Impacts of heat stress and its mitigation by capsaicin in health status and digestive enzymes in house sparrows (Passer domesticus)

Abstract

Heatwaves and warm spells at global level, product of climate change, causes alterations on homeostasis in animals (heat stress), so they must respond to these changes in order to survive. The response involves several physiological changes, such as releasing of glucocorticoids and catecholamines, to restore homeostasis. Due the lack of knowledge on this subject in wild birds, the objective of the present work was study the effect of heat stress on body condition and digestive system in house sparrows (Passer domesticus), as well as a possible role of capsaicin as a dietary additive in mitigating heat stress. In this work, we measure heterophils/lymphocytes ratio (as proxy of stress), body mass, hematocrit, uric acid and digestive enzymes (intestinal and pancreatic) under stress conditions at 32 degrees Celsius and under normal conditions at 22 degrees Celsius. In addition, we evaluate the effect of capsaicin in both situations (heat stress at 32 degrees Celsius and normal condition 22 degrees Celsius). We found an increase of H/L ratio and uric acid in plasma under heat stress, and decrease of H/L ratio with capsaicin on animals exposed to heat stress. Although a loss of intestinal mass was observed in animals exposed at 32 degrees Celsius, digestive enzyme activity does not change under heat stress or under capsaicin administration. Improving knowledge in this field is relevant at the level of animal nutrition and veterinary medicine, reducing the stress of wild birds in captivity and improving dietary mixes for future global warming scenarios.