Keel bone fracture in laying hens -Cause, consequence and ...€¦ · The keel team Bristol Lindsay...
Transcript of Keel bone fracture in laying hens -Cause, consequence and ...€¦ · The keel team Bristol Lindsay...
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Keel bone fracture in laying hens -Cause, consequence and cure?
John Tarlton University of Bristol [email protected]
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• 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
• 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
Introduction
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• 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
Prevalence of fracture rates in UK systems
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18 30 50 70
Free Range
Scottish Free Range
% O
ld B
reak
s
wks
0,5
1,0
1,5
2,0
2,5
3,0
20 40 60 80 100Mea
n se
veri
ty s
core
% broken keels (palpation)
Prevalence
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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)
• 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:
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Three basic factors cause keel bone fractures in laying hens
• Where it does it
• The hen
• What the hen does
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The Hen
Hen factors contributing to keel fracture risk may include
• age
• weight
• breed
• bone strength
• BMD
• Behaviour
• productivity
• diet
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The wrong diet… too little omega-3!
A typical paleolithic community
A foraging hen
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
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
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Source α Linolenic (n3) Linoleic (n6) n6:n3 ratio
Wheat 5 50 10
Corn 0 59 >100
Rice 1 35 35
Soya 7 50 7
Oats 1 35 35
Barley 5 50 10
Rape 7 30 4.3
Peanut 0 29 >100
Sesame 0 45 >100
Flax* 58 14 0.24
Sunflower 0 65 >100
Safflower 3 75 25
Grape 0 71 >100
Cannabis* 20 60 3
Candlenut* 29 40 1.4
Perilla* 55 0 <0.01
Pumpkin 8 50 6.25
Evening primrose 0 81 >100
Chia* 30 40 1.3
Diet … The wrong feed!
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C18: ALA LA
AA C20: EPA
n3 n6
“Anti-inflammatory” prostaglandins, leukotrienes, thromboxanes
COX LOX
“Pro-inflammatory” prostaglandins etc.
COX LOX
DGLA
Resolvins maresins protectins
COX LOX
C22: DHA
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n3 reduces keel bone breakage by 40-60%
… and increases bone strength, toughness and stiffness
Bone 2012
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n3 increases bone density, volume & trabecular thickness
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• Modelling experimental impacts against bone strength, BMD and composition, age weight etc.
What determines a birds fracture susceptibility independent of “environment”?
Keel bone Breakage
Keel bone strength
Failu
re lo
ad (
Kg)
Fracture risk
Strength vs fracture Bone mineral density
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Impact tester Experimental keel fractures
0%
10%
20%
30%
40%
50%
60%
70%
80%
16 28 40 52 64
Fra
ctu
re
Pro
babili
ty
Age weeks
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Pro
bab
ilit
y o
f F
ract
ure
Keel Surface BMD
Fracture risk with age (and KE) Fracture risk with BMD
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• What is the keel? Is it a bone? Is it a cartilage? And when?
Age
20 23 30 40 42 50 60
Tip -1.5cm
-3cm -4.5cm
BM
D
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
• To better understand structural factors influencing fracture, we are modelling keels using finite element analysis based on micro-CT, composition and fine scale biomechanics
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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
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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
0
5
10
15
Impact energy
0%
25%
50%
75%
100%
-3 -2 -1 0 1 2 3
Fra
ctu
re (
%)
Kinetic Energy (+/- SD)
Strong evidence points to hen collisions as being the principle cause of keel fractures
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0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.0 30.0 60.0 90.0 120.0
Barn Free range
20 Weeks 30 Weeks 50 Weeks 70 Weeks
0 6 12 18 24 0 6 12 18 24 0 6 12 18 24 0 6 12 18 24
Ave
rag
e n
os o
f flig
hts
pe
r b
ird
Time of day
Flights and collisions – its what they do!
There is some scope to reduce “flightiness”, but generally mitigation will depend on reducing the consequences of this natural behaviour
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Fracture rates and severity of different housing systems
Rates n % Diss. Mean severity
Free Range 12 67±4cd 1.91±0.07bcd
FR A-frame 7 78±3cd 2.15±0.14cde
FR Arial
suspended 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
Organic with
slats 11 59±5bc 1.83±0.08abcd
Barn 10 63±3bc 1.80±0.10abc
Furnished cage 9 36±5a 1.45±0.09a
Where the hen does it
Severity
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21
Low risk / Low impact?
High risk / High impact?
Medium risk / Medium impact?
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Hazard Score
House Hazard scores based on: Heights of nest boxes, slats above litter, feeders, drinkers and perches. Type of ramps and perches.
R² = 0,6692
0
500
1000
1500
2000
2500
0 20 40 60 80 100
Perc
h h
eigh
t
Fracture prevalence (%)
Perch heights: Previous studies have shown that reducing perch height alone may be beneficial
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• Quantifying fractures associated with particular impact energies in housing systems
High impact system
Low impact system
=
=
What is needed is an objective measure of actual hazards experienced by hens, validated against fracture risk.
0
10
20
30
40
1
144
287
430 57
3
716
859
0
10
20
1
144
287
430 57
3
716
859
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0
2
4
6
8
10
12
00
,059
0,1
180
,177
0,2
360
,29
50
,354
0,4
130
,472
0,5
310
,59
0,6
49
0,7
08
0,7
67
0,8
260
,88
50
,94
4
Acc
ele
rati
on
Time
Accelerometer: Back
0
1
2
3
4
5
6
0
0,0
59
0,1
18
0,1
77
0,2
36
0,2
95
0,3
54
0,4
13
0,4
72
0,5
31
0,5
9
0,6
49
0,7
08
0,7
67
0,8
26
0,8
85
0,9
44
Acc
ele
rati
on
Time
Accelerometer: Keel
The problem with being henpecked….
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What the house is made of Looking at how material properties influence fracture rate
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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
Conclusions
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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
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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