Keel bone fracture in laying hens -Cause, consequence and cure? - John Tarlton University of Bristol
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Keel bone fracture in laying hens -Cause, consequence and cure? John Tarlton University of Bristol John.tarlton@bristol.ac.uk
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
Prevalence
100
90
Free Range
% Old Breaks
80
70 Scottish Free Range
60
50
40
30
20
10
0
18 30 50 70 wks 3,0
2,5
Mean severity score
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 … The wrong feed!
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 0 100
Chia* 30 40 1.3
n3 n6
C18: ALA LA
DGLA
C20: EPA
COX AA
LOX
“Anti-inflammatory”
prostaglandins, COX
leukotrienes, LOX
C22: DHA
thromboxanes
COX “Pro-inflammatory”
LOX
prostaglandins etc.
Resolvins maresins
protectinsn3 reduces keel bone breakage by 40-60%
Bone 2012
… and increases bone strength, toughness and stiffnessn3 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
Keel bone strength Strength vs fracture Bone mineral density
Failure load (Kg)
Fracture riskImpact tester Experimental keel fractures
Fracture risk with BMD Fracture risk with age (and KE)
80%
100%
70%
Probability of Fracture
90%
Fracture Probability
80% 60%
70%
50%
60%
50% 40%
40% 30%
30%
20%
20%
10% 10%
0% 0%
Keel Surface BMD 16 28 40 52 64
Age weeksKeel 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?
Tip -3cm
-1.5cm -4.5cm
BMD
20 23 30 40 42 50 60
Age
• To better understand structural factors
influencing fracture, we are modelling keels
using finite element analysis based on micro-CT,
composition and fine scale biomechanicsThe 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 strainsWhat the hen does…
Strong evidence points to hen collisions 100%
as being the principle cause of keel
fractures 75%
Fracture (%)
• Using a drop weight impact tester 50%
we have been modelling collisions and
fracture occurrence. 25%
• Fractures occur at relatively low
impact energies, and increase rapidly 0%
with greater impact KE -3 -2 -1 0 1 2 3
Kinetic Energy (+/- SD)
15
10
5
0
Impact energyFlights and collisions – its what they do!
Barn Free range
0.60
20 Weeks 30 Weeks 50 Weeks 70 Weeks
Average nos of flights per bird
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 12 18 2490.0
0 6 12 18 24120.0
Time of day
There is some scope to reduce “flightiness”, but generally
mitigation will depend on reducing the consequences of this
natural behaviourWhere the hen does it
Fracture rates and severity of different housing systems
n % Diss.
Severity
Mean severity Rates
Free Range 12 67±4cd 1.91±0.07bcd
FR A-frame 7 78±3cd 2.15±0.14cde
FR Arial
6 86±2d 2.59±0.14de
suspended
Organic Mob 8 45±3ab 1.61±0.03ab
OM Arial Fixed 4 84±5d 2.26±0.02de
Organic with
11 59±5bc 1.83±0.08abcd
slats
Barn 10 63±3bc 1.80±0.10abc
Furnished cage 9 36±5a 1.45±0.09aLow 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
2500
Perch heights:
R² = 0,6692
Perch height
2000
Previous studies have shown 1500
that reducing perch height 1000
alone may be beneficial
500
0
0 20 40 60 80 100
Fracture prevalence (%)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
Low impact
=
20
10
system 0
573
1
287
430
716
144
859
40
30
=
High impact 20
system 10
0
1
573
144
287
430
716
859henpecked….
The problem with being
Acceleration Acceleration
0
1
4
2
3
5
6
2
10
12
0
4
6
8
0 0
0,059 0,059
0,118 0,118
0,177 0,177
0,236 0,236
0,295 0,295
0,354 0,354
0,413 0,413
0,472 0,472
Time
0,531
Time
0,531
0,59 0,59
0,649 0,649
0,708 0,708
0,767 0,767
Accelerometer: Back
Accelerometer: Keel
0,826 0,826
0,885 0,885
0,944 0,944What 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 hazardsBern
Mike Toscano
The keel team Ariane Stratmann
Bristol Michigan
Lindsay Wilkins Daren Kercher
Fran Booth
Gemma Richards Exeter
Christine Nicol Krasi Tsaneva-Atanasova
Steve Brown
Sarah Lambton Noble Foods
Nick Avery Andrew Joret
Kate Robson-Brown
Stonegate
Richard Kempsey
Venco
Lotte van der VenFin(ish)
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