlled atmosphere livestock stunning system capable of improving product quality and minimizing product yield losses, without incurring the complexity and expense of current gas stunning methods and apparatus.

Summary of the Invention

[0003] In a broad aspect, the invention may be characterized as a method for controlled atmosphere stunning of livestock, such as hogs, comprising the steps of: (i) loading a batch of livestock in a stunning chamber; (ii) sealably enclosing the batch of livestock in the stunning chamber to isolate the atmosphere proximate the livestock; (iii) introducing a gaseous mixture to the isolated atmosphere to stun the livestock; (iv) forcibly exhausting the gaseous mixture from the isolated atmosphere; and (v) advancing the stunned livestock from the stunning chamber to a further processing area. [0004] In another aspect, the invention may be characterized as a system for controlled atmosphere stunning of livestock, such as hogs, comprising: a stunning chamber having an entrance and an exit, the stunning chamber defining an isolated atmosphere; an atmosphere re-circulating subsystem adapted to recirculate the isolated atmosphere within the stunning chamber; a gas introduction subsystem adapted to introduce gaseous mixtures into the stunning chamber; an exhaust subsystem adapted to evacuate the stunning chamber of the gaseous mixtures and introduce air into the stunning chamber; and a control system adapted to control the operation of the atmosphere recirculating subsystem, the gas introduction subsystem, and the exhaust subsystem. Brief Description of the Drawings

[0005] The above and other aspects, features, and advantages of the present invention will be more apparent from the following, more descriptive description thereof, presented in conjunction with the following drawings, wherein:

[0006] Fig. 1 is an illustration of a hog stunning system according to an embodiment of the invention; and

[0007] Fig. 2 is an illustration depicting the re-circulating gas flow thru the multi- unit stunning chamber in the stunning system of Fig. 1.

Detailed Description of the Invention

[0008] Turning now to Fig. 1, there is shown an illustration of a batch hog stunning system according to an embodiment of the invention. As illustrated therein, a plurality or batch of hogs are depicted in the stunning chamber 102. The hogs were preferably loaded into the stunning chamber 102 via the front loading door 104 on the front of the housing 106 which is located adjacent to a herding ramp or channel (not shown) adapted to lead the hogs from a live hog staging area to the stunning chamber 102. The stunning chamber 102 as well as the herding ramp or channel are preferably maintained in the dark or under low light conditions in an effort to keep the hogs relatively calm. After loading of the hogs into the stunning chamber 102, the front loading door 104 is closed and the multi-phase stunning operation begins. Upon completion of the multi-phase stunning operation, the side door 108 to the stunning chamber 102 opens and the hogs are advanced or conveyed out of the stunning chamber 102 to a conveyor 120 towards further processing station (not shown) where the hogs are stuck and further processed. [0009] Fig. 2 is an illustration generally depicting the re-circulating gas flow thru the multi-unit stunning chamber in the controlled atmosphere stunning system of Fig. 1. As depicted therein, multiple hogs are positioned on a platform 130 or base of the stunning chamber housing 106. Although not shown, the hogs are loaded into the stunning chamber 102 via a front loading door 104.

[0010] Fig. 2 also shows an arrangement of the gas recirculation circuit, the stunning gas introduction subsystem 140 and recirculation fan 150 with the arrows represent the re-circulating gas flow thru the main stunning chamber 102 and the recirculating circuit 152. Also shown are the fresh air make-up duct 154 and the exhaust duct 156 and the controlled dampers 159, 162 that govern the forced exhausting of the carbon dioxide from the stunning system and introduction of make-up air. During hog loading operations, the carbon dioxide introduction subsystem 140 and the recirculation fan 150 are off or deactivated. Once the hogs are loaded in the stunning chamber, the front loading door is closed and sealed prior to the activation of the carbon dioxide introduction subsystem 140 and the recirculation fan 150. During the multi-phase stunning operation, the damper 159 to the fresh air make-up duct remains closed while the recirculating damper 162 is open. An exhaust flap 158 is positioned between the exhaust duct 156 and the stunning chamber 102 in order to allow pressure within the stunning chamber 102 to be maintained within a desired range.

[0011] As is discussed in more detail below, the carbon dioxide concentration generally increases during each successive phase of the multi-phase stunning operation. Upon completion of the controlled stunning operation, the damper 159 to the fresh air make-up duct 154 is opened and the recirculation damper 162 is closed so as to divert the carbon dioxide gas to the exhaust duct 156 via the exhaust flap 158. As soon as the carbon dioxide gas is evacuated from the stunning chamber 102, the side door 108 is opened and the modules are conveyed or otherwise advanced out of the stunning chamber 102 to a conveyor 120 or other staging area and subsequently to another processing station for further processing of the stunned animals.

[0012] As can be appreciated from the above descriptions of the disclosed embodiments, the livestock stunning process generally comprises the following seven steps: (a) herding the livestock into a stunning chamber; (b) closing or otherwise sealing the stunning chamber to enclose the livestock therein, preferably in the dark; (c) recirculating the atmosphere within the stunning chamber using a fan or other air recirculating means, (d) introducing the stunning gas into the re-circulating atmosphere of the stunning chamber; (e) exhausting the isolated atmosphere and stunning gas; (f) opening the stunning chamber; and (g) unloading or advancing the stunned livestock from the stunning chamber to other post-stunning processes. More specifically, the introduction of the stunning gas (e.g. carbon dioxide) is preferably done in three or four stages, with each successive stage having a greater concentration of stunning gas. The above described stunning process is then repeated for other incoming livestock. [0013] The length of time that is necessary for a stunning operation to render the livestock lethargic and the length of time necessary to reach unconsciousness or unrecoverable will depend on the gas being used, the gas concentration, the gas recirculation rate, the type of livestock and its size. The actual gas concentrations and durations are preferably selected so as to minimize any adverse reactions of the livestock in the stunning chamber and promote the humane treatment of the animals. [0014] Moreover, the size and capacity of the stunning chamber(s) can be selected to best match the downstream line speed or processing speed desired. Also, the use of multiple stunning chambers operating in parallel allows the staggering of the stunning process to further increase the system capacity while simulating a continuous hog stunning process. The hog stunning system preferably would include a control system and panel including appropriate shut-off and flow control valves to facilitate the automatic control of the hog stunning system.

[0015] Carbon dioxide stunning of hogs occurs in three or more phases. The first phase is known as the analgesia phase and can be as short as 10 to 12 seconds depending on the concentration of carbon dioxide. During this first phase, the hog progressively loses the ability to feel pain and there is a faster and deeper respiration. At the end of this first phase, the hog loses consciousness and falls over. Immediately after loss of consciousness, the excitation phase begins and last for 6 to 8 seconds. During the excitation phase, there is uncoordinated movement and vocalization in some animals. It is important to remember, however, that the animal is unconscious during this excitation phase. Following the excitation phase, the hog enters the anesthesia phase, which is a state of deep unconsciousness. During this unconsciousness, the hog will be limp and there will be no kicking. The length of unconsciousness will thereafter depend on the concentration and length of exposure to carbon dioxide, after which the hogs could begin to wake up.

[0016] In an illustrative example of the present hog stunning system, hogs are exposed to a four stages of progressively increasing concentration of carbon dioxide gas sufficient to keep the hogs unconscious for until actual slaughter. The multi-phase or multi-stage carbon dioxide stunning process generally includes: (a) a first stage where carbon dioxide level is increased to slightly less than about 20 percent volume in air or less for a duration of about 60 seconds; (b) a second stage where carbon dioxide level is increased to about 30 percent volume in air for a duration of about 45 seconds; (c) a third stage where carbon dioxide level is increased to between about 40 percent volume in air for a duration of about 30 seconds; and (d) a carbon dioxide level of about 60 percent volume in air for a duration of about 100 seconds such that the livestock to be killed or reach an unrecoverable state. The re-circulation flow rate of the carbon dioxide containing atmosphere can also be increased between stage (a) and stage (d) by adjusting the fan speed. Approximately 60 seconds is allowed for the loading of the hogs into the stunning chamber and approximately 40 seconds is allocated for exhausting the stunning chamber, replacing the oxygen-depleted atmosphere with fresh air and removing the hogs from the stunning chamber. In this example, the overall carbon dioxide stunning operation requires approximately 335 seconds to effectively stun or kill a batch of hogs. [0017] The livestock stunning control system depicted therein is adapted to provide safe and efficient operation of the stunning system. Components of the livestock stunning control system includes a control unit incorporating PLC, an operator interface and display, a plurality of operator buttons and switches. Operatively coupled to the livestock stunning control system is a carbon dioxide gas analyzer and associated sensors; and a plurality of gas valves, dampers, and fans that forcibly circulate selected gases through the isolated atmosphere and exhaust the isolated atmosphere from the stunning chamber upon completion of the stunning operation. Of particular importance to the control of the livestock stunning system are the control of the carbon dioxide injection subsystem, the exhaust subsystem, and the loading/unloading doors. [0018] The carbon dioxide injection subsystem, in conjunction with the control unit, delivers a controlled amount of carbon dioxide vapor to stun the livestock. The control unit automatically adjusts the quantity of carbon dioxide and flow rate based on user inputs to match the changes experienced with size and quantity of livestock, and environmental conditions such as temperature and pressure. In the preferred embodiment, the livestock are exposed to multiple levels of carbon dioxide concentration to effectively stun them and minimize adverse reactions. In the preferred embodiment, the carbon dioxide is administered in three, four, or more stages. The actual times and carbon dioxide concentrations required for each stage may vary according to the livestock conditions and can be modified by the operator during set up or start up of the livestock stunning system. [0019] The preferred carbon dioxide injection subsystem includes a source of carbon dioxide, a carbon dioxide circuit, and one or more injection devices. The preferred carbon dioxide circuit further includes one or more control valves, a flow meter, a pressure gauge, temperature sensors, a pressure regulator, pressure-relief devices, gas analyzer, and appropriate flow conduits and manifolds. In the preferred embodiment, the stunning system produces gaseous carbon dioxide by vaporizing liquid carbon dioxide from a bulk storage tank or other source of liquid carbon dioxide. The carbon dioxide vapor is passed to the carbon dioxide circuit via a main control valve. The main control valve is operatively coupled to the control unit and adapted to isolate the stunning system from the carbon dioxide supply and shut the flow of carbon dioxide under specific conditions, such as abnormal system pressures, adverse safety conditions, hazardous atmosphere conditions, and a user initiated emergency stop. [0020] The flow rate, vapor temperature, supply pressure, and regulated pressure within the carbon dioxide circuit are monitored for abnormal conditions that would cause the system to alert the operator and, in some instances shut the flow of carbon dioxide and otherwise halt the stunning process. The volumetric flow of carbon dioxide is also measured to estimate carbon dioxide use per stunning cycle. Such information on the carbon dioxide injection system are collected are sent to the control unit for subsequent analysis and display.

[0021] The exhaust subsystem includes an exhaust blower and hazardous atmosphere monitors to remove carbon dioxide vapors from the stunning system and immediate surrounding area and safely directs the carbon dioxide vapors away from the process area. Preferably, the exhaust system and the hazardous atmosphere monitor must be activated for the stunning operation to proceed.

[0022] From the foregoing, it should be appreciated that the present invention thus provides a system and method for stunning livestock, such as hogs, with gas. While the invention herein disclosed has been described by means of specific embodiments and processes associated therewith, numerous modifications and variations can be made thereto by those skilled in the art without departing from the scope of the invention as set forth in the claims or sacrificing all its material advantages.

Claims

WHAT IS CLAIMED IS:

1. A method for controlled atmosphere stunning of livestock comprising the steps of: (i) loading livestock in a stunning chamber;

(ii) sealably enclosing the livestock in the stunning chamber to isolate the atmosphere proximate the livestock;

(iii) introducing a gaseous mixture to the isolated atmosphere to stun the livestock;

(iv) forcibly exhausting the gaseous mixture from the isolated atmosphere; and

(v) advancing the stunned livestock from the stunning chamber to a further processing area.

2. The method of claim 1 wherein the step of introducing the gaseous mixture to the isolated atmosphere further comprises introducing a stunning gas into the isolated atmosphere and forcibly recirculating the stunning gas within the stunning chamber.

3. The method of claim 1 wherein the step of introducing the gaseous mixture to the isolated atmosphere further comprises: introducing the gaseous mixture to the isolated atmosphere at a first concentration level and forcibly recirculating the isolated atmosphere within the stunning chamber for a first prescribed duration; introducing additional gaseous mixture to the isolated atmosphere to a second concentration level and forcibly recirculating the isolated atmosphere around the stunning chamber for a second prescribed duration; and introducing additional gaseous mixture to the isolated atmosphere to a third concentration and forcibly recirculating the isolated atmosphere around the stunning chamber for a third prescribed duration sufficient to bring the hogs to an unrecoverable state.

4. The method of claim 1 wherein the gaseous mixture introduced into the isolated atmosphere comprises carbon dioxide.

5. The method of claim 1 wherein the livestock are hogs.

6. The method of claim 1 further comprising the step of loading additional livestock into the stunning chamber as the stunned livestock are advanced from the stunning chamber to the processing area.

7. The method of claim 1 wherein the steps of loading livestock in a stunning chamber and sealably enclosing the livestock in the stunning chamber are performed in low light or dark conditions.

8. The method of claim 1 further comprising at least two stunning chambers and wherein the livestock in the first stunning chamber are being stunned concurrently with the loading of livestock in the second stunning chamber.

9. The method of claim 1 further comprising at least two stunning chambers and wherein livestock in the first stunning chamber are being advanced from the first stunning chamber to the processing area concurrently with the stunning of livestock in a second stunning chamber.

10. A system for controlled atmosphere stunning of livestock comprising: a stunning chamber having an entrance and an exit, the stunning chamber defining an isolated atmosphere; an atmosphere re-circulating subsystem adapted to recirculate the isolated atmosphere within the stunning chamber; a gas introduction subsystem adapted to introduce gaseous mixtures into the stunning chamber; an exhaust subsystem adapted to evacuate the stunning chamber of the gaseous mixtures and introduce air into the stunning chamber; a control system adapted to control the operation of the atmosphere recirculating subsystem, the gas introduction subsystem, and the exhaust subsystem.