Methane emissions and productivity of defaunated and refaunated sheep while grazing

Nguyen, Son Hung; Nguyen, Huyen Duong Thi; Bremner, Graeme; Hegarty, R. S.

doi:10.1016/j.smallrumres.2018.02.004

Cited by 5 publications

(4 citation statements)

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“…The decrease in rumen NH 3 concentrations in vivo, as observed in Experiment 1, is probably the most consistent effect of defaunation reported in the literature (Eugène et al, 2004; Nguyen, Nguyen, Bremner, & Hegarty, 2018), suggesting greater recycling of nitrogen within the rumen in FAU sheep as a consequence of bacterial predation and subsequent protozoal lysis (Jouany, 1996; Williams & Coleman, 1992). The lack of effect of defaunation on total VFA was in agreement with previous findings (Nguyen et al, 2018). However, a reduced concentration of total VFA in the rumen following defaunation has often been reported (Eugène et al, 2004; Newbold et al, 2015).…”

Section: Discussionsupporting

confidence: 73%

Dietary nitrate and presence of protozoa increase nitrate and nitrite reduction in the rumen of sheep

Villar

Hegarty

Clay

et al. 2020

Animal Physiology Nutrition

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Nitrate ( NO3- ) supplementation is an effective methane (CH4) mitigation strategy for ruminants but may produce nitrite ( NO2- ) toxicity. It has been reported that rumen protozoa have greater ability for NO3- and NO2- reduction than bacteria. It was hypothesised that the absence of ruminal protozoa in sheep may lead to higher NO2- accumulation in the rumen and a higher blood methaemoglobin (MetHb) concentration. An in vivo experiment was conducted with defaunated (DEF) and faunated (FAU) sheep supplemented with 1.8% NO3- in DM. The effects of rumen protozoa on concentrations of plasma and ruminal NO3- and NO2- , blood MetHb, ruminal volatile fatty acid (VFA) and ruminal ammonia (NH3) were investigated. Subsequently, two in vitro experiments were conducted to determine the contribution of protozoa to NO3- and NO2- reduction rates in DEF and FAU whole rumen digesta (WRD) and its liquid (LIQ) and solid (SOL) fractions, incubated alone (CON), with the addition of NO3- or with the addition of NO2- . The results from the in vivo experiment showed no differences in total VFA concentrations, although ruminal NH3 was greater (p < .01) in FAU sheep. Ruminal NO3- , NO2- and plasma NO2- concentrations tended to increase (p < .10) 1.5 hr after feeding in FAU relative to DEF sheep. In vitro results showed that NO3- reduction to NH3 was stimulated (p < .01) by incoming NO3- in both DEF and FAU relative to CON digesta. However, adding NO3- increased (p < .05) the rate of NO2- accumulation in the SOL fraction of DEF relative to both fractions of FAU digesta. Results observed in vivo and in vitro suggest that NO3- and NO2- are more rapidly metabolised in the presence of rumen protozoa. Defaunated sheep may have an increased risk of NO2- poisoning due to NO2- accumulation in the rumen.

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Section: Discussionsupporting

confidence: 73%

Dietary nitrate and presence of protozoa increase nitrate and nitrite reduction in the rumen of sheep

Villar

Hegarty

Clay

et al. 2020

Animal Physiology Nutrition

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“…However, protozoa are not essential for ruminal fermentation and removal of protozoa from the rumen, also called defaunation, does not seem to significantly impact animal health, although feed digestibility might be affected [41]. The potential of defaunation to mitigate CH 4 emission has been studied [43,44]. The external surface of protozoa is a site for methanogen attachment (ectosymbionts) or intracellular colonization (endosymbionts), which are attracted by the H 2 produced in protozoan hydrogenosomes [41].…”

Section: Protozoamentioning

confidence: 99%

Alternative pathways for hydrogen sink originated from the ruminal fermentation of carbohydrates: Which microorganisms are involved in lowering methane emission?

2022

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Agriculture is responsible for a great share of the anthropogenic sources of greenhouse gases that, by warming the earth, threaten its biodiversity. Among greenhouse gas emissions, enteric CH4 from livestock is an important target to slow down climate changes. The CH4 is originated from rumen fermentation and its concentration is affected by several factors, including genetics and nutrition. Ruminants have an extraordinary symbiosis with microorganisms (bacteria, fungi, and protozoa) that ferment otherwise indigestible carbohydrates, from which they obtain energy to grow and continue actively producing, among other products, volatile fatty acids, CO2 and H2. Detrimental ruminal accumulation of H2 is avoided by methanogenesis carried out by Archaea methanogens. Importantly, methanogenesis is not the only H2 sink pathway. In fact, other bacteria can reduce substrates using metabolic hydrogen formed during carbohydrate fermentation, namely propionate production and reductive acetogenesis, thus lowering the CH4 produced. Although the complexity of rumen poses challenges to mitigate CH4 production, the emergence of sequencing techniques that allow the study of microbial communities, gene expression, and metabolome are largely contributing to unravel pathways and key players in the rumen. Indeed, it is now recognized that in vivo emissions of CH4 are correlated to microbial communities, and particularly with the abundance of methanogens, several bacterial groups, and their genes. The goal of CH4 mitigation is to work in favor of the natural processes, without compromising rumen function, animal health, and productivity. Notwithstanding, the major challenge continues to be the feasibility and affordability of the proposed solutions.

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“…GreenFeed™ systems are not restricted to housed environments and have been successfully used to measure CH 4 emissions on intensive pasture-based dairy systems (Waghorn et al, 2016). Although GFs have been used primarily on cattle to date, there has been development of systems for use with sheep and calves (Nguyen et al, 2018;Meale et al, 2021). Another breath sampling method termed "the sniffer technique", where a gas sampling inlet is placed within the feed manger of a robotic milking unit, measures CH 4 emissions from the animal at milking events.…”

Section: Methods For Measuring Methanementioning

confidence: 99%

Solutions to enteric methane abatement in Ireland

Cummins

Lanigan

Richards

et al. 2022

Irish Journal of Agricultural and Food Research

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The efficiency of Ireland’s grass-based livestock systems can be attributed to high outputs, low production costs and a low carbon footprint relative to housed systems. Methane (CH4) is a potent greenhouse gas (GHG) of which enteric fermentation from livestock production is a key source, being directly responsible for 57% of Irish agricultural GHG emissions. There are a number of strategies including dietary manipulation and breeding initiatives that have shown promising results as potential mitigation solutions for ruminant livestock production. However, the majority of international research has predominantly been conducted on confined systems. Given the economic viability of Irish livestock systems, it is vital that any mitigation methods are assessed at pasture. Such research cannot be completed without access to suitable equipment for measuring CH4 emissions at grazing. This review documents the current knowledge capacity in Ireland (publications and projects) and includes an inventory of equipment currently available to conduct research. A number of strategic research avenues are identified herein that warrant further investigation including breeding initiatives and dietary manipulation. It was notable that enteric CH4 research seems to be lacking in Ireland as it constituted 14% of Irish agricultural GHG research publications from 2016 to 2021. A number of key infrastructural deficits were identified including respiration chambers (there are none currently operational in the Republic of Ireland) and an urgent need for more pasture-based GreenFeed™ systems. These deficits will need to be addressed to enable inventory refinement, research progression and the development of effective solutions to enteric CH4 abatement in Ireland.

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Methane emissions and productivity of defaunated and refaunated sheep while grazing

Cited by 5 publications

References 32 publications

Dietary nitrate and presence of protozoa increase nitrate and nitrite reduction in the rumen of sheep

Dietary nitrate and presence of protozoa increase nitrate and nitrite reduction in the rumen of sheep

Alternative pathways for hydrogen sink originated from the ruminal fermentation of carbohydrates: Which microorganisms are involved in lowering methane emission?

Solutions to enteric methane abatement in Ireland

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