Effects of dietary supplementation with a thymol-carvacrol blend on growth performance and intestinal health of poultry

Xiaoxia Liu^1*Xiang Li²Ruiying Cheng²Jing Liu³Rui Liu⁴Ruting Zhao³Aiguo Luo¹Jia Zhao¹Jianwei Hao¹Shuming Yang³Ailiang Chen^3*

• ¹Jinzhong University, Jinzhong, China
• ²Shanxi Agricultural University, Taiyuan, China
• ³Institute of Quality Standard and Testing Technology for Agro-Products Chinese Academy of Agricultural Sciences, Haidian, China
• ⁴People's Public Security University of China, Beijing, China

Introduction: A composite essential oil containing carvacrol and thymol was evaluated as an antibiotic alternative in Aibayi-Yijia broiler production. Broilers were fed a basal diet with graded levels of the oil, and growth performance: Average body weight (ABW), average daily gain (ADG), average daily feed intake (ADFI), feed conversion ratio (F/G), serum biochemistry: Total protein (TP), albumin (ALB), globulin (GLB), and cholesterol (CHOL), jejunal histomorphology (villus height, crypt depth, V:C) and cecal microbiota (16S rRNA) were assessed. Dietary supplementation at 600 g/t, or a program of florfenicol (0.15 g/kg) during the starter phase followed by 1,200 g/t oil in the later phase, significantly increased ABW and ADFI (P<0.05); ADG and F/G were not significantly affected (P>0.05). Administration of an antibiotic in the early phase followed by essential oil supplementation in the later phase (200 g/t or 1,200 g/t) significantly decreased TP, ALB, GLB and CHOL (P<0.05). Intestinal morphology was improved, as indicated by increased jejunal villus height and higher V:C ratios, and the cecal microbiota was modulated. Collectively, these results indicated that the carvacrol-thymol blend had potential as an antibiotic substitute under the tested dosing regimens.