Dietary tea tree ( Melaleuca alternifolia ) oil supplementation enhances the expressions of amino acid transporters in goat ileal mucosa and improves intestinal immunity.

Tea tree oil (TTO) is a plant-derived additive with anti-inflammatory, bactericidal, and growth-promoting properties. However, little is known about the effects of TTO on intestinal amino acid transport and immune function in goats. Twenty-four Ganxi goats (initial body weight of 13.5 ± 0.70 kg) were randomly allotted two treatments and fed either control (CON) or CON+TTO (0.2 ml/kg) diet. The addition of TTO to the diet significantly decreased ( p  < .05) tumor necrosis factor-α content and increased ( p  < .05) interleukin-2 (IL-2) content in goat serum; significantly decreased ( p  < .05) IL-12, and increased ( p  < .05) IL-2 content in goat ileal mucosa; significantly increased ( p  < .05) secreted IgA content in the jejunal and ileal mucosa; significantly upregulated ( p  < .05) IL-2 and downregulated ( p  < .05) IL-12 at the mRNA level in the ileal mucosa; significantly elevated the levels of serine, arginine, and total amino acids in the ileal mucosa ( p  < .05); significantly upregulated ( p  < .05) SLC1A1 and SLC7A1 in the ileum; and significantly enhanced ( p  < .05) the protein expression of Claudin-1 in the ileal mucosa. In summary, adding 0.2 ml/kg of TTO to the diet enhanced SLC1A1 and SLC7A1 mRNA expression in the ileal mucosa, and SLC1A1 and SLC7A1 could transport serine and arginine from the chyme to the ileal mucosa. Thus, increased serine and arginine content in the mucosa could improve intestinal immunity. TTO supplementation upregulated the expression of IL-2 and Claudin-1 in goat ileal mucosa, and enhanced immune function in the intestine.