The effect of Alpinia oxyphylla essential oil on growth performance, immune, antioxidant functions and gut microbiota in pigs

<i>Alpinia oxyphylla</i>, a perennial herb belonging to the Zingiberaceae family, has a long history of traditional medicinal use. The present study evaluated the efficacy of different concentrations of <i>Alpinia oxyphylla</i> essential oil (AEO) on the growth performance, serum antioxidation capacities, immune function, apparent digestibility of nutrients, and gut microbiota in fattening pigs. A total of 120 pigs were divided into five treatments, with six replicates each and four pigs per replicate. The pigs were fed a basal diet or basal diet with chlortetracycline (CTC) alone or AEO at 250, 500, and 1,000 mg/kg (referred to as groups AEO1, AEO2, and AEO3, respectively) for 35 days, preceded by a 7-day pre-feed period. The results show that there were no statistically significant differences in growth performance for any dose of AEO supplementation. AEO increased L-DLC content, total protein content and the activity of GSH in serum (<i>p</i> < 0.05). The AEO also exhibited a linear increase in serum IgG content (<i>p</i> < 0.05). Dietary supplementation with AEO improved apparent digestibility of crude ash and calcium (<i>p</i> < 0.05). In gut microbiota, AEO modified the diversity and abundance of bacterial communities in fattening pigs. The abundance of <i>Dorea</i>, <i>Blautia</i>, <i>Butyricicoccus</i>, <i>Bulleidia</i>, and <i>Lactobacillus</i> was higher in the AEO groups compared to the control group, while <i>Clostridium</i> and <i>Turicibacter</i> were lower. The <i>Bifidobacteriales</i> and <i>Pseudomonas</i> were abundant in group AEO1 and AEO3, respectively. In conclusion, dietary supplementation of 1,000 mg/kg AEO has the potential to improve growth performance, immunological, biochemical, and antioxidant statuses. Additionally, AEO can increase the efficiency of nutrient digestion and absorption through the regulation of gut microbiota.