Excessive yellow coloring of down
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DEVELOPMENT OF THE CHICKEN EMBRYO
DAY STAGE OF DEVELOPMENT
1. Blastoderm appears as donut-shaped ring; Area pellucida and area opaca. Infertile germinal disc appears as an undefined mass. 18 hrs - appearance of alimentary tract, 19 hrs beginning of brain crease, 20 hrs- appearance of vertebral column, 21 hrs - beginning of formation of brain and nervous system. 22 hrs - beginning of formation of head, 23 hrs - appearance of blood islands. 24 hrs - beginning of formation of eyes.
2. Appearance of blood islets; Formation of head process, Blood vessels in yolk sac. 25 hrs - beginning of formation of veins and heart, 30 hrs - second, third and fourth vessicles of brain clearly defined, as is 2 chamber heart, starts beating. 35 hrs - ear pits form, 36 hrs - first sign of amnion, 46 hrs - first signs of throat. 48 - 52 hrs - partly to fully turned on left side , 50-55 hrs - Optic cup completely formed.
3. Vascular system well developed. Left side of embryo on yolk; Nose, wings and allantois forms. Amnion surrounds embryo. leg and wing buds begin as swellings of approximately equal size (52-64 hrs).
4. Increase in size of brain and heart. limb buds approximately as long as they are wide (legs longer); 4 1/2 days - limb buds longer than wide. Allantois breaks through amnion.
5. Distinct eye development; elbow and knee joints and demarcation of three toes distance; Proventriculus and gizzard formed. Formation of reproductive organs, sex division. 5.5 - 6 days - ear opening very distinct.
6. Beak being formed; 6-6.5 days - wing bent in elbow joint, no egg tooth yet. Voluntary movement begins.
7. Egg tooth visible, eyes increasing in size , indications of digits in legs and wings, abdomen more prominent due to visceral development. 6.5 - 7 days, leg bent at knee, feather germs along spine and legs visible. 7.5 days - gap narrow between upper and lower beak, distinct feather papillae on thigh.
8. Feet and wings well developed, down formations starts, 7.5 days - nictitating membrane starting to cover eye.
9. Feather follicles on all tracts, large egg tooth, eyelids extend toward beak and start to overgrow eyeball., mouth opening appears.
10. Beak starts to harden, digits separated, claws just visible, flight feathers conspicuous. Comb appears a prominent ridge.
11. Claws flattened, curved; comb more prominent and serrated. foot pads conspicuous and smooth. proportions of head and body changing.
12. Down feathers on body and over eyes; eyelids cover 2/3 to 3/4 of cornea. covert feather germs become conical.
13. Appearance of scales and claws. beak hardened up to egg tooth, ear opening nearly covered with feathers; eyelid opening reduced to thin crescent. appearance of wattles and prominent comb.
14. Embryo turns toward blunt end of egg. Embryo rotates parallel to long axis of egg with head normally toward large end.
15. Small intestines taken into body, increase in size and feathering.
16. Scales and claws and beak becoming hard, fully covered with down; albumen nearly gone and yolk increasingly important as nutrient.
17. Normal hatching position (head under right wing, pointed toward air cell) ; decrease in amniotic fluid.
18. Albumen gone, yolk retraction starts; translucent outer covering of beak pealing away at base.
19. Absorption of allantoic fluid completed, yolk sac about half enclosed by body.
20. Yolk sac completely drawn into body cavity and umbilicus closing over; inner shell membrane pierced, piping begins, embryo breaks into air cell and breathing begins; allantois ceases to function and starts to dry up.
21. Hatch, usually takes 10-20 hours.