Rev. sci. tech. Off. int. Epiz.(2),693-710(1)Koret School of Veterinar - PDF document

Rev. sci. tech. Off. int. Epiz.(2),693-710(1)Koret School of Veterinary Medicine, Hebrew University, POB 12, Rehovot 76100, Israel(2)The Islamic Food and Nutrition Council of America, 5901 N. Cicero Avenue, Chicago, IL 60646, UnitedThis paper brießy describes the formation of the OIE (World Organisation forAd hocSession of the OIE International Committee and have been included in the 14thTerrestrial Animal Health Code include some changes to current definitions of certain terminology, andconsumption, designed to minimise avoidable pain and suffering at every stageGroup were: general principles for slaughter, as related to personnel,animal behaviour, and the removal of distractions which can cause animals tostop or turn back; moving and handling animals following their arrival at theslaughterhouse; lairage design and construction; care of animals in lairages; andstunning and slaughter methods applicable to various relevant species. Thegroup acknowledged the signiÞcance of religious requirements as well as thecultural and ethnic factors associated with slaughter, and appropriate proposalswere included in their Þnal report. Important but less frequently occurring issuessuch as the management of foetuses during the slaughter of pregnant animalswere also included in this work. Finally, the report of the speciÞed methods, procedures and practices that are unacceptable on animalSlaughterhouse Ð Stunning Ð Treatment Ð Welfare. Group on the Humane Slaughter of Animalswas established to develop standards in line with therecommendations of the permanent OIE (WorldOrganisation for Animal Health) Animal Welfare WorkingGroup. In establishing the membership of the group, theDirector General of the OIE sought to achieve a balance ofregional and cultural views without explicitly seekingrepresentation from interested or professional parties.Group convened its Þrst meeting in November consumption. The report of the meeting was presented inFebruary 2004 to participants at the Global Conference onAnimal Welfare organised by the OIE in Paris. During theconference, interested stakeholders participated in adiscussion group on the slaughter of animals for humanconsumption. Members of the Group updated thisdiscussion group on the issues it had considered and theprogress made. The views exchanged during this meetingwere included in the proceedings of the conference andlater presented and discussed, together with writtenresponses from Member Countries and from internationalanimal welfare non-governmental organisations (NGOs), reviewed by the Group and are proposed forÐ irreversible loss of brain activity as demonstratedby loss of brain stem reßexesÐ slaughter of a religiously acceptablespecies, by a trained Muslim slaughterman, with orwithout prior stunning, by cutting the neck in order tosever the jugular veins and carotid arteries, oesophagusand trachea, without severing the spinal cord, while thedecapitation according to the Sikh religionÐ any procedure which causes the death of anÐ slaughter, of a religiously acceptablespecies, by a trained and accredited Jewish slaughterman,by cutting the neck in order to sever the jugular veins andcarotid arteries, oesophagus and trachea of a consciousanimal, without severing the spinal cordÐ pens, yards and other holding areas used foraccommodating animals in order to give them necessaryattention (including water, fodder, rest) before they aremoved on, used for speciÞc purposes, or slaughteredÐ the application to an animal of any proceduredesigned to restrict its movements in order to facilitateeffective managementÐ any procedure which causes the death of anÐ premises, including facilities for movinghuman consumption or animal feeding and approved bythe national Veterinary Services or other competentprocedure which causes immediate loss of consciousnesswhich lasts until either the animal is killed or it recovers.Based upon the Guiding Principles for Animal Welfare, asGroupHuman Consumption. This was done in line with articleThe text is presented in the following 10 articles, which isAnimal Welfare Ð of the These guidelines address the need to ensure the welfare offood animals during pre-slaughter and slaughter processes,until they are dead.commonly slaughtered in slaughterhouses, that is: cattle,buffalo, sheep, goats, deer, horses, pigs, ratites, camelidsand poultry. Other animals, wherever they have beenreared, should be managed to ensure that their transport,lairaging, restraint and slaughter is carried out withoutcausing undue stress to the animals; the principlescare, restraining, stunning, slaughter and bleeding ofanimals play an important role in the welfare of thoseanimals. For this reason, there should be a sufÞcientnumber of personnel, who should be patient, considerate,national context.The management of the slaughterhouse and the VeterinaryServices should ensure that slaughterhouse staff performtheir tasks in accordance with the principles of animal welfare.behaviour patterns of animals and the underlyingThe behaviour of individual animals or groups of animalswill vary, depending on their breed, sex, temperament andage and the way in which they have been reared andhandled. Despite these differences, the following behaviourpatterns, which are always present to some degree inMost domestic livestock are kept in herds and follow aAnimals that are likely to be hostile to each other in agroup situation should not be mixed at slaughterhouses.The desire of some animals to control their personalDomestic animals will try to escape if an animal handlerapproaches closer than a certain distance. This criticalupon previous contact with humans. Animals reared inclose proximity to humans, i.e. tame, have no ßight zone,Rev. sci. tech. Off. int. Epiz., Implements that cause pain and suffering such as largesticks, sticks with sharp ends, metal piping, fencing wire oravoids pain or suffering and physical damage (e.g. bruising, fractures, dislocations). In the case ofappropriate to the species; grasping or lifting such animalsonly by their wool, hair, feet, neck, ears or tails causes painand suffering and should not be permitted, except in anemergency where animal welfare or human safety mayotherwise be compromised.Conscious animals should not be thrown or dragged.Animals should not be forced to move at a speed greaterthan their normal walking pace, in order to minimiseinjury through falling or slipping. Performance standardsshould be established where numerical scoring of theprevalence of animals slipping or falling is used to evaluatebe improved. In properly designed and constructedAnimal handlers should not force an animal to walk overUnder no circumstances should animal handlers resort toviolent acts to move animals, such as crushing or breakinginjurious object or irritant substance to sensitive areas suchas eyes, mouth, ears, the anogenital region or the belly.Containers in which animals are transported should behandled with care, and should not be thrown, dropped orknocked over. Where possible, they should be loaded andunloaded horizontally and mechanically.Animals delivered in containers with perforated or ßexiblebottoms should be unloaded with particular care in orderto avoid injury. Where appropriate, animals should beunloaded from the containers individually.Animals that have been transported in containers shouldbe slaughtered as soon as possible; mammals and ratiteswhich are not taken directly upon arrival to the place offrom appropriate facilities at all times. Delivery of poultryfor slaughter should be scheduled such that they are notdeprived of water at the premises for longer than 12 h.Animals that have not been slaughtered within 12 h ofgiven moderate amounts of food at appropriate intervals.Provisions relevant to restraining animals for stunning orwelfare include:Ðprovision of a non-slip ßoorÐensuring that the restraining equipment does not exertexcessive pressure, thus causing the animal to struggle orÐengineering equipment to reduce the noise of hissing airÐensuring that restraining equipment has no sharp edgesÐusing restraining devices appropriately and not jerkingthem or making other sudden movements.Methods of restraint causing avoidable suffering, such asthe following, should not be used with conscious animalsbecause they cause severe pain and stress:Rev. sci. tech. Off. int. Epiz., Table I DistractionElimination methodReßections on shiny metal or wet ßoorsMove a lamp or change lightingDark entrances to chutes, races, stun boxes or conveyor restrainersIlluminate with indirect lighting that does not shine directAnimals seeing moving people or equipment up aheadInstall solid sides on chutes and races or install shieldsChains or other loose objects hanging in chutes or on fencesRemove themUneven ßoors or a sudden drop in ßoor level at the entrance to conveyor restrainersAvoid uneven ßoor surfaces or install a soliSounds of air hissing from pneumatic equipmentInstall silencers or use hydraulic equipmentClanging and banging of metal objectsInstall rubber stops on gates and other devices to reduce metal to metal contact Air currents from fans or air curtains blowing into the face of animalsRedirect or reposition equipment would have to cross them. Discontinuities or changes inßoor patterns or texture that could cause baulking in themovement of animals should be avoided.Lairages should be provided with adequate lighting, butcare should be taken to avoid harsh lights and shadows,which frighten the animals or affect their movement. Thefact that animals will move more readily from a darker areainto a well-lit area might be exploited by providing lightingthat can be regulated accordingly.Lairages should be well ventilated, and the air ßow shouldbe arranged so that odours and draughts do not adverselyaffect the health and welfare of the animals.Care should be taken to protect the animals frommufßing noisy metal equipment by the use of suitablepadding, or by minimising the transmission of such noiseto the areas where animals are held and slaughtered.Where animals are kept in outdoor lairages without naturalshelter or shade, they should be protected from the effectsAnimals in lairages should be cared for in accordance withÐas far as possible, established groups of animals shouldbe kept together. Each animal should have enough space tostand up, lie down and turn around. Animals hostile toÐwhere tethers, ties or individual stalls are used theyshould allow animals to stand up and lie down withoutcausing injury or distressÐwhere bedding is provided, it should be maintained in athe animals, and sufÞcient quantity should be used so thatanimals do not become soiled with manureÐanimals should be kept securely in the lairage and careshould be taken to prevent them from escaping and frompredatorsÐsuitable drinking water should be available to theanimals on their arrival and throughout the time theyremain in lairages, unless they are to be slaughteredÐif animals are not to be slaughtered as soon as possible,and at intervals appropriate to the species. Unweanedanimals should be slaughtered as soon as possibleÐin order to prevent heat stress, animals subjected to hightemperatures, particularly pigs and poultry, should beÐthe lairage area should be well lit in order to enable theÐthe condition and health status of the animals in alairage should be inspected at least every morning andevening by a veterinarian or, under the latterÕsresponsibility, by another competent person. Animals thatare sick, weak, injured or showing visible signs of distressshould be treated or killed immediatelyÐlactating dairy animals should be slaughtered as soon aspossible. Dairy animals with obvious udder distensionÐpregnant animals giving birth during the journey or inthe lairage should be slaughtered as soon as possible orprovided with conditions that are appropriate for sucklingand the welfare of the newbornÐanimals with horns or tusks capable of injuring otheranimals, if aggressive, should be penned separately.Recommendations for speciÞc species are described inThe welfare of foetuses during the slaughter of pregnantanimals needs to be safeguarded, as follows:Ðthe foetus must be unconscious before being removedfrom the uterus; to ensure that this is the case they shouldbe removed no sooner that 5 min after the maternal neckor chest cut. A foetal heartbeat will usually still be presentand foetal movements may occur at this stage, but these areonly a cause for concern if the exposed foetus successfullybreathes airÐif a live mature foetus is removed from the uterus, itshould be prevented from inßating its lungs and breathingÐwhen uterine, placental or foetal tissues, includingfoetal blood, are not to be collected as part of the post-slaughter processing of pregnant animals, all foetusesshould be left inside the unopened uterus until they aredead. When uterine, placental or foetal tissues are to becollected, where practical, foetuses should not be removedfrom the uterus until at least 15 min to 20 min after thematernal neck or chest cutÐif there is any doubt about consciousness, the foetusThe above guidelines do not refer to foetal rescue. Foetalrescue, the practice of attempting to revive foetuses foundRev. sci. tech. Off. int. Epiz., Rev. sci. tech. Off. int. Epiz., Table II Animal welfare concernsKey animal welfare /implicationsrequirementsAnimals are grouped together Gas stunningImproper handling and the high Competent animal handlers inPigs, poultryin a containerdensity of animals create stresslairage; facilities; stocking densityAnimals remain in the ÞeldFree bulletInappropriate shooting distance, Operator competenceDeerAnimals are held in a group Electrical stunning Uncontrolled movement of animalsCompetent animal handlers inPigs, sheep, goats,stunning pen(head-only); impedes use of hand operated lairage and at stunning pointcalvescaptive boltelectrical and mechanical stunning Individual animals are conÞned Electrical and Accuracy of stunning method, if theCompetent animal handlers;Cattle, buffalo, shein a stunning pen/boxmechanicalßoor is slippery animals may fall proper design and maintenancegoats, horses, pigs,stunning methodsdown as they are being loadedof ßoorsdeer, camelids, ratitesAnimal is held upright in a halterCaptive bolt; free This method is suitable for halter-Competent animal handlersCattle, buffal/head collar/bridlebullettrained animals but will cause camelidsAnimal is held upright in a neck yokeCaptive bolt; electrical Stress of loading and neck capture;Equipment; competent animalCathead-only stunning; stress of prolonged restraint, hornhandlers; prompt stunning and/free bullet; slaughter conÞguration; less suitable for fast or slaughterwithout stunningline speeds, animals struggling and falling due to slippery ßoor, The animalÕs head is restrained Electrical head-onlyStress of capture and positioningCompetent animal handlerOstrichesin an electrical stunning boxstunningAnimal stands on three legs and Captive bolt; free bulletIneffective control of animalCompetent animal handlersBreeding pigs (bthe other leg is tied in ßexionmovement, misdirected shotsand sows)Three of the four legs are tiedMechanical stunning Stress of resisting restraint;Competent animal handlers.Sheep, goats, smallmethods; slaughter prolonged restraint, animalKeep restraint as short ascamelids, pigswithout stunningtemperament; bruisingpossibleAnimal is restrained using a Electrical head-onlyStress of resisting restraintCompetent animal handlers;Ostrichesmechanical leg clampstunningproper equipment design Animal is held at the beakCaptive bolt; electrical Stress of captureSufÞcient competent animalOstricheshead-only stunninghandlersThe whole body is manually Captive bolt; electricalStress of capture and restraint;Competent animal handlersSheep, goats, calveheld uprighthead-only stunning; accuracy of stunning/slaughterratites, smallslaughter without camelids, poultryThe whole body is held upright Captive bolt; electricalStress of loading of animal;Proper design and operationCattle, calves, busing a mechanical clamp/crushmethods; slaughterexcessive pressure, size mismatchof equipmentsheep, goats, deer,/squeeze/V-restrainer (static)without stunningbetween restrainer and animalpigs, ostrichesAnimal is restrained using Slaughter without Stress of loading of animalCompetent animal handlersCattle, sheep, goats,a mechanical straddle (static)stunning; electrical pigsWing shackling with beak holding Electrical stunningExcessive tension applied priorCompetent animal handlersOstriches(mechanical or manual)to stunningAnimal is restrained using Electrical methods;Stress of loading of animal; sizeCompetent animal handlers;Cattle, calves, sheep,a mechanical straddle/captive bolt; slaughtermismatch between restrainerproper design and layout ofgoats, pigsband restrainer (moving)without stunningand animalrestraintAnimal is mechanically restrainedPresentation of birds Stress and injury due to tipping inProper design and operationChickenson a ßat bed/deck before being for shackling prior todump-module systems; height ofof equipmenttipped out of containers on to electrical stunning; tipping; conscious poultry; broken conveyorsgas stunningbones and dislocationsSpeciÞc purpose Table IV SpeciesRecommended current Broilers120Layers (spent hens)120Turkeys150 Ducks and geese130Waterbaths for poultry should be adequate in size anddepth for the type of bird being slaughtered, and theirbird to be immersed. The electrode immersed in the batha way that when the shackles pass over the water they arein continuous contact with the earthed rubbing bar.The control box for the waterbath stunner shouldincorporate an ammeter, which displays the total currentßowing through the birds.The shackle-to-leg contact should be wetted, preferablybefore the birds are inserted in the shackles. In order toimprove the electrical conductivity of the water it isrecommended that salt be added to the waterbath as necessary.Birds should receive the current for at least 4 s.Using waterbaths, birds are stunned in groups anddifferent birds will have different impedances. The voltageshould be adjusted so that the total current is the requiredcurrent per bird as shown in Table IV, multiplied by thenumber of birds in the waterbath at the same time. The table shows values found to be satisfactory whenemploying a 50 Hz sinusoidal alternating current.While a lower current may also be satisfactory, the currentshall in any case be such as to ensure that unconsciousnessoccurs immediately and lasts until the bird has been killedby cardiac arrest or by bleeding. When higher electricalfrequencies are used, higher currents may be required.Every effort should be made to ensure that no conscious orlive birds enter the scalding tank.stunning and bleeding have been introduced, a manualback-up system should be in place to ensure that any birdsautomatic neck-cutter are immediately stunned and/orhumanely killed, and they are dead before entering theTo lessen the number of unstunned birds reaching neckcutters, steps should be taken to ensure that small birds donot go on the line amongst bigger birds and that thesesmall birds are stunned separately.Stunning of pigs by exposure to carbon dioxideThe concentration of carbon dioxide (COthe animals should be conveyed to the point of maximumconcentration of the gas and be kept there until they aredead or brought into a state of insensibility which lastsuntil death occurs due to bleeding. Ideally, pigs should beconcentration of the gas should be such that it minimisesas far as possible all stress of the animal prior to loss of consciousness.The chamber in which animals are exposed to COequipment used for conveying them through it shall beavoid injury or unnecessary stress to the animals. Theis unnecessary to stack animals on top of each other.allow the animals to see their surroundings and, if possible,each other.It should be possible to inspect the COemergency cases.The chamber should be equipped to continuously measureconcentration at the point of stunningand the time of exposure, and to give a clearly visible andaudible warning if the concentration of COrequired level.Rev. sci. tech. Off. int. Epiz., Table III SpeciesMinimum current levels Cattle1.5Calves1.0Pigs1.25Sheep and goats0.5 Ostriches0.4 Rev. sci. tech. Off. int. Epiz., Table VI Animal welfare Key animal welfare concerns/implicationsrequirementsMechanicalFree bulletInaccurate targeting and Accuracy; head shots only;Cattle, calves, buffalo,Care must be taken notinappropriate ballisticscorrect ballisticsdeer, horses, pigs to endanger the safety(boars and sows)of personnelCaptive bolt Ð Inaccurate targeting;Competent operation andCattle, calves, buffalo,Unsuitable for specimenpenetratingvelocity and diameter maintenance of equipment;sheep, goats, deer, horses,collection from TSEof boltrestraint; accuracypigs, camelids, ratitessuspects. A back-up gun should Captive bolt Ð Inaccurate targeting;Competent operation andCattle, calves, sheep, goats,Presently available devicesnon-penetratingvelocity of bolt; maintenance of equipment;deer, pigs, camelids, ratitesare not recommended forpotentially higher restraint; accuracyyoung bulls and animals withfailure rate than thick skullManual percussive Inaccurate targeting;Competent animal handlers;Young and small mammals,Mechanical devices potentiallyblowinsufÞcient power; sizerestraint; accuracy. Notostriches and poultrymore reliable. Where manual of instrumentrecommended for generalpercussive blow is used,useunconsciousness should beElectricalSplit application:Accidental pre-stun Competent operation andCattle, calves, sheep, goats,Systems involving repeated1. across head electric shocks; wrongmaintenance of equipment;pigs, ratites and poultryapplication of head-only orthen head to chestelectrode positioning; restraint; accuracyhead-to-leg with short current2. across head application of a currentdurations ()then across chestto the body while animal application should not be used.is conscious; inadequate Where cardiac arrest occurs,current and voltagethe carcass may not be suitableSingle application:Accidental pre-stun electricCompetent operation andCattle, calves, sheep, goats,Where cardiac arrest occurs,1. head onlyshocks; inadequate currentmaintenance of equipment;pigs, ratites, poultrythe carcass may not be suitable2. head to bodyand voltage; wrong restraint; accuracyfor Halal3. head to legelectrode positioning; WaterbathRestraint, accidental Competent operation andPoultry onlyWhere cardiac arrest occurs,pre-stun electric shocks; maintenance of equipmentthe carcass may not beinadequate current and suitable for HalalGaseousCOAversiveness of high CO;Concentration; duration ofPigs, poultryGaseous methods may not bemixture; respiratory distress;exposure; design,suitable for Halalinert gas inadequate exposuremaintenance andmixtureoperation of equipment; Inert gasesRecovery of consciousnessConcentration; duration of Pigs, poultryGaseous methods may not beexposure; design, suitable for Halal :carbon dioxideTSE:transmissible spongiform encephalopathySpeciesComment current applied leg to leg is ineffective and unacceptable inany species. The electrocution in this way is likely to bepainful. The animal welfare concerns are:Ðaccidental pre-stun electric shocksÐinadequate current and voltageÐincorrect electrode positioningÐrecovery of consciousness.Slaughtering animals by piercing the eye socket or skullbone in order to sever the brain stem is not acceptable inany species covered in this document.The slaughter of animals for human consumption has beendomestication during prehistoric times. Killing animals,the most brutal act in the relationship between humanfood production cycle. In view of the increasinglyprevailing ethical attitude of society, and its recognitionthat animals are capable of suffering, it has becomenecessary to minimise animal suffering during all stages ofGroup approached its work by assessingthe animal welfare concerns associated with everyprocedure during the commercial pre-slaughter andslaughter processes, reviewing them on the basis of theavailable scientiÞc data, independent of any religious orcultural context, and recognising the necessity to avoidstress during each of the stages preceding the death of anmoving, restraining, stunning and bleeding. The Group considered the specific issues associated withcommercial slaughter without stunning, acknowledgingthe signiÞcance of religious requirements and the ritual,cultural and ethnic factors associated with some forms ofcommercial slaughter. It was felt that these should not betreated as exempt from the proposed guidelines, which areintended to provide a framework within which variationsto certain steps in the process may be practised to improveanimal welfare or at least not to compromise it. Thismodifying the way in which restrainers and stunners arestressed, and ensuring that appropriate knives and precisecutting methods are used.The meat industry and other related animal industriesneed to continuously strive to improve their methods andsystems by using the available know-how and technology.desirable animal welfare goals within the commercialslaughter processes. These guidelines are regarded asvoluntary, and not meant to be mandatory standards.However, it is expected that OIE Member Countries willincorporate these guidelines into their standards, enactrelevant regulations, and implement the guidelines.Relevant authorities in Member Countries are alsoexpected to communicate and consult effectively withwhere applicable, to religious, cultural and ethnicrequirements. The guidelines will enable MemberCountries to review and consider updating their respectivenational animal slaughter regulations. The Þnal animalwelfare outcome depends upon the commitment of allstakeholders involved, including producers, marketers,supervised by regulators, veterinarians and other relatedexpert professionals.Group, TempleGrandin, Neville Gregory, David Mellor and Mohan Raj,have actively participated in the preparation of this paperThe authors, on behalf of the members of the Groupwish to express their gratitude to the staff of the OIE, andespecially to the International Trade Department, headedby Dr David Wilson, for the excellent support and valuableadvice which were provided during all stages of the groupÕsactivity Ð before, during and between their meetings. Rev. sci. tech. Off. int. Epiz., SacriÞcio de animales para el consumo humano Tras describir sucintamente la formaci—n del Grupo (Organizaci—n Mundial de Sanidad Animal) sobre el ÒSacriÞcio de los animalesen condiciones decentesÓ, los autores resumen las primeras discusiones quemantuvo ese grupo y exponen con cierto detalle sus recomendaciones, que elComitŽ Internacional de la OIE aprob— en su 73» Sesi—n General y han sidoTerrestres. Entre las recomendaciones Þguran la de modiÞcar la deÞnici—ncomercial de animales para el consumo humano, pensadas para reducir alprincipios generales del sacriÞcio, relativos al personal, el comportamiento delos animales y la eliminaci—n de elementos que puedan distraer al animal y hacerque se detenga o revuelva; desplazamiento y manipulaci—n de los animales trassu llegada al matadero; dise–o y construcci—n de locales de estabulaci—n;cuidado de los animales en esos locales; y cuestiones de bienestar animalrelacionadas con mŽtodos aceptables de manipulaci—n, sujeci—n, aturdimiento ysacriÞcio que puedan aplicarse a varias especies œtiles. El Grupo reconoci— laligados al sacriÞcio, por lo que en su informe Þnal incluy— las oportunasde relevancia, aunque se planteen m‡s rara vez, como la manipulaci—n de losfetos al sacriÞcar hembras gr‡vidas. Por œltimo, en el informe Þnal tambiŽn seindican los mŽtodos, procedimientos y usos que resultan inaceptables por susconsecuencias para el bienestar de los animales. Aturdimiento Ð Bienestar Ð Feto Ð Matadero Ð Proceso previo al sacriÞcio Ð Religioso ÐSacriÞcio Ð SacriÞcio en condiciones decentes Ð Sujeci—n Ð Tratamiento. 1.Bager F., Devine C.E. & Gilbert K.V. (1988). Ð Jugular bloodßow in calves after head-only electrical stunning and throat-2.Chaudry M. (2004). Ð Slaughter of animals for humanGlobal Conference on animal welfare: anOIE initiative, 23-25 February. Appendix III. WorldOrganisation for Animal Health, Paris, 321-322.3.Cortesi M.L. (1994). Ð Slaughterhouses and humanetreatment. Animal welfare and Veterinary Services Rev. sci. tech. Off. int. Epiz.4.Dunn C.S. (1990). Ð Stress reactions of cattle undergoingritual slaughter using two methods of restraint. Vet. Rec.5.Grandin T. (1998). Ð Objective scoring of animal handling6.Grandin T. (2001). Ð Welfare of cattle during slaughter andthe prevention of nonambulatory (downer) cattle. Rev. sci. tech. Off. int. Epiz.,