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Glossary

Air cell - The air space between the inner and outer shell membranes. Usually found at the broader end of the egg.
Albumen - The white of the egg.
Antagonist - An anti-nutritional factor present in feed which reduces its nutritional value.
Calcification - See Shell calcification.
Cannibalism - The vice of eating other birds.
Chalazae - White, twisted, rope-like structures attached to the thick albumen which anchor the yolk in the centre of the egg.
Cloaca - The common external opening for the digestive, urinary and reproductive tracts.
Cull - To remove unprofi table or otherwise unwanted birds from the flock.
Cuticle - The outer membrane covering the egg shell which gives the shell a bloom.
Filler - A moulded tray for packing eggs in an upright position.
Follicle - A sac-like structure in the ovary containing a developing ovum.
Germinal disc - A small, circular, white patch on the upper surface of the yolk, containing cells from which the chick develops if the egg is fertilised.
Grading - The process of classifying eggs by quality and by weight.
Infundibulum - A funnel-shaped section of the oviduct, about 6 to 8 cm long, which collects the ovum as it is released from the ovary.
Isthmus - A section of the oviduct about 12 cm long which secretes the shell membrane and some albumen.
Light programme - The schedule of artificial lighting for poultry flocks. Day length and light intensity are regulated to improve egg production.
Magnum - Part of the oviduct, immediately after the infundibulum. It is about 30 cm long and secretes about 40% of the egg’s albumen.
Ovary - The female reproductive organ in which the ova (yolks) develop. Only the left ovary is functional in hens.
Oviduct - A long, tubular organ which adds the egg white, shell membranes and shell to the yolk as it passes through.
Ovulation - The release of a mature ovum from an ovarian follicle. Ovum (plural ova) - An egg at the stage when it is a yolk without any white (albumen).
Oxidising agent - A substance which brings about chemical changes involving oxygen. In the case of poultry feed, these changes can result in loss of potency or nutritional value.
Premix - A blend of micro-ingredients, usually vitamins or trace minerals and including a carrier substance, added to feed during the mixing process.
Prolapse - The irreversible protrusion of the cloaca.
Pullet - A female bird in her fi rst laying season.
Roll-out tray - An extension of the cage fl oor on which eggs accumulate for collection.
Shell calcification - The process of shell formation during the period the egg is in the shell gland (uterus). Shell membranes - Inner and outer membranes that together line the inside of the shell and adhere very closely to it.
Uterus (shell gland) - Part of the oviduct, about 12 cm long, which secretes water into the albumen and forms the shell.
Vagina - Part of the oviduct, after the uterus, in which the shell cuticle is formed.
Vent (anus) - The external opening of the cloaca.
Vent picking - The vice of pecking other birds around the vent.
Vitelline membrane - A thin, transparent membrane which surrounds and contains the yolk.