HATCHABILITY Understanding timely embryonic developments, as well as analysing hatch residue, are a useful hatchery management tools. They will provide valuable information in isolating problems in both the breeder and the hatchery programs. THE TIMING OF MAJOR EMBRYONIC DEVELOPMENTS BEFORE EGG LAYING Fertilization Division and growth of living cells Segregation of cells into groups of special function (gastrulation) Normal size of air cell at various stage of life BETWEEN LAYING AND INCUBATION No growth, state of inactive embryonic life DURING INCUBATION Day 1 Development of area pellucids and area opaca of blastoderm Major developments visible under microscope 18 hours appearance of alimentary tract 19 hours beginning of brain crease 20 hours appearance of vertebral column 21 hours beginning of formation of brain and nervous system 22 hours beginning of formation of head 23 hours appearance of blood islands Day 2 Day 3 24 hours beginning of formation of eyes Embryo begins to turn on left side Blood vessels appear in the yolk sac Major developments visible under microscope: 25 hours beginning of formation of veins and heart 30 hours second, third and fourth vesicles of brain clearly defined, as is heart, which now starts to beat 35 hours beginning of formation of ear pits 36 hours first sign of amnion 46 hours formation of throat Beginning of formation of nose, wings, legs, allantois Amnion completely surrounds embryo Day 4 Beginning of formation of tongue Embryo completely separates from yolk sac and turned on left side
Day 5 Day 6 Day 7 Day 8 Day 9 Allantois breaks through amnion Preventriculus and gizzard formed Formation of reproductive organs - sex division Beginning of formation of beak and eggtooth Main division of legs and wings Voluntary movement begins Indication of digits in legs and wings Abdomen more prominent due to development of viscera Day 10 Beginning of formation of feathers Embryo begins to look bird-like Mouth opening appears Beak start to harden Skin pores visible to naked aye Digits completely separated Day 16 Small intestines taken into body Scales, claws, and beak becoming firm and horny Embryo fully covered with feathers Albumen nearly gone, yolk increasingly important as nutriment Day 17 Beak turns toward air cell, amniotic fluid decreases, and embryo begins preparation for hatching Day 18 Day 19 Growth of embryo nearly complete Yolk sac draws into body cavity through umbilicus Embryo occupies most of space with in egg except air cell Day 20 Yolk sac completely drawn into body cavity Embryo becomes chick, breaks amnion, starts breathing in air cell Day 21 Allantois ceases to function and starts to dry up Day 12 Toes fully formed First few visible feathers Day 13 Appearance of scales and claws Body fairly well covered with feathers Day 14 Embryo turns its head towards blunt end of egg Day 15
Chick hatches ANALYSING HATCH RESIDUE Analysing hatch residue is a useful management tool that will provide valuable information in isolating problems in both the breeder and the hatchery programs. The following is a list of problems that may be observed and there possible cause(s). 1. Chicks Hatch Late Variable room temperature Large eggs Old eggs Incorrect thermometer Temperature too low, 1 to 19 days Temperature too low in hatchery 2. Fully Developed Embryo with Beak Not in Air Cell Temperature too high, 1 to 10 days Humidity too high, 19th day 3. Fully Developed Embryo with Beak in Air Cell Incubator air circulation poor Humidity too high, 20 to 21 days Shell quality 4. Chicks Pipping Early Temperature too high, 1 to 19 days 5. Chick Dead after Pipping Shell Lethal genes Disease in breeder flock Eggs incubated small end up Thin-shelled eggs Eggs not turned first two weeks Eggs transferred too late Inadequate air circulation, 20 to 21 days CO 2 content of air too high, 20 to 21 days Incorrect temperature, 1 to 19 days Humidity too low, 20 to 21 days 6. Malpositions Egg set small end up Odd-shaped eggs set Inadequate turning 7. Sticky Chicks (albumen sticking to chicks) Eggs transferred too late
Humidity too low, 20 to 21 days Down collectors not adequate 8. Sticky Chicks (albumen sticking to down) Old eggs Air speed too slow, 20 to 21 days Inadequate air in incubator Humidity too high, 20 to 21 days Down collectors inadequate 9. Chicks Covered with Egg Remnants Nutrition Humidity too high Temperature too low 10. Eggs Exploding Bacterial contamination of eggs Dirty eggs Improperly washed eggs Incubator infection 11. Clear Eggs Infertile Eggs held improperly Too much egg fumigation Very early embryonic mortality Immature males Male-female ratio Females fat Nutrition Overcrowding flock 12. Blood Ring (embryonic death 2-4 days) Heredity Diseased breeding flock Old eggs Rough handling of hatching eggs Incubating temperature too high Incubating temperature too low Holding temperature Contamination Shell quality Young flock Nutrition Humidity Fumigation Insufficient turning of eggs 13. Dead Embryos, 2 nd Week of Incubation Disease in breeder flock Eggs not cooled prior to incubation Temperature too high in incubator Temperature too low in incubator Electrical power failure Eggs not turned Too much CO 2 in air (inadequate ventilation) Genetics Contamination Parasites
Shell quality Humidity 14. Air Cell Too Small Large eggs Humidity too high, 1 to 19 days 15. Air Cell Too Large Small eggs 16. Chicks Hatch Early Small eggs Leghorn eggs versus meat-type eggs Incorrect thermometer Temperature too high, 1 to 19 days 17. Chicks Too Small Eggs produced in hot weather Small eggs Thin, porous eggshells 18. Chicks Too Large Large eggs Humidity too high, 1 to 19 days 19. Trays Not Uniform in Hatch or Chick Quality Eggs from different breeds Eggs of different sizes Eggs of different ages when set Disease or stress in some breeder flocks Inadequate incubation air circulation & heat distribution 20. Soft Chicks Unsanitary incubator conditions Temperature too low, 1 to 19 days Humidity too high, 20 to 21 days 21. Chicks Dehydrated Eggs set too early Humidity too low, 20 to 21 days Chicks left in hatcher too long after hatching completed 22. Mushy Chicks Possible cause: Unsanitary incubator conditions 23. Un-healed Navel, Dry Temperature too low, 20 to 21 days Wide temperature variation in incubator
Humidity too high, 20 to 21 days Humidity not lowered after hatching completed 24. Un-healed Navel, Wet and with Odour Omphalitis Unsanitary hatchery and incubators 25. Chicks Cannot Stand Breeder ration inadequate Improper temperature, 1 to 21 days, overheating Humidity too high, 1 to 19 days Inadequate ventilation, 1 to 21 days 26. Crippled Chicks Variation in temperature, 1 to 21 days Malpositions 27. Crooked Toes Improper temperature, 1 to 19 days 28. Spraddle Legs Possible cause: Hatchery trays too smooth 29. Short Down High temperature 30. Closed Eyes Humidity too low, 20 to 21 days