In recent years, there has been growing interest in exploring the potential health benefits of incorporating natural plant substances into the diets of farm animals. Basket willow (Salix viminalis), rich in flavonoids, tannins, and salicylates, has emerged as a candidate with analgesic, anti-inflammatory, and anthelmintic properties, making it appealing for integration into ruminant farming practices. This study aimed to analyze the effects of dietary supplementation with basket willow on the neuroanatomical properties of the small intestine in farmed fallow deer. Immunohistochemical methods and morphometric measurements were employed to assess changes in noradrenergic, galaninergic and nitrergic innervation patterns. Twenty-four fallow deer were divided randomly, with 12 individuals placed in both a control group and an experimental group, with the latter receiving willow supplementation. The results revealed significant alterations in the morphology and innervation patterns of the enteric nervous system (ENS) in the experimental group, including a decrease in ganglion size and nitric oxide synthase (NOS) immunoreactive nerve fibers, and an increase in galanin immunoreactive neurons. These findings suggest a potential modulation of gastrointestinal function by willow supplementation. However, caution is warranted due to the high salicylate content in basket willow, which may pose risks to gastrointestinal integrity. Overall, while basket willow supplementation shows promise in enhancing animal farming methods, further research is needed to elucidate its mechanisms and optimize its use in ruminant farming practices.