Soybean oil supplement induces increased approaching behavior to humans and alters serotonin concentrations in horses.
Abstract: Enhancement of human-horse interaction is crucial for safety in equine management, as poor relationships between humans and horses can lead to accidents. Serotonin is a neurotransmitter that is highly related to social affinity in animals and several studies have been documented that supplementation of tryptophan, which is a precursor of serotonin, can increase calmness of horses. This study aimed to assess the effect of tryptophan through soybean oil supplementation on serotonin concentrations and the behavior of horses. Six horses participated and the horses were treated with or without soybean oil diets in a cross-over design. Daily feed intake was 2 % of the body weight of horses, with a timothy hay to grain ratio of 8:2. Behavioral observations and blood collections were conducted and serotonin and cortisol concentrations were quantified using enzyme-linked immunosorbent assays. Data was analyzed using two-way repeated measures analysis of variance to explore the effects of diet, time, and their interaction. The difference was considered statistically significant when p-value was less than 0.05. The results demonstrated that soybean oil supplementation significantly increased approaching behaviors towards humans (5.57 ± 1.12) compared to baseline scores (1.2 ± 0.57). Moreover, serotonin concentrations were elevated following the soybean oil diet (150.09 ± 21.32 ng/mL) compared to concentrations on day 1 (115.89 ± 22.3 ng/mL). Cortisol concentrations remained stable throughout the experimental period when horses were treated with the soybean oil diet (405.29 ± 35.29 ng/mL vs. 427.64 ± 87.34 ng/mL). In contrast, cortisol concentrations increased significantly in horses on the non-oil diet (405.29 ± 35.29 ng/mL vs. 427.64 ± 87.34 ng/mL). These findings suggest that soybean oil supplementation positively influences horse behavior towards humans, indicating that dietary modification may enhance human-horse interactions.
Copyright © 2025. Published by Elsevier Inc.
Publication Date: 2025-01-16 PubMed ID: 39826778DOI: 10.1016/j.jevs.2025.105361Google Scholar: Lookup
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Summary
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The research paper discusses a study conducted to examine the influence of soybean oil supplement on the serotonin concentrations and behavior of horses, showing that the supplement significantly increases the horses’ approach towards humans and their serotonin levels.
Research Aim and Methodology
- The primary goal of this study was to evaluate the impact of tryptophan, a serotonin precursor, obtained through soybean oil supplementation on the behavior of horses and their serotonin concentrations. The researchers were interested in seeing if diet could be instrumental in enhancing the interaction between humans and horses, which is a safety factor in equine management.
- The study involved six horses, which were given diets either with or without soybean oil, following a cross-over design. The behavioral responses of horses towards humans were observed, and blood samples were collected throughout the experimental phase. This was done to measure levels of serotonin and cortisol in the horses’ bloodstream.
- The average daily feed intake was fixed at 2 % of the horse body weight, breaking down to a ratio of 8:2 timothy hay to grain. Analysis of the collected data was performed using a two-way repeated measures analysis of variance to investigate interactions between diet, time, and their interplay. Application of a significance level (alpha) at 0.05 allowed for determination of statistically significant findings.
Research Findings
- The findings of this research reveal significant effects of the soybean oil supplement on horses’ behavior towards humans and their serotonin levels. The behaviors of the horses approaching humans notably increased after integrating the supplement in their diet with an average score of 5.57, compared to the non-supplemented diet score of 1.2.
- Serotonin concentrations also increased in horses who happened to be on the soybean oil supplement diet, with the concentration levels escalating from initial 115.89 ng/mL to 150.09 ng/mL. This suggests that the soybean oil supplement had a definite influence on serotonin levels.
- On the other hand, cortisol concentrations remained steady throughout the study for horses fed with the soybean oil diet. The non-oil diet showed a significant increase in cortisol levels, hence pointing out no effect of oil supplementation on cortisol concentrations.
Conclusion From Research
- The study indicates that soybean oil supplementation has potential advantages on horse behavior and serotonin concentrations. This shows that by simply adjusting the dietary regime of horses, the interaction between humans and horses can be considerably improved, leading to safer equine management practices.
Cite This Article
APA
Kim S, Choi Y, Kim J, Wickens CL, Yoon M.
(2025).
Soybean oil supplement induces increased approaching behavior to humans and alters serotonin concentrations in horses.
J Equine Vet Sci, 146, 105361.
https://doi.org/10.1016/j.jevs.2025.105361 Publication
Researcher Affiliations
- Department of Animal Science and Biotechnology, The Graduate school, Kyungpook National University, Buksangju-ro 2559, Sangju, Gyeongsangbuk-do 37224, South Korea.
- Department of Animal Science and Biotechnology, The Graduate school, Kyungpook National University, Buksangju-ro 2559, Sangju, Gyeongsangbuk-do 37224, South Korea.
- Department of Animal Science and Biotechnology, The Graduate school, Kyungpook National University, Buksangju-ro 2559, Sangju, Gyeongsangbuk-do 37224, South Korea.
- Departmet of Animal Science, University of Florida, Gainesville, FL 32611, USA.
- Department of Horse, Companion, and Wild Animal Science, College of Ecology and Environmental Science, Kyungpook National University, Buksangju-ro 2559, Sangju, Gyeongsangbuk-do 37224, South Korea; Research Institute for Innovative Animal Science, Kyungpook National University, Buksangju-ro 2559, Sangju, Gyeongsangbuk-do 37224, South Korea. Electronic address: mjyoonemail@gmail.com.
Conflict of Interest Statement
Declaration of competing interest None of the authors has any financial or personal relationships that could inappropriately influence or bias the content of the paper.
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