Egg storage: good practices
Upon arrival at the hatchery, eggs are stored for a number of days before incubation starts. This period of time can vary considerably between 0 to 20 or more days. To minimise embryonic mortality and maximise hatchability/chick quality, it is essential that optimal conditions are achieved in the egg holding room. The purpose of egg storage is to suspend development of the embryo until incubation is initiated. Incorrect storage will result in an increase in early deaths which are often misinterpreted as infertile eggs. In this article, we focus on the two most important parameters for egg storage: temperature and humidity.
By Jason Cormick, Hatchery Specialist
By cooling the embryo, its development is slowed down until it stops. This point is commonly referred to as the physiological zero. There is some debate among scholars as to the actual physiological zero. Edwards (1902) reported it to be 21°C, while Funk and Biellier (1944) claimed it to be 28°C. More recently Fasenko et al., 1992 found that development stopped at 14°C.
We know from experience that a temperature of 21°C is sufficient to hold back embryonic development for a few days.
Actual holding temperatures will depend on how long your eggs are stored. Cooler temperatures are beneficial in case of longer storage as they slow down embryonic development further than warmer temperatures.
It is not advisable to store eggs above 21°C as this can also lead to increased bacterial growth on the eggs’ surface.
Storage longer than 7 days will lead to greater early embryonic mortality due to cell death. Recently, a method has been developed to minimise this, called controlled ‘short periods of incubation during egg storage’ (Dr Dinah Nicholson, Aviagen). This method boosts cellular division and increases the possibility to store eggs longer while minimising losses.
These are some pieces of advice regarding temperature in the egg holding room:
- When storing eggs for long periods, make sure that the temperature is brought down as soon as possible - don’t wait for 7 days before reducing the temperature.
- Create a uniform temperature throughout the egg holding room. Differences in temperature will result in the eggs reaching incubation temperature at different times, and therefore hatching at different times, increasing the hatch window. The best way to ensure a homogenous temperature is to install several thermometers around the egg holding room.
- Use ‘minimum-maximum’ thermometers instead of standard ones. They can be read once per day giving you the extremes of the past 24 hours.
- Don’t place thermometers against walls as they can be influenced by the temperature of the wall and will therefore be slower to react than free hanging ones.
- Make surethat no controlling or monitoring sensors are in the direct line of temperature or humidity sources as this will lead to false readings.
- Air movement within the store can be used to create an even environment. Ceiling fans can assist in this. However, they should not blow air directly down onto the eggs as this can reduce the temperature further due to wind chill effect. Moreover, fast air moving across the eggs can also increase moisture loss. Therefore, fans should draw air rather than push.
During storage, moisture is lost through the egg shell into the atmosphere of the egg holding room. If humidity levels in the air are high, the air cannot take and hold much more moisture from the eggs. Therefore, a relative humidity target of 75-80% is required (see table above) to prevent eggs from losing too much moisture before incubation starts.
Some advice concerning humidity:
- The humidity should be a fine mist, and it should not result in any of the eggs getting wet.
- Humidifiers need routine maintenance and cleaning. Left unchecked, they can be a natural reservoir for bacteria that will be sprayed across the eggs when the humidifier is activated.
- Edwards, C. L., The physiological zero and the index of development from the egg of the domestic fowl. 1902, Am. J. Physiol., 6:351–397.
- Funk, E. M., and H. V. Biellier, The minimum temperature for embryonic development in the domestic fowl (Gallus domesticus). 1944, Poult. Sci. 23:538–540
- Fasenko, G. M., F. E. Robinson, R. T. Hardin, and J. L. Wilson, Variability in preincubation embryonic development in domestic fowl. 2. Effects of duration of egg storage period. 1992, Poult. Sci. 71:2129–2132.