# Ameliorative Impacts of an Essential Oil Blend on Immune Function and Intestinal Health in Broilers Challenged with a High-Dose Coccidial Vaccine

## TL;DR

This study shows that an essential oil blend can improve immune function and intestinal health in chickens challenged with a high-dose coccidial vaccine, performing as well as antibiotics.

## Contribution

The study demonstrates the efficacy of an essential oil blend as a sustainable alternative to antibiotics in managing coccidiosis in broilers.

## Key findings

- The essential oil blend reduced oocyst excretion and improved intestinal health in infected broilers.
- EOB200 showed superior effects compared to EOB400 and antibiotics in enhancing immune markers and intestinal structure.
- The blend improved villus height and V:C ratio, indicating better intestinal integrity.

## Abstract

Background: The emergence of coccidial drug resistance has intensified the search for sustainable, residue-free solutions to control poultry coccidiosis. This challenge has positioned plant essential oils as promising candidates among the priority research areas. The study aimed to investigate the efficacy of essential oils in improving immune function and intestinal health in white-feathered broilers challenged with a high-dose coccidial vaccine. Methods: A total of 480 one-day-old broilers were randomly assigned to five treatments: uninfected (CON), infected (EC), infected + 500 g/t narasin (AT), and infected + 200 or 400 g/t essential oil blend (EOB200 or EOB400). There were 6 replicates per treatment and 16 broilers per replicate. All infected treatments received a 30-fold coccidial vaccine on d 14. The CON group was administered an equal volume of sterile normal saline on d 14 of the experiment. One bird per replicate was sampled on d 22, and the remainder were raised until d 42. Results: Results showed that the challenge increased the fecal oocyst counts on d 21 and 28 and elevated intestinal lesion scores and serum interleukin-6 (IL-6) levels on d 21, while it decreased IL-10 levels on d 21 and reduced the villus height-to-crypt depth (V:C) ratio in the duodenum and jejunum (p < 0.05). Additionally, compared with the EC group, the AT, EOB200, and EOB400 groups reduced oocyst excretion and serum superoxide dismutase (SOD) (p < 0.05). The EOB200 group also showed the highest serum transforming growth factor-β (TGF-β) concentration, along with the lowest immunoglobulin G (IgG) level (p < 0.05). Moreover, within the infected groups, the EOB200 group exhibited the highest duodenal villus height and V:C ratio (p < 0.05). Conclusions: These findings indicated that the EOB200 and EOB400 groups alleviated intestinal damage caused by the coccidial vaccine with an efficacy comparable to that of antibiotics, and the EOB200 group exhibited a superior effect. The results confirm that the essential oil blend holds great application potential as an alternative to antibiotics.