Tags: Chick handling | Whitepaper
30 September 2015,
Measuring body temperature (BT) is a standard method of checking the health status of animals. Each species has its specific standard, or ‘normal body temperature‘. Increased temperature indicates fever, while deviation below normal signifies less than optimal condition. Like all birds, normal BT in domestic fowl is 40.5°C.
BT measurement in day-old chicks has become fashionable, possibly because many new hatchery managers are more familiar with this technique than looking at behaviour.
When checking BT, the hatchery manager must decide:
The physiological mechanism for maintaining BT develops late in the chicken, at around day 3 of life. Until then, the chick’s physiology is largely dependent on its environment, much like that of a cold-blooded animal, eg. a reptile. Measuring BT in the day-old chick is therefore more a reflection of climate conditions: temperature, humidity and the wind speed of an environment. Deviation from the standard means either that the chicks were exposed for long enough to a chilling effect or that they got overheated. Both situations can be also observed in the chicks’ behaviour. Huddling, gathering close to each other and peeping loudly indicate cold distress, while open wings and beaks and panting are typical symptoms of overheating. When chilled, the feet get cold first, which can be ‘tested' by touching ‘chick to cheek’. Fluctuation of BT can still be seen when the chicks remain quite comfortable: just 30 minutes from take-off in the warm chick handling room is enough to reduce BT by 0.5 °C, which causes no signs of discomfort in the birds. This instability has prompted the use of a conventional veterinary thermometer to measure BT internally (per rectum), with the logic being that more stable results can be expected from an internal measurement than on the surface of the chick’s body.
To verify this thesis, two methods have been compared in a field trial: measuring BT on vent by an IR-ear thermometer (eg. Braun ThermoScan) and by a conventional thermometer inside the rectum. The trial showed that: