Pain: Abolishing a Necessary Evil - Donald C. Lay Jr., PhD, Research Leader, Livestock Behavior Research Unit, USDA, from the 2014 NIAA Annual Conference titled 'The Precautionary Principle: How Agriculture Will Thrive', March 31 - April 2, 2014, Omaha, NE, USA. More presentations at http://www.trufflemedia.com/agmedia/conference/2014_niaa_how_animal_agriculture_will_thrive

1. Pain: Abolishing a Necessary Evil
Donald C. Lay Jr.
Research Leader
Livestock Behavior Research Unit
Agricultural Research Unit, USDA
West Lafayette IN, on Purdue University Campus

2. Livestock Behavior Research Unit Mission
(Agricultural Research Service-USDA)
• to develop scientific measures of animal
welfare that will allow an objective evaluation
of animal agricultural practices
• to improve existing practices and invent new
practices that can enhance animal welfare and
increase animal productivity

3. Publications on “Farm Animal Welfare”
(18,521, Science Direct)
0
200
400
600
800
1000
1200
1400
1600
1800
1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013

4. Mounting Regulation, Policy, Standards
and Assessments
• Tyson Announcement, Jan. 8th, 2014
– Stop the use of Blunt Force Trauma
– Eliminate or reduce pain from tail docking and
castration
• Producer Groups and External On-Farm
Assessment Programs

5. Skin
Dorsal gray horn
(Spinal cord)
Reticular formation
(Brain stem)
Thalamus
(Diencephalon)
Somatosensory
(Cortex)
A, C -fibers
Injury
Skin
A-, C-fibers
Cheng, 2005; Modified from Neuroscience Exploring the brain, 2001
Pain in Humans
A-thickly myelinated = fast
C – unmyelinated = slow, polymodal

6. Cheng, 2005
Pain Mediators

7. Function of Pain
• Adaptive evolutionary strategy to protect the
body.
– Early warning system.
– Allows animals to learn what not to do.
– The more intense the pain, the greater the threat.
• Non-adaptive pain.
– Pain that persists after trauma is healed.
– Neuromas and other neuropathic pain

8. CIPA and HSAN
Congenital insensitivity to pain with anhidrosis
Hereditary Sensory and autonomic neuropathy
• Never feel the stick of a
needle
• Never feel a cut or a burn
• Never feel hunger
• Never feel uncomfortable
in a chair

9. Pain is Necessary!
• Babies gnaw their fingers bloody
• Poke their eye so hard as to cause abrasions
• Lean on hot surfaces to cause 3rd degree burns
• Most die before 3 years of age
• Cause of death
– Heat stroke
– Dehydration
– Fever
– Blood poisoning

10. Pain is difficult to measure
• Pain has both physiological and psychological components.
• Animals cannot communicate verbally regarding their sensory and
emotional experience.
• Pain can be overridden with other feelings, such as fear, fighting, and
feeding motivation ….
• Pain is also affected by multiple
factors, such as genetic strain, age,
production status; environments,
and lesion and lesion size.

11. Neuroanatomy associated with
pain in chickens
Sensory receptors
Lunam, 2005
In humans:
• Mechanical
nociceptors
• Thermal nociceptors
• Chemical nociceptors
In chickens:
• Herbst corpuscles and
• Grandry’s corpuscles
• Free Nerve endings

12. • Behavioral and physiological
studies
There are similar behavioral and
physiological changes in response to
injury between chickens and mammals
(Cheng, 2005; Kuenzel, 2007).
• Pharmacological studies
Pain killers (analgesics) can reduce
pain in both chickens and humans.
(Gentle, 1991; Glatz et al., 1992; Paul-Murphy & Ludders, 2001).

13. Conclusions
• Chickens can feel pain.
• Chickens feel pain in a similar
manner to that in mammals.

14. Definition of pain in animals
In animals
• Pain is an aversive sensory and emotional
experience by the animal in response to
damage or a threat to the integrity of its
tissues (Molony & Kent, 1997; Robertson, 2002; Vinuela-Fernandz et
al., 2007)
In humans
• Pain is an unpleasant sensory and emotional
experience associated with actual or potential
tissue damage (Merskey and Bogduk, 1994)

15. Pain can be recognized and
assessed indirectly
• Physical parameters
Body score (body injury)
Growth rate
• Physiological parameters
Neurotransmitters
Neuropeptides
• Behavioral parameters
General behavior (eating, drinking)
Guarding behavior (protect injured areas)

16. Neuroma
Trigeminal ganglia Beak
Normal nerve fibers
Regrowth
Neuroma
Degenerating of neuroma
Neuromas may increase pain sensitivity --- chronic pain
Soma Fibers Terminals
Ending of beak stump (post-trimming)
Tissue Scar
Targets
Target

17. Neuromas
Histological characteristics
A neuroma is a tangled mass of a damaged (cut)
axon terminal inside the injured area.
Consists of unmyelinated fibers, and then becomes
myelinated fibers (A-fibers)
Physiological characteristics
A source of substantial ectopic firing (spontaneous
pain)
Increase pain sensitivity

18. Painful Situations in Agriculture
• Controllable
– Beak Trimming
– Castration
– Tail docking
– Branding
• Uncontrollable
– Birth
– Accidents
– Injury

19. Analgesics are Beneficial
Coetzee et al., 2012
Bulls castrated without
analgesic (meloxicam)
show a greater incidence
of Bovine Respiratory
Disease

20. Why not just use analgesics?
They would need to be:
1) readily available and registered for use
2) easy to administer
3) quick and long acting
4) have short withdrawal periods
5) show return on investment
Only 1 approved anti-inflammatory in the U.S. for
swine and cattle; a few for cattle and swine in E.U.
and U.K.
Schwartzkopf-Genswein et al., 2012

21. Cannibalism will Increase
in Prevalence with More Space
a c
N. intramand.
N. ophthal. med.
C

22. 1
Furnished Cage Non-cage (Barn) Outdoor
(Free-
Range)
Behavioral
Opportunities
Conventional
Cage Small Large
Slats /
Litter Aviaries
Nesting + +++ +++ ++++ ++++ ++++
Brooding + + + + + +
Perching + ++ ++ +++ +++ +++
Mating + + + + + +
Stereotyped
and sham
behaviors
++++ ++ ++ + + +
Cannibalism
and feather
pecking
++ ++ +++ ++++ ++++ ++++
Social
aggession
++ +++ ++++ ++ ++ ++
Smothering ++ ++ +++ ++++ ++++ +++
2
Lay et al., 2010

23. Infrared trimmed
ControlHeated blade trimmed
Does Beak Trimming
Cause Pain? Funded by AFRI

24. Control
Hot Blade
trimmed
Infrared
trimmed
Drinking Behavior
During Warm Water Pain Test
Infrared Beak trimming has been adopted by
the United Egg Producers, 2010
Five
Weeks
Later!

25. Hen Behavior is Positive but ……
Keel Bone Fractures
• 46 % to 90 % have fractures
Nicol et al, 2010

26. Effect of Analgesic on Perching Behavior of
Hens with Keel Bone Fractures
Latencytoland
First two bars are hens with and without analgesic that do not have
fractures.
The second two bars are hens with and without analgesic that do
have fractures.
Nasr et al, 2012

27. Routine Piglet Processing
• Soon after birth, piglets undergo processing procedures,
which are likely sources of stress:
- Teeth resection
- Tail docking
- Identification
- Iron administration
- Castration
• For each process, there is a choice of methods
Marchant-Forde et al., 2009 Funded by the National Pork Board

28. Objectives
• To evaluate stress responses evoked by two
alternative methods performed singly:
– Teeth (TR) – clip vs. grind
– Tails (TD) – cold clip vs. hot clip
– Identification (ID) – ear notch vs. ear tag
– Iron (FE) – injection vs. oral paste
– Castration (CA) – cords cut vs. cords torn

29. Results
• To evaluate stress responses evoked by two
alternative methods performed singly:
– Teeth (TR) – clip vs. grind
– Tails (TD) – cold clip vs. hot clip
– Identification (ID) – ear notch vs. ear tag
– Iron (FE) – injection vs. oral paste
– Castration (CA) – cords cut vs. cords torn
= worse

30. Conclusions
• Carried out singly, we can identify which method
has least impact on piglet welfare
• Carried out together, it’s much less clear
• The key combination is accuracy and speed

31. Piglet Aversion to Euthanasia Gases
1
3 3
2
4
5
6
7
90% Carbon Dioxide
or
70:30 mixtures of:
Nitrogen:Carbon Dioxide
Nitrous Oxide:Carbon Dioxide
Nitrous Oxide:Oxygen
Rault et al., 2012, in press
Funded by the National Pork Board

32. Euthanasia: Stress and Death
Two-Step Procedure
Gas treatment CO2 N2/CO2 N2O/CO2 N2O/O2
p-value
Transfer from
treatment to CO2
chamber (seconds)
2.9 ± 0.3a 6.4 ± 0.6b 6.7 ± 1.0b 14.7 ± 2.1c
0.001
Time to death after
transfer (seconds)
7.8 ± 1.3 7.6 ± 1.0 5.6 ± 0.3 9.3 ± 1.2 0.20
Total procedure
duration (seconds)
10.8 ± 1.3a 13.9 ± 1.2a
11.3 ± 1.4a 24.0 ± 3.0b 0.005
Rault et al., 2012

33. EEG and Euthanasia
Carbon
Dioxide
Nitrous
Oxide

34. Lameness in Sows
Exercised sows will have:
– An increase in bone density and
an increase in muscular weight
compared to control sows
– An increase in osteoblastic
activity and a decrease in
osteoclastic activity compared to
control sows
– Improved condition of joints and
hooves compared to control
sows

35. Lameness in Sows will Likely
Increase with Increase Movement
Loose housing of Sows will likely acerbate this problem as the increase in
movement will provide opportunity for torn cartilage to worsen.

36. Tail Docking Practice in Dairy Cows
Introduced in 1990s in New Zealand to
combat Leptospirosis

37. DOCKED INTACT
Behaviors Recorded:
Tail Swing, Weight Shift, Foot Stomp, Tail Curve
Eicher et al., 2000
Are Docked Tails more Sensitive to Heat and Cold?

38. Bottom Line:
Docking causes
pain, but less pain
in adult cows.
Docked cows have
more flies and
avoidance
behaviors.
Docked tails show
signs of neuromas
(possibly painful).
Docking doesn’t
decrease somatic
cell counts.

39. Conclusions
• Life without pain doesn’t exist.
• We recognize that animals feel pain.
• Our responsibility is to alleviate or minimize
pain.
• We support future efforts to develop
management tools to minimize pain and
create alternative practices that alleviate pain.

40. Thank You
ARS-USDA
Meeting Tomorrow’s Challenges Today