Evaluation of the Effects of Mitigation on Methane and Ammonia Production by Using Origanum vulgare L. and Rosmarinus officinalis L. Essential Oils on in Vitro Rumen Fermentation Systems

Gabriella Cobellis,Mara Orrù,Andrea Nicolini,Andrea Aquino,Claudio Forte,Alessandro Petrozzi,Valentina Mazza,Maria Marcotullio,Gabriele Acuti,Massimo Trabalza-Marinucci

doi:10.3390/su70912856

Abstract

The effects of increasing concentrations of oregano (Origanum vulgare L.) and rosemary (Rosmarinus officinalis L.) essentials oil (EO) on ruminal gas emissions were tested in vitro using 50 mL serum bottles. Each bottle contained a 200 mg substrate (alfalfa hay and corn meal 1:1) and a 20 mL solution composed of a buffered medium and rumen fluid (1:2). The percentage of ruminal fermentation products was quantified by an infrared analyzer. The reduction of total gas production was 6% and 9% respectively when using the 1.5 and 2.0 g/L oregano EO measurements. The reduction of methane production was 55%, 72% and 71% respectively with regard to the 1.0, 1.5 and 2.0 g/L oregano EO doses, while rosemary EO (2.0 g/L) reduced the methane production by 9%. The production of ammonia was significantly reduced (59%–78%) by all treatments with the exception of rosemary EO at the lowest dose. Dry matter and neutral detergent fiber degradability was reduced by most of the treatments (respectively 4%–9% and 8%–24%). The total volatile fatty acids (VFA) concentration was markedly decreased by oregano EO and was not affected by rosemary EO. Both EOs mitigated rumen fermentations, but oregano EO gave rise to the highest reduction in methane and ammonia production. However, further research is needed to evaluate the use of these essential oils as dietary supplements by taking into account the negative effects on feed degradability.

Highlights

Agriculture produces about 10%–12% of the total global anthropogenic greenhouse gas (GHG)emissions: it contributes about 9% of the carbon dioxide (CO2), 50% of the anthropogenic methane (CH4) and 93% of the ammonia (NH3) emissions [1]
Sixteen compounds were identified in oregano essentials oil (EO)
The composition of oregano EO was characterized by a high percentage

Summary

Introduction

Agriculture produces about 10%–12% of the total global anthropogenic greenhouse gas (GHG)emissions: it contributes about 9% of the carbon dioxide (CO2), 50% of the anthropogenic methane (CH4) and 93% of the ammonia (NH3) emissions [1]. Carbon dioxide gives the reference value of global warming potential (GWP) but is the most important GHG due to its high concentration in the atmosphere. Carbon dioxide emissions from metabolic and respiratory activities are not considered in the total GHG amount because they are balanced by CO2 captured by plants used for animal feeding. For this reason, animal respiratory activities are not considered to be a CO2 source by the Kyoto Protocol. Ruminant animals produce significant amounts of CH4 (33% of global CH4 emissions) and contribute significantly to global warming through the emission of 4% of total GHG [6]

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