Thermoregulatory capacity and muscle membrane integrity are compromised in broilers compared with layers at the same age or body weight

Abstract

1. The effects of acute heat stress (2 h at 32°C and 75% RH) on body temperature and indices of respiratory thermoregulation and skeletal muscle function were examined in two divergently selected male grandparent lines of broiler and layer-type chickens at two ages (35 and 63 d), or at a similar body weight (∼2·2 kg).

2. The two chicken lines exhibited markedly different baseline blood acid–base and skeletal muscle characteristics. At the same age or live weight, birds from the broiler line had significantly higher venous blood carbon dioxide tensions associated with lower blood pH. Plasma creatine kinase (CK) activities reflecting muscle membrane damage were also greatly elevated in the broiler line.

3. Exposure to acute heat stress caused an increase in deep body temperature, panting-induced acid–base disturbances and elevated plasma CK activity in both lines of chicken, an effect that increased with age. The extent of disturbances in acid–base regulation and heat-stress-induced myopathy were more pronounced in the broiler than the layer line at the same age or similar live weights.

4. It is suggested that genetic selection for high muscle growth in broiler lines has compromised their capacity to respond to an acute thermal challenge, leading to detrimental consequences for muscle function. This reduction in heat tolerance may have important implications for bird welfare and subsequent meat quality.

Acknowledgements

The authors gratefully acknowledge the technical assistance from Ailsa Carlisle, Graeme Robertson, Dorothy McKeegan and Nick Gonet. The research was funded by DEFRA. The chickens were kindly supplied by Aviagen Limited, Newbridge, Midlothian, Scotland and Lohmann GB Ltd. and Lohmann Tierzucht GmbH, Cuxhaven, Germany.

Notes

†Current address: Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush Veterinary Centre, Roslin EH25 9RG, Scotland.

Additional information

Notes on contributors

D.A. Sandercock†

†Current address: Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush Veterinary Centre, Roslin EH25 9RG, Scotland.