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Eggshell Quality in Laying Hens D. R. Korver University of Alberta Edmonton, Alberta, Canada
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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 – 180-200 mg Ca/hour
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Eggshell Formation ~5.5 g of eggshell per egg ~2.2 g of Ca Eggshell composition – 95% CaCO 3 – 0.3% P – 0.3% Mg
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Eggshell Formation Egg size increases with hen age (body weight) Shell deposition remains constant
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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
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Calcium Metabolism Eggshell formation – demand for Ca from ~6-24 hrs of ovulation cycle enough skeletal calcium for ten eggshells enough medullary bone for one eggshell ANSC 463
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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
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Implications Shell quality problems are often seen before bone problems
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172224262830311820 18 wks 20 wks 22 wks 24 wks 26 wks Experimental Design 1.00 % Ca (grower) 3.25 % Ca (breeder)
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a ab bc c c cd c c de e 20182224262018222426 P<0.01 Average Egg Weight to 31 Weeks
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20182224262018222426 ab a b b bb ccc P<0.0008 Shell Weight
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20182224262018222426 P<0.0605 Specific Gravity
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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?
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Soluciones
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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
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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
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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
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Management & Eggshell Formation Environmental temperature – Minimize heat stress Electrolyte balance – Panting causes a loss of CO 2 – Blood pH increases from 7.2 to 7.5-7.7 Loss of bicarbonate ions limits CaCO 3 – Limits shell formation
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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)
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Eggshell Formation Hendrix Genetics
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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
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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
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ANSC 463 Possible solutions to low calcium status: – midnight feeding allow access to feed for 1 hour in the middle of the night dietary calcium available during peak eggshell formation short duration of lighting does not appear to affect photoresponsiveness Calcium Metabolism
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ANSC 463 Egg Production in Layers response to 1 hr of light @ 12 AM Supplemental Lighting begun
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Feed Supplements Phytate Vitamin C Trace Minerals Vitamin D 3 – 25-OH Vitamin D 3
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Strain0.0005 Diet0.0449 S x DNS Defective Shells 4.6 7.7 1.9 2.9 0 1 2 3 4 5 6 7 8 9 W36-D W36-25-OH D 3 W98-DW98-25-OH D 3 Number of Eggs per Hen
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Bone Density Strain NS Diet P=0.0386 S x D NS 105.8 95.8 107.3 95.4 0 25 50 75 100 125 W36-DW36-25-OH D 3 W98-D W98-25-OH D 3 Bone Mineral Density (mg/cm 3 ) 892.5 885.8 916.2 898.1 0 200 400 600 800 1000 W36-DW36-25-OH D 3 W98-DW98-25-OH D 3 Strain P=0.0296 Diet NS S x D NS Cortical Medullary a bb a
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Heat Stress Electrolyte balance – Panting causes a loss of CO 2 Replace 30-35% of NaCl with NaHCO 3
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ANSC 463 Possible solutions to low calcium status: – water supplementation of calcium Calcium Metabolism
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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
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Muchas gracias
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