A total of 19 Federally inspected pork plants were audited in 8 different states. Seventeen out of 19 plants (89%) induced instant insensibility in 100% of the pigs. Pig handling has greatly improved and this was reflected by less squealing. This fact made it possible to develop a new scoring system for objective scoring of the amount of squealing. This was not possible in 1996 because pigs squealed continuously in most plants. Eleven plants were evaluated with the new system and eight out of 11 plants (72%) had either acceptable or excellent scores. Compared to 1996 there is one major problem area. In some plants, there were greater numbers of heavy weight pigs from excitable genetic lines which had a higher incidence of "stressor" pigs which became non-ambulatory. Some producers are starting to correct this problem. This problem must be corrected through selective breeding. Overall throughout the meat industry handling and stunning has greatly improved compared to survey data collected in 1996.
Good handling also has economic benefits. Practical experience in many pork plants has shown that reducing electric prod use and quiet handling in the stunning chute reduces PSE about 10%. PSE is a serious quality defect. Quiet careful handling of cattle will significantly reduce bruising (Grandin, 1981). Other benefits of the improved cattle handling are safer working conditions and prevention of loss of production caused by agitated cattle.
The 1996 survey done for the USDA (Grandin, 1997a, 1998a) was used as the basis for developing objective scoring guidelines for the American Meat Institute (Grandin, 1997b). The data contained in these 1999 audits has verified that the American Meat Institute scoring system is practical and can be easily implemented in the field to assess animal handling and stunning in beef plants. However, the pork scoring system has have been more difficult to implement. Data collected during the 1999 audits has now been used to develop a more practical way to score pig handling.
The 1999 audits of animal handling cover more than half of the medium sized and large beef and pork plants in the U.S. This sample is very representative of U.S. beef and pork plants. The McDonald's Corporation has been a leader in improving both food safety and animal welfare. I have been working with them to develop auditing procedures and to train their HACCP food safety team. One goal of the 1999 audits is to identify "Best Practices" which can be used throughout the industry. Many plants had greatly reduced electric prod use and replaced many of the electric prods with other driving aids such as flags, plastic bags and plastic paddle sticks. Large 30 in x 30 in flags made from plasticized tarp cloth were a major innovation for moving pigs. Other "Best Practices" were ergonomic handles on pneumatic stunners and the use of spot lights to improve animal movement into restrainers. In several plants a rack was built to hold cartridge fired stunners. This rack facilitated rotation of the stunners to prevent them from getting overheated. Overheated stunners are less effective. For both pigs and cattle, filling the crowd pen and staging areas half full greatly improves handling. The good news is that these changes did not require expensive plant renovations to enable a plant to obtain an acceptable score for animal handling and stunning. In beef, only 2 plants (5%) had to make major renovations to their handling systems. In pork plants, no major renovations were needed.
New methods were developed for evaluating squealing in pigs as a measure of the quality of handling. They will be described later in this paper. In some beef and pork plants, electric prod use was scored. Vocalization was used as the primary method for evaluating handling because it is easier to score and it is a sensitive indicator of animal stress and discomfort (Grandin, 1998b; Dunn, 1990; Warris et al., 1994; White et al., 1995; Watts and Stookey, 1998; Weary, 1998). All scoring methods have been designed to be simple to use in the field. Stunning, vocalization and insensibility are scored on a yes/no basis to help remove subjectivity. For example, a steer either vocalizes (moos or bellows) or he does not. The vocalization score is the percentage of cattle that vocalize during stunning and handling in the chutes. Vocalization of cattle standing undisturbed in the yards is not scored.
The audits were done by either the author or a member of the McDonald's HACCP team which had been trained by the author. The author collected data in approximately half of the plants. On the tables, plant numbers cannot be compared between tables. They are scrambled for confidentiality reasons. Line speeds were rounded off to the nearest interval of 10 to insure confidentiality.
One of the biggest concerns is attempting to stun 380-390 cattle per hour with one person. All plants operating at 380-390 per hour with two people using cartridge-fired stunners were able to stun 95% or more of the cattle with a single shot. Plants with line speeds of 333 or less per hour were able to achieve the 95% or better level with one operator when they used a pneumatic stunner equipped with an ergonomic handle. This handle prevented twisting strain on the operator's wrists. The pneumatic stunner was suspended on the balancer at a 30-degree angle to facilitate stunning in a conveyor restrainer. The handle was mounted on the back of the stunner housing and it enabled the operator to position the stunner by using a sideways swinging motion. This sideways motion replaced a wrist twisting motion.
One plant had a pneumatic stunner with a worn cylinder bore which no longer provided sufficient compression. When an animal was shot correctly it was not always rendered completely insensible. Even though the stunner was well maintained, the cylinder was too worn to provide sufficient hitting force to render an animal instantly insensible. There is a point where a pneumatic stunner must be discarded. The plant was not tabulated in the audit data because the author was called to help them fix problems prior to the audit. Shortly after my visit they purchased a new pneumatic stunner. A few months later they were audited and they were able to render 100% of the cattle insensible before hoisting to the bleed rail.
The makers of cartridge fired stunners have developed a test stand to determine hitting force. There is a need for a similar test stand for pneumatic stunners. Hitting force measurements obtained on a test stand could be used to determine when a pneumatic stunner should be replaced.
The data was then tabulated to determine if there was a difference between cow plants and fed beef plants (Table 4). Eighty-five percent of the fed beef plants and 57% of the cow plants had vocalization percentages of 3% or less. Table 5 shows the causes of elevated vocalization percentages of greater than 3% of the animals in 12 cow and fed beef plants. In six plants (14%) of the total sample excessive electric prod use due to balking was the major cause of elevated vocalization percentages. Two plants had 17% and 12% vocalization percentages that were caused by excessive electric prod use due to balking.
In two plants cattle balked at seeing movement or cattle feet under the stun box door. In two other plants cattle balked at seeing a steep drop off under a conveyor restrainer. This is easily fixed by installing a false floor (Grandin 1996, 1997a). In an Australian plant which was not tabulated with U.S. data, a 9% vocalization percentage was reduced to 0% by installing a false floor below the restrainer to reduce balking. Lack of proper lighting at the restrainer entrance, airhissing, flapping plastic strips or seeing movement up ahead caused balking in two other plants.
During one test an 8% vocalization percentage due to balking and electric prod use was reduced to 0% by installing a light at the restrainer entrance. For more information on eliminating distractions that cause balking refer to the reference list. Sharp edges on worn and broken restraint equipment caused vocalizations in two plants. In one plant (2%) an excessively charged electric prod caused 7% of the cattle to vocalize. Reducing prod voltage reduced vocalization to 2%. Animals should never be left alone waiting in a stun box or alley. In three small plants with line speeds under 50 per hour isolated lone animals left alone in the stun box or alley were the cause of vocalization percentages of 4%, 6% and 4%.
In 18 plants it was possible to obtain fairly accurate electric prod use scores because the prod was only picked up when needed to move balking animals or it was used on almost every animal due to constant balking. These plants fell into two distinct groups - plants with balking problems and plants where cattle moved easily with a minimum of electric prod use. Most beef plants have eliminated electric prods in the crowd pen leading to the single file chute and electric prod use was mainly confined to the entrance of the stunning box or restrainer. Eleven plants out of 17 (64%) had electric prod usages of 5% or less of the cattle and four plants (24%) used an electric prod on more than 25% of the cattle. Table 6 shows electric prod use percentages for 17 plants. Data collected on electric prod usage clearly indicates that a beef plant can easily attain an electric prod use percentage of 5% or less.
In the 1999 audits, most plants were scored on both electric stunning wand placement and the percentage of pigs that squealed when the stunning wand was applied. Correct placement of the stunning wand is essential to insure that the electric current passes through the brain, A pig will squeal when the stunner is applied if the wand is energized before it contacts the pig's head. When the wand is applied correctly, the pig will remain silent. Table 7 shows data for 14 plants on the percentage of pigs that squealed when the stunning wand was applied. Squealing during stunning is detrimental to animal welfare because it indicates that the pig felt the shock prior to being rendered insensible. Pigs which remain silent during stunning are instantly rendered insensible and probably feel absolutely nothing. See reference lists in Grandin 1997a, 1994 and Gregory and Grandin 1998.
Measuring squealing was used to assess handling in the pork plants. Squealing is an indicator of pig distress and stress (Warris et al., 1994; White et al., 1995 and Weary et al., 1998). In 1996 squeal scoring was almost impossible because handling was so poor that pigs squealed almost 100% of the time in response to being driven through alleys, chutes and restrainers.
Handling of pigs in many plants has improved since the 1996 USDA survey and it became possible to develop an easy to use squeal scoring system. Many plants have replaced electric prods with other driving tools such as large plastic flags or rattle paddles. Table 9 shows data from 11 pork plants where handling was scored with the new method. The method is very simple and it makes it possible to make rough comparisons between different plants, without the use of specialized equipment. A sound meter works well for measuring squealing within a plant but readings are greatly affected by building materials and machinery noise. A simple decibel meter cannot be used for squeal score comparisons between different plants.
The person scoring squealing during handling stands near the restrainer entrance and enters data as each pig is stunned. One hundred pigs are scored with a yes/no scoring system. As each pig is stunned data is entered for "heard a squeal" or "room quiet." The entire stunning room which consists of the restrainer, chutes (races) and crowd pen is scored. Each stunning cycle serves as a timer for scoring. The system is very objective and simple because no attempt is made to score squeal intensity. The smallest squeal is marked as "squeal." On a CO2 stunning system, data is entered after each gondola is filled. Squealing caused by application of the stunner is not scored because it is scored when stunning is evaluated. Squeals in the restrainer which are not caused by application of the stunner are scored for the handling assessment.
Four plants out of 11(36%) had excellent handling and the room was quiet over 30% of the time (Table 8). Three plants (27%) had poor scores where pigs were squealing 94% to 96% of the time. Excessive electric prod use was the cause of excessive squealing in two plants.
Some plants are installed two restrainers and chute systems so that 1200 pigs per hour can be reduced to 600 per hour. If these two systems are in the same room it is not possible to determine which chute or crowd pen a squeal came from. Score the entire room and convert the score by taking the percentage of time the pigs are quiet and doubling it.
For plants with one restrainer and chute system no conversion is needed. Example 87% of time squeal remains 87%
Score a minimum of 100 pigs for stunning and a separate group of 100 pigs for squealing during handling. Two separate groups must be scored to avoid mixing up "hot wands" with squealing caused by electric prods and handling problems. In CO2 systems, squealing caused by electric prods or handling problems must be separated from squealing caused by a pig's reaction to the gas.
Calculation of Scores - A plant automatically FAILS if a pig showing any sign of sensibility is observed on the bleed rail. A separate stunning score and squeal score during handling is tabulated. The two scores are combined to determine an overall stunning and handling audit score. The scoring system is explained below.
Stunning - Subtract one point off for each misplaced wand and for every pig which squeals when the wand is applied, to obtain a combined stunning score. Score a minimum of lOO pigs. If the same pig both squeals and the wand is placed in the wrong position, take 2 points off.
|100 to 99||Excellent||0 to 1 point off|
|98 to 97||Acceptable||3 points off|
|96 to 95||Not Acceptable||5 points off|
|Below 95||Serious Problem||10 points off|
Squealing during handling - Calculate percentage of stunning cycles that pigs were squealing. The smallest little squeals are recorded.
|70% or less of the time squealing||Excellent||0 points off|
|85% to 71% of the time squealing||Acceptable||2 points off|
|86% to 95% of the time squealing||Not Acceptable||5 points off|
|over 95% of the time squealing||Serious Problem||10 points off|
If a one number overall audit score is desired, it can be calculated by subtracting points from 100. The points off for the stunning score and squeal score are subtracted. This system is designed to equally weight stunning and handling. The stunning score and the handling score are combined to form an overall audit score for stunning and handling.
|Excellent||98 to 100|
|Acceptable||95 to 97|
|Not Acceptable||94 to 90|
|Serious Problem||Below 90|
In a second beef plant, emaciated, downers had been tagged with USDA "suspect" tags which would allow them onto the slaughter floor. These cattle should have been condemned at ante-mortem inspection, which would have prevented them from being allowed inside the plant? They were emaciated and covered completely with manure. They were no longer able to lie in sternal recumbency or raise their heads. Inspectors in most other plants would have condemned these cattle. There is a need for objective guidelines for ante-mortem condemnation for USDA field personnel. They need better training so that standards are more uniform. USDA personnel working in the field need guidelines and several have told the author that they receive little or no information. Good training materials are available but they are not getting out to people in the plants.
Producers should bring in animals when they are still fit. Emaciated cattle which are too weak to raise their heads should be euthanized on the farm. Producers will stop bringing in emaciated downers if they were euthanized by plant employees before unloading from the truck or condemned by the USDA. I recommend that plant management should make sure that emaciated downers are humanely euthanized with a captive bolt as soon as the trucks pull up to the unloading dock. For both welfare and food safety reasons, these cattle should be condemned for human consumption.
Acknowledgements - The author wishes to thank the McDonald's Corporation and all the members of the supplier HACCP teams who participated in doing the audits. The efforts of the entire team have brought about significant improvements in animal welfare.
Grandin, T. 2000. Livestock Handling and Transport, Edition, CAB International Wallingford, Oxon, K (In Press).
Grandin T. 1998a. Objective scoring of animal handling and stunning practices in slaughter plants. J. Amer. Vet. Med. Assoc. 212:36-39.
Grandin, T. 1998b. Feasibility of using vocalization scoring as an indicator of poor welfare during slaughter, Applied Animal Behavior Science, 56:121-128.
Grandin T. 1997a. Survey of Handling and Stunning in Federally Inspected Beef, Pork, Veal and Sheep Slaughter Plants. ARS Research Project No.3602-32000-002-08G, USDA.
Grandin, T. 1997b. Good Management Practices for Animal Handling and Stunning, American Meat Institute, Washington, D.C.
Grandin T. 1994. Euthanasia and slaughter of livestock, J. of American Veterinary Medical Assoc. 204:1354-1360.
Grandin, T. 1996. Factors that impede animal movement at slaughter plants. J. American Veterinary Medical Assoc. 209:757-759.
Grandin T. - grandin.com. Source of additional information on handling and stunning.
Gregory, N. G. and Grandin, T. 1998. Animal Welfare and Meat Science, CAB International Warnngford, Oxon, UK.
Humane Slaughter Act of 1978. Public Law 95-445-October 10, 1978. Federal Meat Inspection Regulations part 313, Humane Slaughter of Livestock, Section 313.2.
Warris, P. D., Brown, S. N. and Adams, S. J. M. 1994. Relationship between subjective and objective assessment of stress at slaughter and meat quality in pigs. Meat Science 38:329-340.
Watts. J. M. and Stookey, J. M. 1998. Effects of restraint and branding on rates and acoustic parameters of vocalization in beef cattle. Applied Animal Behaviour Science 62:125-135.
Weary, D. M., Braithwaite, L. A. and Fraser, D. 1998. Vocal response to pain in piglets. Applied Animal Behavior Science 56:161-172.
White, R. G., DeShazer, J. A. and Trassler, C. J. et al. 1995. Vocalizations and physiological response of pigs during castration with and without anesthetic. J. Animal Science, 73:381-386.
|Percent stunned with one shot||Number of plants||Percentage of plants||Line speed range|
|15||37%||5 to 390/hr|
|22||53%||29 to 390/hr|
|2BD||5%||250 to 330/hr|
Less than 90%
|2C||5%||70 to 140/hr|
|Percent stunned with one shot||Cow Plants, n=20||Fed Beef Plants, n=21|
|# of Plants||Percentage||# of Plants||Percentage|
98% to 95%
94% to 90%
Less than 90%
|Number of Plants||Percentage of Plants||Plant Line speed range|
0 to l%
|19||45%||5 to 390/hr|
2 to 3%
|11||28%||70 to 390/hr|
4 to 10%
|10||24%||29 to 250/hr|
|2||5%B||200 to 390/hr|
|Fed Beef Plants
|Number of Plants||Percentage||Number of Plants||Percentage|
0 to 1%
2 to 3%
4 to 10%
|Cause of Vocalization||Number of Plants||% of plants in total sample|
|Excessive electric prod use due to balking||6||14%|
|Sharp broken edges in a restraint device||2||5%|
|Isolated lone animal left in chute or stun box for too long||3||7%|
|Slipping in stun box||1||2%|
|Electric prod too strong||1||2%|
|Rating AMI Guidelines for Electric Prod Use||Number of Plants||Percentage of Plants||Plant Line Speed Range|
0 to l%
|5||29%||150 to 330/hr|
2 to 5%
|6||35%||50 to 330/hr|
6% to 25%
|2||12%||70 to 100/hr|
26% to 49%
|2||12%||70 to 390/hr|
50% or more
|2||12%||330 to 390/hr|
|% of pigs with correct wand placement||% of pigs that squeal when wand is appliedA||Combined Stunning Score||% Insensible on the bleed rail||Rating||Line SpeedB Per Hour|
|Rating||% of time squealing||Line speed per hour||Comments|
|2||Excellent||53||970||Avg. of 7 groups of 100 pigs each|
|3||Excellent||56||850||Avg. of 5 groups of 100 pigs each|
|8||Acceptable||68||1250||625/hr with 2 restrainers in same room|
|9||Not acceptable||94||850||Excessive electric prod use|
|11||Serious Problem||96||1020||Improved after taking away 3 electric prods to 82%|
|Plant No.||% of pigs electric prodded in entire system||% prodded at restrainer entrance||LineB speed per hour||Comments|
|7||38||6||850||Balked at reflections|
|8||40||-||850||Pigs backed out of chute|
|Plant||% correct stunning wand placement||% of pigs squealing when stunners applied||Combined stun score||% time squealing||Combined1 Welfare Audit Score||Rating|
|J||All scores invalid - Sensible pigs on bleed rail||FAIL|
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