By: Dr.Temple Grandin
Department of Animal Sciences
Colorado State University
Fort Collins, Colorado 80523, U.S.A.
Another problem is pigs and cattle from excitable genetic lines which are more likely to become agitated during handling To maintain a high standard of welfare, all five problem areas must be addressed. A survey of 29 Canadian slaughter plants indicated that 27% had excellent non-slip floors and 21% had slick floors which would cause animals to slip. Twenty-four percent had high pitched motor noise or hissing air exhausts that caused animals to balk. Air drafts blowing down the race toward approaching animals were a problem in 9% of the plants. Air drafts will often impede animal movement.
To correct an animal welfare problem, one has to determine the cause of it. For example, installation of new stunning equipment will not solve an abuse problem caused by untrained, poorly supervised employees or animal agitation caused by air hissing. This paper will review both the scientific literature and the author's observations in over 200 slaughter plants in the United States, Canada, Mexico, Europe, Australia and New Zealand. Surveys were conducted in plants in the U.S. and Canada to determine the incidence of distractions and equipment problems that impeded animal movement or caused animals to become excited. In the last section, the economic benefits of good animal welfare and public concerns will be covered.
Carbon dioxide stunning is used for stunning pigs in many countries. There have been welfare concerns about CO2 because it is a pungent gas which is irritating to the respiratory tract (Gregory, 1994). Hoenderken (1982) reported that a motorific excitation phase occurs while the pig is still conscious. Forslid (1987) found that the excitation phase starts after the pig is unconscious in purebred Yorkshires. There is a large variation in a pig's reaction to CO2 (Dodman, 1977; Grandin, 1988a). The reaction ranges from none when the pigs first sniff the gas, to violent attempts to escape. Halothane-positive pigs have more excitation (Troeger and Waltersdorf, 1991). Carbon dioxide stunning may be a good method for certain genetic types of pigs and very stressful to others.
Click Here for more information on stunning.
In the U.S., large stunning boxes which held more than one bovine have been replaced with conveyor restrainers. The V conveyor restrainer was introduced for cattle in the 1970s (Schmidt, 1972; Willems and Markley, 1972). It was replaced in the l990's with the center track double rail restrainer (Giger et al., 1977; Grandin, 1988b; 1991). Cattle and sheep will remain calm in conveyors because they are touching the animal in front and back of them. V conveyors work less well for pigs. The author has observed that slender, lean pigs are not supported properly and heavily muscled pigs are pinched on the hams, whereas round, fat pigs are held in a comfortable position. Lean pigs are properly supported on a center track restrainer.
In England, head restraint devices are required by legislation to hold a bovine's head for captive bolt stunning. The purpose of the legislation was to improve stunning accuracy. In some circumstances, head restraint can increase stress. Ewbank et al. (1992) found that cortisol levels were higher in a head restraint compared to a conventional single animal stunning box. It took an average of 32 seconds to induce the cattle to put their heads in the poorly designed yoke used in this study. Stress can be minimal in a well designed head restraint where the animal is stunned immediately after the head is caught (Tume and Shaw, 1992; Frank Shaw, personal communication). The author has observed electrical stunning of cattle in a head restraint in New Zealand. Each animal quietly entered the stunning box and was stunned within 2 seconds after the head was clamped. Information on the design of head restraint devices can be found in CSIRO (1989) and Grandin (1993; 1994). Stress caused by prolonged restraint will be a severe problem if live animals are subjected to intravenous injections shortly prior to slaughter. Payne and Young (1995) report that intravenous injections of lambs with antifreeze glycoproteins may improve the quality of frozen meat.
Design mistakes in races and forcing pens will cause stress. One of the most serious design mistakes is laying the race out so that its entrance appears to be a dead end. Cattle will move more easily through a curved race compared to a straight race, but it must be laid out correctly (Grandin, 1980; 1990; 1993). Practical experience has shown that an animal standing in the forcing pen must be able to see a minimum of two to three body lengths up the single file race before it curves. Bending the single file race too sharply where it joins the forcing pen will cause animals to balk.
Warris et al., (1994) found that pigs were more stressed in abattoirs with single file races compared to plants where pigs were stunned in small groups on the floor. The intensity of squealing was highly correlated with physiological stress measurements and PSE. Electrical stunning of pigs on the floor is most practical for abattoirs that slaughter under 240 pigs per hour. The author has observed that floor stunning often becomes rough and sloppy at higher speeds. In larger plants, a well designed race will produce less stress than a poor one. Weeding et al., (1993) found that both design and staff expertise affected stress levels in pigs.
Stress caused by forcing pigs to move through a single file race could be eliminated by stunning groups of pigs in CO2 gas. Barton Gade et al., (1993) has developed a low stress driving and lairage system for moving groups of five pigs onto an elevator which descends into CO2 gas. An entire system approach should be used for evaluating CO2 stunning. Some discomfort during the induction of anesthesia may be a small price to pay for great reductions in handling stress.
|Type of distraction||Acceptable,
|Lighting problems (too dim or too bright)||28 (85%)||5 (15%)|
|Ventilation air blowing towards approaching animals||30 (91%)||3 ( 9%)|
|Seeing movement or sparking reflections||25 (76%)||8 (24%)|
|High pitched motor noise or hissing air exhausts||25 (76%)||8(24%)|
These distractions will ruin the performance of well designed restrainers and races because animals often have to be prodded when they refuse to move. Sometimes, adding more light or moving a light to eliminate sparkling reflections on floors or walls will improve the movement of pigs or cattle. In two plants a new double rail conveyor system worked well when the plant was new, but balking at the restrainer entrance gradually worsened as the lamps over the restrainer grew dimmer with age. Animals have a tendency to move from a darker place to a more brightly illuminated place (Grandin, 1980; Van Putten and Elshoff, 1978). The light must not shine directly in the eyes of approaching animals.
Air blowing through a stunning box entrance or down a race will make both pigs and cattle stop. Nine percent of the surveyed plants had serious balking problems caused by ventilation blowing air either out the entrance of the stunning area or down a race . Seeing people moving up ahead or jiggling gates will also impede livestock movement. In one plant, cattle balked at a small chain jiggling in the race and in another, cattle balked at a shiny reflection on a vibrating metal wall. When animals are calm, they will stop and look directly at things that make them balk.
In 24% of the plants visited, animals became visibly frightened by sudden air hissing noises or extremely high pitched noises. Observations by the author indicate that high pitched noise causes more agitation than a low pitched rumble of chains and gears . The ears of cattle are most sensitive at 8,000 Hz (Ames, 1974) and they can hear up to 21,000 Hz (Algers, 1984). Clanging and banging noises will make animals flinch or jump. Sheep slaughtered in a noisy commercial abattoir had higher cortisol levels than sheep slaughtered in a quiet research abattoir (Pearson et al., 1977). Sudden noise of a door slamming and banging on a wall increased heart rate in deer (Price et al., 1993). In the eight plants that had balking caused by noise, five were due to air hissing and three were due to high pitched motor noise. At one plant, elimination of a high pitched hydraulic whine resulted in calmer cattle. Stunning box entrance doors had hissing air in three plants. In one plant, installation silencers to stop hissing air resulted in a dramatic reduction of excited cattle. Other distractions which can impede movement are shadows, drain grates and changes of fencing or flooring types.
The author has observed that the most common mistake made by employees is attempting to move too many animals at a time. For all species, forcing pens should not be filled more than three-quarters full. Employees should also be taught how to time bunches of animals. The next bunch should not be driven into the forcing pen until there is space in the race for them to walk into. This procedure utilizes natural following behavior. Most important is that employees need to remain calm and avoid sudden, jerky motions or yelling. Electric prods should be used as little as possible.
|Number of slaughter systems||Percentage||Flooring condition|
|8||(27%)||Excellent, non-slip floor|
|6||(21%)||Slick floor, not acceptable|
The majority of slippery floor problems were due to either the rough finish wearing off a concrete floor, or a slick floor in a cattle stunning box. The author has conducted welfare surveys in plants in both the U.S. and Canada. Slick floors which caused animals to fall down was the number one equipment problem. Cockrum, Corley (1991) found that slipping increased stress and also noted that it is a problem area. The author has observed that the second most common equipment maintenance problem in U.S. plants is poor maintenance of pneumatic captive bolt stunner. Stunners require careful maintenance to maintain maximum hitting power.
Dunn (1990) found that investing cattle onto their backs for 103 seconds caused the cortisol levels to be twice as high compared to cattle held in an upright restraint device. The use of devices that hold cattle in an upright position is now required in the United Kingdom. The author has observed that proper design and gentle operation of upright restraint devices can eliminate visible signs of animal discomfort, such as struggling. The restrainer must be equipped with pressure limiting valves to prevent excessive pressure that would cause pain or discomfort from being applied to the animal's body (Grandin, 1994a). Parts of the apparatus which press against the animal should move slowly, because sudden, jerky motion tends to excite the animal. The throat cut should be made immediately after the head is restrained.
The animal's reaction to the throat cut can be observed when the animal is held in a comfortable, upright position. Most researchers agree that cutting the throat without stunning does not induce instantaneous unconsciousness (Daly et al., 1988; Blackmore, 1984). In some cases, consciousness in calves can last for over a minute (Blackmore, 1984). Occlusion of the blood vessels will sometimes delay the drop in blood pressure which is required to induce unconsciousness (Anil et al., 1995a).
Cattle have very little behavioral reaction to a correctly made kosher cut (shechitah) done with a razor-sharp long knife (Grandin, 1994a). Bager et al., (1984) made a similar observation. Behavioral observations and measurements are a major method of pain assessment (Short and Poznak, 1992). Halal slaughter done with hacking cuts with a short knife resulted in vigorous struggling and obvious distress (Grandin, 1994a). Allowing the incision to close back over the knife during the cut caused the animal to struggle, and excited cattle took longer to collapse. One can conclude that a correctly done cut is much less distressful than a poorly done cut.
Head-only electrical stunning is used in many halal slaughter plants on both sheep and cattle. Due to differences in the anatomy of the blood vessels in sheep compared to cattle, head only stunning of cattle must be followed by a chest sticking method to ensure rapid loss of blood pressure (Anil et al., l995b). Minimizing stress and discomfort during ritual slaughter requires a skilled slaughterman and a well designed restraint device which holds the animal in a comfortable, upright position.
Ames,D.R. (1974) Sound stress and meat animals. Proceedings: International Livestock Environmental
American Society of Agricultural Engineers
St.Joseph,Michigan (page 324).
Anil,M.H. & McKinstry,J.H. (1995) Program British Society of Animal Scientists. Winter Meeting Paper. 190.
Anil,M.H., McKinstry,J.L., Wotton,S.B. & Gregory,N.G. (1995a). Meat Science 41: 101-112.
Anil,M.H., McKisntry,J.L., Gregory,N.G., Wotton,S.B. & Symonds,H. (1995b). Meat Science 41: 113-123.
Bager,F., Braggins,T.J., Devine,C.F. et al. (1992). Resource Veterinary Science 52: 162.
Barton-Gade,P., Blaabjerg & Christensen,L. (1993). Meat Focus 2: 115.
Blackmore, D. K. (1984) Differences between sheep and cattle during slaughter. Resource Veterinary Science 37: 223-226.
Blackshaw,J.K., Blackshaw,A.W. & Kusano,T. (1987). Australian Journal of Experimental Agriculture 27: 753.
Calkins,C.R., Davis,G.W., Cole,A.B. & Hustsell,D.A. (1980). Incidence of bloodsplashed hams from hogs subjected to certain ante-mortem handling methods. Journal of Animal Science 50: (Supplement 1) 15 (Abstract).
Cockrum, M.S. & Corley, K.T.T. (1991). Effect of pre-slaughter handling on the behaviour and blood composition of beef cattle.British Veterinary Journal 147: 444-454.
Colorado State University (1992) National Beef Quality Audit. National Cattlemen's Association, Englewood, Colorado, USA.
Colorado State University (1995) National Non-Fed Beef Quality Audit. National Cattlemen's Association, Englewood, Colorado, USA.
Cook, C. J., Devine, C. E. & Gilbert, K. V. (1991). Electroencephalograms and electrocardiograms in young bulls following upper cervical vertebrae to brisket stunning. New Zealand Veterinary Journal 39: 121-125.
CSIRO (1989) Head capture unit. Meat Science Meat Resource Newsletter, CSIRO Cannon Hill, Brisbane, Australia.
Daly,C.C., Kallweit,E. & Ellendorf,F. (1988). Conventional captive bolt stunning followed by exsanguination compared to shechitah slaughter. Veterinary Record 122: 325-329.
Dodman,N.H. (1977) Observations on the use of the Wernberg dip-lift carbon dioxide apparatus for pre-slaughter anesthesia of pigs. British Veterinary Journal. 133:71-80.
Dunn,C.S. (1990) Stress reations of cattle undergoing ritual slaughter using two methods of restraint. Veterinary Record. 126:522.
Eikelenboom,G. (editor) 1983. Stunning of Animals for Slaughter. Martinus-Nijhoff, The Hague.
Ewbank,R., Parker,M.J. & Mason,C.W. (1992). Reations of cattle to head restraint at stunning: a practical dilemma. Animal Welfare 1: 55-63.
Forslid,A. (1987). Transient neocortical, hippocampal and amygdaloid EEG silence by one minute inhalation of high concentrations of CO2 in swine. Acta Physiol Scand 130: 1.
Giger,W., Prince,R.P., Westervelt,R.G. and Kinsman,D.M.(1977). Equipment for low stress small animal slaughter. Trans American Society of Agricultural Engineers. 20:571.
Grandin,T. (1980). Observations of cattle behaviour applied to the design of cattle handling facilities. Applied Animal Behavioural Science. 6:19.
Grandin,T. (1985/86). Cardiac arrest stunning of livestock and poultry. In: Advances in Animal Welfare Science (edited by M.W.Fox & L.D.Mickley). Martinus Nijhoff, The Hague.
Grandin,T. (1988a). Possible genetic effect in pig's reation to CO2 stunning. Proceedings: 34th International Conference, Meat Science Technologies. 23.
Grandin,T. (1988b). Double rail restrainer for livestock handling. Journal of Agricultural Engineers Resource. 41:327-338.
Grandin,T. (1988c). Behavior of slaughter plant and auction employees towards animals. Anthrozoos. 1: 205-213.
Grandin,T. (1990). Design of loading facilities and loading pens. Applied Animal Behavioural Science. 28:187-201.
Grandin,T.(1991). Double rail restrainer for handling beef cattle. American Society of Agricultural Engineers, Paper Number 91-5004. St. Joseph, Michigan.
Grandin,T. (1992). Enviornmental and genetic factors which contribute to handling problems in pork slaughter plants. In: Livestock Environment IV (edited by E.Collins). American Society of Agricultural Engineers. St. Joseph, Michigan USA (page 64).
Grandin,T. (1993). Behavioural principles of cattle handling under extensive conditions. In: Livestock Handling and Transport (edited by T. Grandin). CAB, International Oxon United Kingdom (43).
Grandin,T. (1994a). Farm animal welfare during handling, transport, and slaughter. Journal of American Veterinary Medical Association. 204: 372-377.
Grandin,T. (1994b). Veterinary Medicine (October 1989).
Grandin,T. & Regenstein,J.M. (1994). Religious slaughter: a discussion for animal scientists. Meat Focus 3: 115-123.
Gregory, N.G. (1994). Meat Science. 36:45.
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. (1982) Electrical and carbon dioxide stunning of pigs for slaughter. In: Stunning Animals for Slaughter (edited by G.Eikelenboom). Martinus Nijhoff, The Hague.
Hornbuckle,P.A. & Beall,T. (1974). Behavioural Biology. 12:573.
Kilgour,R. (1978) The application of animal behaviour and the humane care of farm animals. Journal of Animal Science. 46: 1478-1476.
Kilgour,R. & Dalton (1984). Livestock Behaviour: A Practical Guide. Granada, Herts, United Kingdom.
Leach,T.M. (1985) In: Developments in Meat Science. (edited by R. Lawrie) Elsevier, Amsterdam .
National Pork Producers Council (1994). Pork Chain Quality Audit. Des Moines, Iowa, USA.
Payne,S.R. & Young,O.A. (1995). Meat Science. 41:147-155.
Pearson,A.J., Kilgour,R., deLangen,H. & Payne,E. (1977). Hormonal responses of lambs to trucking, handling and electric stunning. New Zealand Society of Animal Producers. 37:243-248.
Price,S., Sibley,R.M. & Davies,M.H.(1993). Applied Animal Behavioral Science. 37:111.
Schmidt,C.O.(1972). Cattle handling apparatus. U.S. Patent No. 3657,76.
Short,C.E. & Poznak,A.V.(1992). Animal Pai. Churchill Livingstone, London.
Stevens,D.A. & Gerzog-Thomas,D.A.(1977). Fright reations in rats to conspecific tissue. Physiology of Behavior. 18:47-51.
Stevens,D.A. & Saplikoski (1973). Rats' reations to conspecific muscle and blood evidence for alarm substances. Behavioral Biology. 8:75-82.
Troeger,K. & Waltersdorf, W.(1991). Gas anesesthesia of slaughter pigs. Fleischwirtsch International 4:43-49.
Tume,R.K. & Shaw,F.D.(1992). Beta-endorphine and cortisol concentrations in plasma of blood samples collected during exsanguination of cattle. Meat Science 31: 211-217.
Van Putten,G. & Elshof,W.J.(1978). Observations on the effect of transport on
the well being and lean quality of pigs. Animal Regulatory Studies. 1:247-271. Vieville-Thomas,C. & Signoiet,J.P.(1992). Journal of Chemical Endocrinology 18, 1551.
Warrington, P.D.(1974) Electrical stunning: A review of the literature. Veterinary Record 44: 617-633.
Warris,P.D., Brown,S.N. & Adams,S.J.M.(1994) Relationship between subjective and objective assesments of stress at slaughter and meat quality. Meat Science 38:329-340.
Weeding,C.M., Hunter,E.J., Guise,H.J. & Penny,R.H.C.(1993). Veterinary Record 133: 10.
Willems,D. and Markey,E.F.(1972). Animal shackling device. U.S. Patent No. 3,693,216.
Click here to return to the Homepage for more information on animal behavior, welfare, and care.
Click Here to look at data form more recent surveys.
Click Here for slaughter welfare audit information.