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Eggshell Formation First phase – First ~5 hours of calcification Ca crystals begin to form Second phase – Next 12 hours of calcification – 90% of Ca deposition – mg Ca/hour
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Eggshell Quality in Laying Hens
D. R. Korver
University of AlbertaEdmonton, Alberta, Canada
Eggshell Formation• First phase
– First ~5 hours of calcification
• Ca crystals begin to form
• Second phase– Next 12 hours of
calcification– 90% of Ca deposition– 180-200 mg Ca/hour
Eggshell Formation• ~5.5 g of eggshell per egg• ~2.2 g of Ca
• Eggshell composition– 95% CaCO3
– 0.3% P– 0.3% Mg
Eggshell Formation• Egg size increases with hen age (body weight)• Shell deposition remains constant
Issues in Shell Quality• 250 eggs = ~20 times total bone Ca reserves• After peak production, a consistent amount of
shell material is put on each egg– Larger eggs, thinner shells
Calcium Metabolism• Eggshell formation
– demand for Ca from ~6-24 hrs of ovulation cycle• enough skeletal calcium for ten
eggshells
• enough medullary bonefor one eggshell
ANSC 463
Calcium Metabolism• Eggshell formation
– 60-80% of calcium required for eggshell formation derived directly from the diet on shell-forming days
– the greater the proportion of eggshell calcium derived from bone stores, the poorer the shell quality
ANSC 463
Implications• Shell quality problems are often seen before
bone problems
17 22 24 26 28 30 3118 20
18 wks
20 wks
22 wks
24 wks
26 wks
Experimental Design
• 1.00 % Ca (grower)
3.25 % Ca (breeder)
5051525354555657
18 C 28 C
Egg
Wei
ght (
g)
a abbc c c
cdcc
dee
2018 22 24 26 2018 22 24 26
P<0.01
Average Egg Weight to 31 Weeks
0
1
2
3
4
5
6
18 C 28 C
Shel
l Wt (
g)
2018 22 24 26 2018 22 24 26
ab ab ab bbb c c c
P<0.0008
Shell Weight
1.075
1.078
1.080
1.083
1.085
18 C 28 C
Spec
ific
Grav
ity
2018 22 24 26 2018 22 24 26
P<0.0605
Specific Gravity
Broiler Breeders vs Layers• Time of switch to high Ca diet is important in
broiler breeders– Especially at high temperatures
• Laying hens seem to be less sensitive to early switch– Effect of high temperature?
Soluciones
Nutrients & Eggshell Formation• Ca level; Ca-P ratio
– Change with age• Vitamin D
– Reduced metabolism with hen age• NaCl – feed, water
– High NaCl reduces shell quality• Phytate
– Binds Ca, P
Nutrients & Eggshell Formation• Trace minerals
– Copper – lysyl oxidase• Cross-links in shell membrane fibers
– Manganese• Mucopolysaccharide formation – mammilary layer
– Zinc• Carbonic anhydrase – bicarbonate ion secretion
Management & Eggshell Formation • Body weight at placement
– Small pullets may lack sufficient medullary bone
• Pre-lay or not pre-lay?– Not before 10 days prior to first egg
• Switch to high Ca layer diet– ~5% production
Management & Eggshell Formation • Environmental temperature
– Minimize heat stress
• Electrolyte balance– Panting causes a loss of CO2
– Blood pH increases from 7.2 to 7.5-7.7• Loss of bicarbonate ions limits CaCO3
– Limits shell formation
Feed Intake• Feed particle size
– large particle calcium sources• 2/3 large particle (> 1mm)
– Retained in gizzard• 1/3 small particle (<1 mm)
– Quickly available
• Top-dress feed (emergency)
Eggshell Formation
Hendrix Genetics
Feed Intake• Brown layers
– Begin eggshell formation ~4 hours before lights out
– Encourage feed intake during the last 6 hours of the day
– Midnight feeding– Particle size
• 70% particles of 2-4 mm – slow release• 30% particles of <1 mm – quick release
Feed Intake• White layers
– Begin eggshell formation just before lights out– Encourage feed intake during the last 4 hours of
the day– Midnight feeding
• 50% particles of 2-4 mm – slow release• 50% particles of <1 mm – quick release
ANSC 463
Egg Production in Layersresponse to 1 hr of light @ 12 AM
Weeks of Production20 22 24 26 28 30 32 34 36 38
% H
en D
ay P
rodu
ction
0
10
80
90
100
***
**
*
SupplementalLighting
begun
Feed Supplements• Phytate• Vitamin C• Trace Minerals• Vitamin D3
– 25-OH Vitamin D3
Strain 0.0005Diet 0.0449S x D NS
Defective Shells
4.6
7.7
1.92.9
0123456789
W36-D W36-25-OH D3 W98-D W98-25-OH D3
Num
ber
of E
ggs p
er H
en
Bone Density
Strain NS Diet P=0.0386 S x D NS
105.8 95.8 107.3 95.4
0255075
100125
W36-D W36-25-OH D3 W98-D W98-25-OH D3
Bon
e M
iner
al D
ensi
ty (m
g/cm
3 ) 892.5 885.8916.2898.1
0200400600800
1000
W36-D W36-25-OH D3 W98-D W98-25-OH D3
Strain P=0.0296 Diet NS S x D NS
Cortical
Medullarya bb a
Heat Stress• Electrolyte balance
– Panting causes a loss of CO2
• Replace 30-35% of NaCl with NaHCO3
ANSC 463
• Possible solutions to low calcium status:– water supplementation of calcium
Calcium Metabolism
Conclusions• Shell quality problems can be caused by many
factors
• Shell quality problems often precede bone quality problems.
• Practical solutions can be used to prevent & correct problems
Muchas gracias