# Essential Oils in Nellore Beef Cattle: In Vivo Impact on Rumen Emissions

## TL;DR

This study found that adding oregano and white thyme essential oils to the diet of Nellore beef cattle did not reduce methane emissions or affect rumen parameters in real-life conditions.

## Contribution

The study provides new in vivo evidence that oregano and white thyme essential oils are ineffective in reducing methane emissions in beef cattle.

## Key findings

- Oregano and white thyme essential oils did not reduce in vivo methane emissions in Nellore cattle.
- The oils had no effect on rumen parameters like pH, ammoniacal nitrogen, or short-chain fatty acids.
- Results contrast with previous in vitro findings, highlighting the need for further in vivo research.

## Abstract

The impact of livestock on climate change has prompted animal nutrition researchers to reassess ruminant feeding strategies that minimize negative repercussions on the ecosystem. Essential oils (EOs), derived from natural plant extracts, have emerged as promising substances capable of inhibiting rumen methanogenesis. This study elucidated the effects of oregano and white thyme EOs on in vivo rumen methane emissions and rumen parameters in Nellore beef cattle. In contrast to results obtained through in vitro methods, our in vivo results indicated that oregano and white thyme EOs included in the diet at 3 mL/kg dry matter were not effective in reducing rumen methane emissions.

Essential oils (EOs), as rumen additives, decreased CH4 emissions in in vitro trials but results from in vivo studies are still limited. We investigated the effects of Origanum vulgare (OEO) and Thymus vulgaris (TEO) EOs on in vivo methane emissions from Nellore beef cattle. Six adult rumen-cannulated Nellore cattle were used in a double 3 × 3 Latin square design. Treatments consisted of three diets containing either 3 mL OEO per kg of concentrate, 3 mL TEO/kg of concentrate, or no EO addition. The experimental period consisted of three 21 d feeding periods and methane production was measured using the sulfur hexafluoride (SF6) technique from Day 16 to Day 21 of each feeding period. Intake, total apparent digestibility (dry matter as well as neutral and acid detergent fiber), and rumen parameters (pH, ammoniacal nitrogen concentration, and short-chain fatty acids) were also evaluated. The EOs did not decrease CH4 emissions and had no effect on rumen parameters.