Egg size matters in free-range egg production, and it can be influenced by the farmer from the moment the pullets arrive on farm.

In episode 8 of the Wynnstay Agri-Hub Podcast, my colleagues: Fiona Hunt, Steve Marriott and I joined host Tony Morris to discuss how egg size can be controlled through flock management in free-range egg production.

Egg size is determined by the weight of the egg. A large egg must be at least 63g and a medium egg at least 53g, with anything lower classed as small.

For a flock aiming for large eggs, it is ideal to raise the egg size up to 64g, then keep it at the same level for as long as possible. There is no benefit of increasing beyond 65g, as there’s no increase in payment.

Medium eggs are favourable from a welfare perspective, as free-range layers are not genetically suited to lay large eggs straight away.

In the UK, producing as many large eggs as possible tends to be the most profitable option for free-range egg producers. This trend is driven by cookbooks and celebrity chefs, with many recipe ingredient lists specifying large eggs, increasing consumer demand for them.

However, with rising costs of production in recent months, this trend is starting to reverse. We are now looking at a possible shift where the most profitable approach for new flocks could be to produce a higher number of medium eggs instead.

It’s worth noting that the potential egg mass from a flock - the weight of all the eggs produced combined – does not change. So, at the start of a new flock producers must decide between aiming for a higher number of medium eggs or a lower number of large eggs. This requires looking at the price of medium vs large eggs and agreeing with the egg packer as to which approach will be most profitable for the entire lay cycle. Flock management can then be adjusted accordingly.

There are numerous factors which impact egg size and the timing of coming into lay.

• The time of day and time of year they arrive at the laying shed
• Nutrition
• Ventilation
• Shed temperature
• Light levels

Careful balancing of these factors from chick-rearing and throughout the lay cycle is required to manage egg size in a flock.

Whatever the breed, management from day one to 16 is crucial. The building blocks for achieving desired egg size start with taking on pullets which have lived well during the entire rearing period.

Once the pullets have arrived at the laying shed, there are five to six weeks ahead of the onset of lay to get them on track for producing target egg weights. 

There is an optimum temperature for each breed of laying hen to be kept at. Having sheds a degree cooler than their optimum temperature means they eat more, which can impact cost of production.

Temperature can be used to manipulate feed intakes and therefore weight gain in a new flock. Lowering the temperature to boost feed intake can result in birds being larger when they start to lay, meaning large eggs can be achieved earlier in the cycle. In general, lighter birds come into lay more quickly but produce lower egg sizes. On the other hand, heavier birds are slower coming into lay but quicker to reach larger eggs.

Temperature can also be used to manipulate egg weights if they are increasing too quickly. The shed temperature can be increased slightly to reduce the flock’s feed intake and maintain a similar egg size for longer.

When pullets come into the laying shed they are initially exposed to 10 hours of light per day. When this is increased, they are stimulated to start laying.

The heavier the weight of the birds, the quicker they will start laying large eggs. To set up a flock for large eggs, keep them on ten hours of light for longer, to allow their body weight and frame to get bigger. Once stimulated with light, add an extra hour every week. This effectively mimics spring transitioning into summer, so the birds think it is summer and achieve a steady production for the rest of the cycle.

Egg weight can be controlled through flock management by using temperature and light levels to manipulate the size of birds when they come into lay.

Listen to our Wynnstay Agri-Hub podcast to hear more on how this can be achieved and why it matters. Or, if you are thinking about going into free-range egg production, listen back to season 1, episode 4 where Jim Turner gives his tips for starting out.