Table 2. Plasma concentration of melatonin among different horse breeds1)
| Neurotransmitter | Breed of horses |
| Thoroughbred(n = 15) | Warmblood(n = 7) | Cold-blooded horse(n = 6) |
| MEL (pg/mL) | 120.3 ± 28.66a | 134.1 ± 59.03ab | 34.8 ± 5.07b |
Data represent the mean ± SEM.
Means with a different superscript in the same row are significantly different (p < 0.05).