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]
• 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
• 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
0
10
20
30
40
50
60
70
80
90
100
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
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:
Three basic factors cause keel bone fractures in laying hens
• Where it does it
• The hen
• What the hen does
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!
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
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!
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
n3 reduces keel bone breakage by 40-60%
… and increases bone strength, toughness and stiffness
Bone 2012
n3 increases bone density, volume & trabecular thickness
• 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
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
• 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
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
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
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
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
21
Low risk / Low impact?
High risk / High impact?
Medium risk / Medium impact?
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
• 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
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….
What the house is made of Looking at how material properties influence fracture rate
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
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
