Relationship between maximum daily temperature and mortality of broiler chickens during transport and lairage

1. Based on records of all (n = 59 171 843) broiler chickens slaughtered over three years at one processing plant, the overall mortality of birds in transit was 0·126%. 2. There was a pronounced seasonal effect with increased mortality in the summer months, particularly June, July and August. Mortality increased when the maximum daily temperature (measured in the shade) rose above about 17°C at the start of the summer. 3. Between 17·0 and 19·9°C, mortality was 30% higher than at lower temperatures. Between 20·0 and 22·9°C it increased 2·6-fold, and at temperatures of above 23°C 6·6-fold. There was no evidence of birds dying from hypothermia at very low ambient temperatures (down to −1°C). 4. The implication from the results is that above a maximum daily temperature of 17°C steps may need to be taken to ameliorate the damaging effects of transport on bird welfare.