Effects of Thymol Supplementation on Goat Rumen Fermentation and Rumen Microbiota In Vitro.

Jiangkun Yu,Jiacai Zhang,Le Luo Guan,Lei Zhang,Ao Yang,Desheng Qi,Yanan Wang,Liyuan Cai

doi:10.3390/microorganisms8081160

Jiangkun Yu, Jiacai Zhang + Show 6 more

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https://doi.org/10.3390/microorganisms8081160

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Abstract

This study was performed to explore the predominant responses of rumen microbiota with thymol supplementation as well as effective dose of thymol on rumen fermentation. Thymol at different concentrations, i.e., 0, 100 mg/L, 200 mg/L, and 400 mg/L (four groups × five replications) was applied for 24 h of fermentation in a rumen fluid incubation system. Illumina MiSeq sequencing was applied to investigate the ruminal microbes in addition to the examination of rumen fermentation. Thymol doses reached 200 mg/L and significantly decreased (p < 0.05) total gas production (TGP) and methane production; the production of total volatile fatty acids (VFA), propionate, and ammonia nitrogen, and the digestibility of dry matter and organic matter were apparently decreased (p < 0.05) when the thymol dose reached 400 mg/L. A thymol dose of 200 mg/L significantly affected (p < 0.05) the relative abundance of 14 genera of bacteria, three species of archaea, and two genera of protozoa. Network analysis showed that bacteria, archaea, and protozoa significantly correlated with methane production and VFA production. This study indicates an optimal dose of thymol at 200 mg/L to facilitate rumen fermentation, the critical roles of bacteria in rumen fermentation, and their interactions with the archaea and protozoa.

Highlights

Ruminants are unique livestock species for their exquisite rumen structure that harbors a complex microbiota responsible for converting indigestible plant mass into energy available to the host [1]
Compared with control (CON) group, a significant increase in ruminal pH (p < 0.01) as well as a notable reduction (p < 0.01) in total gas production (TGP) was observed in the medium concentration (MC) and high concentration (HC) groups supplemented with thymol (Table 2)
CH4 production based on fermented dry matter (DM) or organic matter (OM) was significantly decreased (p < 0.01) in the MC and HC groups (Table 2)

Summary

Introduction

Ruminants are unique livestock species for their exquisite rumen structure that harbors a complex microbiota responsible for converting indigestible plant mass into energy available to the host [1]. Mainly volatile fatty acids (VFA), contribute to 70% of the daily energy requirement [3,4]. As a result of rumen fermentation, ruminants contribute greatly to the production of the greenhouse gas methane (CH4) [5,6]. Manipulation of rumen microbial fermentation could both improve animal production and alleviate adverse environment impacts. To modify rumen fermentation, feed additives are commonly applied. The application of EOs as a feed additive is constrained by the absence of production standards (proportion of active compounds) and acknowledged quantified dosages. Further studies are required to study the active compounds in EOs and their impact on rumen fermentation for future practical applications

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