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INTRODUCTION
Good management combined with well-designed equipment must be used together to insure adequate animal welfare during transport and slaughter. In this paper, I will discuss some of the major factors which affect welfare during transport and slaughter. The first section will cover transport and the second section will cover welfare in slaughter plants up to the point of stunning. Stunning methods have been well researched and validated, but there needs to be more emphasis on how the animals are handled. Large restaurant and supermarket companies have been instrumental in enforcing welfare standards in both the U.S. and Europe and the effects of these programs in the U.S. will be discussed.
The U.S. is a huge country which is larger than Western Europe. There are no Federal (country wide) regulations on the transport of cattle, pigs or sheep. Animals used in bio-medical research are covered by Federal regulations, but the transport of agricultural animals with the exception of slaughter horses is unregulated. Animals on the premises of a Federally inspected slaughter plant are covered by the 1978 Humane Slaughter Act, which is similar to European regulations.
Rest Stops
Rest stops during transport is an area of great controversy. One must be careful not to turn rest stops into stress stops. In the U.S., practical experience has shown that the health of 250 kg weaner calves from rangeland will be better if they travel non-stop for up to 32 hours (Grandin, 1997a). The stress of loading and unloading of wild cattle not accustomed to close contact with people increases stress. If the trip is longer than 32 hours, the animals will stay in better condition if they are unloaded and rested.
In other situations, rest stops will be beneficial. One area that needs to be researched is the use of different stocking densities for long and short trips. Pigs stocked loosely enough so that they can all lie down would benefit from a rest stop where they could remain on the vehicle. However, in the southern U.S., this might not be practical due to extremely hot summer weather. Heat builds up rapidly in a stationary vehicle, unless the rest stop had fans to cool the animals.
Fit Animals for Transport
The single most important transportation issue is having a physically fit animal for transport. The author has observed that the greatest welfare problems during transport were caused by death losses in stress susceptible pigs, and downers in old cows and sows which have been allowed to deteriorate into a skinny, weak condition prior to transport. Genetic selection for ever increasing productivity has resulted in weaker pigs and dairy cattle which may be less fit for long distance transport.
For old dairy and beef cows, timely marketing is the single biggest issue. The author estimates that 10% of the dairies are responsible for 90% of the problems with cows that go down in the truck during transport. These unethical people allow their cows to deteriorate to a weak condition.
The National Market Cow and Bull Quality Audit in the U.S. indicated that the percentage of dairy cows arriving at a slaughter plant with a poor body score of 1 or 2 increased from 4.8% in 1994 to 5.4% in 1999 (Smith et al., 1994, 2000). Cows with a body condition score of 1 or 2 are emaciated and their ribs are sticking out.
The most alarming finding was that the percentage of dairy cows arriving with arthritic leg joints has tripled. In 1993, 4.7% of cull dairy cows had arthritic joints and in 1999 the percentage increased to 14.5%. This increase in lameness may have contributed to the increased incidence of downers. There is a need for producers to put more emphasis on breeding good feet and legs and a little less emphasis on production.
Old Breeding Sows
A slaughter plant manager wrote to me complaining about the deteriorating condition of old sows (Grandin, 1997b) found that 16% of the sows that arrived at a large Midwestern slaughter plant were lame. A major indicator that sow condition is declining is increasing sow mortality on large farms. Koketsu (2000) collected data from 825 U.S. and 240 Canadian farms. One clear result was that the largest farms had the highest mortality (Koketsu, 2000). The cause of the increase appears to be a combination of genetic selection for leanness and poor management. Average mortality increased from 4.3% to 5.8% from 1993 to 1997.
Koketsu (2000) reports that the sows died from a combination of acute and chronic conditions. Lameness was one of the conditions listed. Some of these lame sows would have ended up in the transportation system.
Market Pigs and Baby Calves
Pigs which have been selected for huge muscle growth and the stress susceptibility gene will have the greatest death losses during transport. The author has observed death losses of 0.5% in these pigs during transport. It is my opinion that these pigs are simply not fit for transport. Murray and Johnson (1998) report that 9.2% of pigs that were homozygous for the stress gene died during transport. The death loss percentages were 0.27% for heterozygote carriers and 0.05% for pigs which were stress gene free. Many integrated producers in the U.S. have eliminated the stress gene. The only producers that still breed pigs with the stress gene are producers whose payment is based on the size of the loin. The integrated companies eliminated the stress gene to improve pork quality. Payment systems should be changed to reward quality instead of quantity. Changing the payment system would improve animal welfare because the producer would be rewarded for quality instead of quantity.
Another problem area in the U.S. is transport of day-old baby Holstein dairy calves. In some instances, 10 to 20% die either during or shortly after transport. Some of these calves have not received colostrum A few unethical dairy producers treat calves like rubbish that they have to get rid of.
Improving the Fitness of Animals for Transport
1. Breed good, strong feet and legs.
2. Grow dairy heifers and gilts more slowly to provide time for the skeleton to develop.
3. Weak, sick or emaciated animals should be euthanized on the farm.
4. Use calm, quiet handling practices.
5. Develop audit systems for monitoring the body condition of dairy and breeding sows. People manage the things that they measure.
6. Do not overload trucks.
7. Avoid sudden braking and acceleration.
8. In the U.S., many animals cannot be traced back to their origin. Accountability for losses provides an incentive to maintain breeding stock in better condition.
9. Market old breeding animals when they are still fit to travel.
10. Producers will be more motivated to take care of old breeding animals and baby Holstein calves if they have more economic value. Develop markets for these animals. Many baby Holstein calves are raised by calf raising companies and then fed in feedlots to produce grain fed beef.
Continuous Measurement and Monitoring
People who handle and stun hundreds or even thousands of animals in slaughter plants often become numb and desensitized to animal suffering (Grandin, 1994). The author has observed that handling transport and stunning procedures have a tendency to become rough and careless unless they are continuously monitored. A one-time meeting of showing a handling video to employees is not sufficient to maintain good animal welfare. The manager who is most effective in maintaining high standards of animal welfare must be involved enough to care, but not so involved in day-to-day operations that he/she becomes desensitized.
The author strongly recommends using a HACCP-type approach to measuring the efficacy of stunning and the performance of animal handlers. HACCP stands for Hazard Analysis Critical Control Points and it is used around the world to maintain food safety standards. An objective scoring system is described fully in Grandin (1997b, 1998a). The five major critical control points of stunning and animal handling are briefly outlined here. Each item is scored on a yes/no basis for each animal. An auditing system has to be simple so that it is easy to use under commercial conditions. Therefore, each animal is scored for each variable on a yes/no basis. For example, prodded with an electric goad or not prodded. Score a minimum of 100 pigs and in cattle plants with line speeds of under 100 per hour score 50 animals.
1. Stunning Efficacy - Percentage of animals rendered insensible on the first attempt.
2. Insensibility - Percentage of animals that remain insensible after stunning.
3. Vocalization - Percentage of cattle or pigs that vocalize (bellow, moo or squeal). Each animal is scored on either being a vocalizer or a non-vocalizer.
Vocalization is highly correlated with physiological stress measurements and adverse events such as missed stuns, excessive electric prod use, excessive pressure from a restraint device, slipping or falling, surgery and isolation of a single animal (Dunn, 1990; Grandin, 1998b; Warriss et al., 1994; White et al., 1995). Do not use on sheep. Each pig or bovine is scored as either a vocalizer or non-vocalizer during handling and stunning. Vocalization is not scored while animals are standing in the holding pens because animals standing undisturbed often vocalize to each other. Data collected in beef slaughter plants clearly shows that vocalization scoring can be used to document improvements in handling. When the shock intensity on an electric goad was reduced, the percentage of cattle that vocalized decreased from 7% to 2.5% (Grandin, 2000a). In two other plants, vocalization percentages of 8 and 9% were reduced to 0% after simple equipment modifications were made. These modifications reduced cattle balking and refusing to move which reduced electric goad usage. In a fourth plant, reducing the pressure applied by a head restraint device reduced the percentage of cattle that vocalized from 23% to 0%.
In large plants where counting of individual squeals is difficult, a sound level meter can be used. Another simple way to monitor the amount of pig squealing is to determine the percentage of time that pigs are squealing. As each pig is stunned, the auditor marks down "yes heard a squeal" or "no room quiet." The entire stunning area is scored. If an animal is immobilized with electricity it may still be conscious, but unable to vocalize. This is extremely distressful for animals and must not be used as a method to keep animals still (Pascoe, 1986; Grandin et al., 1986; Rushen, 1986; Lambooy, 1985). Electro immobilization must not be confused with electrical stunning where a high amperage current is passed through the brain. Vocalization scoring should not be used on sheep.
4. Slipping and Falling - Percentage of animals that slip or fall during handling and stunning.
5. Electric Goads - Percentage prodded (poked) with an electric prod (goad). Reducing the percentage of animals shocked with an electric goad reduces stress and improves welfare.
Audits of these critical control points must be done on a regular basis, the same way microbiological audits are conducted. Bacteria counts would increase and sanitation procedures would become sloppy unless continuous monitoring was done. Handling and stunning must be audited the same way in order to maintain high standards. One factor that contributes to a deterioration of handling and stunning practices is an emphasis only on speed and efficiency. Abuse is more likely to occur if employees are evaluated only on speed and efficiency.
The critical control point welfare auditing system can be used in plants around the world from the most sophisticated to the most primitive. The standards of performance which would be considered acceptable are debatable. The auditing system can be used to continually improve handling and stunning.
Meat Quality Correlations
Measurements of meat quality and bruises are important. Progressive plant managers have found that quiet handling in the stunning area will reduce PSE (pale, soft, exudative) in pork. In four different plants, the author has found that reducing electric prod use and quiet handling of pigs resulted in 10% more pork which was suitable for high quality export to discriminating customers in Japan. Reduced levels of squealing are correlated with improved meat quality (Warriss, 1994). Cattle that become agitated during handling have lower weight gains and tougher meat (Voisinet et al., 1997; P. Niendre, personal communication). An over emphasis on preventing gaps in the production line may result in more animal stress and poorer meat quality. Handling must be measured on a regular basis to maintain high standards. Animal welfare is also part of quality.
Effect of Customer Audits
Two of the major hamburger chains are using HACCP-type audits of animal handling and stunning. They are done in the same manner as microbiological audits. Audits by McDonald's Corporation in the U.S. have resulted in great improvements (Grandin, 2000). Major meat buying customers are in a position to require their suppliers to maintain high standards. In the U.S., the meat industry started to take animal welfare seriously after a major slaughter plant was removed from the McDonald's supplier list after they failed an audit.
How Stressful is Slaughter?
People often wonder "are animals afraid of slaughter." I have observed that cattle and pig behavior during handling and stunning is the same both on the farm and at the plant. Extensively raised cattle in the U.S. often become highly agitated and vocal when they are restrained for vaccinations. Often they are calmer at the slaughter plant because being restrained and held for ear tagging and vaccination takes longer than stunning.
Animal handling both on the farm and in the slaughter plant will cause physiological measures of stress to increase. When animals become agitated during handling it is most likely to be motivated by fear. The fear circuits in the animal's brain have been completely mapped (LeDoux, 1996; Rogan and LeDoux, 1996). Grandin (1997a) reviewed numerous studies of cortisol (stress hormone) levels during handling both on the farm and at slaughter. The range of values for cattle were similar for both on-farm restraint in a squeeze chute and slaughter. The range was 24 ng/ml to over 63 ng/ml (Crookshank et al., 1979; Mitchell et al., 1988; Tume and Shaw, 1992; Zavy et al., 1992; Lay et al., 1992; Ewbank et al., 1992 and Dunn et al., 1990). Rough handling, slipping on the floor and electric prod use resulted in higher cortisol levels. The highest levels recorded in a slaughter plant was 93 ng/ml (Dunn, 1990). Cattle were inverted on their backs for 103 seconds prior to slaughter. Properly performed cattle slaughter seems to be no more stressful than on-farm restraint for vaccination and eartagging. One must remember that cortisol is a time dependent measure. Twenty measures is required to reach peak value (Lay et al., 1992).
Causes of Poor Welfare Audit Scores
When an audit reveals poor performance, management must determine the exact cause of the problem. The correct diagnosis of problems can help avoid costly purchases of new equipment. Many managers have a tendency to assume that equipment may have to be replaced when a problem could be easily fixed without a major expense. The major causes of poor stunning and high percentages of vocalizing animals are listed below.
1. People using improper handling procedures. This is usually the number one problem. The author has observed that the two most common animal handling mistakes are overloading the crowd (forcing) pens and over use of electric prods. Pigs and cattle need room to turn. Crowd pens should be filled only half full. Moving small groups of pigs and cattle will facilitate handling. Sheep can be moved in larger groups because this species has more intense following behavior.
2. Distractions that cause balking and backing up - This is the second most common problem. All species of animals may balk and refuse to move when they see things in the race that scare them such as sparkling reflections, dangling chains, moving people or equipment, shadows or water dripping (Grandin 1996, 1998c). A calm animal will stop and look right at the distractions that scare it. You should crouch down and look up the race to see what the animals are seeing. It is important to get right down at the animal's eye level. Shields can be installed to prevent animals from seeing moving people or moving objects up ahead. One of the worst causes of balking is air blowing down the race into the faces of approaching animals. Animals also balk and may refuse to enter a dark place. They have a tendency to move from a darker place to a brighter place (Van Putton and Elshof, 1978; Grandin, 1982). Adding a light to illuminate a race entrance or moving a lamp to eliminate a sparkling reflection will often improve animal movement (Grandin, 1998e). Sometimes moving a ceiling light off the center line of a race will eliminate a sparkling reflection. If air is blowing towards the animals, the plant ventilation should be changed. Simple inexpensive changes can often greatly improve animal movement. People who are working to remove the distractions that impede animal movement must be very observant of small details that may be insignificant to them. A person may not notice a sparkling reflection, but the animal does. Animals should move through the system easily. If they balk or refuse to move forward, you should find the distraction that is causing balking instead of increasing electric goad usage. In the very best systems, 95% of the cattle could be moved through a slaughter line which processed over 200 cattle per hour without an electric prod. There will be more information on facilitating animal movement in the behavior and equipment design sections.
3. Equipment maintenance - Poor maintenance of captive bolt guns was the main cause of poor stunning (Grandin 1998a). Employees will become frustrated and will be more likely to handle animals in a rough manner if they have use broken or malfunctioning equipment.
4. Equipment design - Will be discussed in the equipment section (Grandin, 1991, 1990, 1984, 1992; Grandin 2000 www.grandin.com).
5. Excitable genetics or excessively wild animals - There are some animals which have a very excitable temperament and are difficult to drive. Some lean pigs and cattle are very excitable (Grandin, 1991a; 2000). These animals will often have high vocalization scores. Hunter et al., (1994) have also observed that animals from certain farms are more difficult to drive. Plant management should work with producers to solve this problem. Pigs with excitable genetics will be easier to handle at the meat slaughter plant if producers have walked through the pens every day during the finishing period. Only 10 to 15 seconds per 50 pigs is needed. Such interaction trains excitable pigs to be more comfortable with human handling. Pigs which had been walked in the alley during finishing were less excitable and easier to handle (Grandin et al., 1991a; 1998c and Geverink et al., 1998). Producers should be encouraged to produce animals which will be reasonably easy to handle.
Another problem the author has observed are extremely wild cattle which become highly agitated and difficult to handle at a slaughter plant (Grandin and Deesing, 1998). This problem is caused by both genetics and previous experience with handling. Cattle with an excitable temperament which are raised on large pastures where they seldom see people should be exposed to people on foot, months before they arrive at a slaughter plant. The author has observed that cattle which have never seen a person on foot can be difficult and dangerous to handle at the slaughter plant. Ranchers should be encouraged to get their animals accustomed to people on foot.
Animal Vision, Hearing and Smell
Vision
Ruminant animals can discriminate between different colors (Arave, 1996). The latest research shows that sheep, goats and cattle are dicromats which means they may be partially color blind. The cones in the ruminant eye are most sensitive to yellowish green light (552 to 555 nm wavelength) and blue (444 to 455 nm)(Jacobs, et al., 1998). They lack cones which are maximally sensitive to the color red. Practical experience has shown that cattle and pigs are very sensitive to anything that has high contrast. This causes them to balk at drain grates or a change from a concrete to metal floor (Grandin, 2000, 1980, 1982). Lighting should be even and diffuse and harsh contrasts of light and dark should be avoided. Cattle and other grazing animals have wide angle vision and they can see in excess of 300 degrees (Prince, 1970). To prevent the animals from becoming scared of distractions outside the race, stunning boxes, races and crowd pens should have solid fences (Grandin, 2000). The crowd gate should also be solid.
Hearing
Cattle and sheep have very sensitive hearing. They are more sensitive to high frequency noise than people and they are especially sensitive to high frequency sound around 7000 to 8000 Hz (Ames, 1974). Cattle can easily hear up to 21,000 Hz (Algers, 1984) and there is also evidence that cattle have a lower hearing threshold than people (Heffner and Heffner, 1983). This could mean that sounds that may not bother people may hurt the animals ears. Intermittent noise is very aversive to pigs (Talling et al., 1998).
Reducing noise will improve animal movement. High-pitched noise is worse than low-pitched noise. Employees should not yell, whistle or make loud noises; clanging and banging equipment should be silenced by installing rubber stops and noisy air exhausts should be piped outside or silenced with inexpensive mufflers (muffling devices wear out and should be replaced every 6 months to keep noise levels low). Hissing air is one of the worse noises, but it is also the easiest to eliminate.
Yelling, screaming and whistling is aversive to livestock. Waynert et al. (1999) reported that the sound of people yelling was more stressful to cattle than the sound of a gate slamming. Pajor et al. (2000) also found that yelling is aversive to cattle. People handling animals should be quiet. Cattle that have an excitable temperament are more likely to flinch and react to sudden movements and intermittent high pitched noise than animals that have a calmer temperament (Lanier et al., 2000).
A high-pitched whine from a hydraulic pump or undersized plumbing is disturbing to animals and can make them balk. At one plant, installing larger-diameter plumbing to eliminate a high-pitched whine from a hydraulic system resulted in calmer, easier to move animals. In another plant, excessive noise from ventilation fans made pigs balk. Noise from the fans increased as the pigs approached the restrainer.
Noise increases physiological stress levels. Slaughter in a quiet research abattoir resulted in lower cortisol levels compared to slaughter in a large noisy commercial plant (Pearson et al., 1977).
When new systems are built, there needs to be more emphasis on noise reduction. Recently, the author visited an up-to-date pork slaughter plant. Over 800 pigs per hour were quietly moved through the plant with very little balking or backing up. The race system, overhead conveyors and restrainer system were engineered to reduce noise greatly. Gates on the race had rubber pads to prevent clanging and banging; motors and conveyors were designed to reduce high-pitched noise. Well trained handlers quietly moved the pigs up the race with very little squealing.
The type of building used in the animal handling area will also influence sound levels. Buildings constructed from pre-cast concrete with a high ceiling will have higher sound levels due to echoes than a building constructed from cooler board panels which have foam insulation sandwiches between two pieces of metal. Lowering the ceiling can sometimes help reduce sound levels. Hanging baffles from the ceiling may also help.
Smell
Many people interested in the welfare of livestock are concerned about animals seeing or smelling blood. Cattle will balk and sniff spots of blood on the floor (Grandin, 1980); washing blood off facilitates movement. Balking may be a reaction to novelty. A piece of paper thrown in the race or stunning box elicits a similar response. Cattle will balk and sometimes refuse to enter a stunning box or restrainer if the ventilation system blows blood smells into their faces at the stunning box entrance. They will enter more easily of an exhaust fan is used to create a localized zone of negative air pressure. This will suck smells away from cattle as they approach the stunning box entrance.
Observations in Kosher slaughter plants indicate that cattle will readily walk into a restraining box which is covered with blood. In Jewish ritual (Kosher) slaughter, the throat of a fully conscious animal is cut with a razor sharp knife. The cattle will calmly place their heads into the head restraint device and some animals will lick blood or drink it. Kosher slaughter can proceed very calmly with a few signs of behavioural agitation if the restraining box is operated gently (Grandin, 1992). However, if an animal becomes very agitated and frenzied during restraint, subsequent animals often become agitated. An entire slaughter day can turn into a continuous chain reaction of excited animals. The next day after the equipment has been washed, the animals will be calm. The excited animals may be smelling an alarm pheromone from the blood of severely stressed cattle. Blood from relatively low-stressed cattle may have little effect. However, blood from severely stressed animals, which have shown signs of behavioural agitation for several minutes, may elicit a fear response. Eibl-Eibesfeldt (1970) observed that if a rat is killed instantly in a trap, the trap can be used again. The trap will be ineffective if it injures and fails to kill instantly.
Research with rats support this idea. Rats showed a fear response to the blood of rats and mice that had been killed with carbon dioxide (Steven and Gerzog-Thomas, 1977; Stevens and Sapiloski, 1973).
Recent research with pigs and cattle indicates that stress pheromones are secreted in the saliva and urine. Vieville-Thomas and Signoret (1992) and Boissey et. Al. (1998) both report that pigs and cattle tend to avoid objects or places which have urine on them from a stressed animal. This stress response is not instantaneous. The stressor was applied for 15 to 20 minutes to induce the effect. In the cattle experiment, cattle were given repeated shocks during a 15 minute period.
Basic Handling Principles
The first principle of animal handling is to avoid getting the animal excited. It takes up to 30 minutes for an animal to calm down and have its heart rate return to normal after it has been handled roughly (Stermer et al., 1981). Calm animals move more easily and they are less likely to bunch together and be difficult to remove from a pen (Grandin, 1998e). Handlers should move with slow deliberate movement and refrain from yelling.
All species become agitated when they are isolated form other animals. In sheep and cattle, isolation can cause cortisol levels to rise (Boissy and Boissou, 1995). Cattle, elk, bison and other large animals can be become agitated and very dangerous when isolated. If an isolated animal becomes agitated, other animals should be put in with it. Electric goads should be replaced as much as possible with other driving aids such as flags, panels and plastic bags. A piece of plastic fabric which is stiffened on the top with a rod makes a good tool for moving pigs down an alley. Electric goads should not be constantly carried around. A flag or other aid should be used as the primary driving tool. If an animal refuses to enter the stun box, the electric goad can be used. After use, it should be immediately put back down. I have observed that employee attitudes and behavior become more caring towards the animals when they were not allowed to constantly hold an electric goad.
Handlers also need to learn how to use the following behavior. The crowd pen should not be filled until there is room in the single file race for the animals to enter. If the single file race is full, animals in the crowd pen will turn around. Good handling requires paying attention to many small details of exactly how to do a procedure. The crowd pen and the alley that leads to it from the yard should be filled only half full.
Handlers must also be careful not to force animals with crowd gates. This is especially a problem with power crowd gates. If a system is designed and operated correctly, animals should walk up the race without being forcibly pushed. When animals are pushed up too tightly with a power crowd gate, handling becomes more difficult. Tightly packed animals are unable to turn around to enter the race.
Handler Movement Patterns
People who handle animals need to understand the principles of the flight zone and point of balance (Grandin 1987, 1998c). Handlers should work on the edge of the animal's flight zone. Flight zone size depends upon the wildness or tameness of the animal. A completely tame animal has no flight zone and may be difficult to drive. To make an animal move forward the handler must be behind the point of balance at the shoulder. To back it up he/she stands in front of the point of balance. Cattle, pigs or sheep will move forward in a race when a handler walks quickly past the animal in the opposite direction of desired movement. The handler must move quickly past the point of balance at the shoulder to induce the animal to move forward. The animal will not move forward until the handler passes the shoulder and reaches the hips.
Design of Handling Facilities
Non-Slip Flooring - A minimum essential for all species is non-slip flooring. Careful, quiet handling is impossible if animals slip or fall. Slipping in a cattle stunning box will cause animals to become agitated and difficult to stun. A grating constructed from 2 cm steel bars welded in a 30 cm x 30 cm grid will prevent slipping in high traffic areas where floors have become worn.
Pen Space - Stockyard or ante mortem pens must provide enough space. The American Meat Institute (1991a) has guidelines for minimum pen space requirements (Grandin, 1991a). Many countries have Codes of Practice which stipulate the amount of pen space required. A good rule of thumb is that there should be sufficient space for all the animals to lie down at once. In the United States, the Humane Slaughter Act of 1978 requires that all holding pens be equipped with water troughs or some other watering devices. In hot weather, pigs require additional space to prevent death losses due to heat stress.
Design of Races and Crowd Pens
Detailed information of race and crowd pen designs can be obtained in Grandin (1990, 1991a, 2000c, www.grandin.com). There are three major design mistakes which can make quiet, calm handling extremely difficult: a single-file race that is too wide, a race which appears as a dead end and a crowding pen on a ramp. Single-file races and stunning boxes must be narrow enough to prevent animals from turning around or becoming wedged beside each other. A cattle race should be 76 cm wide and races for pigs should have only 3 cm of clearance on each side of the largest pigs. For cattle, a curved race is more efficient (Grandin, 1991-2000c). Curved races work well because cattle entering the race cannot see people or other activity up ahead. However, a curved race must be laid out correctly. If it is bent too sharply at the junction between the single file race and the crowding pen, the animals may refuse to enter because the race entrance appears to be a dead end. Curved races must be laid out so that animals standing in the crowding-pen can see a minimum of three body lengths up the race before it turns. Grandin (1984, 1990, 1991a, 200b) illustrated correctly curved race layouts.
Another serious design mistake is to build a crowding pen on a ramp. In facilities where a ramp is required to reach the stunning box or restrainer, it should be located in the single-file race. Groups of animals in a crowding pen will tend to pile up on the back gate if the crowding pen is located on a ramp. Cattle and sheep will readily move up a ramp but pigs will move easier in a level system with no ramps. New pig handling facilities should be level.
Design and operation of restraint devices
If animals vocalize during handling, restraint or stunning they are being subjected to something that is aversive, vocalization scoring is one of the most important measures of animal distress.
In small plants with line speeds of under 240 pigs per hour, it was less stressful to electrically stun pigs with hand held tongs while they were standing in groups on the floor compared to moving them through a single file or double file race (Warriss et al., 1994). At higher speeds floor stunning with tongs tends to become rough and sloppy and a system which uses single file or double file races would be preferable for moving pigs to an electric stunner. Whereas cattle and sheep move easily through a single file race, pigs tend to be more difficult to drive. This is a species difference, cattle and sheep naturally move in single file whereas pigs do not. Cattle and sheep will move very easily and quietly through a well designed single file race. A new Danish system for CO2 stunning has eliminated lining pigs up a single file race. Pigs are moved in small groups into the stunner. Pigs can be moved without electric goads in the system.
Design of animal restraint (holding) devices for both conventional slaughter where the animal in stunned and ritual slaughter are covered in detail in Grandin (1988, 1991ac, 1992, 1995, 2000d). The behavioral principles of low stress restraint are:
1. Animals should never be left in a stunning box or restraint device. Stun or ritually slaughter immediately after the animal enters.
2. Animals should enter the device easily. If they balk or back up, check for distractions discussed previously. A lamp can be used to illuminate the entrance. It must provide indirect lighting. Devices that are above the floor should have a false floor to prevent the entering animal from perceiving the visual cliff effect (Grandin 1991c). Ruminants can perceive depth (Lemon and Patterson, 1964).
3. Block the animal's vision so that they do not see people or suddenly moving objects. Install metal shields around the animal's head on box type restrainers. This is not necessary on conveyor restrainers. Block the animal's vision of an escape route until it is fully held in a restraint device (Grandin 1991d). This is especially important on restrainer conveyors. Cattle often become agitated in conveyor restrainers if they can see out from under the solid metal hold down cover before their back feet are off the entrance ramp. Extending the solid hold down cover which is over the animal's back on a conveyor restrainer will usually have a calming effect. Most cattle will ride quietly. Solid hold downs over the animal's back can also be beneficial for pigs on conveyor restrainers. The solid hold down should not touch the animal's back. It's purpose is to block vision and control what the animal sees.
4. Provide non-slip flooring in box-type retrainers and a non-slip cleated entrance ramp on conveyor restrainers. Animals tend to panic when they lose their footing.
5. Parts of a restraint device that press against the animal's body should move with slow steady motion. Sudden jerking motion excites animals. On existing equipment, install flow controls to provide smooth, steady movement of moving parts which press against the animal.
6. 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 regular to reduce the maximum pressure that can be applied. Very little pressure is required to hold an animal if it is fully supposed by the device. If an animal bellows or squeals in direct response to the application of pressure, the pressure should be reduced.
7. A restraint device must either fully support an animal or have non-slip footing. Animals panic if they feel like they may fall. Restraint devices should hold fully sensible animals in a comfortable, upright position.
8. Equip restraint devices with 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 which unable a cylinder on the device to be stopped in mid stroke.
9. 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.
10. The operator must be adequately trained and supervised. One big problem in many slaughter plants is that the people who handle and stun animals are the lowest paid in the plant. In England, their pay has been raised and people who stun animals must be licensed.
11. If a restrainer conveyor is mounted above the floor level, it must have a false floor to prevent the incoming animal from seeing the visual cliff effect (Grandin, 2000, 1991). Ruminants can perceive depth (Lemman and Patterson, 1964).
CONCLUSIONS
To maintain an adequate level of animal welfare requires constant auditing of handling and stunning to prevent people from becoming careless and sloppy. We manage what we measure. Economic incentives and accountability for losses such as bruises and PSE will also improve welfare. Grandin (1981) found that cattle sold liveweight where the slaughter plant paid for the bruises, had twice as many bruises as cattle sold in the carcass where the producer paid for bruises. Large supermarket and restaurant companies such as McDonald's have greatly improved welfare by requiring their suppliers to maintain high standards.
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