Microbial community structure of the bovine rumen as affected by feeding cashew nut shell liquid, a methane‐inhibiting and propionate‐enhancing agent

Abstract

The effect of cashew nut shell liquid (CNSL) feeding on bacterial and archaeal community of the bovine rumen was investigated by analyzing clone libraries targeting 16S rRNA genes, methyl‐coenzyme reductase A‐encoding genes (mcrA), and their respective transcripts. Rumen samples were collected from three non‐lactating cows fed on a hay and concentrate diet with or without CNSL supplementation. DNA and complementary DNA (cDNA) libraries were generated for investigating rumen microbial communities. MiSeq analysis also was performed to understand more comprehensively the changes in the microbial community structures. Following CNSL supplementation, the number of operational taxonomical unit (OTU) and diversity indices of bacterial and archaeal community were decreased. Bacterial OTUs belonging to Proteobacteria, including Succinivibrio, occurred at a higher frequency with CNSL feeding, especially in cDNA libraries. The methanogenic archaeal community became dominated by Methanomicrobium. A bacterial community shift also was observed in the MiSeq data, indicating that CNSL increased the proportion of Succinivibrio and other genera known to be involved in propionate production. Methanogenic archaeal community shifts to increase Methanoplanus and to decrease Methanobrevibacter also were observed. Together, these results imply the occurrence of significant changes in rumen communities, not only for bacteria but also for methanogens, following CNSL feeding.

Growth and morphologic response of rumen methanogenic archaea and bacteria to cashew nut shell liquid and its alkylphenol components

“…These results agree with the results of the above mentioned feeding (Konda et al, 2019;Maeda et al, 2021;Su et al, 2021) and rumen simulation technique (S. Oh, Shintani, et al, 2017) studies and strongly suggest that alkylphenols selectively inhibit growth once delivered to the rumen environment.…”

“…In addition, the effects of alkylphenol components of CNSL on cell morphology, in particular anacardic acid, were clearly visualized using microscopic observations. Taken together, these data suggest that the rumen microbial community can be altered to reduce methane emissions and enhance propionate production via selective suppression of hydrogen-and formate-producing bacteria, as reported previously (Kang et al, 2018;Konda et al, 2019;Maeda et al, 2021;Shinkai et al, 2012;Su et al, 2021;Watanabe et al, 2010). Specific genera/ species/strains of methanogenic archaea affected by CNSL were also identified in the present study.…”

“…These shifts included decreases in Methanobrevibacter (Maeda et al, 2021;S. Oh, Shintani, et al, 2017;Su et al, 2021) and…”

“…The former two materials inhibit methyl‐coenzyme M reductase, which is involved in the final step of ruminal methanogenesis, whereas CNSL inhibits bacteria that produce hydrogen and formate, substrates for methane synthesis. All three additives can cause significant shifts in the rumen microbial community, based on sequencing analyses of bacterial and methanogenic archaeal genes (Hristov et al, 2015; Konda et al, 2019; Maeda et al, 2021; Roque et al, 2019; Su et al, 2021).…”

Feeding cashew nut shell liquid decreases methane production from feces by altering fecal bacterial and archaeal communities in Thai local ruminants

“…A > 50% decrease in methane production potential was achieved in Thai ruminant animals by altering the rumen microbial community structure through selective inhibition of specific microbes mediated by CNSL (Konda et al, 2019). A similar result was observed in Holstein cattle fed CNSL (Su et al, 2021). Konda et al (2019) reported that the surfactant action of alkyl phenols, in particular anacardic acid, is stably maintained in the rumen, although anacardic acid is decarboxylated and becomes less active in the rumen of Japanese Holstein cows (Shinkai, unpublished results).…”