Dietary mitigation of enteric methane emissions from ruminants: A review of plant tannin mitigation options

Abstract

Methane gas from livestock production activities is a significant source of greenhouse gas (GHG) emissions which have been shown to influence climate change. New technologies offer a potential to manipulate the rumen biome through genetic selection reducing CH₄ production. Methane production may also be mitigated to varying degrees by various dietary intervention strategies. Strategies to reduce GHG emissions need to be developed which increase ruminant production efficiency whereas reducing production of CH₄ from cattle, sheep, and goats. Methane emissions may be efficiently mitigated by manipulation of natural ruminal microbiota with various dietary interventions and animal production efficiency improved. Although some CH₄ abatement strategies have shown efficacy in vivo, more research is required to make any of these approaches pertinent to modern animal production systems. The objective of this review is to explain how anti-methanogenic compounds (e.g., plant tannins) affect ruminal microbiota, reduce CH₄ emission, and the effects on host responses. Thus, this review provides information relevant to understanding the impact of tannins on methanogenesis, which may provide a cost-effective means to reduce enteric CH₄ production and the influence of ruminant animals on global GHG emissions.

Keywords: Feed efficiency; Greenhouse gas (GHG) emission; Methanogenesis; Ruminant; Tannin.

Fig. 1

Schematic microbial fermentation of polysaccharides, acetogenesis, and methanogenesis in the rumen. VFA = volatile fatty acids. Boxes with bold solid lines are potential targets for suppressing CH₄ emissions. Sources: Attwood and McSweeney (2008), Beauchemin et al. (2008), Morgavi et al. (2010), Patra (2012, .

Fig. 2

Selected studies of methane emissions from widely used techniques. (A) Effects of dry matter intake (DMI) on daily CH₄ emissions in dairy and beef cattle associated with detection methods, and (B) effects of DMI on average daily CH₄ emissions in dairy and beef cattle. SF₆ = sulfur hexafluoride tracer technique; IRC = indirect respiration chamber; GF = GreenFeed system (C-Lock Inc., Rapid City, SD, USA). Source: adapted from Table 1.

Fig. 3

Feed dry matter intake and methane production from beef cattle selected for variance in residual feed intake (RFI). Low (L)-RFI are efficient, high (H)-RFI are inefficient. RFI is expected feed requirements for maintenance and growth, with the expected feed requirements obtained by regression of feeding standards formula. IRC = indirect respiratory chamber; GF = GreenFeed system (C-Lock Inc., Rapid City, SD, USA). Sources: Dini et al. (2019; beef, BW = 357 kg BW; SF₆); Hegarty et al. (2007; beef, BW = 590 kg; SF₆); Alemu et al. (2017; beef heifers, BW = 380 kg; IRC and GF); Mercadante et al. (2015; cattle, BW = 238 to 326 kg BW; SF₆); Flay et al. (2019; dairy cattle, BW = 448 kg; GF); Lansink, (2018; beef, BW = 269 kg; GF).

Fig. 4

Effects of predominant bacterial phylum, total protozoa, and methanogen on methane emissions (A) Relationships between CH₄ productions and populations of total protozoa, (B) total bacteria, (C) Firmicutes-to-Bacteroidetes ratio, and (D) total methanogens in the rumen and in vitro rumen incubations. Source: Animut et al. (2008a, ; respiratory chamber), Liu et al. (2011; respiratory chamber), Puchala et al. (2005, , ; respiratory chamber), Min et al. (2019a; in vitro).

Fig. 5

Methane emission abatement strategies for ruminants. FCE = feed conversion efficiency, RFI = residual feed intake. Low (L)-RFI are efficient, high (H)-RFI are inefficient. RFI is expected feed requirements for maintenance and growth, with the expected feed requirements obtained by regression of feeding standards formula. Sources: Arthur et al. (2001), Beauchemin et al. (2007, , Broucek (2018), Charmley et al. (2016), Carstens, (2019), Hegarty et al. (2007), Hristov et al. (2013a, , Min and Solaiman (2018), Nkrumah et al. (2006), Patra et al. (2017), Roeche et al. (2016), Ross et al. (2013), Tavendale et al. (2005), and Woodward et al. (2001).

Fig. 6

Effect of condensed tannin-rich diets on rumen methane production per kilogram of dry matter intake for meat goats. Sources: Animut et al. (2008a, ; Puchala et al. (2005, , .

Fig. 7

Relative abundance (%) of major gastrointestinal methanogenic archaea diversity (>0.9%) present in meat goats (n = 6) fed condensed tannins (CT)-containing ground pine bark (PB) supplementation with grain mixed diets as analyzed using pyrosequencing. Control, 0 PB, 19% CT DM; 15% PB, 1.63% CT DM; and 30% PB, 3.20% CT DM, as-fed basis (Min et al., 2014b).