Abstract

The ban on antibiotic growth promoters in livestock feeding has encouraged the utilization of phytogenic feed additives. These phytogenics recently attracted much attention and are generally recognized as residue-free ideal feed additives in animal Production. The current study was conducted to investigate the effects of the phytogenic herbs on feed intake, feed conversion ratio, and immune responses associated with the infectious bursal disease (IBD) vaccine in broiler chickens. For this study, 360 day-old broiler chicks were randomly assigned to six feeding trials, each with three replicates containing 20 chicks. The control group (T1) was only fed a basal diet alone, while the treatment groups were given the basal diet supplemented with 1% of basil (T2), lemongrass (T3), peppermint (T4), rosemary (T5), and thyme (T6) leaves powder, respectively. Body weight, feed intake, and feed conversion ratio were recorded. All chicks were vaccinated against IBD on days 7 and 19. A serology test was conducted to check the antibody titer against the IBD vaccine. The findings of this study showed that chickens in group T2 had significantly consumed more feed, followed by T1 and T6. During the overall study period, chickens in group T4 had significantly better feed conversion efficiency, followed by T3 and T6. Chickens in groups T5 and T6 showed a more pronounced antibody titer against the IBD vaccine at days 21 and 42 of the experiment. Therefore, these findings indicated that supplementation of basil leaf powder improved feed intake. Moreover, peppermint and lemongrass leaf powder improved the feed conversion ratio. In addition, supplementation of rosemary and thyme enhances the immune status of broiler chickens and could be considered a natural growth promoter feed additive. Therefore, further studies should be done to discover their beneficial effects to use as alternative feed additives in broiler chickens.