Lonicera japonica Flos as a Natural Anticoccidial Agent Against Eimeria tenella: In Vivo Efficacy and Compositional Insights

This study aimed to evaluate the potential of Lonicera japonica Flos (LJF) as an alternative agent against Eimeria tenella (E. tenella) in chickens and to conduct phytochemical analysis to obtain compositional insights. Seventy-two one-day-old chickens were allocated to six groups and fed diets supplemented with LJF powder (LJFp) at three concentrations (LJFp-L, LJFp-M, and LJFp-H) or maduramicin (MDM) or two non-supplemented control diets, namely, an infected unmedicated control (IUC) and an uninfected unmedicated control (UUC). Dietary treatments were initiated at chick arrival (Day 0) and continued for 28 days. At 21 days of age, all groups except the UUC group were orally challenged with a field isolate of E. tenella (PT-Te003; 2.0 × 104 oocysts/bird). Anticoccidial efficacy was assessed using the lesion score (LS), oocysts per gram of feces (OPG), relative body weight gain (rBWG), and anticoccidial index (ACI). The results demonstrated that all LJFp treatment groups had significantly reduced cecal OPG and LS (all LJFp treatments: p < 0.05 vs. IUC), indicating the effective suppression of E. tenella replication and intestinal damage. Regarding growth performance, the rBWG values of the LJFp-L and LJFp-M groups were the highest and comparable to those of the UUC group, showing no significant differences. In contrast, the LJFp-H and MDM groups exhibited significantly lower values (p < 0.05). Based on ACI evaluation, all LJFp-treated groups exhibited moderate to partial efficacy (LJFp-L > LJFp-M > LJFp-H), while MDM showed limited effectiveness. A gas chromatography–mass spectrometry (GC-MS) analysis of the LJFp ethanol extract revealed 15 essential oils, 10 organic acids, and three other compound classes, several of which have been associated with anticoccidial activity. Overall, the in vivo results suggest that LJF may exert potential anticoccidial effects against a field isolate of E. tenella. Phytochemical analysis provided preliminary compositional insights, and further studies are warranted to optimize extraction methods and evaluate efficacy at lower concentrations under additional in vitro and in vivo conditions. However, the current evidence remains insufficient to determine whether the field isolate exhibits reduced sensitivity to commercially available anticoccidial drugs, and additional studies are needed to clarify this issue.