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Temple Grandin, PhD
Associate Professor of Animal Science
Dept. of Animal Science
Colorado State University
American Meat Institute Animal Welfare Committee
The major 2010 updates have been added. Refer to the PDF Version at www.animalhandlingfor updates on minor wording changes.
The Humane Methods of Slaughter Act of 1958 was the first federal law governing the handling of livestock in meat plants. The 1958 law applied only to livestock that were slaughtered for sale to the government. In 1978, the Humane Methods of Slaughter Act was reauthorized and covered all livestock slaughtered in federally inspected meat plants. As a result of the Act, federal veterinarians are in meat packing plants continuously, monitoring compliance with humane slaughter regulations. Additional guidance is found in the Code of Federal Regulations and in specific USDA regulations and notices.
The AMI Foundation has a demonstrated commitment to voluntary animal handling programs that go above and beyond regulatory requirements.
In 1991, the American Meat Institute published Recommended Animal Handling Guidelines for Meat Packers, the first voluntary animal welfare guidelines for meat packing operations. Authored by Temple Grandin, Ph.D. of Colorado State University, the illustrated guidelines offered detailed information about optimal handling of animals, how to troubleshoot animal handling problems in packing plants, how to stun animals effectively and maintain equipment thoroughly and how to move non-ambulatory animals while minimizing stress. The guidelines were implemented widely by members of the meat packing industry.
In 1997, Dr. Grandin developed a new document called Good Management Practices (GMPs) for Animal Handling and Stunning. The new document detailed measurable, objective criteria that could be used to evaluate the well-being of livestock in meat packing plants. Self-audits using the criteria were recommended in an effort to identify and address any problems and sustain continuous improvement. When the GMPs were developed and implemented, they were envisioned as a tool for use voluntarily by meat companies. In the years that followed, major restaurant chains began developing animal welfare committees and conducting audits of their meat suppliers. They utilized the AMIF Good Management Practices as their audit tool. Beginning in 1999, compliance with AMIFпїЅs GMPs became part of many customer purchasing specifications.
In 2004, the American Meat Institute Animal Welfare Committee determined that the two animal welfare documents should be merged into a single, updated document. Also included are official AMI Foundation audits for pig, cattle and sheep slaughter. These forms can be recognized by the use of the official AMI Foundation logo. The forms can be reformatted to suit corporate needs, but any change to the numerical criteria on the forms would make the audit inconsistent with the AMIF audit.
Relative to other areas of scholarly research, only limited basic research has been conducted in the area of animal welfare. The objective criteria in the document were developed based on survey data collected over time in plants throughout the United States. The AMI Animal Welfare Committee, together with Dr. Temple Grandin, have determined what пїЅtargetsпїЅ are reasonably achievable when plants employ good animal handling and stunning practices.
AMIFпїЅs audit guidelines recommend that companies conduct both internal (self-audits) and third party audits using the following criteria:
Effective Stunning пїЅ Cattle and sheep should be rendered insensible with one captive bolt shot at least 95 percent of the time. For pigs, electrical wands should be placed in the proper position at least 99 percent of the time. For gas stunned pigs, no more than 4 percent of gondolas may be overloaded.
Hot Wanding (Pigs only) пїЅ No more than one percent of pigs should vocalize due to hot wanding. Hot wanding is defined as the application of electrodes that are already energized.
Bleed Rail Insensibility пїЅ A sensible animal on the bleed rail is an automatic failure. However, it is possible that over longer time spans, this may occur. Plants are encouraged to aggregate audit scores to monitor system performance. While the target is clearly zero, no more than two cattle per 1,000 and no more than one pig or sheep per 1,000 should be sensible on the bleed rail. Numbers in excess of this indicate a serious system problem. Animals showing any sign of return to sensibility should be immediately re-stunned. All animals must be completely insensible before procedures such as skinning, head removal or dehorning.
Falls (2010 Update) пїЅ For all species 1% or fewer animals should fall. Score a fall if the body touches the floor. The OIE also limits falls to 1% or less of the animals. In the 2010 guide, slipping was changed to a secondary criteria due to difficulty in achieving inter-observer consistency and reliability. The goal is 3% or less of the animals slipping.
Vocalizations пїЅ Vocalization levels should be monitored in the restrainer. Three percent or fewer of cattle should vocalize and 5 percent or fewer of pigs should vocalize. For pigs, room vocalizations (vocalizations heard throughout a room and not strictly in the restrainer) should be monitored for internal audits only. For pigs, noise should be heard during fewer than 50% of stunning cycles. Due to differences in plant acoustics and the potential for auditor variability, these numbers cannot be compared from plant to plant and should not be measured on third-party audits. Do not measure vocalizations for sheep as they are not meaningful.
Electric Prod Use (2010 Update) пїЅ Prods should be used on 25% or less of cattle and pigs. Prods should never be used in CO2 or group stunning systems. In cases where a single file chute is used for loading the gondala, prods could be used and scored at 25 percent or less mentioned above (2007 update). Since the OIE states that electric prods should not be used on sheep, the 2010 guideline has been changed. Electric prods should not be used on more than 5% of the sheep. For an excellent score, electric prod use on sheep should be 0%. The OIE states that electric prods should be battery operated.
Any willful act of abuse is grounds for failure (2010 Update) пїЅ Willful acts of abuse include, but are not limited to: (1) dragging a conscious, non-ambulatory animal, (2) intentionally applying prods to sensitive parts of the animal such as the eyes, ears, nose, anus, or testicles, (3) deliberate slamming of gates on livestock, (4) malicious driving of ambulatory livestock on top of one another either manually or with direct contact with motorized equipment (This excludes loading a non-ambulatory animal for transport), (5) hitting or beating an animal, or (6) live animals frozen to the floor or sides of the trailer. In sheep operations, lifting an animal by the wool or throwing a sheep also is an act of abuse.
The Committee noted, however, that audits represent a пїЅsnapshot in time.пїЅ Many variables can impact audit outcomes, especially when live animals are involved.
Change in plant personnel. It may take time for a new employee to become as skilled an animal handler as a more experienced employee. However, willful acts of abuse can NEVER be tolerated.
Breed, age and gender of livestock. These factors all can affect temperament.
Previous handling or lack of handling and human contact at the farm level). Animals that are accustomed to seeing people generally are less skittish at the plant.
Weather. Livestock sometimes react to weather or seasonal changes, like a thunderstorm.
Auditor influence. This includes reaction by staff, auditor expertise and management response to auditor presence.
For these reasons, it is essential that if a plant performs poorly on an audit, those results should be viewed in the context of historical performance to determine if this is an anomaly or a pattern. A plantпїЅs proposed corrective/preventive measures also should be considered.
Just as plants strive for continuous improvement based on new practices and information, so, too, the AMI Foundation will strive for continuous improvement and refinement of this document. The general recommendations and the audit criteria are based on real data and observation. However, as additional research is completed and new information is generated, the AMI Foundation will seek to improve and update these documents based upon new information.
Optimal livestock handling is extremely important to meat packers for obvious ethical reasons. Once livestock пїЅ cattle, pigs and sheep пїЅ arrive at packing plants, proper handling procedures are not only important for the animalпїЅs well-being, they can also mean the difference between profit and loss. Research clearly demonstrates that many meat quality benefits can be obtained with careful, quiet animal handling. In addition, the Humane Slaughter Act of 1978, the regulations that evolved from it, as well as more than two decades of directives and notices, dictates strict animal handling and slaughtering standards for packing plants. This booklet provides practical information that can be used to develop animal handling programs and to train employees in the principles of good animal handling practices.
A key factor in establishing and maintaining optimal animal handling and stunning in plants is a clearly communicated management commitment to animal handling. Top management must play an active role. This can include:
Development of an animal welfare mission statement that is widely circulated and/or posted visibly in various places in a plant.
Ongoing monitoring and measurement of animal handling and stunning practices and outcomes (See Chapter 2).
Regular internal training and providing opportunities to attend outside training programs.
This manual provides employees and managers with information that will help them improve both handling and stunning. Properly handled animals are not only an important ethical goal, they also keep the meat industry running safely, efficiently and profitably.
For the 2010 AMI transport guide, go to www.animalhandling(PDF).
Managing the transportation and holding of livestock, including careful temperature management, can result in enhanced livestock welfare and improved meat quality.
The following items should be considered when transporting livestock.
Maintenance пїЅ Trailers should be kept in good repair, should be kept clean (which is especially helpful in preventing pig skin blemishes) and should have non-slip floors.
Truck Driving Practices пїЅ Careful truck driving helps prevent bruises, shrink and injuries. Sudden stops and acceleration that is too rapid increases injuries and stress. Selection of routes that are the most direct, but which minimize time on unpaved roads and avoidance of potholes will also provide benefits.
Design пїЅ It is essential that semi-trailers have sufficient height between decks to prevent back injuries. To comply with environmental regulations, truck floors should be leak proof to prevent urine and manure from dripping onto the highway.
Loading пїЅ Research shows that overloading livestock trucks can increase bruising. Overloading pig trucks can increase death losses and pale, soft exudative tissue (PSE).
Temperature extremes can be harmful to livestock, but careful planning and temperature mitigation strategies can protect livestock.
Freezing temperatures and wind chills can be dangerous as well as, particularly for pigs. The combination of cold ambient temperatures and wind speed can create significant wind chill. For example, if a truck is moving at 40 miles per hour (64 km per hour) in 40пїЅF. (3.7пїЅC.) weather, pigs are exposed to a wind chill that makes it feel to the pigs like it is 10пїЅF. or -12.2пїЅC. Rain can exacerbate these extremes. Wind protection should be provided when the air temperature drops below 32пїЅF. or zeroпїЅC.
The following chart offers guidance or Truck set-up procedures during temperature extremes.
Truck SetпїЅUp Procedures During Temperature Extremes
*Minimum openings are needed for ventilation even in the coldest weather **Consider using sand or wetting bedding if it is not too humid and trucks are moving
Source: National Pork Board, Trucker Quality Assurance Handbook
The chart on offers rough guidelines for the space that should be provided per running foot of truck floor for various pig weights when temperatures are below 75пїЅF. When the Livestock Weather Safety Index is in the пїЅAlertпїЅ condition, load 10 to 20% fewer pigs. Pigs that will travel more than 12 hours may need more space. Non-ambulatory pigs and dead pigs increase after 12 hours.
Number of Hogs Per Running Foot Of Truck Floor, Normal Weather Truck or Trailer Width (inches)
Source: National Pork Board, Trucker Quality Assurance Handbook
While cattle and sheep are less sensitive than pigs to cold weather, it is still important to manage temperatures to protect animals and ensure meat quality.
Keeping livestock dry when possible is essential to protecting them from wind chill. Veal calves also are particularly temperature sensitive and require special care during transport. Take care in cooler temperatures (below 60пїЅF. / 16пїЅC.) to provide straw bedding and plug some air holes so in trucks so the calves do not become too cold. Also, it is critical to keep calves dry. Wetting a calf is the equivalent of lowering the outside temperature by 40-50пїЅF. (4.4 пїЅ 10пїЅC.).
The charts below offers rough guidelines for the space that should be provided. These charts offer two approaches to calculating space: based upon square foot needed for various weights or per running foot of truck floor (based on 92-inch truck width) for various cattle, calf and sheep weights.
Recommended Truck Loading Densities
(Source: National Institute for Animal Agriculture)
Horned or Tipped or more than 10% Horned and Tipped
Truck Space Requirements for Cattle
(Cows, range animals or feedlot animals with horns or tipped horns; for feedlot steers and heifers without horns, increase by 5 percent)
Number Cattle per running foot of truck floor
(92 in. internal truck width or 233.7 cm.) *
Example (120 lb. sheep) 44 ft. triple deck trailer - 44 X 3 X 2.4 = 317 shorn sheep, 302 wooly sheep. * In metric, this is the number of animals in each 31 cm. long segment of truck length.
According to federal regulation, all livestock must have access to clean drinking water in lairage. Water also can help prevent heat stress because it replaces fluids. Hot weather and humidity are deadly to pigs because they do not have functioning sweat glands. Therefore, special precautionary measures must be taken in hot weather conditions.
Use the following procedures to keep animals cool and eliminate unnecessary transport losses during extreme weather conditions.
Stockyards at packing plants should have sufficient capacity so that animals can be promptly unloaded from trucks. Heat builds up rapidly in a stationary vehicle. If trucks canпїЅt be unloaded, they may need to keep driving until they can.
In the stockyard pens, when the temperature is greater than 70пїЅF (21пїЅ C.), facilities should be available and procedures for sprinkling pigs with water should be undertaken. For maximum cooling effect, the sprinklers should have a spray coarse enough to penetrate the hair and wet the skin. Sprinklers that create a fine mist can increase humidity without penetrating the hair and should not be used.
If it is not possible to follow these recommendations and protect the animals during hot conditions, make every effort to postpone the shipment until weather moderates.
When postponing is impossible, trucks should be kept moving and drivers should not be allowed to stop with a loaded trailer. When the truckers reach the plant, livestock must be unloaded promptly. Heat and humidity become extremely critical at 80пїЅF. (27пїЅ C.)and 80% humidity.
During hot weather, cattle, calves, sheep and goats should be hauled in early morning or at night whenever possible.
It is important to keep trucks moving and avoid any unnecessary stops. In addition, livestock should be unloaded promptly upon arrival at a plant and water should be provided.
It is essential that plants have an emergency livestock management plan in place. Each plant should assess potential vulnerabilities based on geographic location, climate and other issues that would require swift action to assure animal welfare. The plan should include:
The plant also should develop a contingency plan for truckers that may, for example, state that trucks should keep driving under certain conditions until unloading can occur or, if they park at a plant, that fans or water be used to keep the internal truck temperature at an optimal level.
To improve meat quality, pigs should be rested two hours prior to stunning. When possible, animals should be kept in their transport groups. In large plants, pens should be designed to hold one or two truckloads. A few smaller pens will also be required for small lots. Pen space allocations may vary depending upon weather conditions, animal sizes and varying holding times. As a rough guideline, 20 sq. feet (1.87 sq. m) should be allotted for each 1,200-pound (545 kg) steer or cow and six sq. feet (.55 sq. m) per pig. Sows will require 11-12 sq. feet (1.03 пїЅ 1.12 sq. m) and boars require 40 sq. feet (3.74 sq. m). (Source: Swine Care Handbook, National Pork Board, 2003). These stocking rates will provide adequate room for пїЅworking spaceпїЅ when animals are moved out of the pen. If the animals are stocked in the pen more tightly, it will be more difficult for the handler to empty the pen. The recommended stocking rates provide adequate space for all animals to lie down.
Recommended Handling Facility Layout пїЅ This diagram illustrates a modern cattle stockyard and chute system. Animal movement is one-way and there is no cross traffic. Each long narrow pen holds one truckload. The animals enter through one end and leave through the other. The round crowd pen and curved chute facilitate movement of cattle to the stunner.
Facility" /> The round crowd pen and curved single file chute take advantage of the natural tendency of cattle to circle. A curved chute is more efficient for cattle because it takes advantage of their natural circling behavior. It also prevents them from seeing the other end while they are standing in the crowd pen. A curved chute should be laid out correctly. Too sharp a bend at the junction between the single file chute and the crowd pen will create the appearance of a dead end. In fact, all species of livestock will balk if a chute looks like a dead end.
As a guideline, the recommended radii (length of crowd gate) are: Cattle, 12 feet; (3.5 m) pigs, 8 feet (2.5 m) and sheep, 8 feet (2.5 m). The basic layout principles are similar for all species, but there is one important difference. Cattle and sheep crowd pens should have a funnel entrance and pig crowd pens must have an abrupt entrance. Pigs will jam in a funnel. A crowd pen should never be installed on a ramp because animals will pile up in the crowd pen. If ramps have to be used, the sloped portion should be in the single file chutes. In pig facilities, level stockyards and chute systems with no ramp are most effective.
For all species, a plant should have sufficient unloading ramp capacity so trucks can be unloaded promptly. Unloading ramps should have a level dock before the ramps go down so that animals have a level surface to walk on when they exit the truck. A good target for the slope of the ramp is no more than 20пїЅ (It may go up to 25пїЅ for pigs if the ramp is adjustable). With concrete ramps, stair steps are recommended because they provide better traction than cleats or grooves when ramps become dirty.
Truck drivers should seldom need to use an electric prod, also termed a hot shot, to unload a truck. Attempting to rush livestock during unloading can be a major cause of bruises, particularly loin bruises. Management should closely supervise truck unloading. For cattle, the recommended stair step dimensions are 3 пїЅ inch (10 cm) rise and a 12-inch (30 cm) long tread. If space permits, an 18-inch (45 cm) long tread will create a more gradual ramp. For market pigs, a 2 пїЅ inch (6.5 cm) rise and a 10-inch (26 cm) tread works well. On adjustable ramps, cleats with 8 inches (20 cm) of space between them are recommended. All flooring and ramp surfaces should be non-slip to avoid injury.
The principles of good livestock handling are similar for the different species. All livestock are herd animals and will become agitated when separated from the others. If a lone animal becomes agitated, place it with other animals where it is likely to become calmer. Never get in the crowd pen or other confined space with one or two agitated, excited livestock.
Handlers who understand the concepts of flight zone and point of balance will be able to move animals more easily. The flight zone is the animalпїЅs personal space and the size of the flight zone is determined by the wildness or tameness of the animal. Completely tame animals have no flight zone and people can touch them. Other animals will begin to move away when the handler penetrates the edge of the flight zone. If all the animals are facing the handler, the handler is outside the flight zone.
To keep animals calm and move them easily, the handler should work on the edge of the flight zone. The handler penetrates the flight zone to make the animals move and he backs up if he wants them to stop moving. The best positions are shown on the diagram. The handler should avoid the blind spot behind the animalпїЅs rear. Deep penetration of the flight zone should be avoided. Animals become upset when a person is inside their personal space and they are unable to move away. If cattle turn back and run past the handler while they are being driven down a drive alley in the stockyard, overly deep penetration of the flight zone is a likely cause. If animals start to turn back away from the handler, the handler should back up and increase distance between him and the animals. Backing up must be done at the first indication of a turn back.
If a group of animals balk at a smell or a shadow up ahead, be patient and wait for the leader to cross the shadow. The rest of the animals will follow. If cattle rear up in the single file chute, back away from them. Do not touch them or hit them. They are rearing in an attempt to increase the distance between themselves and the handler. They will usually settle down if left alone.
The point of balance is at the animalпїЅs shoulder. All species of livestock will move forward if the handler stands behind the point of balance. They will back up if the handler stands in front of the point of balance. Many handlers make the mistake of standing in front of the point of balance while attempting to make an animal move forward in a chute. Groups of cattle or pigs in a chute will often move forward without prodding when the handler walks past the point of balance in the opposite direction of each animal in the chute. If the animals are moving through the chute by themselves, leave them alone. It is not necessary and not recommended to prod every animal; often they can be moved by lightly tapping.
Livestock will follow the leader and handlers need to take advantage of this natural behavior to move animals easily. Animals will move more easily into the single file chute if it is allowed to become partially empty (though livestock must be able to see the animal ahead) before attempting to fill it. A partially empty chute provides room to take advantage of following behavior. Handlers are often reluctant to do this because they are afraid gaps will form in the line and slow the process. But once a handler learns to use this method, he will find that keeping up with the line will be easier. As animals enter the crowd pen, they will head right up the chute. Calm animals are easier to move than excited animals. Pigs hauled for a short, 15-minute trip may be harder to unload because they have not had sufficient time to calm down after being loaded on the farm. It takes 20 to 30 minutes for excited pigs or cattle to calm down.
One of the most common mistakes is overloading the crowd pen that leads to the single file chute. The crowd pen and the staging alley between the crowd pen and the yards should be filled half full so that animals have room to turn. Handlers must also be careful not to push the crowd gate up too tightly on the animals. It often works best to leave the crowd gate on the first notch and to let the animals flow into the single file chute. This will work after all the distractions have been removed from a facility. The crowd pen should become the пїЅpassing throughпїЅ pen. The crowd gate may be used to follow the animals and should never be used to forcibly push them. The handler should concentrate on moving the leaders into the chute instead of pushing animals at the rear of the group. One-way or sliding gates at the entrance to the single file chute must be open when livestock are brought into the crowd pen. Cattle will balk at a closed gate.
One-way flapper gates can be equipped with a rope to open them by remote control from the crowd pen. When the crowd pen is operated correctly, electric prods can usually be eliminated and non-electric driving aids such as flags, paddles and sticks with streamers can be used. Animals can easily be turned with these aids. To turn an animal, block the vision on one side of its head with the aid. If the leader balks at the chute entrance, a single touch with the prod may be all that is required. Once the leader enters, the rest of the animals will follow.
Some highly excitable pigs are difficult to drive at the packing plant. These animals squeal, bunch and pile up and it can be difficult to make these pigs separate and walk up the chute. Highly excitable pigs can have severe pale, soft, exudative tissue or PSE due to agitation during handling, even though these pigs are negative on the genetic test for the halothane gene.
Excitability problems can be reduced and pigs will be easier to drive if people walk through the finishing pens at least once a week. The person should walk quietly in a different random direction each time to train the pigs to get up quietly and flow around them. Playing a radio in the finishing barn also gets the animals accustomed to different kinds of sounds.
Non-slip flooring is essential to prevent falls and crippling injuries. Humane, efficient handling is very difficult on slick floors because animals can become agitated and excited when they lose their footing. All areas where livestock walk should have a non-slip surface. Existing floors can be roughened with a concrete grooving machine. Grooves should be пїЅ-inch (.64 cm) deep, пїЅ inch (.64 cm) wide and spaced пїЅ inch (.64 cm) apart. For pigs, steel bars may be used. Concrete flooring also can be used on weight scales to prevent slipping.
For cattle, on scales, crowd pens and other high traffic areas, a grid of one-inch steel bars will provide secure footing. Construct a 12-inch (30 cm) by 12-inch (30 cm) grid and weld each intersection. Use heavy rod to prevent the grid from bending. Non-slip flooring is particularly important in stunning boxes and restrainer entrances.
New concrete floors for cattle should have an 8-inch (20 cm) diamond or square pattern with deep 1-inch (2. 5 cm) grooves. For pigs and sheep, stamp the pattern of raised expanded metal into the wet concrete. A rough broom finish will become worn smooth. It is also essential to use the right concrete mix for maximum resistance to wear.
Smooth Edges and Surfaces пїЅ Gates, fences and chutes should have smooth surfaces to prevent bruises. Sharp edges with a small diameter, such as angle irons, exposed pipe ends and channels, will cause bruises. Round pipe posts with a diameter larger than 3 inches (8 cm) are less likely to bruise. Vertical slide gates in chutes should be counter-weighted to prevent back bruises. The bottom of these gates should be padded with cut tires or conveyor belting. The gate track should be recessed into the chute wall to eliminate a sharp edge that will bruise.
In pork plants, the bottom 18 inch (46 cm) to 24 inch (61 cm) of a vertical slide gate (guillotine) can be cut off and replaced with a curtain made from conveyor belting. The pigs will not attempt to go through the curtain. This change will prevent back injuries if the gate is closed on a pig.
Pressing up against a smooth flat surface such as a concrete chute fence will not cause bruises. However, a protruding bolt or piece of metal will damage hides and bruise the meat. Bruise points can be detected by tufts of hair or a shiny surface. Contrary to popular belief, livestock can be bruised moments before slaughter until they are bled. The entrance to the restrainer should be inspected often for broken parts with sharp edges.
Surveys show that groups of horned cattle will have twice as many bruises as polled (hornless) cattle. A few horned animals can do a lot of damage. Cutting off the horn tips will not reduce bruising because the animal still has most of its horn length.
Calm animals are easier to handle and move than excited animals. Animals can become agitated very quickly, but it can require 20 to 30 minutes for them to become calm again. Calm animals will move naturally through well-designed systems with a minimum of driving and prodding. To keep animals calm, take the following steps:
Handlers should be quiet and calm. Yelling and arm-waving excite and agitate animals.
When handling sheep, never, ever grab or lift the animal by the wool.
Use lighting to your advantage. Animals tend to move from a darker area to a more brightly lit area and may refuse to enter a dark place. Lamps can be used to attract animals into chutes. The light should illuminate the chute up ahead. It should never glare directly into the eyes of approaching animals. Another approach is illuminating the entire chute area. This approach eliminates patches of light and dark which may confuse animals. Animals may be difficult to drive out of the crowd pen if the pen is brightly illuminated by sunlight and the chute is inside a darker building. Another common lighting problem is that a handling system may work well when lamps are new, but the animals will balk more and more as the lamps dim with age. Experiment with portable lights to find the most efficient and consistent lighting.
Eliminate visual distractions. Get down in the chutes to see them from the animalпїЅs perspective. Livestock balk at shadows, puddles of water or any object that stands in their way, from a coffee cup to a piece of paper. A drain or a metal plate running across an alley can cause animals to stop and should be located outside the areas where animals walk. Flapping objects, such as a coat hung over a fence or a hanging chain, will also make livestock balk. Install shields or strips of discarded conveyor belting to prevent animals from seeing movement up ahead as they approach the restrainer or stunning box.
Redirect air flow. Air hissing and ventilation drafts blowing in the faces of approaching animals can seriously impede movement. Ventilation systems may need to be adjusted.
Use solid sides in chutes and crowd pens leading up to chutes. Solid sides in these areas help prevent animals from becoming agitated when they see activity outside the fence пїЅ such as people. Cattle tend to be calmer in a chute with solid sides. The crowd gate on the crowd pen should also be solid to prevent animals from attempting to turn back towards the stockyard pens they just left.
Reduce noise. Animals are very sensitive to noise. Reducing high-pitched motor and hydraulic system noise along with banging or reverberation can improve animal movement. Clanging and banging metal should be reduced and hissing air should be muffled.
Move animals in small groups пїЅ When cattle and pigs are being handled, the crowd pen and the staging areas which lead up to the crowd pen should never be filled more than three-quarters full. Do not push crowd gates up tight against the animals as cattle and pigs need room to turn. For sheep, large groups may be moved and the crowd pen can be filled all the way up.
Spray water from above. When wetting pigs in the chute, be sure not to spray the animalпїЅs face with water because they will back up.
Electric prods should be used sparingly to move livestock and should not be a personпїЅs primary driving tool. In most plants, the only place an electric prod is needed is at the entrance to the stun box or restrainer. Cattle and pigs can often be moved along a chute when the handler walks by them in the opposite direction of desired movement, taking advantage of the point of balance at the animalпїЅs shoulder. Electric prods should only be picked up and used on a stubborn animal and then put back down. Certainly, the need for electric prod use can vary depending on breeds of animals, production practices on the farm, gender, the group of animals, the day and the handling system used.
Many well-managed plants have totally eliminated electric prods in the holding pens and the crowd pen that leads to the single file chute. In beef plants with well-trained handlers, survey data showed that up to 95 percent of the animals could be moved through the entire plant without the use of an electric prod. Plants should strive to use the electric prod on 25 percent or fewer cattle, pigs and sheep. Plants that use prods on five percent or fewer cattle and pigs are achieving excellent scores. A well-designed plant that has eliminated distractions and other handling impediments detailed above can greatly reduce electric prods, though they may not be entirely eliminated.
Substitutions for electric prods are possible in many instances. They include plastic paddles, sticks with flags on the end or large flags for pigs. Plastic streamers or strips cut from garbage bags attached to a stick also can be used. Cattle can be easily turned and moved in the crowd pen by shaking the streamers near their heads. For moving pigs, a large flag on a short handle or rattle paddle work well. Rattles work well for moving sheep.
Flags can be made from lightweight plasticized tarp material and can vary in size from 20 inches x 20 inches to 30 inches x 30 inches (50 cm x 50 cm to 76 cm x 76 cm). Lightweight sorting boards can be used to move livestock, although they quickly become heavy for handlers to use. In addition, a new vibrating prod that does not use electrical stimulus is showing promise in moving animals with a minimum of stress.
USDA regulations require that electric prods have a voltage of 50 volts or less. If most livestock bellow or squal in direct response to being touched with the electric prod, the power may need to be reduced. Prods which have sufficient power to knock an animal down or paralyze it must not be used. Electric prods must never be applied to sensitive parts of the animal such as the eyes, ears, mouth, nose or anus. In practical terms, the proud should not be used on the animalпїЅs head.
When used, electric prods must never be wired directly to house current. A transformer must be used; a doorbell transformer works well for pigs. Fifty volts is the maximum voltage for prods hooked to an overhead wire. Progressive managers have removed wired-in prods and use only battery-operated prods.
Electric prods should have the voltage low enough that it does not consistently produce a "bark" or "squeal" in pigs or a "moo" or a "bellow" in cattle, but still enough of a voltage to be a persuasion. The voltage required to move an animal will vary depending upon the wetness of the animal and the floor.
International standards from the World Organization for Animal Health (OIE) state that electric prods should be limited to battery operated prods. They should not be used on horses, on calves less than two weeks of age, or on piglets (OIE 2008).
Electric prods are ineffective on sheep, as the wool insulates the shock of a properly applied prod. This lack of response could lead handlers to prod animals in sensitive areas such as the anus or vulva, which is considered a willful act of abuse. Additionally, the application of the electric prod can cause damage to the pelt. Current international animal welfare guidelines recommend that electric prods not be used in sheep. As a result, electric prods should be a tool of last resort and used only when absolutely necessary.
The prod voltage for pigs should be lower than for cattle, which can help reduce both PSE and blood spots in the meat. The voltage required to move an animal will vary depending on the wetness of the animal and the floor. Battery-operated prods are best for livestock handling because they provide a localized directional stimulus between two prongs. Prods also should have an off switch and not be on constantly.
Pigs and cattle should enter a restraint device easily with a minimum of balking. Correcting problems with animal restraint devices can also help reduce bruises and meat quality defects such as blood splash. The basic principles of low stress restraint which will minimize vocalization and agitation are:
For cattle, block the animalпїЅs vision with shields so that they do not see people or objects that move while they are entering the restrainer. Install metal shields around the animalпїЅs head on box-type restrainers to block the animalпїЅs vision.
Block the animalпїЅs vision of an escape route until it is fully held in a restraint device. This is especially important on restrainer conveyors. A flexible curtain made from discarded conveyor belts at the discharge end of the conveyor works well. Cattle often become agitated in a conveyor restrainer if they can see out from under the solid hold down cover before their back feet are off the entrance ramp. Extending the solid hold down cover on a conveyor restrainer will usually have a calming effect and most animals will ride quietly. Solid hold-downs can also be beneficial for pigs on conveyor restrainers.
Eliminate air hissing and other distractions such as clanging and banging. Refer to the section on distractions.
The restraint device must be properly lighted. Animals will not enter a dark place or a place where direct glare from a light is blinding them. To reduce balking at the entrance of a conveyor restrainer, install a light above the entrance. The light should be above the lead-up chute. It should illuminate the entrance of the restrainer, but it must not glare into the eyes of approaching animals. Light coming up from under a conveyor restrainer should be blocked with a false floor to prevent animals from balking at the пїЅvisual cliff effect.пїЅ
Provide non-slip flooring in box-type restrainers and a non-slip, cleated entrance ramp on conveyor restrainers. Animals tend to panic and become agitated when they lose their footing. Stunning boxes should have a non-slip floor.
Parts of a restrainer device operated by pneumatic or hydraulic cylinders that press against the animalпїЅs body should move with a slow steady motion. Sudden jerky motion excites animals. On existing equipment, install flow control valves to provide smooth steady movement of moving parts that press against the animal.
Use the concept of optimum pressure. The restraint device must apply sufficient pressure to provide the feeling of being held, but excessive pressure that causes pain should be avoided. Install a pressure regulator to reduce the maximum pressure that can be applied. Very little pressure is required to hold an animal if it is fully supported by the device. If an animal bellows or squeals in direct response to the application of pressure, the pressure should be reduced.
A restraint device must either fully support an animal or have non-slip footing so the animal can stand without slipping. Animals panic if they feel like they may fall.
Restraint devices should hold fully sensible animals in a comfortable, upright position. Shackling and hoisting, shackling and dragging, trip floor boxes and leg clamping boxes are not accept able. Restrainers that rotate animals on their backs are used rarely in glatt Kosher operations in the United States, but more commonly in glatt Kosher operation in South America and Europe. For information on using and auditing these devices, refer to: www.grandin(Ritual Slaughter Section).
Restraint devices must have controls that enable the operator to control the amount of pressure that is applied. Different sized animals may require differing amounts of pressure. Hydraulic or pneumatic systems should have controls that enable a cylinder on the device to be stopped in mid stroke.
Never hold an animal in a head restraint device for more than a few seconds. The animal should be stunned or ritually slaughtered immediately after the head holder is applied. Head restraint is much more aversive than body restraint. Animals can be held in a comfortable body restraint for longer periods. The animalпїЅs reaction should be observed. If the animal struggles or vocalizes, it is an indication that the device is causing discomfort.
Restraint devices should not have sharp edges that dig into an animal. Parts that contact the animal should have smooth rounded surfaces and be designed so that uncomfortable pressure points are avoided.
On V conveyor restrainers, both sides should move at the same speed. To test this, mark each side with tape or a crayon. If after a minute of movement the marks do not appear in synch, the speed should be adjusted.
It is possible to modify existing restraint devices to lower vocalization and agitation scores. Balking at the entrance is also easy to reduce. Most of the modifications that would reduce animal agitation and vocalizations can be installed at a minimum expense. Floor grating, lighting and shields to block vision are examples of some relatively inexpensive but effective modifications.
Good stunning practices are also required to achieve compliance with federal humane slaughter regulations. Good stunning also promotes animal welfare and meat quality. When stunning is done correctly, the animal feels no pain and it becomes instantly unconscious. Stunning an animal correctly also results in better meat quality. When using electric stunning systems, improper stunning will cause bloodspots in the meat and bone fractures.
Because animals are so sensitive to noises, it is important to reduce noise in the stunning area in particular. Calm animals facilitate accurate and effective stunning. As in other areas, mufflers can be used on air valve exhausts or they can be located outside. Rubber stops on gates can be used to stop clanging and braking devices on the shackle return improve safety and reduce noise.
In addition, consider replacing small with large diameter plumbing, which makes less noise, and replace pumps with quieter ones. Rubber hose connections between the power unit and metal plumbing will help prevent power unit noise from being transmitted throughout the facility. Any new equipment that is installed in animal holding or stunning areas should be engineered for quietness.
To produce instantaneous unconsciousness, the bolt must penetrate the brain with a high concussive impact. The correct positions for stunner placement are shown in the diagram. For cattle, the stunner is placed on the middle of the forehead on an пїЅXпїЅ formed between the eyes and the base of the horns. Stunning 2 cm above the intersection of the X is also very effective. If a non-penetrating mushroom-head stunner is used, accurate aim is very critical to achieve instantaneous insensibility. A head-holding device may be needed to position the head for non-penetrating captive bolt.
For sheep, a captive bolt is placed on the top of the head. This position is more effective for sheep because they have a very thick skull over the forehead. For pigs, the captive bolt is placed on the forehead.
A good stunner operator learns not to chase the animalпїЅs head. He takes the time to aim and get one good, effective shot. The stunner must be placed squarely on the animalпїЅs head. All equipment manufacturersпїЅ recommendations and instructions must be followed. Pneumatic stunners must have an adequate air supply. Low air pressure is one cause of poor stunning. The pressure gauge on the compressor should be checked to make sure that the stunner is receiving the air pressure recommended by the manufacturer. Heavy pneumatic stunners should be equipped with an ergonomic handle to aid positioning.
Poor maintenance of captive bolt stunners is a major cause of bad stunning. Stunners must be cleaned and maintained per the manufacturerпїЅs instructions. Good maintenance requires a person who has dedicated time each day to maintain stunners. A verified maintenance program where a mechanic signs off each day that he/she has tested the stunners is recommended. If a test stand is available for your brand of stunner, it should be used daily to test bolt velocity. It is important to keep stunner cartridges dry and the correct cartridge strength must be used. Store cartridges in a room with low humidity such as an office. Damp cartridges which have not been stored properly will cause poor stunning.
The most common cause of poor captive bolt stunning is poor maintenance of the captive bolt stunners. Stunners must be cleaned and serviced per the manufacturerпїЅs recommendations to maintain maximum hitting power and to prevent misfiring or partial firing. If a пїЅtest standпїЅ to measure bolt velocity is available, daily use is strongly recommended. Each plant should develop a system of verified maintenance for captive bolt stunners.
Another major cause of failure to render animals insensible with one shot is a poor ergonomic design of bulky pneumatic stunners. Aversive methods of restraint, which cause three percent or more of the cattle or pigs to vocalize, must not be used as a substitute for improvements in gun ergonomics. Ergonomics for stunning in a conveyor or restrainer can be improved with a handle extension on the stunner and hanging the pneumatic stunner on an angle. Still another cause of poor stunning is damp cartridges. Cartridges must be stored in a dry place.
Another cause of missed captive bolt shots is an overworked or fatigued operator. Scoring at the end of the shift will pinpoint this problem. In some large plants two stunner operators may be required. Rotating the stunner operator to other jobs throughout the day may help prevent errors caused by fatigue.
Using electrical devices to cause immobilization prior to or during stunning is not recommended. Several scientific studies have shown that it is highly aversive. Vocalization scoring is impossible in electrically immobilized animals because paralysis prevents vocalization. Electrical immobilization must not be confused with electric stunning. Properly done, electric stunning passes high amperage current through the brain and induces instantaneous insensibility. Electrical immobilization keeps a sensible animal still by paralyzing the muscles. It does not induce epileptiform changes in an electroencephalogram (EEG).
If a stunning box is used, it should be narrow enough to prevent the animal from turning around. The floor should be non-slip so the animal can stand without losing its footing. It is much easier to stun an animal that is standing quietly. Only one animal should be placed in each stunning box compartment to prevent animals from trampling each other.
Most large plants restrain cattle and pigs in a conveyor restrainer system. There are two types of conveyor restraints: the V restrainer and the center track system, which is used in many beef plants. In a V restrainer system, the cattle or pigs are held between two angled conveyors. In the center track system the cattle ride astride a moving conveyor. The center track system provides the advantages of easier cattle stunning and improved ergonomics because the stunner operator can stand closer to the animal. Either type of restrainer system is much safer for workers than cattle in a stunning box. Restrainer conveyors are recommended for all plants that slaughter more than 100 head per hour.
Lighting over the top of the conveyor in the restrainer room will help induce cattle to raise their heads for the stunner. However, both cattle and pigs should not be able to see light coming up from under the restrainer because it may cause balking at the entrance. Restrainer systems should be equipped with a long, solid hold-down rack to prevent rearing. For cattle, the hold-down should be long enough so that the animal is fully settled down onto the conveyor before it emerges from under it. This hold-down should not press on the animalпїЅs back. It is a visual barrier.
If an animal is walking into the restrainer by itself, do not poke it with an electric prod. Center track systems require less prodding to induce cattle to enter it. Workers need to break the пїЅautomatic prod reflexпїЅ habit.
To produce instantaneous, painless unconsciousness, sufficient amperage (current) must pass through the animalпїЅs brain to induce a grand mal epileptic seizure. Insufficient amperage or a current path that fails to go through the brain will be painful for the animal. It will feel a large electric shock or heart attack symptoms, even though it may be paralyzed and unable to move. When electric stunning is done correctly, the animal will feel nothing. Animals that are dehydrated also may have high electrical resistance and be difficult to stun.
There are two types of electric stunning: head only stunning, which is reversible, and head-to-back cardiac arrest stunning, which stops the heart. When head-only stunning is used, the signs of a grand mal epileptic seizure can be easily observed. The first phase is a still, rigid (tome) phase, followed by vigorous kicking (clonic) phase. If the animal is not bled, it will return to sensibility when the kicking phase stops.
When head only stunning is used with scissors type tongs, the electrodes may be either placed on the forehead or clamped around the sides of the head like ear muffs. Pigs should be wetted prior to stunning. Electrodes also may be placed in a пїЅtop to bottomпїЅ position on top of the head and below the jaw. When a wand with two stationary electrodes is used, they may be placed either on the forehead or in the hollow behind the ears. Stunning tongs and wands must never be place on the neck. The stunning wand must be applied to the animal for at least two to three seconds to stun properly. Stunners should be equipped with a timer. Pigs and sheep that are stunned with a head only stunner for a minimum of two seconds must be bled within a maximum interval of 30 seconds to prevent them from regaining consciousness. Both practical experience and scientific research shows that a shorter interval of 15 seconds is strongly recommended.
Small plants may achieve cardiac arrest stunning by first applying the tongs to the head to induce insensibility and then immediately reapply to the chest. Most large plants use cardiac arrest head to back or head to side-of-body stunning. It produces a still carcass that is safer and easier to bleed. Cardiac arrest stunning requires the use of a restraining device to prevent the animal from falling away from the stunning wand before it receives the complete stun. Cardiac arrest stunning kills the animal by electrocution.
When cardiac arrest stunning is used, one electrode must be placed on either the forehead or in the hollow behind the ears. The other electrode is placed on either the back or the side of the body. The head electrode should not he allowed to slide back onto the neck or onto the pigпїЅs jowls. Placement is critical. If the head electrode is placed too far back, it can miss the brain. To prevent return to sensibility after head-only stunning, the stunning tong can be reapplied to the chest. This will stop the heart.
Meat packers should use amperage, voltage and frequency settings, which will reliably induce unconsciousness. Both properly and improperly stunned cardiac arrested animals can look similar. Current flow through the spine masks the epileptic seizure and a clear, rigid and kicking phase cannot be easily observed. Properly stunned cardiac arrested animals sometimes have kicking back legs.
To prevent bloodspots in the meat and pain to the animal, the wand must be pressed against the animal before the button is pushed. The operator must be careful not to break and re-make the circuit during the stun. This causes the animalпїЅs muscles to tense up more than once and bloodspots may increase. If the stunning wand is energized before it is in full contact with the pig, the pig will squeal. This is called пїЅhot wanding.пїЅ This is detrimental to pig welfare and is likely to increase blood spots in the meat. Stunning wands and wiring should be checked often for electrical continuity. A worn switch may break the circuit enough to cause bloodspots. Electrodes must be kept clean to provide a good electrical contact. Operators must never double stun animals or use the stunning wand as a prod.
Electric stunning equipment must operate within the electrical parameters that have been verified by scientific research to induce instantaneous insensibility.
Modern stunning circuits use a constant amperage design. The amperage is set and the voltage varies with the pig or sheepпїЅs resistance. Older style circuits are voltage regulated. These circuits are inferior because they allow large amperage surges, which can fracture bones and cause blood splash. The distance between the head electrode and the back electrode should not exceed 14 inches. The most modern sheep stunners from New Zealand use water jets to conduct electricity down through the wool.
Amperage пїЅ Scientific research has shown that an electric stunner must have sufficient amperage to induce a grand mal seizure to insure that the animal will be made instantly insensible. Insufficient amperage can cause an animal to be paralyzed without losing sensibility. For market pigs (180 - 200 lbs. / 82-91 kg. пїЅ not mature sows or boars) a minimum of 1.25 amps is required (Stunning market pigs with less than 1.25 amps should not be permitted unless the results of lower amperages are verified by either electrical or neurotransmitter recordings taken from the brain). Large sows (more than 350 lbs. / more than 160 kg.) will require 2 or more amps. If lower amperages are used, the stunner may induce cardiac arrest but the animal will feel the shock because the seizure was not induced. For sheep a minimum of one amp is required. These amperages must be maintained for a minimum of one second to give instant insensibility.
The Council of Europe (1991) and OIE 2008 recommends the above minimum amperages. Some plants stun animals below the Council of Europe recommended minimum amperages in an attempt to reduce blood spots in the meat. Since only a one-second application at 1.25 amps is required to induce instant insensibility in market pigs, it is the authorпїЅs opinion that plants should be permitted to use circuits that lower the amperage setting after an initial, one second stun at 1.25 amps for pigs and one amp for sheep. Plants should also be encouraged to use electronic constant amperage electronic circuits that prevent amperage spiking. Both practical experience and research has shown that these types of circuits greatly reduce petechial hemorrhages (blood spots).
Voltage пїЅ There must be sufficient voltage to deliver the recommended minimum amperage; 250 volts is the recommended minimum voltage for pigs to ensure insensibility. Amperage is the most important variable to measure. The voltage that will be required will depend on the type of stunner, the wetness of the animal and whether or not it is dehydrated. For sheep, a minimum of one amp is required.
Frequency пїЅ Research has shown that too high an electrical frequency will fail to induce insensibility. Research indicates that insensibility is most effectively induced at frequencies of 50 cycles. Frequencies from 2000 to 3000 hz failed to induce instant insensibility and may cause pain. However, in pigs weighing under 200 lbs (80 kg), research has shown that a high frequency 1592 hz sine-wave or 1642 hz square wave head; only stunning at 800 ma (0.80 amp) would induce seizure activity and insensibility in small pigs. One disadvantage is that the pigs regained sensibility more quickly compared to stunning at 50 to 60 cycles. The pigs in this experiment weighed one-third less than comparable U.S. market pigs and this probably explains why the lower amperages were effective.
Equipment is commercially available for stunning pigs at 800 hz applied across the head by two electrodes and a second stun with 50 to 60 hz from head to body. Research has shown that 800 hz is effective when applied by two electrodes across the head.
Research has shown that stunning pigs with frequencies higher than 50 to 60 cycles is effective. In this experiment, the pigs were stunned with a head only applicator. High frequency stunning has never been verified to induce instant insensibility when applied as a single stun with a head to body electrode. This is the type of electrode used in many large U.S. pork slaughter plants.
Vocalizations immediately prior to stunning, such as squeals in pigs, and moos and bellows in cattle and pigs, can be signs of discomfort and stress. To prevent vocalizations the electrodes must be in firm contact with the animal prior to being energized.
Squealing of pigs during electric stunning can be more frequent in plants that have return to sensibility problems. Research conducted in commercial pork slaughter plants where squealing was measured with a sound meter indicated that the intensity of pigs squealing in the stunning chute area is correlated with physiological measures of stress and poorer meat quality determined that the intensity of pig squeals is correlated with discomfort.
Due to natural vocalization behavior, vocalization scoring is not recommended for sheep. Sheep ususally will not vocalize when they are feeling pain.
Adequate electrical parameters for cardiac arrest stunning cannot be determined by clinical signs, because cardiac arrest masks the clinical signs of a seizure. Measurement of brain function is required to verify any new electrical parameters that may be used in the future. Common causes of a return to sensibility after electric stunning are:
Other factors that may contribute to poor electrical stunning are: dirty electrodes, insufficient wetness, electrode contact area that is too small, animal dehydration, dirty animals and long hair or wool. Interrupted contact during the stun may also be a problem. For all species, processing plants with an excessively long stunning to bleed time are more likely to have return to sensibility problems. Electrodes must be cleaned frequently to ensure a good electrical connection. The minimum cleaning schedule should be once a day. For personal safety, the electrode wand must be disconnected from the power supply before cleaning.
Unlike pigs and sheep, electrical stunning of cattle may require a two-phase stun. Due to the large size of cattle, a current should first be applied across the head to render the animal insensible before a second current is applied from the head to the body to induce cardiac arrest. Modern systems may have a third current to reduce convulsions. A single 400 volt, 1.5 amp current passed from the neck to the brisket failed to induce epileptic form changes in the brain. Observations in plants outside the U.S. indicate that a single current passed from the middle of the forehead to the body appears to be effective. Research is needed to verify this. To insure that the electrodes remain in firm contact with the bovineпїЅs head for the duration of the stun, the animalпїЅs head must be restrained in a mechanical apparatus. Due to the high electrical resistance of cattle hair, the electrode should be equipped with a water system to provide continuous wetting during the stun.
The Council of Europe (1991) requires a minimum of 2.5 amps applied across the head to induce immediate epileptiform activity in the electro-encephalogram (EEG) of large cattle. A frequency of 60 or 50 cycles should be used unless higher frequencies are verified in cattle by either electrical or neurotransmitter measurements taken from the brain. A more recent study has shown that 1.15 amps sinusoidal AC 50 Hz applied for one second across a bovineпїЅs head is effective to induce insensibility (Wotton et al. 2000). A longer application is usually required to depolarize the spine to reduce kicking (up to 15 seconds).
According to CFR 9, Section 313.5, CO2 stunning may be used in swine to induce death or to result in a state of surgical anesthesia. These states are dependent on the relationship between exposure time and CO2 concentration, and systems will produce pigs in both states. Handlers must be careful not to overload the gondolas (elevator boxes) that hold groups of pigs. In a properly loaded gondola, the pigs must have sufficient room to stand or lie down without being on top of each other. Handlers must never overload the gondolas by forcing pigs to jump on top of each other. CO2 Stunning Parameters In the scientific literature, there are conflicting results on how pigs react to the induction of CO2 anesthesia. One researcher found that purebred Yorkshire pigs have a calm induction and that convulsions and excitation occur after the pig becomes unconscious. Some genetic types of pigs actively attempt to escape from the container when they first sniff the gas and others respond with a calm anesthetic induction. Other research has observed that the reaction of pigs to CO2 was highly variable. A Dutch researcher found that the excitation phase occurred prior to the onset of unconsciousness. Australian researchers found that being shocked with an electric prod was more aversive than inhaling CO2. Research in people indicates that genetics affect the aversiveness of CO2 inhalation.
In evaluating gas stunning, one must look at the entire system, which includes the handling system and the gas mixture. One advantage of gas stunning is that these systems can be designed to eliminate the need for pigs to line up in single file chutes, which is contrary to their natural behavior. Regardless of gas type or mixture, the pigs should have little reaction when they first contact the gas and convulsions should not begin until after the pigs collapse.
If conscious pigs squeal, struggle vigorously or attempt to escape when they first contact the gas, this is a serious problem. Genetics may be a contributing factor and may require a different gas mixture or other adjustment. Observations in several plants indicate that elimination of the stress Halothane gene may reduce problems with stressful anesthetic induction. The gas parameters for each plant should be evaluated for ease of anesthesia induction by observing the behavior of the animals. The gas mixture is not acceptable if the pigs attempt to climb out of the container. It is normal to have violent kicking and convulsions after the pig falls over.
In both captive bolt and electrically stunned animals, kicking will occur. Ignore the kicking and look at the head. To put it simply, THE HEAD MUST BE DEAD. When cattle are shot with a captive bolt, it is normal to have a spasm for 5 to 15 seconds. After the animal is rolled out of the box or hung up, its eyes should relax and be wide open.
When pigs are stunned using CO2 to induce surgical anesthesia, some animals may have slow limb movement or gasping. This is permissible. However, there must be no spontaneous eye blinking, righting reflex or response to a painful stimulus applied to the nose.Below are the signs of a properly stunned animal:
Order of the events indicating Return to Sensibility in head only electrically stunned pigs (In CO2 stunned pigs, the order of the first two events is reversed):
Signs of a Properly Stunned Animal by Stunning Method