Biology subjects

Kebreab, E.

Publications and source records attributed to Kebreab, E..

8 recordsLinked to original sources

bioRxiv2025

A meta-analysis of 3-nitrooxypropanol effects on methane production and yield in beef cattle

Beef cattle are a major source of enteric methane (CH4) emissions, a potent greenhouse gas (GHG). The feed additive 3-nitrooxypropanol (3-NOP) has been shown to reduce CH4 emissions by inhibiting methyl-coenzyme M reductase, an enzyme critical to methanogenesis in archaea. This study aimed to quantify the effects of 3-NOP on CH4 production (g/d) and yield (g/kg DM intake; DMI) in beef cattle and to evaluate how diet composition influences the mitigation response. A systematic literature review identified 17 peer-reviewed in vivo studies, yielding 45 treatment means. Treatment effects were expressed as absolute and relative mean differences versus control groups. Predictor variables included 3-NOP dose, 3-NOP dose2, DMI, dietary concentration of NDF, CP, starch, fat, and organic matter (OM), roughage proportion, BW, and dietary inclusion of monensin (yes/no). Four types of models were developed, all including the intercept and 3-NOP dose as fixed predictors, differing as follows: (model 1) optional inclusion of 3-NOP dose2 when P < 0.10; (model 2) model 1 plus pre-inclusion of NDF concentration; (model 3) pre-inclusion of NDF concentration plus additional predictors (pairwise r [≤] 0.5) that significantly improved model accuracy (P < 0.10); and (model 4) additional predictors selected under the same criteria as model 3, without pre-inclusion of NDF concentration. For models 3 and 4, a maximum of 5 predictors were considered and evaluated using leave-one-out cross-validation. Across studies, 3-NOP doses ranged from 32 to 338 mg/kg of DM. On average, 3-NOP reduced CH4 production by 49.9 {+/-} 28.61 g/d (36.2 {+/-} 24.42%) and CH4 yield by 5.3 {+/-} 3.61 g/kg DMI (33.2 {+/-} 25.54%). The best models were selected based on biological interpretability, statistical significance, and predictive accuracy (as measured by RMSE) and included 3-NOP dose, dietary NDF concentration, DMI, and BW as significant predictors (the latter two only for absolute CH4 production). Mitigation efficacy increased with higher DMI and declined with increasing NDF concentration and BW. Absolute reductions of 53.1 g/d and 5.88 g/kg of DMI, and relative reductions of 37.6% in CH4 production and 35.0% in CH4 yield were predicted when moderators were at their mean value (3-NOP dose = 134.4 mg/kg of DM; NDF concentration = 32.8% of DM; DMI of 8.6 kg/d). These results support the effectiveness of 3-NOP in mitigating enteric CH4 emission in beef cattle and provide quantitative models to be used in assessment tools and GHG inventory methodology. ImplicationsThe feed additive 3-nitrooxypropanol effectively reduces enteric methane emissions in beef cattle. This meta-analysis found average reductions of 36.2% in methane production and 33.2% in methane yield. Efficacy depended on diet composition; declining with increasing NDF concentration for both methane production (g/d) and yield (g/kg of DM intake; DMI). Greater DMI increased absolute methane production reduction but did not influence absolute methane yield reduction or relative reduction of both methane production and yield. These results support the targeted use of 3-nitrooxypropanol as a mitigation strategy and provide empirical models to inform greenhouse gas inventories and carbon accounting.

systems biology↗

bioRxiv2025

A meta-analysis of effects of seaweed and other bromoform containing feed ingredients on methane production, yield, and intensity in cattle

Methane (CH4) emissions from ruminants contribute significantly to global GHG emissions. Bromoform (CHBr3)-containing feed ingredients, such as Asparagopsis seaweed, have emerged as promising tools to reduce enteric CH4 emissions. This meta-analysis quantitatively assessed the effects of CHBr3-containing seaweeds and synthetic CHBr3-based additives on CH4 production (g/day), CH4 yield (g/kg DMI), and DMI, as well as CH4 intensity (g/kg product) and production (milk or daily gain in dairy and beef cattle, respectively). Data were collected from 14 studies, with 39 treatment mean differences for CH4 production, comprising both beef and dairy cattle fed CHBr3-containing ingredients, while accounting for dose, DMI, and diet composition. The random-effects models estimates revealed that at an average CHBr3 dose of {approx}28.3 mg/kg DM, CH4 production was reduced by 47.3%, CH4 yield by 43.3%, and CH4 intensity by 39.0%, with increases in CHBr3 dose resulting in larger efficacy in mitigating CH4 emissions. The efficacy of CHBr3 was influenced by cattle type, with greater mitigation effects in beef cattle than dairy catle, and by dietary composition, with greater reductions observed in diets higher in starch, whereas higher NDF levels attenuate its effect. At the average CHBr3 dose, estimated DMI was significantly reduced by 6.45% and 3.26% in dairy and beef cattle, respectively. The significant reduction in DMI did translate into a significant effect on milk yield (-4.60%) at average CHBr3 dose. Carrier type (oil vs. biomass), measurement technique and cattle type influenced the results. Oil carrier potentially leading to more pronounced reductions, particularly for CH4 intensity, respiration chambers yielded significantly greater CH4 reductions compared to other methods, and beef cattle showed stronger mitigation effects than dairy cattle. This study highlights the CH4 mitigating potential of CHBr3-containing feed ingredients, providing predictive models to optimize CH4 reduction strategies under diverse production conditions. Future research should address long-term effects, dietary optimization, and practical implementation.

systems biology↗

bioRxiv2024

Red seaweed supplementation suppresses methanogenesis in the rumen, revealing potentially advantageous traits among hydrogenotrophic bacteria

Macroalgae belonging to the genus Asparagopsis have been shown to reduce the production of methane (CH4) during rumen fermentation, while increasing feed efficiency when added to the feed of cattle. However, little is known about how the microbial community in the rumen responds to Asparagopsis supplementation, and how changes in the rumen microbiome may contribute to shifts in rumen function and ultimately the hosts phenotype. In this study, we generated and analyzed metagenomic and metatranscriptomic data from the microbiome associated with rumen fluid collected from two cohorts of lactating dairy cows, one fed a diet supplemented with Asparagopsis armata (treatment) and another fed the same diet without A. armata supplementation (control). The reduction of CH4 emission from animals that received A. armata was coupled to a qualitative decrease in relative archaeal abundance and a significant reduction in the transcription of methanogenesis pathways. Additionally, a significant decrease in the transcription of genes for complex carbon catabolism and a re-organization of the expression profile of carbon catabolic genes at the species level was observed in treated animals. Increased H2 production, a consequence of methanogenesis suppression, was coupled to a significant increase in the transcription of hydrogenases that mediate hydrogenotrophic metabolism in the treatment group. Analysis of metatranscriptome data identified a single uncultured hydrogenotrophic bacterial species (a Duodenibacillus sp.) as the dominant driver of this transcriptional change. Comparative genomic analysis between the Duodenibacillus sp. and other hydrogenotrophic rumen organisms revealed metabolic traits in the Duodenibacillus that may provide a competitive advantage in H2 scavenging. These findings provide an initial understanding of how rumen microbiota respond to a promising CH4 reducing feed additive, and may serve as a model to understand alternative stable rumen microbiome states that produce less methane and increase animal productivity.

microbiology↗

bioRxiv2022

Carbon footprint of South Dakota dairy production system and assessment of mitigation options

Livestock production contributes to greenhouse gas (GHG) emissions. However, there is a considerable variability in the carbon footprint associated with livestock production. Site specific estimates of GHG emissions are needed to accurately focus GHG emission reduction efforts. A holistic approach must be taken to assess the full environmental impact of livestock production using appropriate geographical scale. The objective of this study was to determine baseline GHG emissions from dairy production in South Dakota using a life cycle assessment (LCA) approach. A cradle-to-farm gate LCA was used to estimate the GHG emissions to produce 1 kg of energy-and-protein corrected milk (ECM) in South Dakota. The system boundary was divided into feed production, farm management, enteric methane emissions, and manure management as these activities are the main contributors to the overall GHG emissions. The production of 1 kg ECM in South Dakota dairies was estimated to emit 1.21 kg CO2 equivalents. The major contributors were enteric methane emissions (46.3%) and manure management (32.6%). Feed production and farm management made up 13.9 and 7.2 %, respectively. The estimate was similar to the national average but slightly higher than the California dairy system. The source of corn used in the dairies influences the footprint. For example, South Dakota corn had fewer GHG emissions than grain produced in Iowa. Therefore, locally and more sustainably sourced feed input will contribute to further reducing the environmental impacts. Improvements in efficiency of milk production through better genetics, nutrition animal welfare and feed production are expected to further reduce the carbon footprint of South Dakota dairies. Furthermore, use of feed additives and anaerobic digesters will reduce emissions from enteric and manure sources, respectively.

systems biology↗

bioRxiv2020

Red seaweed (Asparagopsis taxiformis) supplementation reduces enteric methane by over 80 percent in beef steers

The red macroalgae (seaweed) Asparagopsis spp. has shown to reduce ruminant enteric methane (CH4) production up to 99% in vitro. The objective of this study was to determine the effect of Asparagopsis taxiformis on CH4 production (g/day per animal), CH4 yield (g CH4/kg dry matter intake (DMI)), average daily gain (ADG), feed conversion efficiency (FCE), and carcass and meat quality in growing beef steers. Twenty-one Angus-Hereford beef steers were randomly allocated to one of three treatment groups: 0% (Control), 0.25% (Low Dose; LD), and 0.5% (High Dose; HD) A. taxiformis inclusion based on organic matter intake. Steers were fed 3 diets: high, medium, and low forage total mixed ration (TMR) representing typical life-stage diets of growing beef steers. The LD and HD treatments over 147 days reduced enteric CH4 yield 45 and 68%, respectively; however, there was an interaction between TMR type and the magnitude of CH4 yield reduction. Supplementing the low forage TMR reduced CH4 yield 69.8% (P <0.001) for LD and 80% (P <0.001) for HD treatment. Hydrogen (H2) yield (g H2/DMI) increased significantly (P<0.001) 336 and 590% compared to Control for the LD and HD treatments, respectively. No differences were found in carbon dioxide (CO2) yield (g CO2/DMI), ADG, carcass quality, strip loin proximate analysis and shear force, or consumer taste preferences. DMI tended (P = 0.08) to decrease 8% in steers in LD treatment but significantly (P = 0.002) reduced 14% in steers in HD treatment. Conversely, FCE tended to increase 7% in steers in LD treatment (P = 0.06) and increased 14% in steers in HD (P < 0.01) treatment compared to Control. The persistent reduction of CH4 by A. taxiformis supplementation suggests that this is a viable feed additive to significantly decrease the carbon footprint of ruminant livestock and potentially increase production efficiency.

systems biology↗

bioRxiv2020

Net reductions in greenhouse gas emissions from feed additive use in California dairy cattle

The livestock industry is one of the main contributors to greenhouse gas emissions and there is an increasing demand for the industry to reduce its carbon footprint. Several studies have shown that feed additives 3-nitroxypropanol and nitrate to be effective in reducing enteric methane emissions. The objective of this study was to estimate the net mitigating effect of using 3-nitroxypropanol and nitrate on total greenhouse gas emissions in California dairy industry. A life cycle assessment approach was used to conduct a cradle-to-farm gate environmental impact analysis based on dairy production system in California. Emissions associated with crop production, feed additive production, enteric methane, farm management, and manure storage were calculated and expressed as kg CO2 equivalents (CO2e) per kg of energy corrected milk. The total greenhouse gas emissions from baseline, two 3-nitroxypropanol and three nitrate scenarios were 1.12, 0.993, 0.991, 1.08, 1.07, and 1.09 kg CO2e/kg energy corrected milk. The average net reduction rates for 3-nitroxypropanol and nitrate were 11.7% and 3.95%, respectively. In both cases, using the feed additives on the whole herd slightly improved overall carbon footprint reduction compared to limiting its use during lactation phase. Although both 3-nitroxypropanol and nitrate had effects on decreasing the total greenhouse gas emission, the former was much more effective with no known safety issues in reducing the carbon footprint of dairy production in California.

ecology↗

bioRxiv2018

Methane Reduction Potential of Two Pacific Coast Macroalgae During in-vitro Ruminant Fermentation.

With increasing interest in feed based methane mitigation strategies, fueled by local legal directives aimed at methane production from the agricultural sector in California, identifying local sources of biological feed additives will be critical in keeping the implementation of these strategies affordable. In a recent study, the red alga Asparagopsis taxiformis stood out as the most effective species of seaweed to reduce methane production from enteric fermentation. Due to the potential differences in effectiveness based on the location from where A. taxiformis is collected and the financial burden of collection and transport, we tested the potential of A. taxiformis, as well as the brown seaweed Zonaria farlowii collected in the nearshore waters off Santa Catalina Island, CA, USA, for their ability to mitigate methane production during in-vitro rumen fermentation. At a dose rate of 5% dry matter (DM), A. taxiformis reduced methane production by 74% (p [≤] 0.01) and Z. farlowii reduced methane production by 11% (p [≤] 0.04) after 48 hours and 24 hours of in-vitro rumen fermentation respectively. The methane reducing effect of A. taxiformis and Z. farlowii described here make these local macroalgae promising candidates for biotic methane mitigation strategies in the largest milk producing state in the US. To determine their real potential as methane mitigating feed supplements in the dairy industry, their effect in-vivo requires investigation.

systems biology↗

bioRxiv2018

Effect of the macroalgae Asparagopsis taxiformis on methane production and the rumen microbiome assemblage

BackgroundRecent studies using batch-fermentation suggest that the red macroalgae Asparagopsis taxiformis might reduce methane (CH4) emission from beef cattle by up to ~99% when added to rhodes grass hay, a common feed in the Australian beef industry. These experiments have shown significant reductions in methane without compromising other fermentation parameters (i.e. volatile fatty acid production) with A. taxiformis organic matter (OM) inclusion rates of up to 5%. In the study presented here, A. taxiformis was evaluated for its ability to reduce methane production from dairy cattle fed a mixed ration widely utilized in California; the largest milk producer in the US.\n\nResultsFermentation in a semi-continuous in-vitro rumen system suggests that A. taxiformis can reduce methane production from enteric fermentation in dairy cattle by 95% when added at a 5% OM inclusion rate without any obvious negative impacts on volatile fatty acid production. High-throughput 16S ribosomal RNA (rRNA) gene amplicon sequencing showed that seaweed amendment effects rumen microbiome communities consistent with the Anna Karenina hypothesis, with increased beta-diversity, over time scales of approximately three days. The relative abundance of methanogens in the fermentation vessels amended with A. taxiformis decreased significantly compared to control vessels, but this reduction in methanogen abundance was only significant when averaged over the course of the experiment. Alternatively, significant reductions of methane in the A. taxiformis amended vessels was measured in the early stages of the experiment. This suggests that A. taxiformis has an immediate effect on the metabolic functionality of rumen methanogens whereas its impact on microbiome assemblage, specifically methanogen abundance, is delayed.\n\nConclusionsThe methane reducing effect of A. taxiformis during rumen fermentation makes this macroalgae a promising candidate as a biotic methane mitigation strategy in the largest milk producing state in the US. But its effect in-vivo (i.e. in dairy cattle) remains to be investigated in animal trials. Furthermore, to obtain a holistic understanding of the biochemistry responsible for the significant reduction of methane, gene expression profiles of the rumen microbiome and the host animal are warranted.

systems biology↗