(Updated July 1, 1999)
by Temple Grandin, Ph.D.
Dept. of Animal Science
Colorado State University
Fort Collins, CO 8O523
These guidelines are a supplement to the 1991 Recommended animal handling Guideline for Meat Packers. The main emphasis of this guide is on the use of a welfare performance standards which can be objectively scored instead of specifying equipment design or practices. Scoring procedares for accessing animal welfare and recommendations which will help improve animal welfare are described. The recommended scoring procedures are simple enough to be conducted easily under commercial conditions and they should be conducted a minimum of once a week. Scoring should be done at both the beginning and the end of a shift to determine the effect of employee fatigue. If a score falls below the acceptable range specified in the guide, plant management should take steps to correct the problem. The results of the 1996 Survey of Stunning and Handling in Federally Inspected Beef, Pork, Veal and Sheep slaughter Plants indicated that the recommended minimum acceptable levels specified in this guide can be achieved easily at a minimum of expense. Objective scoring should be done in the following areas which are critical control points for good animal welfare. The minimum acceptable percentage scores in this were determined by the author based on over twenty years of practical experience in over 100 different slaughter plants.
Poor performance in any one of the above critical control points would result in reduced welfare. This guideline also contains criteria for stunning equipment and recommendations which will enable a plant to maintain acceptable welfare scores. Other areas of welfare concern which will be covered are ritual slaughter and the handling of non-ambulatory animals.
Some plants stun animals below the Council of Europe recommended minimum amperages in an attempt to reduce blood spots in the meat. Stunning market weight pigs with less than 1.25 amps should not be permitted (Hoenderden 1982, Grandin 1994a) unless different electrical parameters are verified by either electrical or neurotransmitter recordings from the brain. Since only a one second application at 1.25 amps is required to induce instant insensibility in market weight pigs, it is the author's opinion that plants should be permitted to use circuits which lower the amperage setting after an initial, one second stun at 1.25 amps for pigs and 1 amp for sheep. Plants should also be encouraged to use electronic constant amperage circuits which prevent amperage spiking. Both practical experience and research has shown that these types of circuits greatly reduce petechial hemorrhages (blood spots) (Grandin 1985, Blackmore and Peterson 1981).
Since U.S. market pigs are slaughtered at heavier weights compared to European pigs an electric stunner must deliver the minimum amperage recommended by the Council of Europe (1991) to insure instantaneous insensibility. It is the author's opinion that high frequency stunning should not be permtted in the U.S. until research is conducted to prove that it is capable of inducing an instantaneous grand mal seizure in heavier U.S. market weight pigs. In the Anil and McKinstry (1994) experiment, the pigs were stunned with a head only applicator. High frequency stunning has never been verified to induce instant insensibility when applied with a head to body cardiac arrest stunning electrode. This is the type of electrode used in almost all large U.S. pork slaughter plants. However, at the present time, pork plants should be permitted to use higher frequencies in their stunning cycle provided that their initial stun is a minimum of 1.25 amps at 50 to 60 hz for a minimum of one second.
Unlike pigs and sheep, electrical stunning of cattle requires a two phase stun. Due to the large size of cattle, a current must first be applied across the head to render the animal insensible before a second current is applied from the head to body to induce cardiac arrest (Gregory 1993). A single 400 volt, 1.5 amp current passed from the neck to the brisket failed to induce epileptic form changes in the brain (Cook et al 1991). To insure that the electrodes remain in firm contact with the bovine's head for the duration of the stun, the animal's head must be restrained in a mechanical apparatus. The Council of Europe requires a minimum of 2.5 amps applied across the head to induce immediate epileptiform activity in the EEG of large cattle. A frequency of 60 or 50 cycles should be used unless higher frequencies are verified by either electrical or neurotransmitter measurements taken from the brain.
Electrodes must be cleaned frequently to insure a good electrical connection. The minimum cleaning schedule is once a day. For safety, the electrode wand must be disconnected from the power supply before cleaning. Adequate electrical parameters for cardiac avert stunning can not 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 which may be used in the future.
If head only stunning is used, the tongs must be placed so that the current passes through the brain (Croft, 1952, Warrington 1974). Tongs may be placed on both sides of the head or one tong on the top and the other on the bottom of the head. Another scientifically verified location for head only stunning is one electrode placed under the jaw, and the other is placed on side of the neck right behind the ears. For cardiac arrest stunning of pigs and sheep, one electrode must be placed on the head and the other one may be placed at any location on the body, which will induce cardiac arrest. The head electrode may be placed on the forehead, side of the head, top of the head, under the jaw, or in the hollow behind the ear. The head electrode must never be placed on the neck because this would cause the current to bypass the brain. Electrodes must not be applied to sensitive areas such as inside the ear or in the eye or rectum.
The survey indicated that the most common cause of a low captive bolt stunning efficacy score was poor maintenance of the captive bolt guns. Guns must be cleaned and serviced per the manufacturer's recommendations to maintain maximum hitting power and prevent misfiring or partial firing. 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 poor ergonomic design of bulky pneumatic stunners. Ergonomics can sometimes be improved with the use of a handle extension and improved balancers.
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. Electrical immobilization must never be used as a method for restraining sensible animals prior to or during stunning. Several scientific studies have shown that it is highly aversive (Lambooy 1985, Pascoe, 1986, Grandin et al 1986, Rushen 1986). Vocalizing scoring is impossible in electrically immobilized animals because paralysis prevents vocaliztion. Electrical immobilization must not be confused with electric stunning. Properly done, electric stunning passes a high amperage current through the brain and induces instantaneous insensibility. Electrical immobilization holds a sensible animal still by paralyzing the muscles. It does not induce epileptiform changes in the EEG (Lambooy 1985). A third cause of missed captive bolt shots is an overloaded or fatigued operator. Scoring at the end of the shift will pinpoint this problem. In some large plants either two stunner operators or rotating the operators frequently may be required.
Electric Stunning Bleed Interval- Cardiac Arrest - Sixty second maximum. All large plants are already less than this interval.
Head Only Reversible Electric - Fifteen seconds is strongIy recommended (Blackmore and Newhook 1981), 30 seconds maximum (Hoenderken 1983). Scientific research clearly shows that pigs will start returning to sensibility after 30 seconds when stunned by the head only method.
Scoring of Slipping and Falling in the Stunning Chute Area (All Species) (Score a minimum of 50 animals in large plants.) Includes restrainer entrance, stunning box, lead up chute and crowd pen.
The 1996 survey results indicated that the percentage of cattle which vocalized in the stunning chute area ranged from three percent or less of the cattle in the three best plants to 12 percent to 32 percent in the two worst plants. Cattle vocalizations in the stunning chute area were caused by prodding with an electric prod, slipping in the stunning box, missed captive bolt stuns or excessive pressure applied by a restraint device. The survey results showed that plants with a high percentage of cattle vocalizing could easily reduce this percentage. The average vocalization percentage in the two roughest plants was reduced from 22 percent of the cattle to 4.5 percent by reducing electric prod usage. The 1996 survey results clearly showed that cattle seldom vocalize during handling or stunning unless an easily observed aversive event occurred. A total of 1125 cattle were vocalization scored and 112 animals vocalized. Only two animals vocalized which were not responding to an aversive event such as electric prodding, slipping, falling, missed stuns, or excessive pressure from a restraint device. Other aversive events which can cause vocalization are hitting cattle with gates or pinching an animal in a restraint device. This indicates that vocalization is an indicator of discomfort.
Criteria for Vocalization of Cattle In the Crowd Pen. Lead-Up Chute, Stunning Box or Restraining Device (Score a minimum of 100 animals in large plants.)
Cattle vocalizations should be tabulated during handling in the crowd pen, lead up chute, restrainer or stunning box. Vocalizations occurring in the yards should not be tabulated because cattle standing quietly in the yards will often vocalize to each other. In one plant hungry HoIsteins vocalized and turned to face a man bedding a pen with sawdust. It appeared that they perceived the sawdust as feed.
Observations at one of the sheep slaughter plants indicated that vocalization during handling is absolutely useless as a measure of handling problems in sheep. Sheep walking quietly up the stunning chute often vocalized to each other. Sheep which balked and had to be pushed by a person never vocalized. This is a species difference between cattle and sheep.
Since it is impossible to count individual pig squeals when a group of pigs is being handled, vocalization scoring of individual pigs can only be conducted in the restrainer. The 1996 survey results indicted that there were two major causes of pig vocalizations. They were mis-applied electric stuns and pinching in the restrainer. The 1996 survey results indicated that vocalization in the restrainer ranged from 0 percent to 14 percent of the pigs. Out of 11 plants, 72 percent ( 8 plants) had no pigs squealing due to mis-applied electric stuns. In two plants, two percent to four percent squealed during stunning. The use of sound level meters should be studied for monitoring pig vocalizations during handling.
Criteria for Vocalization of Pigs in the Restrainer or During Stunning
In several different publications the author has outlined the behavioral principles of low stress animal restraint and handling (Grandin l99l,1993,1994, 1995, 1996). 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:
|Criteria||Crowd Pen to Chute||Entrance of Stunning
Box or Restrainer
of Cattle Prodded
|Excellent||none||5% or less||5% or less|
|Acceptable||5% or less||20% or less||25% or less|
|Serious Problem||--||--||50% or more|
|Criteria||Crowd Pen to Chute||Entrance of Restrainer||Total Percentages
of Pigs Prodded
|Excellent||none||10% or less||10% or less|
|Acceptable||--||--||25% or less|
which must be corrected
|--||--||80% or more|
2. Provide Adequate Lighting - Animals may refuise to enter a dark place. Entry into a restrainer can be facilitated by aiming a Iight into the entrance. The light must NOT shine into the eyes of approaching animals. Animals may be difficult to drive out of the crowd pen if it is brightly illuminated by sunlight and the chute is inside a darker building. Lighting problems can make quiet handling almost impossible. 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 lamps dim with age. Experiment with portable lights to find the most efficient lights. Animals may also balk at shiny reflections off a piece of metal or sparkling water on the floor. Moving a light will often eliminate the reflections.
3. Reduce Noise - Animals are very sensitive to high pitched noise. Reducing high pitched motor and hydraulic system noise can improve animal noise can improve animal movement. Clanging and banging metal should be reduced and hissing air should be muffled.
4. Move Small Groups - 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 quarers full. Half full is best. Do not push crowd gates up tight against the animals. 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.
5. Use Other Driving Aids - Electric prods should be replaced as much as possible with other driving aids such as plastic paddles, stick with a flag on the end or panels for pigs. The animals should move easily and handlers should not hit them. Cattle and pigs can often be moved along a chute when the handler walks back by them in the opposite direction of desired movement.
6. Problems With Excitable Animals - There are some animals which have a very excitable tempernment and are difficult to drive. Some lean pigs and cattle are very excitable. These animals will often have high vocaliztion scores. Plant management needs to work with producers to solve this problem. Pigs with excitable genetics can be made easier to handle at the meat packing plant if producers walk through the pens during finishing. This trains excitable pigs to handling. Producers should be encouraged to produce animals which will be reasonably easy to handle.
The AMI and the USDA should develop ways to safely inspect non-ambulatory animals which arrive on the trucks so they do not have to be removed from the truck prior to anti-mortem inspection. Animal welfare would be greatly improved because non-ambulatory animals could be stunned on the truck.
Plant personnel should develop procedures to help reduce the occurrence of non-ambulatory animals on the premises. Non-slip flooring is essential. Mounting activity. and animal fights can cause injuries. This is especially a problem with bulls and boars. Bulls which are mounting other animals should be placed in separate pen. Mounting by bulls is a common cause of bruises and crippling injuries on cows.
Pen Stocking Density - Pens should be stocked per the AMI 1991 guidelines. Animals must all have room to lie down. All animals should have access to water.
Maintenance - Pens, alleys, chutes, restrains and other equipment should be kept clean and well maintained. It should be free of protrusions which could injure animals.
In conclusion, managers must be committed to good animal welfare. Plants which have managers who insist on good handling and stunning practices have management who insists that employees handle and stun animals correctly.
Bergaus, A. and Troeger L. 1998. Electrical stunning of pigs: Minimum current flow time required to induce epilepsy at various frequencies. Proceedings 44th International Congress of Meat Science and Technology, Barcelona, Spain, pp 1070-1081.
Blackmore, D.K. 1988. Quality control of stunning Proceedings of the International Congress of Meat Science and Technology, CSIRO, Brisbane, Australia.
Blackmore, D.K. and Peterson, G.V. 1981a. Stunning and slaughter of sheep and calves in New Zealand. New Zealand Veterinary Journal, 29:99-102.
Blackmore, D.K. and Newhook, J.C. 1981b. Insensibility during slaughter of pigs in comparison to other domestic stock. New Zealand Veterinary Journal, 29:219-222.
Blackmore, D.K and Newhook, J.C. 1983. The assessment of insensibility in sheep, calves, and pigs during slaughter. In:G. Eikelenboom editor). Stunning Animal's for Slaughter, Marinus Nijhoff Boston, pp 13-25.
Cook, C.J. 1992. Stunning Science, a guide to better electrical stunning. Meat Industry Research Conference, MIRINZ, HamiIton, New Zealand.
Cook, C.J; Devine, C.E. and Gilbert, KV., et al 1991. Electroencephalograms and electrocardiograms in young bulls following upper cerrical vertebrae to brisket stunning. New Zealand Veterinary Journal, 39:121-125.
Council of Europe 1991. Council Directive of 18 November on Stunning of Animals Before Slaughter (74/577/EEC). Official Journal of the European Communities, No.L 316, 26 November, 10-11.
Croft, P.S. 1952. Problems with electrical stunning. Veterinary Record, 64:255-258.
Dunn, C.S. 1990. Stress reaction of cattle undergoing ritual slaughter using two methods of restraint. Veterinary Record, 126: 522-525.
Gilbert K.V. ; Cook, C.J.; and Devine, C.E.; et al. Electrical stunning in cattle and sheep: electrode placement and effectiveness, in Proceedings. 37th International Congress of Meat Science Technology 1991; 245-248.
Grandin, T. 1997. Survey of Handling and Stunning in Federally Inspected Beef Pork, Veal and Sheep Slaughter Plants. ARS Research Project No. 3602-32OOO-002-O8G, USDA
Grandin, T. 1996. Factors that impede animal movement at slaughter plants. Journal of American Veterinary Medical Association 209: 757-759.
Grandin, T. 1995. Restrunt of livestock, Proceedings of the Animal Behavior and the Design of Livestock and Poultry Systems International Conference, Northeast Regional Agricultural Engineering Service, Cornell University, Cooperative Extension, Ithaca, New York. pp.208-223..
Grandin, T. 1994. Euthanasia and slaughter of livestock. Journal of American Veterinary Medical Assoc. 204:1354-1360.
Grandin, T. 1993a. Report on Handling and Stunning Practices in Canadian Meat Packing Plants, conducted for Agriculture Canada, The Canadian Federation of Humane Societies and The Canadian Meat Council.
Grandin, T. 1993b. Welfare of livestock in slaughter plants. In: Grandin T. ed. Livestock handling and transport. Wallingford, Oxon, UK: CAB International, 289-311.
Grandin, T. 1991a. Recommended animal handling guidelines for meat packers. Washington, DC: American Meat Institute.
Grandin, T. 1991b. Principles of abattoir design to improve animal welfare. In: J. Matthews (editor) Progress in Agricultural Physics and Engineering, CAB International, Wallingford, Oxon U.K. pp.279-304.
Grandin, T. 1988. Behavior of slaughter plant and auction employees towards animals. Anthrozoo; 1:205-213.
Grandin, T. 1985/1986. Cardiac arrest stunning of livestock and poultry. In: Fox MW, Mickley LD, editors. Advances in Animal Welfare Science. Boston: Martinus Nijhoff Publishers, 1-30.
Grandin, T.; Curtis, S.E.; Widowski, T.M.; et al. 1986. Electro-immobilization versus mechanical restraint in an avoid-avoid choice test. Journal of Animal Science; 62:1469-1480.
Grandin, T. and Regenstein, J.M. 1994. Religious Slaughter and Animal Welfare: A Discussion for Meat Scientists; Meat Focus International, March, CAB International, Wallingford, Oxon, U.K. pp.115-123.
Gregory, N.G. 1994. Preslaughter handling, stunning and slaughter, Meat Science; 36: 45-56.
Gregory, N.G. 1993. Slaughter technology. Electrical stunning of large cattle, Meat Focus International, CAB International, Wallingford, Oxon U.K. January.
Gregory, N.G. 1988. Humane slaughter, in Proceedings 34th International Congress of Meat Science Technology, workshop on Stunning Livestock.
Gregory, N.G. and Wotton, S.B. 1984. Sheep slaughtering procedures. III head to back electrical stunning British Veterinary Journal; 140: 570-575.
Hoenderken, R. 1983. Electrical and carbon dioxide stunning of pigs for slaughter. In: Eikelenboom G. ed. Stunning of Animals for Slaughter. Boston: Martinus Nijhoff Publishers, 59-63.
Lambooy, E. 1985. Electro-anesthesia or electro immobization of calves, sheep, and pigs, by Feenix Stockstill. Veterinary Quarterly, 7: 120-126.
Pascoe, P.J. 1986. Humaneness of electro-immobilization unit for cattle, American Journal of Veterinary Research, 10: 2252-2256.
Rushen, J. 1986. Aversion of sheep to electro-immobilization and physical restraint. Applied Animal Behavior Science, 15: 315-324.
Troeger, K. and Woltersdorf, W. 1989. Measuring stress in pigs during slaughter, Fleischwirtsch, 69: (3) 373-376.
Warrington, P.D. 1974. Electrical stunning: A review of literature, Veterinary Bulletin, 44: 617-633.
Warriss, P.D.; Brown, S.N. and Adams, S.J.M. 1994. Relationships between subjective and objective assessments of stress at slaughter and meat quality in pigs. Meat Science, 38: 329-340.
White, R.G.; DeShazer, J.A. and Tressler, C.J. et al 1995. Vocalizations and physiological response of pigs during castration with and without anesthetic. Journal of Animal Science, 73: 381-386.