Effects of melatonin on hematologic and biochemical changes and the effects of circadian rhythm on hematologic changes in donkeys (Equus asinus) subjected to packing during the hot-dry season.

This research investigates how melatonin — a hormone known for its antioxidant and anti-inflammatory properties — can affect blood and other biochemical changes in pack donkeys during the hot-dry season, and how it interacts with the animals’ circadian rhythms.

Objective and Methodology

• The aim of the study was to evaluate how melatonin influences the blood and biochemical responses in pack donkeys working in the hot-dry season. The researchers also sought to understand its impact on the animals’ circadian rhythms.
• The study involved ten male Nubian pack donkeys. Half of these donkeys were given melatonin (Packing + Melatonin, P + M) and the other half were not (Packing – Melatonin, P – M).
• Blood samples were taken at several points: before and immediately after packing, and then again at regular intervals ranging from 16 hours to over 27 hours post-packing.
• The blood samples were analyzed for various factors, including levels of blood cells and proteins. The researchers also tested serum from the blood samples for muscle enzyme activities and electrolyte concentrations.
• The researchers used a variety of statistical tests to analyze their data, such as the t-test, one-way ANOVA, and online cosinor analysis.

Results

• The packed cell volumes (PCVs) of the P + M donkeys did not change before and after packing. For the P – M donkeys, however, the PCV dropped after packing.
• The blood analysis results from the P + M donkeys were generally higher than those from the P – M donkeys, especially during the night phase (scotophase). This included metrics such as the mesor PCV, hemoglobin (Hb), and red blood cell (RBC) values.
• Lactate dehydrogenase (LDH) activity, a key muscle enzyme, did not change in the P + M donkeys before or after packing. In contrast, this activity significantly increased in the P-M donkeys after packing.
• There was a significant negative relationship between meteorological parameters and PCV, Hb, and RBC concentrations in the P + M donkeys.

Conclusion

• The administration of melatonin prevented a decrease in Packed Cell Volume (PCV) and an increase in Lactate Dehydrogenase (LDH) activity in the donkeys after packing compared to those not treated with melatonin.
• Notable effects were observed during the scotophase (a period of darkness or biological night) on PCV, Hemoglobin (Hb), and Red Blood Cell (RBC) concentrations.
• The study also found the circadian parameters highlighted a significant effect of melatonin on the rhythmicity of the donkeys. Particularly notable were the impacts on PCV, Hb, and RBC concentrations in the treated donkeys.
• Based on the results, the study suggests that administering melatonin may reduce the risks associated with environmental stress and the stress of packing in donkeys during the hot-dry season.