Effects of Dietary Supplementation with Eucalyptus Essential Oil and Soy Isoflavones on the Growth Performance, Intestinal Health and Meat Quality of Weaned Meat Rabbits

This study investigated the effects of individual and combined supplementation of eucalyptus essential oil (EEO) and soy isoflavones (SI) on the growth performance, intestinal health and meat quality of weaned meat rabbits. A total of 120 Ira female rabbits were stratified by body weight (BW) and randomly allocated into four treatment groups. The rabbits were fed for 35 days using (a) basal diet (Control), (b) basal diet + 150 mg/kg EEO, (c) basal diet + 25 mg/kg SI, or (d) basal diet + 150 mg/kg EEO + 25 mg/kg SI. The results showed that supplementing EEO and SI in the diet had a synergistic effect on production performance by increasing BW and average daily gain and reducing the feed intake/gain ratio. The EEO + SI group exhibited the most pronounced improvement in growth performance. Compared with the Control group, individual or combined supplementation significantly increased both semi-clean slaughter and total eviscerated slaughter rates, and showed a synergistic effect when supplemented together. The antioxidant capacity of the rabbits was enhanced, with the EEO + SI group showing the largest improvement. Serum biochemical analysis revealed that the combined treatment improved hepatic and cardiovascular functions. Additionally, we observed that the combined addition of EEO and SI has a synergistic effect on increasing the height of intestinal villi and the villus height/crypt depth ratio. Moreover, EEO and SI synergistically improved meat quality by elevating pH value, water-holding capacity, tenderness, and fat proportion. Notably, supplementation of EEO and SI in the diet regulated the composition of the intestinal microbiota, demonstrating increased relative abundance of beneficial <i>Bacteroides</i> and <i>Lachnospiraceae_NK4A136_group</i>. In conclusion, the combination of EEO and SI outperformed individual supplements in promoting growth and intestinal barrier function, potentially through enhancing antioxidant activity, attenuating oxidative stress, protecting the hepatic/cardiovascular systems, and improving intestinal morphology and microbial composition, thereby collectively enhancing growth performance, slaughter traits, and meat quality.