Auditing and Scoring of Vocalization of Cattle and Pigs at Slaughter Plants as an Indicator of Poor Practices that are Detrimental to Animal Welfare

by Temple Grandin
Department of Animal Science
Colorado State University

Vocalization scores in cattle greatly improved after the restaurant audits started (Grandin, 2005a). Each animal was scored on a yes/no basis as being either a silent animal or a vocalizer. Vocalizations (moos and bellows) were scored in the stun box, single file chute (race), and crowd pen. Vocalizations in the stockyards (lairage) were not scored. Table 1 shows reductions in cattle vocalizations after the audits started.

Table 1: Percentage of Cattle Vocalizing During Stunning and Handling
Average Best Plant Worst Plant
1996 - USDA survey baseline data before the audits started 7.7% 0% 32%
1999 - First year of Audits 2.4% 0% 17%
Scores for Plants that have been audited for 3 or more years 1.7% 0% 6%

Grandin (1998) found that 98% of vocalizations occurred immediately after aversive events such as missed stuns, electric prod use, slipping on the floor, excessive pressure from a restraint device or sharp edges that stuck into an animal. Reduction of electric prod use resulted in less vocalizations. In one plant, the vocalization score was reduced from 4% to 1% after electric prod use was reduced from 31% to 7% of the cattle (Grandin, 2005). In two other plants, simple changes that made it possible to reduce electric prod use greatly reduced vocalization. The changes were: adding a light at a restrainer entrance to facilitate cattle entry and adding a false floor in a restrainer to eliminate the "visual cliff effect." The percentage of cattle vocalizing was reduced from 8% to 0% and 9% to 0%. In another plant, reducing pressure applied by a head restrainer reduced vocalization from 23% to 0% (Grandin, 1996, 2003).

Scoring Vocalization

The American Meat Institute guidelines (Grandin, 2005b) states a bovine is scored as a vocalizer regardless of the intensity of the vocalization. An auditor MUST write down WHY the animal vocalized. Missed stuns, falling, electric prod use, beating, slamming gates on animals, or acts of abuse are obvious, but often other serious problems that cause vocalization are less obvious. Slight slipping in either the stun box or single file chute (race)often causes cattle to vocalize. Installing a grating made from welded steel rods to reduce slipping will reduce vocalizations. To the auditor the animal appears to just be agitated, but this is often caused by repeated rapid small slips. Loud bellows in a stun box are often caused by either excessive pressure from a restraint device or a sharp edge. A very small sharp edge may cause vocalization. Two other serious welfare problems that will cause vocalization in holding an animal too long in a restraint device or leaving it isolated and alone too long in a stun box. All of the above aversive situations are serious problems and the audit is FAILED if the percentage of cattle that vocalizes exceeds 3% in plants with no head restraint and 5% in plants that use head holders for either stunning or religious slaughter.

Scoring Small Cattle Plants

There have been some problems evaluating vocalization scores in small plants. Small plants have less machinery noise and very soft low moos "humming" that would not be heard by an auditor in a large plant may be heard in a small plant. Another problem in small plants is that cattle may stand for a long period in the single file race. If they stand too long, the race is no longer an "active" handling system and cattle in the race may "talk" to cattle in the yards. If a bovine vocalizes in this situation, the auditor must write it down that this was not associated with an aversive event. The auditor should also write down if it was a small vocalization "hum" that probably could not be heard in a larger plant.

Cattle Vocalizations that are Immediately Associated with the Following Aversive Events are Counted on the Vocalization Audit

  1. Missed stuns or partial stuns.
  2. Falling down.
  3. Electric prod use.
  4. Hitting, beating, or poking sensitive parts of the animal.
  5. Slamming gates on animals.
  6. Shackling and hoisting or dragging of sensible animals.
  7. Repeated rapid small slips in the stun box or single file chute that causes the animal to become agitated.
  8. Excessive pressure from a restraint device. Animal vocalizes in direct response to application of a pusher gate, body restraint, or head holder.
  9. Sharp edge on a restraint device. Animal vocalizes in the restraint device or while riding on a conveyor.
  10. Holding an animal in a restraint device for too long. Stun or conduct religious slaughter before vocalization occurs.
  11. Leaving a lone animal isolated too long in a stun box or single file chute.
  12. Running an animal over the top of another one on purpose.

Vocalization Scoring of Pigs

There have been questions about the2005 American Meat Institute guideline on vocalization scoring of pigs in the restrainer. The first sets of data arriving from the plants show that the plants that use either V conveyor restrainers or center track restrainers for either market pigs or sows are able to comply with the standard of 5% or less of the pigs squealing in the restrainer (Table 2 & 3). Each pig is scored using yes/no scoring as either silent or a vocalizer (squealing). It has to be fully in the restrainer to be scored. The reason pigs are not scored like cattle, in all parts of the facility, is because it is difficult to determine which pig is squealing. Common causes of pigs squealing in the restrainer are: holddown rack is pushing on their backs, restrainer is too narrow, sharp edges, or one side runs faster than the other. Vocalizations that occur immediately after an electric stunner is applied are scored as a separate "hot wand" score. They are NOT included in the restrainer vocalization score. The auditor does NOT need to determine other reasons for squealing. All squeals count because they are easy to hear regardless of plant size. Grunting and dog bark "wuff" sounds are not counted.

Table 2: Percentage of Market Pigs Squealing in the Restrainer (2006 Data)
Vocalization Score Percentage of Pigs Prodded with an Electric Prod
Plant 1 3% - Pass 12%
Plant 2 3% - Pass 3%
Plant 3 0% - Pass 4%
Plant 4 2% - Pass 0%
Plant 5 2% - Pass 14%
Plant 6 5% - Pass 1%
Plant 7 12% - Fail 4%
Plant 8 0% - Pass 1%

Table 3: Percentage of Sows Squealing in the Restrainer (2006 Data)
Vocalization Score Percentage of Sows Prodded with an Electric Prod
Plant 1 3% - Pass 5%
Plant 2 4% - Pass 2%
Plant 3 Less than 5% - Pass Not Available
Plant 4 Less than 5% - Pass Not Available
Plant 5 - First 25 Sows 28% - Fail 8%
Plant 5 - Last 25 Sows 4% - Pass 8%

Plant 3 and 4 had data from numerous internal audits. Data from plant 3 showed improvement over a period of several months. Manager at plants 3 and 4 are very proud of the work they have done to reduce squealing. Plant 5 had finished building a new facility two days before the audit. The false floor which prevents sows from seeing the "visual cliff" effect under the V restrainer had not been re-installed and was still missing. This caused balking. The line speed was 30 to 35 per hour. The squeal score greatly improved for the second 25 sows because fewer sows were put in the leadup chute. To promote following behavior, two sows were moved into the restrainer at a time.


Grandin, T., 1996. Factors that impede animal movement in slaughter plants. J. Amer. Vet. Med. Assoc. 209:757-759.

Grandin, T., 1998. The feasibility of vocalization scoring as an indicator of poor welfare during slaughter. Applied Animal Behavior Science. 56:121-128.

Grandin, T., 2003. Cattle vocalizations are associated with handling and equipment problems in beef slaughter plants. Applied Animal Behavior Science. 71:191-201.

Grandin, T., 2005a. Maintenance of good animal welfare standards in beef slaughter plants by use of auditing programs. J. Amer. Vet. Med. Assoc. 226:370-373.

Grandin, T., 2005b. Recommended animal handling guidelines and audit guide. Amer. Meat Institute. Washington D.C.

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