Effects of thymol–carvacrol combined with organic acids on carcass traits, meat quality, and stress indicators in broilers under enteric disease challenge

The effects of a feeding program combining thymol–carvacrol and organic acids were evaluated as an alternative to an antibiotic growth promoter (AGP) in broilers under a coccidial challenge. A total of 750 male Ross 308 chicks were assigned to a negative control (T1), an AGP group with bacitracin methylene disalicylate (T2), or a thymol-carvacrol–organic acid group (T3). Slaughter weight, dressing percentage, retail cut yields, and meat quality traits did not differ among treatments (P > 0.05). T2 had the highest number of birds without foot pad lesions, significantly exceeding T1 and comparable to T3, which also outperformed T1 (P < 0.05). T2 recorded the fewest mild and severe lesions, while T3 showed a numerical reduction in severe lesions compared with T1. Both T2 and T3 reduced lesion severity relative to T1, with T2 showing the most favorable scores and T3 demonstrating meaningful potential as a non-antibiotic alternative. Thigh meat malondialdehyde (MDA) levels increased during storage (P < 0.01), but no treatment effects were observed (P > 0.05). Serum MDA and the proportions of lymphocytes, monocytes, eosinophils, and basophils were unaffected; however, heterophil percentage and the heterophil-to-lymphocyte ratio were significantly higher in T1 than in T2 and T3 (P < 0.01), indicating reduced physiological stress with both AGP and thymol-carvacrol–organic acid supplementation. Overall, thymol–carvacrol with organic acids-maintained carcass yield and meat quality while mitigating stress responses and improving foot pad health, supporting its potential as a viable alternative to AGPs in broilers under enteric challenge.