# Feeding an Essential Oil Blend to Growing Crossbred Lambs Mitigates Heat Stress to Improve Growth Performance via Enhanced Antioxidant Capacity

## TL;DR

Feeding an essential oil blend to lambs under heat stress improves their growth and health by boosting their antioxidant capacity.

## Contribution

The study shows that an essential oil blend can mitigate heat stress in lambs, improving growth and physiological responses.

## Key findings

- Lambs fed the essential oil blend had a 50% increase in body weight gain compared to controls.
- The blend reduced respiration rates and body temperatures in heat-stressed lambs.
- The essential oil blend improved antioxidant activity and immune status in lambs.

## Abstract

Heat poses a significant stress challenge to sheep farming around the world, especially in arid and semi-arid regions, impacting lamb growth performance, health, and physiological status. This experiment evaluated feeding an essential oil blend, as a potential feed supplement, to ameliorate HS in thirty-two female growing lambs measuring growth performance, blood metabolites, antioxidant capacity, and physiological responses. Treatments were a control and an essential oil blend supplemented at 4 g/kg in the concentrate mix. Lambs were fed separately free-choice concentrate mix and forage mix. Lambs experienced extreme heat stress for 39 of the 45 d experiment. Growing heat-stressed lambs fed essential oil blend demonstrated approximately 50% improvement in body weight gain compared with control fed lambs. Forage, dry matter intake, and feed efficiency were greater for essential oil blend fed lambs compared with control fed lambs. Respiration rates, rectal temperatures, and skin temperatures were lower for lambs fed the essential oil blend compared with control fed lambs. The feeding of an essential oil blend as a dietary feed supplement at 4 g/kg concentrate mix has the potential to mitigate HS impacts on growing lambs while improving their antioxidant and immunity status.

Heat stress (HS) poses a significant stress challenge to growing lambs, impacting growth performance, health, and physiological responses. The study evaluated feeding an essential oil blend (EOB) on growth performance, physiological and blood parameters, oxidative, and immune responses. Thirty-two 3 mo old female (BW 18.6 ± 2.43 kg) crossbred (Mongolian × Thin-tailed Han F1) lambs were randomly assigned to either: (1) control (CON)—grain mix without EOB; or (2) EOB—an EOB blend supplemented at 4 g/kg grain mix. The EOB blend was comprised of 4.34% Zanthoxylum, 1% capsicum, and 1.06% cinnamon oils with 93.6% attapulgite carrier containing linalool, sabinene, limonene, capsaicin, cinnamaldehyde and eugenol. Extreme heat stress occurred for 39 out of the 45 d experiment. Feeding HS lambs EOB increased (p < 0.05) ADG (107.4 and 162.0 g/d for CON and EOB, respectively), forage intake (239.2 and 287.0 g/d), DMI (863.1 and 930.2 g/d), and feed efficiency (0.123 and 0.181 ADG, g/DMI, g) compared with lambs fed CON. Feeding EOB reduced (p < 0.01) respiration rates (RR) and rectal (RT) and skin temperatures (ST) compared to CON-fed lambs. Lambs fed EOB had a higher T-SOD activity and IgM concentration (0.05 < p < 0.10) than CON-fed lambs. Growing heat-stressed lambs fed EOB demonstrated a lower (p < 0.05) eosinophil percentage. Feeding EOB ameliorated HS conditions for growing crossbred lambs, which demonstrate improved growth performance, enhanced physiological responses, and overall health status.