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.

• 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.
• 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).
• 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.

Acceptable methods of stunning:

• Mechanical
  • Concussion
  • Penetration
• Chemical
  • CO₂ is 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:

1. Head only
2. Head-to-back
3. Head-to-rib

Problems with electrical stunning: (1) bone breakage, and (2) 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)
  

Stunning ---> Want to comatize, not kill. Proper stunning should result in continued breathing and heart beating. Medulla oblongata must not be destroyed; if it is, blood will not be completely removed.

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."

Dressing

Swine

Removal of hair ---> Scald, dehair, shave, singe, depilate.

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

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 restrainer
• Continuous powered rail system
• Hock and horn cutters
• Air dehiders
• Hide-pullers
  • 3-in-a-row (IBP)
    • Can-Pak
    • Banana Bar
    • Davis Roll-a-Hide
  • Tandem (Monfort)
    • Can-Pak
    • Davis Roll-a-Hide
• Moving top viscera table
• In-motion, side-moving, splitting platform
• Band-saw splitting saws
• Automatic carcass washers

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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 on the Internet

Dr. Temple Grandin's Web Page

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