Effects of dietary Chinese yam— Rehmannia glutinosa ‘medicine pair’ on growth performance, body size trait, slaughtering performance, antioxidant capacity, and cecum microbiota of broilers

Objectives Chinese yam and Rehmannia glutinosa , Henan province local medicinal herbs, have received attention owing to its positive nutritional and medicinal characteristics. The combination of Chinese yam and Rehmannia glutinosa , known as a ‘medicine pair’, has a long history of use. However, no published study has evaluated Chinese yam — Rehmannia glutinosa medicine pair (CYRG) as a dietary additive in broilers. This study aimed to evaluate the impact of dietary CYRG on growth performance, body measurements, slaughtering performance, antioxidant capacity and cecum microbiota of broilers. Methods Total of 300 23-day-old Arbor Acres female broilers were randomly assigned to the 5 treatment groups (CON, 0.5% CYRG, 1% CYRG, 1.5% CYRG, and 2% CYRG) with 6 replications and 10 birds/replicate. In the CON group, broilers received the basal diet, and other 4 groups received the basal diet supplemented with 0.5, 1, 1.5, and 2% CYRG, respectively. The feeding trial lasted for 19 days, until to 42 days. Results The results showed that 0.5% CYRG group had the highest of body weight gain, average daily gain, and average daily feed intake among the 5 groups. Supplementation CYRG significantly improved the slaughter percentage and semi-evisceration weight percentage of broilers ( P < 0.05). Supplementation 0.5% CYRG and 1% CYRG significantly increased the level of anti-inflammatory cytokines (IL-4) and decreased the pro-inflammatory cytokines (IL-6) level ( P < 0.05). Supplementation 1.5% CYRG improved the levels of serum immunoglobulins G (IgG) and IgM ( P < 0.05). 0.5% CYRG significantly increased the levels of catalase (CAT), glutathione peroxidase (GSH-Px), and total antioxidant capacity (T- AOC), and decreased the levels of malondialdehyde (MDA) ( P < 0.05). Microbiological analysis showed that CYRG supplementation increased the abundance of beneficial bacteria (Firmicutes) and decreased the quantity of harmful bacteria (Proteobacteria and Cyanobacteria). Correlation analysis indicated that Lactobacillus salivarius and Lactobacillus_crispatus were positively associated with serum IgA and IgG ( P