Ferric citrate, nitrate, saponin and their combinations affect in vitro ruminal fermentation, production of sulphide and methane and abundance of select microbial populations

Abstract

Aims This study investigated the effects of ferric citrate, nitrate and saponin, both individually and in combination, on sulphidogenesis, methanogenesis, rumen fermentation and abundances of select microbial populations using in vitro rumen cultures. Methods and Results Ferric citrate (50 mg l−1), Quillaja saponin (0·6 g l−1) and sodium nitrate (5 mmol l−1) were used in in vitro ruminal fermentation. Ferric citrate alone, its combination with saponin and/or nitrate lowered the aqueous sulphide concentration and total sulphide production. Methane production was suppressed by nitrate alone (by up to 32·92%), its combination with saponin (25·04%) and with both saponins with nitrate (25·92%). None of the treatments adversely affected feed digestion or rumen fermentation. The population of sulphate‐reducing bacteria was increased by nitrate and saponin individually, while that of total Archaea was decreased by nitrate alone and the combination of the three inhibitors. Conclusions Nitrate and its combination with saponin or both ferric citrate and saponin substantially decreased methane production. Most importantly, the decreased methane production was not at the expense of feed digestion or fermentation. Sulphidogenesis from the sulphate present in the high‐sulphur diets can be suppressed competitively by ferric citrate, although it was elevated by saponin and nitrate. Significance and Impact of the Study The results of this study demonstrated that combinations of certain methane inhibitors, which have different mechanisms of antimethanogenic actions or inhibit different guilds of microbes involved in methane production and sulphate reduction, can be more effective and practical than individual inhibitors, not only in mitigating enteric methane emission but also in lowering the risk of sulphur‐associated polioencephalomalacia in feedlot cattle fed high sulphur diets.

The effect of total and individual alfalfa saponins on rumen methane production

“…Saponins, which are plant secondary metabolites, have the ability to modulate rumen fermentation while reducing methane production and ammonia concentration, by modulating ruminal microbial populations, especially, of protozoa . Saponins act against protozoa by reducing the integrity of their cell membranes . Saponin extracts, whether from tropical plants (like Yucca schidigera , Quillaja saponaria , Sapindus saponaria , Garcinia mangostana , Gliricidia sepium , Enterolobium cyclocarpum , and Hedara helix ) or from plants not previously used in ruminant nutrition have been widely used in research …”

“…[4][5][6] Saponins act against protozoa by reducing the integrity of their cell membranes. 7,8 Saponin extracts, whether from tropical plants (like Yucca schidigera, Quillaja saponaria, Sapindus saponaria, Garcinia mangostana, Gliricidia sepium, Enterolobium cyclocarpum, and Hedara helix) or from plants not previously used in ruminant nutrition have been widely used in research. 5,9,10 Alfalfa (Medicago sativa L.) is rich in secondary metabolites, especially saponins.…”

The effects of feeding ferric citrate on ruminal bacteria, methanogenic archaea and methane production in growing beef steers

“…Although research in cattle has begun to examine use of ferric citrate as a methane mitigation strategy, few to date have determined the effects of feeding ferric citrate to beef cattle and its influence on the rumen microbiota, potentially impacting methane production [10,11], and no studies have been conducted in vivo to evaluate the effect of ferric citrate on the ruminal microbial communities. Therefore, it was hypothesized that the addition of ferric citrate to the diet of growing beef steers would impact the ruminal environment via populations of bacteria and methanogenic archaea and thus decreasing methane production.…”

Research progress on the application of feed additives in ruminal methane emission reduction: a review

“…Full-size DOI: 10.7717/peerj.11151/fig- 1 activity of participating CH 4 -producing enzymes and competing for hydrogen (Table 1), in addition to supplementing NH 4 + -N. Among them, nitrate-N (NO − 3 -N) is considered to be a urea substitute; it can not only meet the requirements of rumen microorganisms for NH 4 + -N, but can also decrease CH 4 production substantially (Adejoro et al, 2020;Adejoro, Hassen & Thantsha, 2018;Alvarez-Hess et al, 2019;Wu et al, 2019). The mechanism of action is linked to the competitive effects of NO − 3 -N over H 2 consumption and the inhibitory effect of the generated nitrite (NO − 2 -N) on methanogen proliferation.…”

“…The structure of 3-NOP is similar to that of methyl-coenzyme M, which is associated with the last step of CH 4 production, and 3-NOP can inhibit the activity of the reductase. (Wu et al, 2019) 5 mM; 43. 26% Liu et al, 2017) (1) Hydrogen consumption;…”