Effects of herbal mixture supplementation on growth performance and physiological responses in broilers under experimental coccidial challenge

This study evaluated the effects of two herbal extract mixtures as alternatives to salinomycin on growth performance and physiological responses in broilers subjected to experimental coccidial challenge. A total of 840 Ross 308 broilers were assigned to four dietary treatments: a basal diet (CON), CON supplemented with 0.1% salinomycin (Group 1), CON supplemented with 0.015% herbal extract mixture (Group 2), and CON supplemented with 0.02% herbal extract mixture (Group 3). All birds were orally challenged with a 30-fold dose of a live coccidiosis vaccine at 14 days of age. During the post-challenge period, broilers in Group 1 and Group 3 showed significantly higher body weight gain (BWG) and lower feed conversion ratio (FCR) compared with the control group (p < 0.05), whereas feed intake was not affected. Dietary treatments induced selective changes in blood biochemical and hematological parameters, including increased serum calcium and sodium concentrations and altered leukocyte profiles (p < 0.05). However, relative organ weights, fecal oocyst shedding, intestinal morphology, and circulating cytokine levels were not significantly affected by dietary treatments (p > 0.05). Notably, ZO-1 gene expression was upregulated in selected treatment groups (p < 0.05), while other barrier- and proliferation-related genes remained unchanged. Overall, these findings suggest that herbal extract supplementation improves growth performance in broilers under coccidial challenge primarily through modulation of host physiological responses rather than direct inhibition of parasite replication.