Mitigating Heat Stress Effects:Impact of Melatonin on Blood Cell Morphology in Ewes

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Published: May 15, 2026
DOI: https://doi.org/10.12681/jhvms.38049
Keywords:
ewes heat stress melatonin morphological changes PCV
EG Katsogiannou
Faculty of Veterinary Medicine, University of Thessaly, Karditsa, Greece
EV Bouroutzika
Faculty of Veterinary Medicine, University of Thessaly, Karditsa, Greece
PD Katsoulos
Clinic of Farm Animals, Faculty of Veterinary Medicine, Aristotle University of Thessaloniki, Thessaloniki, Greece
EK Theodosiadou
Faculty of Veterinary Medicine, University of Thessaly, Karditsa, Greece
MC Naskou
Department of Pathobiology, College of Veterinary Medicine, Auburn University, AL, USA
LV Athanasiou
Faculty of Veterinary Medicine, University of Thessaly, Karditsa, Greece
I Valasi
Faculty of Veterinary Medicine, University of Thessaly, Karditsa, Greece
Abstract

Sheep exposed to excessive heat can suffer various adverse effects, particularly on their hematological system, including blood cell integrity and function. Melatonin has a protective role by mediating antioxidant pathways and acts as a regulator on apoptosis. The objective of this study was to evaluate the impact of heat stress on blood cell morphology and hematological variables in ewes and whether melatonin administration could mitigate it. Seventy-four ewes of Karagouniko breed participated in the study and were divided into three groups; the heat stress-melatonin group (HM, n = 20) and the heat stress-control group (HC, n = 20) and the control group (C, n=34). The heat stress-melatonin group as well as the heat-stress control group were evaluated during the summer period, whereas the control group was evaluated in autumn. All the animals in the HM and HC groups experienced heat stress, while those in group C did not. Following the administration of melatonin implants to the HM group (D0), blood samples were collected forty days later (D40) as well as from those in HC and C group. Blood smears were prepared and Giemsa stained, and thereafter, the packed cell volume (PCV), hemoglobin (Hgb), and mean corpuscular hemoglobin concentrations (MCHC) were estimated in all blood samples. Lower values of MCHC (P<0.05) were observed in the HC group compared to the HM or C group. The percentage of ewes exhibiting echinocytes, polychromatophils, red blood cell (RBC) and platelet (PLT) aggregates was significantly higher (P<0.05) in the HC group than in the HM or C group. This study represents the first report documenting blood cell morphological changes and highlights the potential benefits of melatonin supplementation in preserving blood cell integrity under heat-stress conditions.

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References
Alhaidary, A., 2004. Physiological responses of Naimey Sheep to heat
stress challenge under semi-arid environments. INTERNATIONAL
JOURNAL OF AGRICULTURE & BIOLOGY 8530, 6-2.
Autukaitė, J., Poskiene, I., Juozaitienė, V., Antanaitis, R., Zilinskas, H.,
The impact of temperature-humidity index on blood morphology
and β-hydroxybutyrate in different sheep breeds. Acta
Veterinaria Brno 89, 247-254.
Banerjee, A., Chattopadhyay, A., Pal, P.K., Bandyopadhyay, D., 2020.
Melatonin is a potential therapeutic molecule for oxidative stress
induced red blood cell (RBC) injury : A review. Melatonin Research
, 1-31.
Bouroutzika, E., Proikakis, S., Theodosiadou, E., Vougas, K., Katsafadou,
A., Tsangaris, G., Valasi, I., 2024. Proteomics Analysis of
Pregnancy in Ewes under Heat Stress Conditions and Melatonin
Administration. Animals 14, 400.
Bouroutzika, E.V., Theodosiadou, E.K., Barbagianni, M.S., Papadopoulos,
S., Kalogiannis, D., Chadio, S., Skaperda, Z., Kouretas, D.,
Katsogiannou, E.G., Valasi, I., 2022. Redox Status and Hematological
Variables in Melatonin-Treated Ewes during Early Pregnancy
under Heat Stress. Veterinary sciences 9.
Bull, B.S., Koepke, J.A., Simson, E., Van Assendelft, O.W., 2000. Procedure
for Determining Packed Cell Volume by Microhematocrit
Method, 3rd ed. NCCLS Document H07-A3.
Byers, S.R., Kramer, J.W., 2010. Normal Hematology of Sheep and
Goats In: Schalm’s Veterinary Hematology, 6th ed. Blackwell Publishing
Ltd, Ames, Iowa, USA, pp. 836- 842.
Chemineau, P., Malpaux, B., Pelletier, J., Leboeuf, B., Delgadillo, J.A.,
Deletang, F., Pobel, T., Brice, G., 1996. Emploi des implants de
mélatonine et des traitements photopériodiques pour maîtriser la
reproduction saisonnière chez les ovins et les caprins. INRAE Productions
Animales 9, 45-60.
Chitimus, D.M., Popescu, M.R., Voiculescu, S.E., Panaitescu, A.M.,
Pavel, B., Zagrean, L., Zagrean, A.M., 2020. Melatonin’s Impact
on Antioxidative and Anti-Inflammatory Reprogramming in Homeostasis
and Disease. Biomolecules 10.
Freedman, J.E., 2008. Oxidative stress and platelets. Arteriosclerosis,
thrombosis, and vascular biology 28, s11-16.
Harvey, J.W., 2012. Hematology Procedures. , In: Veterinary Hematology
- Diagnostic Guide and Color Atlas. Elsevier, St Louis,
Missouri, pp. 11-32.
Hulstein, J.J., Lenting, P.J., de Laat, B., Derksen, R.H., Fijnheer, R.,
de Groot, P.G., 2007. beta2-Glycoprotein I inhibits von Willebrand
factor dependent platelet adhesion and aggregation. Blood 110,
-1491.
Iba, T., Helms, J., Levi, M., Levy, J.H., 2023. The role of platelets in
heat-related illness and heat-induced coagulopathy. Thrombosis
Research 231, 152-158.
Iba, T., Sawada, T., Kondo, Y., Kondo, K., Levy, J.H., 2022. Morphological
Changes in Blood Cells in a Rat Model of Heatstroke: A
Pilot Study. Journal of clinical medicine 11.
Katsogiannou, E.G., Athanasiou, L.V., Christodoulopoulos, G., Polizopoulou,
Z.S., 2018. Diagnostic approach of anemia in ruminants.
Journal of the Hellenic Veterinary Medical Society 69, 1033-1046.
Katsogiannou, E.G., Athanasiou, L.V., Katsoulos, P.D., Polizopoulou,
Z.S., Tzivara, A., Christodoulopoulos, G., 2020. Estimation of
white blood cell and platelet counts in ovine blood smears, and a
comparison with the ADVIA 120 hematology analyzer. Veterinary
clinical pathology 49, 222-226.
Ke, H.Y., Chen, J.H., Kao, S.Y., Tsao, C.M., Kuo, C.W., Wu, C.C., Shih,
C.C., 2024. Heat stress-induced platelet dysfunction is associated
with loss of fibrinogen and is improved by fibrinogen supplementation.
Thromb Res 241, 109091.
Kornblihtt, L.I., Finocchiaro, L., Molinas, F.C., 1993. Inhibitory effect
of melatonin on platelet activation induced by collagen and arachidonic
acid. Journal of pineal research 14, 184-191.
REFERENCES
Kurhaluk, N., Zaitseva, O., Sliuta, A., Kyriienko, S., Winklewski, P.,
Melatonin diminishes oxidative stress in plasma, retains
erythrocyte resistance and restores white blood cell count after
low-dose lipopolysaccharide exposure in mice. General physiology
and biophysics 37, 571-580.
Kuzmenko, N.V., Tsyrlin, V.A., Pliss, M.G., 2021. Seasonal Dynamics
of Red Blood Parameters in Healthy People in Regions with Different
Types of Climate: a Meta-Analysis. Izvestiya, Atmospheric
and Oceanic Physics 57, 1271-1292.
Marai, I.F.M., El-Darawany, A.A., Fadiel, A., Abdel-Hafez, M.A.M.,
Physiological traits as affected by heat stress in sheep—A
review. Small Ruminant Research 71, 1-12.
Masselli, E., Pozzi, G., Vaccarezza, M., Mirandola, P., Galli, D., Vitale,
M., Carubbi, C., Gobbi, G., 2020. ROS in Platelet Biology:
Functional Aspects and Methodological Insights, In: International
journal of molecular sciences.
Moore, T., Sorokulova, I., Pustovyy, O., Globa, L., Pascoe, D., Rudisill,
M., Vodyanoy, V., 2013. Microscopic and thermodynamic evaluation
of vesicles shed by erythrocytes at elevated temperatures.
Mutinati, M., Piccinno, M., Roncetti, M., Campanile, D., Rizzo, A.,
Sciorsci, R., 2013. Oxidative stress during pregnancy in the sheep.
Reproduction in domestic animals = Zuchthygiene 48, 353-357.
Nathawat, M.S., Gupta, B., Gottam, G., Singh, M., 2023. Profiling of
hematological parameters due to seasonal variation in Sirohi goat.
The Pharma Innovation Journal 12(7S), 1890-1895.
NaveenKumar, S.K., Hemshekhar, M., Kemparaju, K., Girish, K.S.,
Hemin-induced platelet activation and ferroptosis is mediated
through ROS-driven proteasomal activity and inflammasome
activation: Protection by Melatonin. Biochimica et Biophysica Acta
(BBA) - Molecular Basis of Disease 1865, 2303-2316.
Nimpf, J., Wurm, H., Kostner, G.M., 1987. Beta 2-glycoprotein-I
(apo-H) inhibits the release reaction of human platelets during
ADP-induced aggregation. Atherosclerosis 63, 109-114.
Pashalieva, I., Stancheva, E., Decheva, L., Nyagolov, Y., Negrev, N.,
Experimental data about melatonin effects on platelet count
and functional activity. Comptes Rendus de L’Academie Bulgare
des Sciences 65, 855-860.
Polizopoulou, Z.S., 2010. Haematological tests in sheep health management.
Small Ruminant Research 92, 88-91.
Rudenko, S.V., 2010. Erythrocyte morphological states, phases, transitions
and trajectories. Biochimica et Biophysica Acta (BBA) -
Biomembranes 1798, 1767-1778.
Sarma, P.R., 1990. Red Cell Indices, In: Clinical Methods: The History,
Physical, and Laboratory Examinations. Butterworths Copyright
© 1990, Butterworth Publishers, a division of Reed Publishing.,
Boston.
Tesoriere, L., D’Arpa, D., Conti, S., Giaccone, V., Pintaudi, A.M.,
Livrea, M.A., 1999. Melatonin protects human red blood cells from
oxidative hemolysis: new insights into the radical-scavenging activity.
Journal of pineal research 27, 95-105.
Waltz, X., Baillot, M., Connes, P., Bocage, B., Renaudeau, D., 2014.
Effects of hydration level and heat stress on thermoregulatory responses,
hematological and blood rheological properties in growing
pigs. PloS one 9, e102537.
Wang, Z., Cai, F., Chen, X., Luo, M., Hu, L., Lu, Y., 2013. The Role
of Mitochondria-Derived Reactive Oxygen Species in Hyperthermia-
Induced Platelet Apoptosis. PloS one 8, e75044.
Weiser, G., 2012. Introduction to Leukocytes and the Leukogram, In:
Veterinary Hematology and Clinical Chemistry, 2nd ed. John Wiley
& Sons, Inc., pp. 118- 122.
Weiss, D.J., 1984. Uniform evaluation and semiquantitative reporting
of hematologic data in veterinary laboratories. Veterinary clinical
pathology 13, 27-31.
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