Monitoring the Temperature Exposure Profiles of Eggs

Miniature battery-powered data loggers, such as Tinytags, will record temperatures for a pre-set period and make the investigation of egg handling conditions easy. A data logger can be placed in the nest box overnight, be collected with the eggs and then used to follow the temperature profile that the eggs are exposed to through all the ensuing processes, including incubation.

Author, Dr Steve Tullett

On the farm, the eggs should be cooled to below 24°C (75.2°F), within four hours of collection and then held at the optimum temperature for the expected period of storage. 24°C (75.2°F) is known to be 'Physiological Zero' for broiler breeder eggs and cooling eggs below this temperature will ensure that there is no chance of embryo development during storage.

Common problems in relation to temperature during egg handling include:

• Eggs left too long in the nest, allowing them to re-warm when another hen occupies the nest.
• Infrequent collection in automatic nests where eggs are held at house temperature without cooling.
• Eggs packed on to fibre egg trays, which only allow very slow cooling. Use plastic egg trays.
• Eggs held in the poultry house after packing until the end of the working day, rather than being moved into the cooled store immediately.
• Egg store door left open, especially during hot weather.
• Temperature control in egg store inadequate with high diurnal variation due to hot weather, poor cooler capacity and/or poor insulation. This will weaken the embryos and could result in weaker chicks
• Trolleys held outside the egg store prior to arrival and loading of egg collection vehicle.
• Egg collection vehicle not temperature-controlled.
• Farm and hatchery stores held at different temperatures, and
• Prolonged pre-warming of eggs in an environment fluctuating around Physiological Zero.

Any of the above will increase the 'early dead' and 'blood ring' mortality. The use of temperature data loggers may allow the problem areas to be identified.

Temperature data loggers can also be useful in evaluating incubation conditions and identifying where there are hot and cold spots in the setters that need to be rectified.

Measuring Eggshell Temperatures During Incubation

Embryos are resistant to periods of cooling, but short periods of heat stress can cause malformations, malpositions or may be lethal. Rather than just allowing an incubator temperature programme to run its course, it is prudent to monitor eggshell temperatures in order to prevent overheating of the embryos. This can be done using a relatively cheap infra-red thermometer such as the Braun Thermoscan which works accurately within the temperature range found in incubators. Check egg surface temperatures at the equator of the egg, not at the air cell.

All setters have 'hot spots' and 'cold spots' and it is important to check that the embryos in the hot spots are not subjected to damaging heat stress during days 16 to 18 of incubation. An ideal eggshell temperature is 37.8°C (100°F) but towards the end of the setter phase, eggshell temperatures up to 38.3°C (101°F) are common and largely without effect. However, eggshell temperatures higher than this can be damaging and temperatures of 39.4°C (103°F) and above are known to be detrimental to hatchability and chick quality.

Further Reading

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You can see other articles in this series Investigating Hatchery Practice by clicking here.