The temperament of horses appears linked to levels of two important hormones, according to a fresh study.
Researchers at Kyungpook National University in South Korea concluded that levels of oxytocin and serotonin could be used as biomarkers to monitor the fearfulness, dominance, and trainability of horses.
Oxytocin and serotonin are essential neurotransmitters associated with the behavior of animals.
The study, described in the Journal of Animal Science and Technology, centered around 34 horses at the Horse Industry Complex Center at the Jeonju Kijeon College in South Korea.
Junyoung Kim and his fellow researchers said they recently found that the plasma concentration of oxytocin is positively correlated with horse docility and friendliness toward humans.
However, the relationships between key neurotransmitters and other traits such as fearfulness, dominance, and trainability are unknown.
For their study, blood samples from 34 horses were collected at the complex and plasma concentrations of both oxytocin and serotonin were measured.
The fearfulness, dominance, and trainability of each horse was scored by three professors who were very familiar with the animals.
The study team found that horses with lower plasma oxytocin concentrations appeared to show a higher degree of fearfulness, although it was not statistically significant. No differences in plasma serotonin concentrations were found among high, medium, and low fearfulness groups.
They found that plasma oxytocin concentrations were not significantly different among high, medium, and low dominance groups. However, horses with low plasma oxytocin concentrations tended to be more dominant than those with high concentrations.
The plasma serotonin concentration in the high dominance group was significantly lower than those in the low and medium dominance groups.
Interestingly, they said, there was no significant difference in the plasma serotonin concentration between the medium and low dominance group.
The researchers said there was a significant positive correlation between the plasma oxytocin concentrations and the degree of trainability.
Horses assessed by the professors as being highly trainable had significantly higher plasma oxytocin concentrations compared with those grouped in the medium trainability category.
Plasma concentrations of serotonin was not significantly correlated with the degree of trainability. However, plasma serotonin concentrations tended to be higher in the high trainability group compared with those in the medium trainability group.
Discussing their research, the researchers said their findings were in agreement with other studies showing that oxytocin reduces fearfulness in many species.
The findings support the study team’s speculation that a high concentration of oxytocin can enhance the interrelationship between horses and humans, and this relationship is associated with higher trainability.
“Although it was not statistically significant, a positive correlation between the concentration of serotonin in horse blood plasma and the trainability of horses appeared to be present.
“Interestingly, in humans, the depletion of serotonin caused several problems such as decreasing the level of cooperation and being discredited between partners.
“Combining the results in horses and humans, serotonin appears to play a positive role in cooperation and trust, leading to high trainability.”
The authors said further studies into the effects of treatment with these neurotransmitters on the temperaments of horses should be conducted.
The study team comprised Junyoung Kim, Eun Joong Kim, Heejun Jung and Minjung Yoon, all with Kyungpook National University; and Youngjae Park, with Jeonju Kijeon College.
Kim Junyoung, Park Youngjae, Kim Eun Joong, Jung Heejun, Yoon Minjung. Relationship between oxytocin and serotonin and the fearfulness, dominance, and trainability of horses. J Anim Sci Technol 2021;63(2):453-460.