Jeremy N. Marchant-Forde USDA-ARS, Livestock Behavior Research Unit The Ethology of Sow Aggression
Jeremy N. Marchant-Forde
USDA-ARS, Livestock Behavior Research Unit
The Ethology of Sow Aggression
Overview of the Talk
Introduction to social behavior
Natural behavior of pigs
oCompare and Contrast – “Natural” vs “Farmed”
Why and when does aggression occur?
The detail within sow aggression
Management factors influencing aggression
Take home message
Being social is good, right?
Reduces predation
Improves successful foraging
Improves rearing of offspring
Increases chances of mating
Helps thermoregulation
But….
Increases conspicuousness
Increases risk of infectious disease
Decreases access to resources
Competition!
Social Behavior
“those patterns of behavior that involve two or more members of a species.”
Social Behavior
“those patterns of behavior that involve two or more members of a species.”
Natural Social Behavior
To better understand how to manage thepig‟s behavior in our current systems, weneed to take a step back….
Wild boar - social group
2-4 adult females – related
Mother-daughters or Siblings
Un-weaned juveniles
Sub-adults – previous litters
Boar(s) – breeding season
Group size will vary according to season and available resources
Groups distribute around resources
Boars distribute around groups
Wild boar - social group
Sows are dominant to allother members
Overt aggression in coregroups is rare
Dominant sows will displace subordinates from choice feeding sites
Litters are introduced to the group gradually
Home ranges can overlap, but groups won‟t interact
Where‟s the relevance?
•Not the same animal?
Domestic pig - social group
Studies on feral pigs and pigs in semi-natural enclosures show that:
Domestic pigs behave like Wild Boar
Social behavior
Domestic pigs form „family‟ groups
Small core groups of related females + progeny
Solitary males, associate with groups at mating
Domestic pig – social behavior
Groups may share common space in home ranges but do not merge
Groups maintain distance from each other when foraging in the same area
When foraging, average distance between group members is 4 m
Aggression in core groups is rare = 1 every 2h per animal
Strategy is avoidance
Contrasting Features
Natural FarmedGroup size Small Single to Large
Social structure Stable Unstable
Relatedness Related Variable
Age/Size profile Wide Narrow
Space Unlimited Restricted
Behavioral repertoire Complex Constrained
Activity Active - foraging Inactive
When & why does aggression occur?
Two major opportunities for aggression in sows:
Mixing
Feeding
Mixing
Formation of social hierarchy
Feeding
Access to, and defense of, scarce resources
Reinforcement of social hierarchy
Factors Impacting Aggression
Housing
Groups vs. stalls
Mixing
How many times
How many pigs
Feeding
Method
Quantity
Ingredients
Space
Amount
Quality
Impact of Aggression for the Pig
Activation of sympathetic-adrenal-medullary axis Catecholamines
Increased heart rate/blood pressure
Activation of hypothalamic-pituitary-adrenal axis Cortisol
Health Skin lesions/Leg injuries
Immunity
Productivity Feed intake/Growth/Body condition
Pregnancy
Litter size
Life cycle of breeding sows
Gestation
Lactation
Service
Gilts
Cull
Gilts
MIX
MIX
MIX
Getting to know you…..
Sequencing Aggressive Behavior
Break
Ano-genital nosing
Bite
Follow/Approach
Head over body/threat
Knock
Mount
Nose to nose
No Response
Other
Push/lift
Withdraw
Walk
NN
NRP
OTH
PU
WD
WLK
BRK
AGN
BT
F/A
HO/T
K
MO
Markov analysis to distinguish meaningful pairs from randomly occurring pairs
Break
AGN
BT
Fo/Apr
HO/T
K
MO
NN
NRP
OTH
PU
WD
WLK
AGN
BT
Fo/Apr
HO/T
K
MO
NN
NRP
OTH
PU
WD
WLK
Break
AGN
BT
Fo/Apr
HO/T
K
MO
NN
NRP
OTH
PU
WD
WLK
0.47
0.23
0.19
0.15
0.37
0.16
0.10
0.29
0.24
0.18
0.31
0.05
0.03
0.02
0.06
0.18
0.06
0.23
0.02
0.36
0.20
0.49
0.32
0.42
0.65
0.45
0.08
0.10 0.20
0.13
0.11
0.19
0.29
0.12
0.10
0.25
0.17
0.42
0.16
0.12
0.23
0.09
0.04
0.43
0.17
0.60
0.28
0.29
0.06
0.26
0.35
0.17
0.30
0.42
0.37
0.18
0.38
0.50
0.30
0.36
0.13
0.17
0.21
0.03
0.02
0.17
0.20
0.14
0.60
0.15
0.14
0.42
0.14
0.19
0.07
0.13
TO FROMBreak
Mixing Aggression - Scenarios
We investigated four different scenarios:
Indoors – 11 pairs at 3.0 m2/sow (n=11)
Outdoors – 15 pairs at 2500 m2/sow
Indoors – 7 × 2 sub-groups of 3 sows at 3.2 m2/sow
Outdoors – 14 × 2 sub-groups of 3 sows at 833 m2/sow
Similarities and differences….
Mixing Aggression - Scenarios
In all 47 mixings, social interactions occurred
In 45 mixings, aggressive interactions occurred
2 outdoor pairs did not engage in aggression
More aggressive actions in indoor groups
0
100
200
300
400
500
600
Indoor Group Indoor Pair Outdoor Group Outdoor Pair
Num
ber
of
actions
a
b b
c
Mixing Aggression - Scenarios
In indoor pairs, aggression ramped up gradually
In all other scenarios, aggression was immediately high intensity
0
20
40
60
80
100
120
Indoor Group Indoor Pair Outdoor Group Outdoor Pair
Num
ber
of
actions
Pushes
Knocks
Bites
a
x
x
y
xm
n
mn
m
ab
a
b
Mean number of actions before first push, knock and bite
Mixing Aggression - Scenarios
In groups, 9 possible unacquainted pairs, 6 acquainted pairs
Mean number of pairs interacting in groups
0123456789
101112131415
Interacting socially Interacting non-aggressivelyInteracting aggressively Fighting
Nu
mb
er
of p
airs
Indoor all
Indoor between sub-groups
Indoor within sub-groups
Outdoor all
Outdoor between sub-groups
Outdoor within sub-groups
Mixing Aggression - Scenarios
Space especially affects how the sows behave at mixing
When space is „limitless‟, strategy quickly involves avoidance
When space is limited, avoidance is difficult – same behavior can have different results
In Pair
In Group
Out Pair
Out Group
„Break‟ preceded by „Withdraw‟ 11.7 % 15.6 % 44.8 % 61.1 %
„Break‟ preceded by „No Response‟ 46.0 % 51.6 % 35.7 % 18.4 %
„Bite‟ preceded by „No Response‟ 32.3 % 39.7 % 18.4 % 8.5 %
„Nose-to-Nose‟ or „Ano-Genital Nosing‟ followed by „Bite‟,„Knock‟, „Push‟
4.3 % 6.3 % 12.4 % 6.5 %
Mixing and Aggression
Methods tried to reduce aggression at mixing
• Get-away areas
• Chemical intervention /
• Time of day /
• Fresh bedding
• Ad libitum food
• Boar presence /
• Sub-groups
• Space /
• Pre-exposure /(Marchant-Forde & Marchant-Forde, 2005)
Space
(Edwards et al., 1993)
6.1 m2/sow 3.7 m2/sow
barriers
3.7 m2 6.1 m2
No. of interactions (0-12h) 187 324
Damage scores 13.5 8
Space
Little evidence for optimum space allowance to reduce aggression
Aggression may be reduced at high density conditions (1.4 m2 v 3.4 m2) but only initially
1.4 m2 3.4 m2
No. of interactions (0-1.5 h) 5.9 6.6
No. of interactions (d 2) 2.6 1.9
No. of interactions (d 3-10) 13.7 8.7
(Barnett et al., 1993)
Space
Limited space in the longer term may result in increased aggression and higher lesion scores
(Weng et al., 1998)
0
50
100
150
200
250
300
350
2 2.4 3.6 4.8
Aggressive interactions Lesion scores
Pre-exposure pen
Pre-exposure
• Can we let the sows get to know each other
without letting them fight?
Pre-exposure
**
0
20
40
60
80
100
120
140
Bites Knocks Threats Total
Control
Pre-exposed
*
**
*
• Aggression was reduced at day of mixing, +1d, +1wk, +2wks
(Kennedy, 1997)
Pre-exposure
• These results are telling us that vocal, olfactory, visual and limited physical cues are conveying important information:
• „Familiarity‟?
• Relative social rank?
• Relative fighting ability?
• When we mix, not all possible combinations of pigs fight, yet hierarchy is established
Pre-exposure
Pre-selecting your group out of the farrowing house
Next to each other
Randomly separated
Housed in service crates
7d post-service
35d post-service
Pre-exposure
Grouped after 7 days in service crates
5
6
7
8
9
10
11
12
13
14
15
Grouping 24h 2wk 4wk 5wk 6wk 8wk 12wk
Time relative to moving to gestation pen
Le
sio
n S
co
re
Grouped
Random
Pre-exposure
Grouped after 35 days in service crates
5
6
7
8
9
10
11
12
13
14
15
Grouping 24h 2wk 4wk 5wk 6wk 8wk 12wk
Time relative to moving to gestation pen
Le
sio
n S
co
re
Grouped
Random
What if we keep sows in crates
• Crate housing is not trouble-free
• Inter-sow aggression can be high
• But physical consequences are reduced
(Barnett et al., 1987; Broom et al., 1995)
Agonistic interactions – groups vs. stalls
0
0.5
1
1.5
2
2.5
3
1st Parity
Nu
mb
er o
f in
tera
ctio
ns
per
h
• Agonistic interactions start higher in groups
(Broom et al., 1995)
0
0.01
0.02
0.03
0.04
0.05
0.06
1st Parity
Pro
po
rtio
n w
hic
h e
sca
late
Crates
Small Group
Large Group
Agonistic interactions – groups vs. stalls
0
0.5
1
1.5
2
2.5
3
4th Parity
Nu
mb
er o
f in
tera
ctio
ns
per
h
• Over time, numbers same, escalation higher
(Broom et al., 1995)
0
0.05
0.1
0.15
0.2
0.25
0.3
4th Parity
Prop
orti
on
wh
ich
esc
ala
te
Crates
Small Group
Large Group
Take Home Message
A thorough understanding of social behavior is critically important when housing pigs in groups
Commercial practice conflicts with „natural‟ social behavior
Where system design or management is inadequate, aggression can be problematical
May have “low impact” overall, but “high impact” on some individuals
Take Home Message
Still a great many unknowns
Many types of “Group Housing”
Feeding system/group size/space/stability/flooring etc.
Genetics – influence on behavior
Research tends to focus on individual components
How do all these components interact?
Husbandry is key!
The act or practice of breeding and raising livestock
Farming, especially the care of farm animals
Farming, especially when regarded as a science, skill, or art
Invest in your people!
Questions?