Chicken eggs: 10 questions and answers

How can hens lay eggs without a rooster?

Indeed, a hen lays regularly even in absence of a cockerel. Simply because an egg is an ovum that has reached maturity and a hen ovulates practically every day. All these ova are stored in an ovarian follicle awaiting maturity. These clusters of ova form a kind of bead-like chain that actually represents all future eggs of a hen. Then the follicle releases the mature ovum which moves towards the uterus via the oviduct. When one chain ends, another forms, marking the start of a new laying cycle. It usually takes about twenty days for this new chain to form, a period during which your hens stop laying.

A hen ovulates daily and does not need a cockerel to lay. However, a cockerel is useful for fertilising eggs

Each egg consists of a yolk, white and a shell. The yolk corresponds to the amniotic egg, the white is albumen secreted by the oviduct which protects the yolk. Finally, the shell, made mainly of calcium crystals, forms in about fifteen hours and protects the egg.

Unlike other birds, the hen can ovulate almost throughout the year. Simply because it has been domesticated for thousands of years, cross-bred and artificially selected… But originally, a hen, like other birds, produced ova (laid) only at specific times.

How to tell if an egg is fertilised?

An egg can only be fertilised if your hens encounter a cock. And mating must take place! But believe me, cocks are more than willing to serve several hens! Moreover, at each mating, almost all the ova that make up the row and are stored in the follicle are fertilised. Thus, a cock in his prime can fertilise up to 80% of the ova. Afterwards, at each laying, the hen releases her eggs (fertilised or not) and incubates them. This explains why chicks are not all hatched on the same day…

Theoretically, all a hen’s eggs can be fertilised once mating has occurred. However, an embryo will only develop (in 21 days) if the egg is incubated. This means an egg collected daily may be fertilised yet still edible.

Once the hen begins to incubate, embryos may develop.

Eggs being incubated by a hen must be candled to check whether they are fertilised

But sometimes not all eggs are viable. How can you tell whether an egg is really fertilised or not? You must candle it, that is to say observe it against a light, using a strong light source. Hold the egg in your hand and place the light under the rounded end. This lets you see what is happening beneath the shell:

• if the egg is completely transparent, it is not fertilised (or has just been laid)
• if the egg is streaked with red veins, it is fertilised
• if the egg looks dark and a shape can be made out, it is not only fertilised but a chick is developing.

Why are hens' eggs different colours?

Colour of a hen’s eggs does not depend on her diet or health, but only on her breed. Colour palette is fairly wide, ranging from lighter to darker shades depending on each hen’s genetic makeup. As for shell colour, it is fixed by pigments derived from the blood or bile of your pullets.

From pure white to chocolate brown, eggs vary in colour according to breed

So, if you want to collect eggs in different shades, keep hens of different breeds. Here is the colour palette:

• Marans hens lay dark brown to brown eggs, almost chocolate-coloured
• Leghorn and Gatinaise hens lay perfectly white eggs
• Araucana, Ameraucana, Javanese and Cream Legbar hens lay eggs that range in colour from green to pale blue
• Barnevelder and Welsummer hens lay reddish-brown eggs

Other hens such as Poule rousse, Orpington, Vorwerk, Sussex… produce light brown eggs.

→ Also see our advice sheet: Why do chicken eggs come in different colours?

Short answer - Per day: typically about 0.8–1 egg/day at peak (so most hens lay an egg most days, but not literally every day). - Per year: depends on breed and conditions — roughly 250–320 eggs/year for high‑performing commercial layers; 150–250/year for typical backyard hybrids; 80–180/year for heritage breeds and bantams. Details and factors - Breed: hybrid commercial layers (e.g. ISA Brown, Leghorn types) are bred for high output (250–320 eggs/year). Dual‑purpose or traditional breeds lay much less. Bantams lay fewer and smaller eggs. - Age: peak production is during first laying year. Output usually falls each following year. - Photoperiod: hens need about 14–16 hours light to maintain good laying. Short winter days reduce laying unless supplemented with light. - Moult and broody behaviour: moult and broodiness pause or greatly reduce laying for weeks or months. - Health and nutrition: good feed, clean water and low stress are essential for consistent laying. Practical example - If a hen averages 5.5 eggs/week (≈0.79 eggs/day), that’s about 286 eggs/year. So three good backyard layers will typically supply a household with a dozen eggs per week.

Answer to the first question is simple (though…), the answer to the second is a little more variable. Generally, a hen lays one egg a day but, occasionally, she may lay two in a day, or more precisely two in a 24-hour cycle, bearing in mind it takes 15 to 26 hours for an egg to form.

By contrast, determining number of eggs in a year is more complicated, because it varies according to hen breed, her age and the season. Some breeds such as Poule rousse, Sussex, Gatinaise, Vorwerk, Marans and Harco are top performers, laying 200 to 300 eggs a year, a figure that can vary depending on diet and comfort provided. Also note hens lay less in winter because of lack of light and cold. Summer heat can also disturb them.

Poule rousse, Sussex, Gatinaise, Vorwerk, Harco and Marans are among the most productive egg-laying hens

How many years does a hen lay eggs?

Again, the duration of laying varies according to several factors such as breed, diet and living conditions… In general, hens lay prolifically until about three years old. After that, laying declines by about 20% per year. Most hens stop laying altogether at around eight years.

Why do hens sometimes lay eggs without shells?

Several reasons can explain a hen laying a shell-less egg, which is very soft. Starting with onset of laying in a young pullet. These first eggs often have a very thin or absent shell.

A hen lacking calcium also lays shell-less eggs, the shell being essentially formed of calcium crystals. To remedy this, provide hens with crushed oyster shells or crushed eggshells (risk they may eat their eggs!).

Finally, laying of shell-less eggs can also be explained by a period of stress caused by predator attacks, poor hygiene, moulting or excessive heat.

How to store eggs?

This question has long sparked disagreements between those who favour keeping eggs in the fridge and those who do not. Generally, it’s recommended to store eggs at room temperature, but only up to 22 °C. In fact, that’s how they are kept in supermarkets. However, there’s nothing to stop you keeping them in the fridge. Ultimately, it’s temperature fluctuations that are more to be feared for proliferation of bacteria such as Salmonella.

Whether stored outside or in the fridge, eggs must not be exposed to temperature fluctuations

You can therefore store your eggs in a garage, cellar or unheated conservatory, but avoid leaving them on the kitchen worktop where temperature changes are quite marked. As soon as summer heat arrives, put them in the fridge or in a room that stays reasonably cool.

How long can eggs be kept?

Eggs keep for 30 to 40 days if stored in good conditions. We strongly advise writing laying date in pencil on each freshly collected egg.

If it is slightly cracked or broken, it must be consumed within 2 days at most.

How to tell if an egg is fresh?

You haven’t noted the laying date on your egg and are unsure whether to eat it? A simple trick is to put it raw into a bowl of cold water. If it sinks to the bottom, it’s very fresh. If it stays in the middle, it’s fine for an omelette or to be hard‑boiled. If, however, it floats at the surface of the water, it’s best to throw it away.

Can eggs soiled by dirt or droppings be washed?

Do not wash eggs soiled with earth or droppings. Why? Washing them makes them porous because it removes the thin protective layer that surrounds them. This makes it easier for bacteria to enter. The only time you should clean them is just before cracking them.

An egg should only be washed immediately before cracking