# Mitigating Effects of Rosmarinus officinalis Essential Oil and Sugar Beet Pulp on Immune Response and Growth Performance of Heat-Stressed Lambs

## TL;DR

This study shows that adding rosemary essential oil and sugar beet pulp to the diet of heat-stressed lambs can improve their immune response and growth.

## Contribution

The study introduces a novel combination of rosemary essential oil and sugar beet pulp to enhance lamb performance under heat stress.

## Key findings

- REO reduced rectal temperature and respiration rate in heat-stressed lambs.
- REO increased pro-inflammatory cytokines IL-1β and IL-6, indicating improved immune response.
- Growth performance was not compromised despite the immune system activation.

## Abstract

Recently, essential oils have been widely used as feed additives to improve the sustainability of ruminant production by reducing methane production and enhancing overall health. The aim of the present paper was to evaluate Rosmarinus officinalis essential oil (EO) and the combination of R. officinalis EO and dried sugar beet pulp addition on the immune profile in terms of cytokine secretion and growth performance of heat-stressed fattening lambs. In this context, a partial substitution of feed with by-products may represent a good strategy for improving livestock sustainability and reducing feed cost. Additionally, EO could support lamb thermotolerance and immune response.

Dietary supplementation under high ambient temperatures can be considered crucial for supporting immune responses in livestock. In the present paper, Rosmarinus officinalis essential oil (REO) alone and in combination with dried sugar beet pulp (REO + B) was included in the diet of lambs during the fattening period under heat stress conditions. Environmental conditions and physiological and growth parameters of lambs were monitored throughout the trial. Plasma samples were collected to evaluate cytokine secretion (IL-1β, IL-6, and IL-10). Notably, REO inclusion reduced rectal temperature and respiration rate while increasing pro-inflammatory cytokines (IL-1β and IL-6) at the same time, suggesting an enhanced immune response without compromising growth performance.