Contribution of Ruminal Fungi, Archaea, Protozoa, and Bacteria to the Methane Suppression Caused by Oilseed Supplemented Diets

Abstract

Dietary lipids can suppress methane emission from ruminants, but effects are variable. Especially the role of bacteria, archaea, fungi and protozoa in mediating the lipid effects is unclear. In the present in vitro study, archaea, fungi and protozoa were selectively inhibited by specific agents. This was fully or almost fully successful for fungi and protozoa as well as archaeal activity as determined by the methyl-coenzyme M reductase alpha subunit gene. Five different microbial treatments were generated: rumen fluid being intact (I), without archaea (–A), without fungi (–F), without protozoa (–P) and with bacteria only (–AFP). A forage-concentrate diet given alone or supplemented with crushed full-fat oilseeds of either safflower (Carthamus tinctorius) or poppy (Papaver somniferum) or camelina (Camelina sativa) at 70 g oil kg−1 diet dry matter was incubated. This added up to 20 treatments with six incubation runs per treatment. All oilseeds suppressed methane emission compared to the non-supplemented control. Compared to the non-supplemented control, –F decreased organic matter (OM) degradation, and short-chain fatty acid concentration was greater with camelina and safflower seeds. Methane suppression per OM digested in –F was greater with camelina seeds (−12 vs.−7% with I, P = 0.06), but smaller with poppy seeds (−4 vs. −8% with I, P = 0.03), and not affected with safflower seeds. With –P, camelina seeds decreased the acetate-to-propionate ratio and enhanced the methane suppression per gram dry matter (18 vs. 10% with I, P = 0.08). Hydrogen recovery was improved with –P in any oilseeds compared to non-supplemented control. No methane emission was detected with the –A and –AFP treatments. In conclusion, concerning methanogenesis, camelina seeds seem to exert effects only on archaea and bacteria. By contrast, with safflower and poppy seeds methane was obviously reduced mainly through the interaction with protozoa or archaea associated with protozoa. This demonstrated that the microbial groups differ in their contribution to the methane suppressing effect dependent on the source of lipid. These findings help to understand how lipid supplementation and microbial groups interact, and thus may assist in making this methane mitigation tool more efficient, but await confirmation in vivo.

Identification of Complex Rumen Microbiome Interaction Within Diverse Functional Niches as Mechanisms Affecting the Variation of Methane Emissions in Bovine

“…In addition, its relative abundance seemed to be favored (e.g., substrate and thermodynamics) in LME animals (Auffret et al, 2018). Candidatus Methanomethylophilus was previously identified as metabolically active in ruminants (Wang et al, 2017;Mann et al, 2018). In the same cluster as Candidatus Methanomethylophilus are the acetogens Eubacterium, Blautia, and Acetitomaculum, which are highly active H 2 sinks as recently shown in sheep (Greening et al, 2019).…”

“…Bacterial populations interacting with methanogens that utilize H 2 or involved in different metabolic pathways associated with amino acids, lactate or volatile fatty acids (VFA) are known to have different effects on CH 4 emissions (Moss et al, 2000;Janssen, 2010;Wanapat et al, 2015;Kamke et al, 2016;Sa et al, 2016). In addition, several authors revealed the importance of interactions between bacteria, fungi, protists (protozoa and micro-algae) and archaea in their effects on CH 4 emissions (Kumar et al, 2015;Wang et al, 2017;Huws et al, 2018).…”

Rumen fermentation and microbial community composition influenced by live Enterococcus faecium supplementation

“…Microorganisms inhabiting in the rumen contribute directly or indirectly to dietary organic matter degradation (Wang et al 2017). F. succinogenes and R. flavefaciens are two of the major cellulolytic bacterial species found in the rumen, and F. succinogenes was reported to be present in greater quantities than R. flavefaciens (Koike and Kobayashi 2001), which was confirmed in the present study.…”

Identification of a Candidate Starch Utilizing Strain of Prevotella albensis from Bovine Rumen

“…In these herbivores, the digestion of feed takes place in the rumen, the largest compartment of a four-chambered stomach, through the combined metabolic activities of resident microbial symbionts which precede digestion by host enzymes [ 3 , 4 ]. Ruminal microorganisms, consisting of a diverse array of bacteria, methanogens, protozoa, and fungi, are organized into complex communities that work synergistically to ferment ingested feedstuffs, producing short chain fatty acids (SCFAs) and microbial proteins that can be used by their host as sources of energy and amino acids, respectively [ 5 , 6 ].…”