Journal
JOURNAL OF THERMAL BIOLOGY
Volume 99, Issue -, Pages -Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jtherbio.2021.103017
Keywords
Corticosterone; Body-surface temperature; Behavior; Heat stress; Laying hens
Funding
- Cooperative Research Program for Agriculture Science and Technology Development Rural Development Administration, Republic of Korea [PJ013446]
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This study investigated the impact of a 42-day heat stress on laying hens, focusing on physiological parameters and behaviors. Results showed that high temperature exposure increased rectal temperature, heart rate, body-surface temperature, and H/L ratio, while also elevating plasma CORT and yolk CORT levels. Laying hens in high-temperature conditions exhibited specific behaviors such as panting and wing elevation. The study suggested that rectal and body-surface temperature, heart rate, and behavior can serve as reliable indicators for assessing the stress status of laying hens under prolonged heat stress.
The present study was conducted to investigate the impact of a 42 d period of heat stress on laying hens with respect to rectal temperature, body-surface temperature, heart rate, heterophil to lymphocyte ratio (H/L ratio), corticosterone (CORT) in plasma and yolk samples, and video-assessed behaviors. A total of one hundred twenty 56-week-old ISA-brown laying hens were continuously exposed to one of three temperature regimes: optimal (LT; 22 degrees C), moderate (MT; 27 degrees C), and high (HT; 32 degrees C). The relative humidity was maintained at 50% in all treatments. HT vs. MT and LT increased rectal temperature, heart rate, and body-surface temperature on all days (P < 0.05). HT vs. LT raised (P < 0.05) the H/L ratio in blood at day 42 following heat exposure. On the other hand, both HT- and MT-exposed laying hens had higher (P < 0.05) plasma CORT compared with those on LT group only at 28 and 42 d following heat treatment. Yolk CORT was elevated (P < 0.05) in the HT vs. MT and LT groups at 3 and 14 d following heat treatment. Panting and wing elevation were the most relevant behaviors in laying hens exposed to HT vs. MT and LT. The study shows that rectal and body-surface temperature, heart rate, and behavior, but not CORT or H/L ratio, are the reliable indicators for assessing the stress status of laying hens over extended period of heat stress.
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