Comparison of the Efficacy of Two Forms of Thyme Supplementation (Powder and Essential Oil) in Preventing Natural Coccidiosis in Broiler Chickens: Effects on Oocyst Shedding, Intestinal Lesions, Growth Performance, and Mortality.

Natural coccidiosis is a major health and economic challenge in global broiler production, particularly in intensive systems characterized by high stocking density, damp litter, and limited ventilation. These conditions favor the persistence and transmission of Eimeria oocysts. Once ingested, the parasite damages the intestinal epithelium, disrupting digestion and nutrient absorption. Consequently, infected flocks show depressed growth, poorer feed efficiency, compromised gut integrity, inferior carcass yield, and increased mortality. When performance losses are combined with treatment and management expenses, the annual global cost of poultry coccidiosis exceeds ۱۴ billion USD. Continuous reuse of poultry houses and environmental contamination make natural exposure common, emphasizing the importance of preventive nutritional interventions. Thyme (Thymus vulgaris) has attracted attention as a phytogenic feed additive due to its antimicrobial, anti-inflammatory, and antiparasitic properties. Its primary bioactive constituents-thymol, carvacrol, p-cymene, and y-terpinene- exert anticoccidial effects by disrupting oocyst structure, altering membrane permeability, inhibiting sporulation, and limiting intracellular parasite development. Thyme can be administered as dried powder or as concentrated essential oil, but differences in active compound concentration may influence efficacy. A feeding experiment evaluated these two forms in ۳۰۰ male Ross ۳۰۸ broilers exposed to natural coccidiosis. Birds were randomly allocated to three treatments: a control diet, ۵ g/kg thyme powder, and ۲۰۰ mg/kg thyme essential oil, with five replicates of ۱۵ birds each. Over a ۴۲-day period, oocyst shedding, intestinal lesion scores, growth performance, and mortality were assessed. On day ۲۸, oocyst counts reached ۴۸,۰۰۰ oocysts/g in controls, compared with ۳۳,۱۰۰ in the powder group and ۲۰,۴۰۰ in the essential oil group. By day ۳۵, values declined to ۳۹,۵۰۰, ۲۵,۴۰۰, and ۱۳,۲۰۰ oocysts/g, representing reductions of ۳۶% with powder and ۶۶% with essential oil relative to controls. Lesion scores averaged ۲.۳ in controls, ۱.۸ with powder, and ۱.۲ with essential oil. Final body weights were ۲۲۸۰ g, ۲۴۰۵ g, and ۲۵۱۰ g, respectively, while feed conversion ratios improved from ۱.۷۱ to ۱.۶۳ and ۱.۵۷. Mortality decreased from ۶.۱% in controls to ۴.۰% and ۲.۷% in powder and oil groups. Overall, both forms enhanced intestinal health and productivity, but essential oil showed superior performance, likely due to its higher monoterpene concentration (۳۰-۴۵% vs. ۲-۳%) and greater bioavailability.

کلیدواژه ها:

Thyme essential oil ، Thyme powder ، Natural coccidiosis ، Broiler chickens ، Oocyst shedding (OPG) ، Growth performance