Abstract: A photographic guide to goose embryo development is compiled to help visually determining time of embryo mortality in eggs during incubation.
Goose eggs can be particularly difficult to hatch due to their large size, the hardness of their shells, and the need to cool them regularly. The incubation period of goose eggs takes about 30 days and percent hatch generally does not exceed 70 %.
Candling of hatching eggs during incubation and examination of the clear eggs or dead embryos is a useful tool for poultry hatchery managers.
As a general practice adopted at the Goose Breeding Research Station of the Gödöllő University, goose eggs candled out from the incubator were subjected to a careful examination to identify hatching problems. To help determining time of embryonic mortality in eggs a series of colour photographs were taken on known-age embryos. This collection of reference photos enabled us to compile a photographic guide to goose embryo development and make it available here.
Materials and Methods
A total of 70 eggs were collected from a Hungarian Upgraded Goose flock of the Goose Breeding Research Station and incubated in a laboratory hatchery. Individual eggs were removed from the incubator at 1-3 day intervals until day 26 of incubation. For each interval, one-two eggs were opened using standard procedure then, visually inspected and photographed. Regretfully, no measurements were taken on eggs or embryos as the colour photos were originally designed for "domestic use".
Following is a photographic depiction of goose embryo development, based on prominent external characteristics visible to the unaided eye (Fig. 1)
Day 1: Blastoderm visible in a fertile egg opened after 12 hours incubation.
Day 2: Blastoderm without embryo: the blood ring indicates a dead and probably abnormal embryo from a fertile egg opened after 48 hours incubation.
Day 3: Blood islands apparent in yolk sac after 62 hours incubation.
Day 4: A small, centrally located embryo visible with prominent vitelline vessels after 86 hours incubation; head fold present but no tail fold.
Day 5: Elongated embryo showing early pigmentation of eyes after 100 hours incubation.
Day 6: Iris pigmented, limb buds are noticeable.
Day 9: Embryo discernible in amniotic sac and allantois also visible.
Day 10: Digits appear on wings.
Day 11: Embryo (got rid of foetal membranes) with well discernible body parts.
Day 12: Embryo with well-developed limbs. Feather germs begin to appear on the back.
Day 14: Beginning of bill noticeable, down already visible on the back.
Day 15: Eyelid reaches the pupil, down noticeable on the back and tip of the tail.
Day 17: Down also visible on dorsal part of the neck.
Day 18: Embryo covered by down is visible in a characteristic posture.
Day 19: Embryo well-developed and completely feathered; transverse ridges noticeable at metatarsi.
Day 20: Feathers and bill pigmented, eyelids still not completely closed.
Day 24: Scutes visible on tarsus ending in unguis. Eyelids nearly closed. Uric acid crystals in allantois fluid indicate total utilisation of protein
Day 25: Eyelids close the eyes.
Day 26: Eyes open; yolk sac partly absorbed in abdominal cavity.
At day 27-28 of incubation, egg tooth may penetrate shell membranes (pulmonary respiration begins) or shell may be piped. Finally, at day 29-30 the fully formed embryo with yellow feather colour emerges as hatched gosling.
This photographic guide has been used at the Goose Breeding Research Station and found helpful in research and practice of hatching goose eggs. Hopefully, other goose experts may also make use of this guide.