In the adult hen, the oviduct receives the ovum from the ovary and provides the biological environment for the formation and potential fertilisation of the egg. During egg formation, albumin, from the magnum is deposited around the yolk, followed by the eggshell membranes from the isthmus, which subsequently surround the egg. As the yolk traverses through the oviduct, calcium is deposited on to it, from the uterus, forming a hardened eggshell. Ovalbumin, avidin and ovomucin secreted from magnum provides content and antimicrobial activity in the egg-white. Collagen X and fibrilin 1 from the isthmus make up the fibrous eggshell membranes. Calbindin 1, ovocleidin-116 and secreted phosphoprotein 1 secreted from the shell gland contribute in calcium ion remodelling for eggshell mineralisation. This review summarises the expression pattern and functional role of genes having a leading role in the egg formation.

Conventional feeding systems for laying hens rely on a complete feed available ad libitum in mash, pelleted or crumble form. When complete feeds are used, intake is mainly controlled by the hens’ energy requirement and feed presentation, but the birds cannot adjust their consumption to other nutritional needs and thus over-consume to cover the calcium needed for egg shell formation. Sequential, loose-mix and choice feeding offer birds the opportunity to select different diets in the short term. These feeding strategies have been proposed as alternative feeding systems whose main objectives are to match nutrient supply to individual requirements during the daily changes induced by the temporal sequence of the egg formation. This review discusses some findings related to the use of whole cereals and of alternating low and high energy or protein diets, conditions which may improve feed utilisation efficiency. In addition, the adjustment of calcium and phosphorus levels during the day can have benefits in terms of egg production and quality. This review explores the physiological basis for sequential, loose-mix and choice feeding and evaluates the impact of these systems on egg production and quality.