Increasing relative humidity during storage or transportation is often recommended to reduce the risk of dehydration - but if we look more closely at the effect this has on the chicks, this may not be the best solution.

Optimum body temperature for a day-old chick is approximately 40 - 40.5?C (104 – 105?F). At this temperature, the chick is comfortable. It will move around and explore, and find feed and water. However if the chick’s body temperature fluctuates below or above this optimum, the bird will feel uncomfortable and become lethargic.

Birds have a limited ability to control and regulate their own body temperature, especially when they are young. Older birds can use energy from feeding to produce body heat when they are too cold. Day-old chicks, however, can only huddle together to prevent heat loss, which prevents them from feeding or finding water.

When day-old chicks (or older birds) get too warm, they first spread out their wings to control their temperature. When that is not sufficient, they start to evaporate water to increase their heat loss. As birds can’t sweat, they evaporate this water by panting.

When a day-old chick is comfortable, in other words when it has the correct body temperature, it will breathe through its nostrils. In this way, it produces (loses) moisture at a rate of around 1 to 2 g per 24 hours.

When the chick’s body temperature climbs above 41?C – so an increase of as little as 0.5?C from the norm – it will start to pant. This panting activity will rapidly increase moisture loss , and in extreme situations, a chick may lose up to 5 grammes and sometimes as much as 10 g per 24 hours.

If we increase relative humidity in the chicks’ environment, we prevent that moisture loss and with it dehydration. But we also prevent the bird from cooling itself in an overheated situation. If the bird is comfortable and breathing through its nostrils, relative humidity will have only a limited influence on its moisture loss.

Knowing all this, how can we prevent the dehydration of day-old chicks?

• The most important thing is to control body temperature and prevent the chicks from panting. If the body temperature of the chick is correct, its moisture loss will be limited to 1-2 g per 24 hours. If the bird eats, including its uptake of the yolk, the digestion of feed and yolk will result in the formation of metabolic water. This metabolic water is enough to compensate for any moisture loss at optimal body temperature: the bird will lose some weight, but this will not result in dehydration.
• When chicks are transported over long distances, we can inject them with 1-2 cc of saline. This helps to prevent dehydration as well, but only if the body temperature is correct. If the birds are overheated, the amount of moisture lost will exceed the amount of saline injected to compensate.
• If we give a small quantity of feed during transportation (even in dry form), this will help the bird to metabolise the yolk and therefore produce metabolic water. But this too can only be effective when body temperature is optimal.
• If we provide feed that contains a large quantity of water (for example fruits or a liquid gel), this will provide additional water as well, and once again stimulate yolk uptake and produce metabolic water. Once again, however, this will be only sufficient is body temperature is correct.
• After arrival at the farm, it is important that the birds find water as quickly as possible, to restore any excessive water loss. However, if birds are seriously overheated during transportation, their vitality, and therefore their ability to find water, will be limited.

In conclusion, the only truly effective way to prevent dehydration is to maintain the birds’ body temperatures at optimal levels.

January 2007