1. Eggshell Quality in Laying Hens D. R. Korver University of Alberta Edmonton, Alberta, Canada

3. 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

4. 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

5. Eggshell Formation Egg size increases with hen age (body weight) Shell deposition remains constant

6. 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

7. 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

8. 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

9. Implications Shell quality problems are often seen before bone problems

10. 172224262830311820 18 wks 20 wks 22 wks 24 wks 26 wks Experimental Design 1.00 % Ca (grower) 3.25 % Ca (breeder)

11. a ab bc c c cd c c de e 20182224262018222426 P<0.01 Average Egg Weight to 31 Weeks

12. 20182224262018222426 ab a b b bb ccc P<0.0008 Shell Weight

13. 20182224262018222426 P<0.0605 Specific Gravity

14. 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?

15. Soluciones

16. 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

17. 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

18. 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

19. 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

20. 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)

21. Eggshell Formation Hendrix Genetics

22. 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

23. 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

24. 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

25. ANSC 463 Egg Production in Layers response to 1 hr of light @ 12 AM Supplemental Lighting begun

26. Feed Supplements Phytate Vitamin C Trace Minerals Vitamin D 3 – 25-OH Vitamin D 3

27. 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

28. 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

29. Heat Stress Electrolyte balance – Panting causes a loss of CO 2 Replace 30-35% of NaCl with NaHCO 3

30. ANSC 463 Possible solutions to low calcium status: – water supplementation of calcium Calcium Metabolism

31. 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

32. Muchas gracias