Variability of plasma melatonin level in pony mares (Equus caballus), comparison with the hybrid: mules and with jennies (Equus asinus).

The research compares plasma melatonin concentration levels of mares, mules, and jennies, finding significant differences that suggest these levels might be genetically determined.

Objective of the Study

• The main goal of this study was to assess the inter-animal variability of plasma melatonin concentration levels in domestic mares and then compare these concentration levels with those seen in domestic jennies (female donkeys) and their hybrid offspring, mules.

Sampling and Data Collection

• In the course of the study, the researchers collected blood samples from 110 pony mares, 10 jennies, and 6 mules.
• Samples were collected during two successive nights at three intervals of three weeks apart, specifically at 22 h, 23 h, 0 h, and 1 h.
• This was carried out in the Autumn season under normal light conditions.

Measurement and Analysis Consideration

• The investigation of melatonin levels was done using a validated Radioimmunoassay (RIA) method. This method measures the hormone concentration in the plasma.
• A specific unbalanced analysis of variance (ANOVA) model was employed to analyze the measurement data.

Findings of the Study

• The study found the role of species and individuals nested under species to be significantly influential on the mean melatonin concentration.
• The results revealed that mares had a mean melatonin concentration of 24 pg.mL(-1), which was significantly lower than the values observed in jennies and mules, which were 90 pg.mL(-1) and 169 pg.mL(-1) respectively.
• The melatonin plasma concentration of jennies was found to be higher than that of mares. These results could suggest the likelihood of a genetic factor determining melatonin concentration levels.