impact of climate change on thermoregulation, blood attributes and production performance in laying hens

The objective of the study was to assess the impact of climate change, expressed through the temperature humidity index (thi), on physiological responses, including body temperature, blood parameters, and production indicators on laying hens, the novogen brown strain, from the 22nd to 34th weeks of age. the experiment was conducted in northern algeria during the summer season in two separate buildings. the first building, which housed approximately 85,000 laying hens, was modern with a controlled environment (control group). on the other hand, the second building, housing approximately 40,000 laying hens, was exposed to natural variations in the external climate (experimental group). additionally, the temperature fluctuated between 25.2 and 39.4°c, while humidity ranged from 54.3 to 64.5%. the overall trend of the results revealed notable variations in the parameters studied in the experimental group. body temperature showed a significant (p<0.001) increase of +0.99°c. blood parameters also revealed significant (p<0.001) increases; the amplitudes were +0.18 for the heterophil/lymphocyte ratio, +1.82ng/ml for corticosterone, and +5.06ng/ml for cortisol. furthermore, production performance showed significant reductions (p<0.001) in egg weight (-4.67g) and laying rate (-6.77%) with an increase of +1.75% in the egg breakage rate (p<0.001). the results of the present study highlighted the stress that laying hens may experience due to climate change, particularly when hens are housed in buildings that do not meet the standards. these situations could compromise the sustainability of the poultry industry and threaten food security, given the importance of poultry products in the human food chain.