Keel bone fracture in laying hens

Keel bone fracture in laying hens
-Cause, consequence and cure?
John Tarlton
University of Bristol
[email protected]
Introduction
• Modern commercial laying hens are extremely well adapted to
producing eggs but less well adapted to resisting impact related keel
fractures
• This failing was not apparent in conventional cages due to lack of
collisions
• Due to public pressure and overwhelming evidence of poor welfare,
the EU banned battery cages from 2012
• ~50% of (UK) hens are now kept in free range systems (FRS)
• Despite other welfare benefits, FRS have their own problems the
most urgent of which is keel bone fractures
• These affect an average 60% of FR hens (15 million UK hens per
year), with over 80% in some FRS
Prevalence of fracture rates in UK systems
• Gregory and Wilkins first described the problem of keel breaks in
the early 1990’s, though the full impact of this was not appreciated
• Whitehead and Fleming described “osteoporosis” in laying hens and
proposed a mechanism based on calcium metabolism and loss of
structural cortical bone
100
90
80
70
60
50
40
30
20
10
0
Free Range
Scottish Free Range
18
30
50
70
wks
Mean severity score
% Old Breaks
Prevalence
3,0
2,5
2,0
1,5
1,0
0,5
20
40
60
80
100
% broken keels (palpation)
• Keel bone breakage is recognised by the UK Farm
Animal Welfare Council as THE major welfare issue
facing the egg production industry
• Keel bone breakage also has economic implications
specifically:
 Decrease in egg production and poorer feed
conversion (Nasr et al., 2013)
 Pain and decreased mobility - reversed with
analgesics (Nasr et al., 2014)
 Increased mortality (McCoy et al., 1996)
 Reduced carcase value (Brown 1993)
Three basic factors cause keel bone
fractures in laying hens
• The hen
• What the hen does
• Where it does it
The Hen
Hen factors contributing to keel fracture risk may
include
• age
• weight
• breed
• bone strength
• BMD
• Behaviour
• productivity
• diet
The wrong diet… too little omega-3!
Interest in omega-3 fatty acid originated
in human studies.
Humans evolved to utilise a diet with fatty
acids equal in omega-3 (n3) and n6 (the
paleolithic diet). Typical “Western” diets
have 10-30 fold excess of n6
A typical paleolithic community
Hens are also evolved to utilise a free
foraging diet approximately equal in n3 and
n6. Typical commercial feeds have 6-10
fold excess of n6
A foraging hen
Diet
Source
Wheat
Corn
Rice
Soya
Oats
Barley
Rape
Peanut
Sesame
Flax*
Sunflower
Safflower
Grape
Cannabis*
Candlenut*
Perilla*
Pumpkin
Evening primrose
Chia*
… The wrong feed!
α Linolenic (n3)
5
0
1
7
1
5
7
0
0
58
Linoleic (n6)
50
59
35
50
35
50
30
29
45
14
n6:n3 ratio
10
>100
35
7
35
10
4.3
>100
>100
0.24
0
3
0
20
29
55
8
0
30
65
75
71
60
40
0
50
81
40
>100
25
>100
3
1.4
<0.01
6.25
>100
1.3
n3
n6
C18: ALA
LA
DGLA
C20: EPA
COX
LOX
C22: DHA
“Anti-inflammatory”
prostaglandins,
leukotrienes,
thromboxanes
AA
COX
LOX
“Pro-inflammatory”
prostaglandins etc.
COX
LOX
Resolvins maresins
protectins
n3 reduces keel bone breakage by 40-60%
Bone 2012
… and increases bone strength, toughness and stiffness
n3 increases bone density, volume & trabecular thickness
n3 increases bone remodelling
What determines a birds fracture susceptibility
independent of “environment”?
•
Modelling experimental impacts against bone strength,
BMD and composition, age weight etc.
Keel bone Breakage
Strength vs fracture
Failure load (Kg)
Keel bone strength
Fracture risk
Bone mineral density
Impact tester
Experimental keel fractures
Fracture risk with age (and KE)
80%
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
70%
Fracture Probability
Probability of Fracture
Fracture risk with BMD
60%
50%
40%
30%
20%
10%
0%
Keel Surface BMD
16
28
40
Age weeks
52
64
Keel strength AND flexibility provide protection from breakage.
This results in a susceptible period in mid lay when the keel has
lost flexibility but not yet accumulated strength
•
What is the keel? Is it a bone? Is it a cartilage? And when?
-3cm
-4.5cm
BMD
Tip
-1.5cm
20
23
30
40
Age
•
To better understand structural factors
influencing fracture, we are modelling keels
using finite element analysis based on micro-CT,
composition and fine scale biomechanics
42
50
60
The wrong hen!
•
•
•
•
Hens have been selected on the basis of egg production, from 20
eggs/yr (red jungle fowl), through 130 (1930’s), to over 300
Fleming et al selected hens on the basis of bone index over 6
generations, and improved strength and reduced fracture rate.
Selection is difficult in practice as “grand-daughter” hybrids are not
used for breeding, the phenotype was not stable, and there was a
loss in productivity.
Genome-wide association studies identify genes
associated with individual welfare traits that contribute
to bone health AND productivity. Genes can be
identified in pure-breed stock, and used across strains
What the hen does…
•
Using a drop weight impact tester
we have been modelling collisions and
fracture occurrence.
• Fractures occur at relatively low
impact energies, and increase rapidly
with greater impact KE
100%
Fracture (%)
Strong evidence points to hen collisions
as being the principle cause of keel
fractures
75%
50%
25%
0%
-3
-2
-1
0
1
2
Kinetic Energy (+/- SD)
15
10
5
0
Impact energy
3
Flights and collisions – its what they do!
Barn
Free range
50 Weeks
70 Weeks
0.60
Average nos of flights per bird
20 Weeks
30 Weeks
0.50
0.40
0.30
0.20
0.10
0.00
0
0.0
6
12
18
0 6
2430.0
12
18
2460.0
0 6
Time of day
12
18
2490.0
0 6
12
18
24120.0
There is some scope to reduce “flightiness”, but generally
mitigation will depend on reducing the consequences of this
natural behaviour
Where the hen does it
Fracture rates and severity of different housing systems
Mean severity
Severity
n
% Diss.
Free Range
12
67±4cd
1.91±0.07bcd
FR A-frame
7
78±3cd
2.15±0.14cde
6
86±2d
2.59±0.14de
Organic Mob
8
45±3ab
1.61±0.03ab
OM Arial Fixed
4
84±5d
2.26±0.02de
11
59±5bc
1.83±0.08abcd
10
63±3bc
1.80±0.10abc
Furnished cage 9
36±5a
1.45±0.09a
FR Arial
suspended
Organic with
slats
Barn
Rates
Low risk / Low impact?
Medium risk / Medium impact?
High risk / High impact?
House Hazard scores based on:
Heights of nest boxes, slats
above litter, feeders, drinkers
and perches. Type of ramps and
perches.
Hazard Score
Perch height
Perch heights:
Previous studies have shown
that reducing perch height
alone may be beneficial
2500
R² = 0,6692
2000
1500
1000
500
0
0
20
40
60
80
Fracture prevalence (%)
100
What is needed is an objective measure of actual hazards
experienced by hens, validated against fracture risk.
•
Quantifying fractures associated with
particular impact energies in housing systems
=
20
10
0
1
144
287
430
573
716
859
Low impact
system
40
=
20
10
0
1
144
287
430
573
716
859
High impact
system
30
0
0,059
0,118
0,177
0,236
0,295
0,354
0,413
0,472
0,531
0,59
0,649
0,708
0,767
0,826
0,885
0,944
0
0,059
0,118
0,177
0,236
0,295
0,354
0,413
0,472
0,531
0,59
0,649
0,708
0,767
0,826
0,885
0,944
Acceleration
The problem with being
henpecked….
Acceleration
Accelerometer: Keel
6
5
4
3
2
1
0
Time
Accelerometer: Back
12
10
8
6
4
2
0
Time
What the house is made of
Looking at how material properties influence fracture rate
Conclusions
The bad news…
• Keel bone fracture is the most urgent problem of
commercial egg production
• It represents a severe obstacle to sustainability
• With increased usage of extensive systems, the
problem is likely to get worse
The good news….progress will result from advances in:
•
•
•
•
Genetics – fracture resistant keels by use of genomics
combined with a better understanding of keel function
Diet – improve skeletal resilience using omega-3
alongside current strategies to improve calcium uptake
Rearing – increased activity during rearing results in
stronger bones, “training” for FRS
Housing – Improved housing designs to increase overall
activity and reduce hazards
The keel team
Bristol
Lindsay Wilkins
Fran Booth
Gemma Richards
Christine Nicol
Steve Brown
Sarah Lambton
Nick Avery
Kate Robson-Brown
Bern
Mike Toscano
Ariane Stratmann
Michigan
Daren Kercher
Exeter
Krasi Tsaneva-Atanasova
Noble Foods
Andrew Joret
Stonegate
Richard Kempsey
Venco
Lotte van der Ven
Fin(ish)

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