EGG WEIGHT LOSS

The role of temperature in incubation is well understood. The role of humidity is not. For that reason, humidity is often blamed when anything goes wrong which gave rise to the latest fad of “Dry Incubation.”

But humidity is not a target number that we need to achieve. Humidity is simply the control we use to regulate the amount of moisture leaving the egg.

Humidity is the control. Weight loss is the measurement.

WHY WEIGH THE EGGS?

As an egg loses moisture during incubation, it loses weight.

Our target is approximately 13% weight loss over the incubation period. If an egg begins incubation at 100% of its original weight, our target is therefore approximately 87% at the end. On a graph we can draw a straight line between those two points and we have a diagonal target weight-loss line. That line becomes our guide.

Traditionally, eggs are candled at stages and the air-cell is compared to drawings. For chicken that's at Day 7, Day 14. But comparing the appearance of an air-cell with a picture is subjective.

Weighing is accurate.

And because we have a target line, we don't have to wait until Day 7 or Day 14 to find out what is happening. We can weigh the eggs on any day and compare their actual weight with the target weight for that point in incubation.

WEIGH AS A BATCH AND INDIVIDUALLY

Choose a handful of representative eggs and give each egg an identification number.

At the beginning of incubation, weigh each egg individually and record its weight. Then weigh those same eggs together as a batch.

We weigh the eggs as a batch AND individually.

The batch gives us the overall weight-loss trend.

The individual weights are important because an egg may quit partway through incubation. If that happens, we can identify that egg, go back to our records, remove its data from the batch calculations and restart the plot without allowing the failed egg to distort the result.

FOLLOW THE LINE

The target line is the guide, not the calendar.

The eggs can be weighed on any day.

If their weight is above the target line, they have not lost enough moisture.

If their weight is below the target line, they have lost too much.

We then adjust the incubator humidity accordingly.

And importantly, that correction can be made at any stage of incubation.

We are not trying to achieve a particular humidity reading simply because somebody has told us that is the correct number.

The target egg weight is what matters.

FINDING YOUR “GOLDILOCKS” HUMIDITY

This doesn't mean that you need to weigh eggs throughout every setting. The exercise is a way of finding the relative humidity that produces the correct weight loss in your incubator, with your eggs and under your conditions.

Once you have uncovered your “Goldilocks” RH setting, it simply becomes your routine.

You now have something much more useful than somebody else's recommended humidity number.

You have measured what works for your eggs.

The air-cell is an estimate. Weight loss is a measurement.

Humidity is the control. Weight loss is the measurement.

Bob Peel, Greatlander