Coccidiosis is a major parasitic disease infecting poultry across the globe. Coccidiostat and coccidiocidal drugs are being used frequently, but the issue needs modern medicine for effective control. Herbal products, especially essential oils, have compounds that have proven to be anticoccidial agents. For this purpose, a research experiment was conducted to evaluate the anticoccidial potential of the essential oil of F. vulgare. Broiler chicks of COBB 500 numbering two hundred and sixteen (216) were grouped into six random groups and were replicated thrice. Each group was replicated thrice, containing 12 chicks per replicate. These birds were subjected to oral infection of sporulated oocysts of Eimeria spp. on the 7^th day of age excluding chicks of neutral control, which was a non-infected control. The feed for chicks in three groups contained fennel essential oil at 1, 2, and 3% concentrations. The remaining three groups consisted of a medicated group (treated with Toltrazuril), an infected but untreated group, and a healthy untreated control group. The study's parameters encompassed fecal scores, oocyst scores, oocyst counts per gram of feces, lesion scores, weight gain, feed intake, feed conversion ratio, mortality rates, organ weight ratios, blood profiles, and serum chemistry. The study's findings demonstrated the essential oil's anticoccidial properties. It was observed that fennel essential oil significantly outperformed the nonmedicated control groups (P<0.05) in reducing lesion scores, fecal scores, and oocyst counts per gram when administered at a 3% concentration. Improvements in feed intake, FCR, and reduced mortalities were also observed. Blood and serum parameters remain statistically comparable (P>0.05), showing no toxicity by the fennel oil. Results of this study show that fennel oil has potent anticoccidial effects, which can be used for further research to find out exact active ingredients

To Cite This Article: Wang X, Saeed Z, Abbas A and Wang L, 2026. In vivo anticoccidial activity evaluation of fennel seed essential oil in broiler chicken. Pak Vet J, 46(2): 468-472. http://dx.doi.org/10.29261/pakvetj/2026.035