Dietary Tea Tree (Melaleuca alternifolia) Oil Supplementation Improves Growth Performance, Cecal Microflora, Immunity, and Antioxidant Capacity of Partridge Shank Chickens

Effects of adding tea tree oil on growth performance, immune function, and intestinal function of broilers

The aim of this study was to investigate the effects of adding tea tree oil (TTO) in the basal diet on growth performance, immune function, and intestinal function in broilers. This study utilized 1,650 one-day-old broilers with good health and similar body weight. Subjects were randomized into 5 groups with 6 replicates each: the control group (CON, basal diet), positive control group (PCG, basal diet + 100 mg/kg oregano oil in diet), low-dose TTO group (TTO-L, 50 mg/kg TTO added in the basal diet), medium-dose TTO group (TTO-M, 100 mg/kg TTO added in the basal diet), and high-dose TTO group (TTO-H, 200 mg/kg TTO added in the basal diet). The whole test period lasted 28 d. The results showed that the broilers fed with TTO supplemented diet had significantly higher body weight and average daily gain (ADG) (P = 0.013), and had a lower feed conversion ratio (F/G) (P = 0.010) throughout the trial period. The index of thymus in TTO-M increased significantly compared to CON (P = 0.015) on d 28. On d 14 and 28, C3, IFN-γ, TNF-α, and IL-2 levels in TTO-L serum were significantly increased (P < 0.001); the 3 test groups supplemented with TTO had significantly higher titers of avian influenza H9 subtype in their serum (P < 0.05). Tea tree oil supplement in the diet also had a positive and significant effect on the intestinal morphology of broilers throughout the experiment (P < 0.05). These results indicate that TTO has the ability to promote broiler growth, regulate immunity, and improve intestinal morphology. The proposed dosage of adding 50 mg/kg in broiler basal diets provides a theoretical basis for its subsequent use in livestock feeds.

Evaluating protective effects of botanicals under inflammation and oxidative stress in chicken apical-out enteroids

Botanicals (BOTs) are well known for their anti-inflammatory and antioxidant activities. They have been widely used as feed additives to reduce inflammation and improve intestinal functions in agricultural animals. However, the effects of BOTs on chicken intestinal epithelial functions are not fully understood. The 3D apical-out chicken enteroids recapitulate the intestinal tissue, and allow convenient access to the luminal surface, thus serving as a suitable model for investigating gut functions. The aim of this study was to identify the roles of BOTs in protecting the intestinal epithelium in chicken enteroids under challenging conditions. Apical-out enteroids were isolated from the small intestines of 18 days-old chicken embryos. Lipopolysaccharide (LPS, 10 µg/mL) and menadione (400 µM) challenges were performed in the media with or without BOTs. Paracellular Fluorescein isothiocyanate-dextran 4kD (FD4) permeability, inflammatory cytokine gene expression, and reactive oxygen species (ROS) generation were analyzed post-BOTs and challenges treatments. Statistical analysis was performed using one-way ANOVA and post hoc multiple comparisons among treatments. The results showed that the LPS challenge for 24 h induced a 50% increase in FD4 permeability compared with nontreated control; thymol, thyme essential oil, and phenol-rich extract significantly (P < 0.02) reduced FD4 permeability by 25%, 41%, and 48% respectively, in comparison with LPS treatment. Moreover, the gene expression of inflammatory cytokines was upregulated, tight junction proteins and defensins were downregulated (P < 0.05) after 6 h of LPS treatment, while these BOTs treatments significantly restored the LPS-induced gene expression alterations (P < 0.05). Menadione oxidative challenge for 1 h significantly increased the ROS level compared with unchallenged control. Enteroids treated with thymol and thyme essential oils showed 30% reduced ROS levels, while the phenol-rich extract reduced them by 60%, in comparison with the challenged group (P < 0.0001). These data confirmed the role of BOTs in supporting the barrier function and reducing the disruptive effects of inflammation and oxidation in the chicken intestine.

Effects of tea tree oil supplementation on growth performance, antioxidant capacity, immune status and microbial community in weaned pigs

The objective of this study was to determine whether dietary tea tree oil (TTO) supplementation could effectively replace the antibiotics through modulating the antioxidant capacity and intestinal microbiota profile, and then decreasing the diarrhoea incidence and improving the growth performance of weaned pigs. A total of 216 weaned pigs with initial body weights (BW) of 9.19 ± 1.86 kg were randomly allocated to three dietary treatments in a completely randomised design. The dietary treatments included a corn-soybean meal basal diet (CON) without any antibiotics, and two experimental diets formulated by adding 75 mg/kg aureomycin (AGP) or 100 mg/kg TTO into the basal diet, respectively. Pigs fed the TTO diet showed greater gain to feed ratio (p < 0.05) than those fed CON and AGP diets during d 0-14 and d 14-28. Both dietary TTO and AGP supplementation tended to increase the average daily gain of weaned pigs during d 14-28 (p = 0.06) and the overall 28-d period (p = 0.07), and significantly reduced (p < 0.05) the diarrhoea incidence during d 0-14 compared with the CON treatment. In addition, dietary TTO supplementation improved the apparent total tract digestibility of dry matter and ether extract (p < 0.05), and increased (p < 0.05) the propionate and butyrate concentrations in faecal samples of weaned pigs. Moreover, pigs fed the TTO diet showed greater total antioxidant capacity, greater superoxide dismutase and interleukin-10 concentrations, and lower malondialdehyde concentration in serum than those fed the CON diet (p < 0.05). Furthermore, pigs fed the TTO diet demonstrated greater relative abundance of Clostridiaceae_1, while those fed the AGP diet exhibited greater relative abundance of Lactobacillaceae at family level. In conclusion, dietary TTO supplementation could improve growth performance in weaned pigs, which could be mainly attributed to the benefits on nutrient digestibility, antioxidative capacity and microbial community profile.