Transported Eggs

TRANSPORTED EGGS

WHY DO AIR CELLS BECOME DAMAGED?

The usual advice is to rest posted eggs for twenty-four hours and hope that damaged air cells somehow repair themselves.

But let's stop and think about what a damaged air cell actually is.

A damaged, detached or "saddled" air cell is a tear—a separation between two membranes. One membrane remains attached to the inside of the shell, while the other is pulled away to form the inner wall of the air cell.

Once those membranes have separated, simply leaving the egg sitting on the bench does not cause them to reattach.

So what causes the damage in the first place?

The evidence points to two things acting together:

  • moisture loss, which enlarges the air cell;
  • jolting and rough handling during transport.

The bond between the membranes is otherwise remarkably strong. Shake a fresh egg with a small air cell and very little happens. Yet eggs packed in tissues and other absorbent materials frequently arrive with detached or saddled air cells.

That observation leads us to an important conclusion: transport alone is probably not the whole story.

HOW CAN WE REDUCE THE RISK?

The fresher the egg is when it begins its journey, the better.

If eggs must be stored before posting, keep them at more than 70% relative humidity. The smaller the air cell is when the trip begins, the less opportunity there is for it to detach.

Try to prevent moisture loss during transport. A moisture barrier is preferable.

Avoid placing absorbent materials directly against the shell. An airtight first wrapping, such as cling film around each egg, helps to slow the loss of moisture.

And before someone asks, no—the eggs do not need to breathe while they are being posted.

Ventilation only becomes important once incubation begins and the developing embryo starts producing waste gases.

There is also evidence that eggs stored and transported inverted, with the air-cell end lowermost, show less enlargement of the air cell because the weight of the contents bears against it.

SHOULD POSTED EGGS BE RESTED?

This is where many people will disagree, but think about what is actually happening inside the shell.

While the egg is resting:

  • moisture continues to leave the egg;
  • the air cell continues to enlarge;
  • the membranes remain separated.

The egg is simply becoming older.

Time cannot repair a detached air cell.

Development, however, can.

WHY DO WE TURN FROM DAY ZERO?

The embryo that first begins to develop is surprisingly vulnerable.

At this stage it is not yet enclosed within the familiar fluid-filled embryonic sac. It sits exposed on the surface of the yolk while the edges of the growing membrane spread outward and eventually join above it.

The growing edge of the chorion appears to operate on a "like-to-like" principle. Its purpose is to seek out its matching edge and fuse with it, completing the enclosure of the embryo.

Unfortunately, in an egg with a detached or displaced membrane, the chorion may mistake the nearby inner shell membrane for its intended destination. Instead of joining with its opposite edge, it attaches to the shell membrane and anchors the embryo in place.

An embryo that becomes fixed in this way may remain trapped in the same position throughout incubation, leading to the familiar mid-egg-pip malposition.

For that reason, eggs with damaged air cells are incubated upright and turned through the vertical from the very first day.

CAN A DAMAGED AIR CELL REPAIR ITSELF?

This is the part that gives us hope.

We incubate eggs with damaged or saddled air cells upright and begin turning immediately.

As the embryo grows, it occupies more and more of the available space inside the shell. In doing so, it gradually displaces the detached membrane and pushes the saddle back towards its normal position at the top of the egg.

That, folks, is The Repair.

The repair does not come from waiting.

The repair comes from development.

REMEMBER

Damaged air cells do not appear to be caused by rough handling alone.

The evidence suggests that the problem results from a combination of:

  • moisture loss;
  • enlargement of the air cell;
  • separation of the membranes;
  • and transport.

Our aim, therefore, is to:

  • keep the air cell small before posting;
  • reduce moisture loss during transport;
  • avoid absorbent packaging;
  • incubate damaged eggs upright;
  • and begin turning from day zero.

The goal is not to wait.

The goal is to start the process.