Heat stress, haematology and small intestinal morphology in broiler chickens: insight into impact and antioxidant-induced amelioration

SUMMARY

This paper reviews adverse effects of heat stress on haematology and small intestinal changes as well as the beneficial effects of antioxidant agents, and probable mechanisms by which the agents ameliorate heat stress. High ambient temperature and high relative humidity cause heat stress, which negatively impacts on production, reproduction, immunity and health of broiler chickens. The cardiovascular system, particularly sensitive to changes in temperature, is an indicator of physiological responses to stressors by broiler chickens. Heat stress decreases small intestinal blood flow, erythrocyte count and haemoglobin concentration and alters the ratio of leucocyte types. Impaired blood flow causes injury to small intestinal morphology, including villi and crypts; impairs digestion, decreases rate of nutrient absorption and bird development, resulting in reduced body weight in broiler chickens. Antioxidant supplementation, involving vitamins C and E, fisetin, betaine, probiotic, taurine and melatonin, boosts the capacity of biological antioxidant barrier to combat reactive oxygen species, which are generated in excess during heat stress. In conclusion, antioxidants, by ameliorating adverse effects of heat stress on haematological and small intestinal changes, are promising prophylactic agents in enhancing productivity of broiler chickens under heat-stress conditions.

KEYWORDS:

• Heat stress
• haematology
• intestinal morphology
• antioxidants
• broiler chickens

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Notes on contributors

J. O. Ayo

Joseph Olusegun Ayo studied Russian Language at the Chișinău State University, Chișinău, Republic of Moldova. Thereafter, he studied Veterinary Medicine at the National University of Life and Environmental Sciences of Ukraine, Kyiv, Ukraine, where he obtained combined degrees of Doctor of Veterinary Medicine and Master of Veterinary Science in 1982. He also attended the Ahmadu Bello University (ABU), Zaria, Nigeria and graduated with the degree of Master of Science in Veterinary Physiology in 1990. He enrolled at the National University of Life and Environmental Sciences of Ukraine, Kyiv and conducted research on the Physiology of the Medulla Oblongata at the Bogomoletz Institute of Physiology, Academy of Sciences of Ukraine, Kyiv, Ukraine, where he obtained the degree of Doctor of Philosophy in Physiology in 1994. He obtained the Professional Diploma of the Postgraduate College of Veterinary Surgeons Nigeria in 2010. In 2021, Professor Joseph O. Ayo was elected Fellow, Nigerian Academy of Science. He has taught Physiology to undergraduate and postgraduate students of different Faculties in ABU, Zaria, Nigeria. He rose through the ranks to the position of Professor of Veterinary Physiology in 2002. His research efforts are currently focused on chrono- and stress physiology in animals, with emphasis on oxidative stress mechanism and antioxidant intervention. He had served as Head, former Department of Veterinary Physiology and Pharmacology, and Deputy Dean of the Faculty of Veterinary Medicine, ABU, Zaria, Nigeria. He was the President of the Neuroscience Society of Nigeria.

N. E. Ogbuagu

Ngozi Ejum Ogbuagu graduated with the degree of Doctor of Veterinary Medicine from the Ahmadu Bello University (ABU), Zaria, Nigeria in 2015. Upon completion of the mandatory National Youth Service Corps, she enrolled in ABU, Zaria for Master of Science programme and conducted research in Environmental Physiology with emphasis on Avian Stress Physiology. She graduated with the degree of Master of Science (Veterinary Physiology) in 2018. The findings of her studies, published as journal articles, were on prophylactic measures adopted to mitigate the risk of adverse effects of thermal stress on broiler chickens under hot climatic conditions. Dr Ogbuagu is currently a PhD (Veterinary Physiology) student, registered with the Department of Physiology, Faculty of Veterinary Medicine, ABU, Zaria, Nigeria. Her current areas of research interest are focused on pathophysiology of heat stress in broiler chickens and antioxidant amelioration.