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Slaughterhouses · United States & Europe

When the Line Goes Too Fast: Line Speeds and Stunning Failures

US regulators have allowed some chicken plants to run at up to 175 birds a minute. Studies of commercial slaughter show that stunning does not always work the first time.

2021 · Reporting by USDA FSIS, EFSA and peer-reviewed research

Summary

Line speed is the number of animals a slaughter line processes per minute. In the US, a 2018 waiver programme let some young-chicken plants under the New Poultry Inspection System run faster than the standard 140 birds per minute, up to 175. Separately, a peer-reviewed study of 998 cattle shot with captive bolts at commercial plants found signs of inadequate stunning in 12.5%.

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Standard US line speed for young chickens (NPIS)
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Maximum under FSIS waivers
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Cattle with signs of inadequate stunning (2013 study)
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Poultry slaughter hazards identified by EFSA (2019)
An empty stainless-steel poultry processing line with a long overhead shackle conveyor
An empty stainless-steel poultry processing line with a long overhead shackle conveyor. Illustrative photo — not footage from the investigation.

Part 1

How fast the lines run

Under the US New Poultry Inspection System (NPIS), young-chicken plants have a standard maximum of 140 birds per minute. In 2018 the USDA's Food Safety and Inspection Service (FSIS) set out criteria for waivers allowing plants to run faster, up to 175 birds per minute, if they could show that food safety was maintained and had a record of regulatory compliance.

In February 2026 FSIS proposed letting young-chicken plants under NPIS run at up to 175 birds per minute and turkey plants at up to 60; public comments closed in April 2026. The agency's rulemaking page, linked below, shows whether the rule has been finalised.

Part 2

Pigs and the courts

In 2019 a new US swine inspection rule, the New Swine Inspection System, removed evisceration line-speed limits for participating pork plants. In March 2021 a federal court in Minnesota vacated that provision, finding that the USDA had not adequately considered worker safety.

The ruling concerned workers rather than animal welfare, but it shows how contested line speeds remain.

Part 3

When stunning fails

Stunning is meant to make animals unconscious before they are killed. A 2013 study in the journal Animal Welfare examined 998 cattle stunned with captive-bolt guns at commercial slaughterhouses and found signs of inadequate stunning in 12.5% — 16.7% of bulls and 6.5% of other cattle.

For poultry, EFSA's 2019 scientific opinion on slaughter identified 35 welfare hazards, most of them linked to stunning and bleeding. Electrical water-bath and controlled-atmosphere stunning carry different risks, and there is no single, universal failure rate for poultry.

Part 4

What the law requires

In the EU, Regulation 1099/2009 requires animals to be spared avoidable pain, distress and suffering when they are killed, and sets stunning and monitoring requirements for each method, with specified exceptions.

In the US, the Humane Methods of Slaughter Act covers livestock such as cattle and pigs. Poultry are not included in the Act, so their treatment at slaughter is regulated mainly through food-safety and good-commercial-practice rules.

Questions

Questions people ask

What is the maximum line speed in US chicken plants?
The standard maximum under NPIS is 140 birds per minute. Since 2018 some plants have operated at up to 175 birds per minute under FSIS waivers.
How often does stunning fail?
It depends on the species, method and plant. One peer-reviewed study of 998 cattle stunned with captive bolts found signs of inadequate stunning in 12.5%. There is no single figure for all slaughter.
Are chickens covered by the US Humane Methods of Slaughter Act?
No. The Act covers livestock such as cattle and pigs; poultry are excluded.

Sources

Where this reporting comes from

Figures on this page come from the official reports, laws and peer-reviewed studies listed here. Campaign groups are cited only for what their own investigations recorded.

Facts reviewed:

  1. USDA FSIS — Constituent Update, 23 February 2018 (line-speed waiver criteria)
  2. USDA FSIS — Maximum line speed rates for young chicken and turkey establishments (NPIS)
  3. US District Court, Minnesota — UFCW Local 663 v. USDA, order of 31 March 2021
  4. Atkinson, Velarde & Algers — Stun quality in cattle shot with captive bolt, Animal Welfare (2013)
  5. EFSA — Slaughter of animals: poultry (2019)
  6. Berg & Raj — Stunning methods for poultry: animal welfare aspects, Animals (2015)
  7. Council Regulation (EC) No 1099/2009 on the protection of animals at the time of killing
All investigations