Over the past two decades, farm animal-assisted therapies have become popular. However, the effects of farm animals on healthy people's mental states have not yet been investigated. In Study 1, we aimed to explore whether positive effects of human-animal interaction (HAI) can be detected in healthy farm volunteers even after short-term (2-3 hours) work with goats and goatlings on a goat farm. We found that the participants' state anxiety decreased (p < 0.001) while their trust levels increased (p < 0.001) after interacting with goats. Nevertheless, it is possible that time spent in nature alone can have a beneficial effect on well-being. Therefore, in Study 2, we compared the results of Study 1 with those of a similar short-term outdoor treatment, walking in a botanical garden as a visitor. Similar but smaller effects were found for garden visitors. Decreases in anxiety scores and increases in trust scores were more pronounced in farm volunteers (anxiety: 25% vs 13%, p < 0.001; trust: 13% vs 3%, p = 0.002) after the treatments. Overall, the results suggest that the novel experience of interacting with goats and goatlings has a more positive effect on the mental state of healthy humans than walking in a botanical garden. This finding offer a strong foundation for developing animal assisted therapy methods for individuals with short or long term mental problems, but they can also enhance the wellbeing of mentally healthy people.