Systematic Analysis of Embryo Temperature

Dr. Muhammad Siddique
Professor and Chairman Deptt.of Vety.
Microbiology,University of Agriculture, Faisalabad.

A tool for designing All-In/All-Out incubation programs


A consequence of the ongoing selection of high yield breeds is the increased variability in hatchability of eggs from flocks of different ages. Eggs from young and old breeders differ significantly with respect to size, egg shell conductance and heat production.

To achieve the best hatchability and chick quality, the hatchery manager should be able to incubate each batch of eggs under the most optimal conditions.

It is generally excepted that All-In/All-Out or Single-Stage setting has specific advantages in this matter.

With All-In/All-Out incubation all eggs are set in the same setter at the same time, which means
that a hatchery manager can have greater control by providing the heat, cooling, air velocity, venting and humidity that is needed for the embryos at the different stages of incubation.

Depending on variations in strain of breeder, week of lay (size of egg), length of storage time and shell thickness (moisture loss), the incubation program can be adjusted by changes
in temperature, ventilation and relative humidity.

This means that the climate control of incubators must be flexible with regard to temperature, ventilation and humidity setpoints. Furthermore the hatchery manager should be provided with tools to optimise this incubation program. In following instruction guidelines Pas Reform provides a tool for improving the incubator’s temperature program.


A way to improve the incubator’s temperature program is to look at the temperature of a specific number of eggs during the different phases of the incubation process. Because embryo temperature can not be measured without destroying the egg, the temperature of the eggshell is used as a reference.

The cheapest and easiest way to measure eggshell temperature is with an infrared ‘fever thermometer’. It has been proven that for example the Braun Thermoscan (with an accuracy of ± 0.3°F) is a practical instrument for such
measurements, provided the instrument is used properly.

To get a good idea of actual eggshell temperature in a specific incubator, a representative sample of eggs must be measured. The procedure given below describes (A) how to measure the individual egg,(B) how to measure a representative sample and (C) how to use the data.

Please read the safety instructions carefully before starting the procedure!!!!

Safety Instructions

The procedure described below should be performed by qualified personnel only, because data must be collected in an operating Pas Reform incubator in which every section of 19,200 hen eggs is fully loaded with four trolleys of eggs.

When measuring trays from trolleys at the side of the fan, only the trays should be taken out, without displacing the trolley, thus avoiding the need for personnel to come too close to the fan.Measurements taken in a machine which is turned off will result in unreliable data because eggshell temperatures change immediately when the airflow is nil.

A. Eggshell temperature of individual eggs

1. Read the thermometer instruction guide.

2. Before starting, the thermometer should be warmed in the incubator for 15 min (if this is not done, measurements will be inaccurate).

3. Make sure that the plastic cover (lens filter) is on the thermometer’s infrared probe (the thermometer will not function without this filter).

4. Place the infrared probe on the eggshell, just under the air chamber (measuring on the air chamber gives a difference of 0.5°F).

5. Measure with the infrared probe right on the eggshell (measuring at the wrong angle gives 0.5 – 1.5°F deviation).

B. Eggshell temperature of a representative sample

Measure a row of 15 eggs in the middle of a setter tray. The mean temperature of eggs with living embryos is used as a reference for eggshell temperature in that specific tray.

1. Select 1 setter trolley per section of 19,200 hen eggs in a Pas Reform incubator (selecting a trolley at the corridor side is the most convenient).

2. Measure the eggshell temperature of a row of eggs in the middle of trays 3, 9 and 14 (from the top). This means that in one particular position you have 15 eggs in a row at the top, 15 in a row in the middle and 15 in a row at the bottom.

3. Measure the eggshell temperature of these eggs as described under A.

4. Take the mean of these 45 eggs.

C. How to use the data

1. For each trolley you now have the average temperature of all 45 eggs located in different trays. This average temperature is defined as the reference eggshell temperature on that day of incubation.

2. If the eggshell temperature deviates too much from the desired embryo temperature, the incubator temperature setpoint can be adjusted.

The right temperature depends on breed and maternal age and is usually provided by the breeding company. In general it can be stated that the average eggshell temperature must be 37.8 – 38°C (100 – 100.4°F) during the first 2/3 of incubation. The average eggshell temperature should not exceed 38.5°C