Slaughter-Dressing of Livestock

Objectives:

(1) To discuss current methods of slaughter-dressing of livestock.

(2) To detail laws and regulations that impact on the slaughter of livestock.

(3) To demonstrate the various methods of stunning of livestock.


Animals should be handled before slaughter with two main goals (from Dr. Temple Grandin):

  • Freedom from fear
  • Freedom from pain

Slaughter

Before slaughter, livestock should be fasted for 12-24 hours because:

  • Makes evisceration easier.
  • Minimizes migration of bacteria from G.I. tract into meat.

and should be given free access to water because:

  • Facilitates electrical stunning.
  • Provides for easier blood removal.
  • Provides for easier pelt removal.
  • Brightens lean color.

Humane Methods of Slaughter Act of 1978

  • Extends and sets forth humane handling and stunning practices and procedures.
  • Applies to all non-exempt Federal and State plants. Exception for ritualist slaughter such as Kosher (Jewish) and Halal (Muslim). (see Kosher and Halal webpage).
  • Provides standards for maintenance and condition of livestock pens, driveways, etc.
  • Calls for control of the use of electrical prods (limited to under 50 volts) “unless prohibited by inspector.”
  • Disabled animals cannot be dragged unless they are stunned.
  • Animals must have access to water in all holding pens and if held for more than 24 hours, must have access to feed.
  • Approves use of stunning methods, which must be applied to livestock before they can be shackled, hoisted, thrown, cast or cut.

Humane Methods of Slaughter Act of 1978
Title 7 Chapter 48 Humane Methods

Two categories of stunning

  • Recoverable
  • Non-recoverable

Acceptable methods of stunning:

Mechanical

  • Non-penetrating concussion style – mushroom-style head (uses include euthanasia and Halal)
  • Penetrating style — penetrating pneumatic stunner, cartridge stunners

Chemical

  • COis only approved substance.
    • Effective CO2 stun
    • At least 70% CO2 in first position
    • At least 90% CO2 at bottom of pit
  • Principles of CO2 stunning
    • No broken bones
    • No kicking
    • Stun-to-stick interval not as critical
    • Length of unconsciousness or death is related to length of time in CO2

Electrical

  • Applied to swine and sheep under various voltage, amperage, and time parameters
  • Electrical stunning methods:
    • Head only
    • Head-to-back
    • Head-to-rib
  • Problems with electrical stunning:
    • Bone breakage
    • Ecchymosis (“blood splash”)
  • Reason: electrical stunning is both a vasoconstrictor and cardiac stimulator. Prevention: minimize “stun-to-stick” interval.

Guidelines for electrical stunning (Daly, 1999; Grandin, 1999)

  • Pigs should be wetted before stun
  • No hot wands
  • Correct electrode positioning
  • Do not double stun
  • 1.25 amps
  • Duration less than 3 seconds

Effective electrical stunning (Grandin, 1999)

  • Head must be limp and floppy
  • No blinking
  • No rhythmic breathing
  • No response to ear or nose pinching
  • No arched backs
  • No vocalization
  • Ignore limb movement (kicking)

Electrical slaughter is approved for small stock (hogs, sheep, calves, etc.). “The electrical current shall be administered so as to produce, at a minimum, surgical anesthesia, i.e., a state where the animal feels no painful sensation.”

Sticking position for swine

Horizontal

  • Reduces stun-to-stick interval
  • Reduces pale, soft, and exudative (PSE)
  • Reduces bruising

Vertical

  • Acceptable with CO2 stunning

Dressing

Swine

  • Removal of hair —> Scald, dehair, shave, singe, and polish.
  • Removal of skin —> Manual with knives (most locker plants) or mechanical with hide pullers (Wolverine and Jimmy Dean most common).

Sheep

Removal of pelt

  • Cradle dressing —> Skin forelegs and hindlegs, fist over breast, abdomen and sides, and after hanging, fist over legs, back, rump and shoulder.
  • Line dressing —> Skin forelegs, hindlegs, neck and breast; hand-work (facing and fisting) and pulling (backing-down).
  • New Zealand upside-down system is now used by several lamb slaughterers.

Beef

Beef slaughter has undergone major changes since the 1960s that have resulted in faster slaughter speeds and greater throughout. The following is a list of some of these changes:

Beef slaughter advances

SystemRate/hourAdvancements/developments
Floor pritch12Skinning cradle
Cradle15Electric knife
Vertical dressing
On-the-rail, gravity flow40"Up" hide pullers
On-the-rail, intermittent power75"Down" hide pullers (developed because of speed and AQL)
Moving top viscera table
V-Boss Cattle Restrainer/Center Track Conveyor Restrainer System (Temple Grandin)
Davis Roll-A-Hide
In-motion, side-moving splitting platform
On-the-rail, continuous power300Multiple hide pullers, splitting platforms, etc.

The majority of beef slaughtered today is in high-speed operations that will involve some of the following items to help allow a speed of 350-400 head per hour:

  • V-Boss cattle restrainer/Center Track Conveyor Restrainer System — allows for the continuous shackling and stunning of cattle.
  • Continuous powered rail system — once the cattle are on the chain, it takes approximately 45 minutes to get to the cooler.
  • Hydraulic hock and horn cutters — quickly removes hocks and horns (horns must be removed before “down” hide pullers can pull hide over the head).
  • Air dehiders — allows for faster, more efficient removal, preparation for the hide pullers.
  • Hide-pullers— most plants now use two or three hide pullers that each pull the hide from particular sections of the animal.
    • 3-in-a-row (Tyson Fresh Meats)
      • Can-Pak
      • Banana Bar
      • Davis Roll-a-Hide
    • Tandem (JBS)
      • Can-Pak
      • Davis Roll-a-Hide
  • Moving top viscera table — allows for evisceration and identification of the pluck and viscera for inspection purposes while the carcasses move on the chain.
  • In-motion, side-moving, splitting platform — allows for splitting with the carcasses moving on the chain.
  • Band-saw splitting saws — faster and less sawdust than reciprocating saws.
  • Automatic carcass washers — similar to carwashes in that multiple spray nozzles and high-pressure water are used.

Review of Material — What the student should know:

(1) The understanding between different types of stunning procedures.

(2) Regulations regarding stunning and slaughter of livestock.

(3) How cattle, sheep and hogs are dressed commercially.


Links to related sites

Dr. Temple Grandin’s website
Kosher and Halal
Video tour of pork packing plant
Video tour of beef packing plant

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