AI-based predictive modeling for enteric methane mitigation: cross-farm validation using an allicin based essential oil

Introduction We conducted a meta-analysis of quantitative data extracted from selected peer-reviewed papers describing in vivo studies on enteric methane emissions from dairy cattle treated with feed additives, compared with a control group. The aim was to identify feed additives that significantly reduce enteric methane emissions, expressed as g/day, g/kg dry matter intake, g/kg milk produced, and g/kg energy-corrected milk. The feed additives considered were polyunsaturated fatty acids (PUFAs), 3-nitrooxypropanol (3-NOP), essential oils (EO), and monensin. Four electronic databases (PubMed, CAB Abstracts, Web of Science, and Scopus; 2001–2024) were used to retrieve papers, following the PRISMA 2020 statement. Methods Effect sizes were calculated as log response ratio percentages and analyzed using three-level random-effects models. Heterogeneity, cluster-robust variance estimation, and leave-one-out diagnostics were applied. A total of 34 studies met the inclusion criteria. Results Of these, 19 investigated the impact of PUFAs, yielding 45 data points; seven investigated the impact of 3-NOP, yielding 23 data points; eight investigated the impact of essential oils on enteric methane emissions, yielding 12 data points; and three investigated the impact of monensin, yielding four data points. PUFAs significantly reduced enteric methane emissions across all metrics, although high heterogeneity remained (I² ≈ 86%–95%). 3-NOP exhibited the most substantial average reductions in enteric methane emissions; however, the significance of these effects varied depending on the metric and model formulation. In addition, basal crude protein significantly influenced the effectiveness of 3-NOP. The effects of essential oils were generally non-significant and dependent on formulation. Evidence for monensin was limited and descriptive only. Discussion Based on the current body of evidence, PUFAs and 3-NOP represent the most reliable nutritional strategies for mitigating enteric methane emissions in dairy cows. PUFAs supplementation has been shown to reduce methane production without measurable adverse effects on milk yield or energy-corrected milk. Similarly, 3-NOP produced the greatest average reductions in methane emissions without impairing milk production, although its efficacy may vary depending on diet composition and may decline over time. Future research should prioritize standardized dosing, harmonized measurement methodologies, and extended trial durations that simultaneously assess efficacy, dietary covariates, persistence, productivity, and cost-effectiveness.

The dairy Carbon Offset Scenario Tool (COST) was developed to explore the influence of various abatement strategies on greenhouse gas (GHG) emissions for Australian dairy farms. COST is a static spreadsheet-based tool that uses Australian GHG inventory methodologies, algorithms and emission factors to estimate carbon dioxide, methane and nitrous oxide emissions of a dairy farm system. One of the key differences between COST and other inventory-based dairy GHG emissions calculators is the ability to explore the effect of reducing total farm emissions on farm income, assuming the strategy was compliant with Kyoto rules for carbon offsets. COST provides ten abatement strategies across the four broad theme areas of diet manipulation, herd and breeding management, feedbase management and waste management. Each abatement strategy contains four sections; two sections for data entry (baseline farm data specific to the strategy explored and strategy-specific variables) and two sections for results (milk production results and GHG/economic-related results). Key sensitive variables for each strategy, identified from prior research, and prices for milk production and carbon offsets are adjusted through up/down buttons, which allows users to quickly explore the impact of these variables on farm emissions and profitability. For example, if the cost to implement an abatement strategy is doubled, what carbon offset income would be required to negate this additional cost? Results are presented as changes in carbon offset income, strategy implementation cost, additional milk production income and net farm income on a per annum and on a per GHG emissions intensity of milk production basis. COST currently contains a comprehensive range of strategies for GHG abatement, although some strategies are still in development. As new technologies or farm management practices leading to a reduction in GHG emission become available, these too will be incorporated into COST. To date, two dairy-specific abatement methodologies have been legislated as part of Australia’s commitment to reducing on-farm GHG emissions through it’s the carbon offset scheme, the Carbon Farming Initiative (CFI) and are incorporated into COST. These are the ‘Destruction of methane generated from dairy manure in covered anaerobic ponds’ and the ‘Methodology for reducing greenhouse gas emissions in milking cows through feeding dietary additives’. As an example, we explored the mitigation option Replace supplements with a source of dietary fats (reflecting the second above-mentioned CFI legislated abatement strategy) as feeding a diet higher in dietary fats has been shown to reduce enteric methane emissions per unit of feed intake. A 400 milking herd was fed a baseline diet of 2.6% dietary fat. By replacing grain with hominy meal, at a rate of 5.0 kg dry matter/ cow per day for 90 days during the 3 summer months, the summer diet fat concentration was increased to 6.4%. Enteric methane emissions were reduced by 40 tonnes of carbon dioxide equivalents (t CO 2 e) per annum for the farm. Waste methane and nitrous oxide emissions were also reduced by 0.5 and 1.6 t CO 2 e/annum, respectively. However, as reductions from these two sources of GHG emissions do not qualify for payment with this CFI methodology, their reduction could not be included as an offset income. At a carbon price of $20/ t CO 2 e, the reduction in enteric methane emissions was valued at $800/farm. The implementation cost of replacing grain with hominy was valued at $18,000/farm due to the hominy meal costing an additional $100/t dry matter compared to the grain. However, the additional milk production achieved due to the higher energy concentration of the diet resulted in an additional 70,200 litres and based on a summer milk price of $0.38/ litre, this equated to an additional income from milk valued at $26,676/farm. The overall result was a net increase in farm profit of $9,476/farm when paid on a reduction in total GHG emissions. COST can quickly allow users to ascertain the level of GHG emission reduction possible with various mitigation options and explore the sensitivity of key variables on GHG emissions and farm profitability.

The objective of the study was to determine enteric methane emissions using the sulfur hexafluoride (SF6) technique and comparing with The Intergovernmental Panel on Climate Change (IPCC) methodology in lactating cows (LC) and dry cows (DC) in the Peruvian highlands. Enteric methane (CH4) emissions were measured on 5 LC and 6 DC Brown Swiss in a grazing system without concentrate. Forages samples were collected and analyzed for dry matter, crude protein, and neutral detergent fiber. Milk samples were collected and analyzed for fat, crude protein, and lactose to estimate energy-corrected milk. Animal intakes were measured using the external marker titanium dioxide (production of feces) and crude protein in feces (organic digestibility of the feed) and estimated by using performance data. The enteric methane emissions of LC were higher than methane emissions of DC (325 and 266g CH4/cow/day for LC and DC, respectively (P < 0.001)). Methane emissions were 358.5g CH4/day by SF6 technique and 291.6g CH4/day by IPCC methodology for LC and 337.4g CH4/day by SF6 technique and 195.8g CH4/day by IPCC methodology for DC. Methane yields measured by SF6 were higher than methane yields estimated by IPCC methodology (29g CH4/kg DM and 22g CH4/kg DM using SF6 technique and IPCC methodology, respectively (P < 0.001)). Methane yields were differently for all expressions by physiological stage and method. The methane conversion factor (Ym) was 9.7% for LC and 9.6% for DC. Methane intensities were similar by method (P > 0.05). It was concluded that IPCC's methodology underestimate the CH4 emissions of dairy systems in the Peruvian Andes; therefore, in order to obtain precise Ym, direct measurements of enteric CH4 in the different regions of Peruvian highlands are required.

The search for natural products which can increase animal productivity and reduce environmental impact has been intensified. Some plant extracts, such as essential oils, are used as feed additives able of improving ruminal fermentation by modulating the production of short chain fatty acids and inhibiting methanogenesis. The objective of this study was to evaluate the production of enteric and feces methane, as well as feeding behaviour, ruminal fermentation and kinetics of dairy and beef cattle fed with different essential oils. Eight non-pregnant, non-lactating and ruminally canullated cows were used: four were the dairy breed Holstein, and four were the beef breed Nellore. The diet was composed of 70% of roughage (corn silage) and 30% of concentrate (corn grain and soybean meal), the treatments differed only in relation to the essential oil added: CNT, a diet without any additive; EEO, a diet with 500 mg/kg of DM of eucalyptus (Eucalyptus citriodora) essential oil; PEO, a diet with 500 mg/kg of DM of Brazilian peppertree (Schinus terebinthifolius Raddi) essential oil, and LEO, a diet with 500 mg/kg of DM of lemongrass (Cymbopogon citratus Stapf) essential oil. The experimental design was the 4x4 contemporary latin square in a 2x4 factorial arrangement (referring to two specialized cattle breeds and four additives). The evaluation of the CH4 production of the manure was performed through experimental batch anaerobic digesters, in a completely randomized design. The beef cattle had lower DMI (P = 0.0413), they spent more time consuming, ruminating or chewing 1 kg of DM or NDF (min/kg), also had higher values for acetate, butyrate or total SCFA production than dairy cattle. The manure from dairy cattle had higher biogas production (L/gVS add) or CO2 (liters, percentage and L/gVS add) than the manure of beef cattle. The treatments with essential oils had on average 23% more rumination events per day than the control treatment (P = 0.0201). Diet containing essential oils decreased N2O production of feces from dairy cattle. The essential oils in the dosage used did not affect rumen fermentation and kinetics, as well as the emission of enteric methane and feces.

Enteric methane emissions from lactating dairy cows grazing cultivated and native pastures in the high Andes of Peru

&lt;p&gt;&lt;strong&gt;Background&lt;/strong&gt;. Feeding cattle in small-scale silage-based dairy production systems can improve their production efficiency while reducing greenhouse gas emissions. &lt;strong&gt;Objective&lt;/strong&gt;. To determine the effect of partial replacement of corn silage with sorghum silage on the concentration of secondary metabolites in terms of Total Phenols (TP), Total Tannins (TT), and Condensed Tannins (CT), as well as to estimate methane (CH4) and carbon dioxide (CO2) emissions. &lt;strong&gt;Methodology&lt;/strong&gt;. The treatments were analyzed with a split-plot experimental design where the treatments (main plot) were; T1 = 50% sorghum silage cv Top Green + 50% corn silage, T2 = 50% sorghum silage cv Caña Dulce + 50% corn silage, T3 = 100% corn silage cv Cenzontle (control), and the measurement periods were the minor plots. &lt;strong&gt;Results&lt;/strong&gt;. Inclusion of sorghum silage decreased enteric methane and carbon dioxide emissions (P&amp;lt;0.05), even though the concentration of phytochemical compounds among cultivars was not variable (P&amp;gt;0.05). &lt;strong&gt;Implications&lt;/strong&gt;. Understanding the impact of changing forage chemical composition on reducing greenhouse gas (GHG) emissions in dairy systems is an important issue for mitigating climate change. &lt;strong&gt;Conclusions&lt;/strong&gt;. The inclusion of sorghum silage in this study slightly reduced enteric methane and carbon dioxide emissions. Under these conditions, it is suggested that more information be provided on greenhouse gas emission factors and mitigation strategies in small-scale production systems.&lt;/p&gt;

This meta-analysis evaluated the effects of tannin-based feed additives on enteric methane (CH4) emissions, nutrient digestibility, and animal performance in beef and dairy cattle. A total of 23 peer-reviewed studies comprising 75 treatment means were included in the analysis. Random effects and mixed effects models were used to estimate relative mean differences and identify moderators of response. Robust variance estimation accounted for within-study dependence. Overall, tannin supplementation significantly reduced enteric CH4 emissions (-10.2%) and CH4 yield (-9.3%) across studies in beef and dairy cattle. Although no significant differences were detected between cattle types for CH4 emissions or yield, the database was unbalanced (14 beef vs. 9 dairy studies), and statistical support for a reduction in lactating dairy cows (7 studies) was weaker when analyzed separately (df = 1.7). These results warrant cautious interpretation for dairy systems. Likewise, no interactions between cattle type and tannin dose were detected for CH4 emissions or yield. The incomplete factorial representation of tannin types across cattle types further limited the evaluation of potential tannin type × cattle type interactions. No interaction between tannin type and dose was observed for enteric CH4 emissions or yield. Methane intensity in dairy (g/kg ECM) and beef cattle (g/kg average daily gain) was not affected by tannin supplementation, mainly due to differences in performance responses across studies. In dairy cattle, tannins had no significant effect on DM intake, milk yield, or milk composition. In beef cattle, tannins significantly decreased fiber digestibility by 9.8%, which was associated with reductions in enteric CH4 emissions. Ruminal fermentation parameters and pH were unaffected in both dairy and beef cattle. Meta-regression indicated that CH4 yield decreased by 1.0% per 1 g/kg DM increase in tannin dose. Effective mitigation generally required inclusion rates above ∼8,000 to 10,000 mg/kg DM, whereas subtherapeutic levels (<1,000 mg/kg DM) were often ineffective or even associated with increased emissions. Overall, standardized condensed tannin additives appear to be a viable mitigation strategy, particularly in beef cattle, where evidence is strongest. In contrast, results for dairy systems remain limited and require confirmation through additional studies. Finally, between-study differences observed for enteric CH4 emissions and yield highlight that the magnitude of tannin effects is likely driven more by bioactive properties than tannin type or dose. Future studies should quantify tannin bioactivity and evaluate its interaction with diet and rumen microbiota to enhance mitigation strategies.

Enteric methane emissions and nitrogen utilisation efficiency for two genotype of hill hoggets offered fresh, ensiled and pelleted ryegrass

Effects of feeding level on enteric methane emissions and utilisation of energy and nitrogen in dry ewes of two genotypes offered fresh ryegrass

A total of 120 Nellore bulls, [initial body weight (BW) = 307 ± 11.6 kg and 12 mo of age] were allocated into 12 collective pens (10 bulls per pen) in a commercial feedlot to evaluate the effects of a specific blend of tannin and saponins on enteric methane (CH4) emissions. The study was a completely randomized design, in which pens were considered the experimental units (N = 6 pens per treatment) and were randomly allocated into one of two treatments: 1) Control (CON), a basal diet with monensin supplementation (25 mg/kg dry matter [DM]; Rumensin, Elanco Animal Health, Greenfield, IN, USA), or 2) Control + a specific blend of tannin and saponins (TAN; 0.7 g/kg DM; composed of quebracho and chestnut tannin extracts along with carriers from cereals rich in saponins; SilvaFeed BX, Silvateam, San Michele Mondovi, CN, Italy). After the adaptation period (20 d), the experiment was divided into two phases: growing phase (21 to 53 d; total of 33 d) and fattening phase (54 to 139 d; total of 86 d). Enteric methane emissions were estimated using the sulfur hexafluoride (SF6) tracer gas technique. Interactions between treatment and period (growing vs. fattening) were detected for daily CH4 emissions, in which animals fed TAN reduced CH4 emissions by 17.3% during the fattening period compared to bulls fed CON (P = 0.05). In addition, bulls fed TAN had lower CH4 emissions expressed by dry matter intake (DMI) during the fattening period compared to bulls fed CON (P = 0.06). The findings presented herein indicate that a specific blend of tannin and saponins can be used as a strategy to reduce enteric CH4 emissions and its intensity of Nellore bulls finished in feedlot systems under tropical conditions.

Exploration of feed additives from plant origin to modulate rumen fermentation for improvement in feed utilization and reduction in enteric methane emissions from ruminant animals is not only the focus of animal nutritionists, but also the present day need to dispose of worldwide anti-microbial resistance.The present study examined the effects of Eucalyptus and Poplar leaves extracts on in vitro rumen fermentation, methanogenesis and feed digestibility in buffalo (Bubalus bubalis).The green and matured leaves of Eucalyptus (Eucalyptus citriodora) and Poplar (Populus deltoides) were collected from the trees of the CIRB campus.Half of the leaves were dried in an electric oven at 45 to 50C for 24 h and ground to pass through a 1 mm sieve.Other portions of fresh leaves were crushed into small pieces and kept for extraction afresh.Both fresh and dried leaves were extracted in Soxhlet's apparatus with petroleum ether solvent.The extracts at graded dose levels (0.00, 0.5 and 2.0 mL) were added with 200 mg of oats hay substrate in 100 mL calibrated glass syringe and incubated with buffered rumen fluid (30 mL) at 39C for 24 h following standard in vitro gas production protocol (IVGP).The study revealed enhanced (p<0.05)gas production (mL/g DM), feed digestibility, and volatile fatty acids with reduced (p<0.05)methane production at supplementation of either fresh or dried leaves of Eucalyptus extract at lower dose (0.5 mL) level.However, higher dose level (2.0 mL) impeded (p<0.05)all the rumen fermentation parameters.Poplar leaves extracts were ineffective (p>0.05) in methane reduction, feed digestibility, volatile fatty acids and ammonia production at a lower level of supplementation (0.5 mL).However, a higher dose (2.0 mL) also reduced (p<0.05)methane production and feed digestibility.Thus, the study demonstrated the potential of Eucalyptus leaves in reducing enteric methanogenesis and promising to be used as feed additive to improve animal performance and reduce environmental pollution through enteric methane mitigation.

Since livestock account for most of Türkiye’s agricultural greenhouse gas emissions, strategies for estimating livestock emissions must be developed. Methane emissions per animal category were estimated in this study using the Intergovernmental Panel on Climate Change (IPCC) Tier 2 method for enteric and manure methane (CH4) emissions in two sheep breeds (Akkaraman and Anatolian Merino) and three goat breeds (Hairy, Angora, Saanen) raised in Ankara province, Türkiye. Average enteric CH4 emission factor (EF) was 9.61 kg CH4 head-1 yr-1, with the highest value of 10.86 kg CH4 head-1 yr-1 in Hairy goats, and lowest 8.55 kg CH4 head-1 yr-1 in Anatolian Merino. Estimated gross energy (GE) was highest in Hairy goats (30.10 MJ head-1 day-1), and lowest in Anatolian Merino (21.73 MJ head-1 day-1). Average dry matter intake (DMI) was 1.40 kg DM head-1 day-1. The total average volatile solids (VS) excretion was estimated at 0.95 kg DM head-1 yr-1, and the average methane emission factor (EF) for animal manure was 0.46 kg CH4 head-1 yr-1. Total mean VS estimate was twice as much as the IPCC default values, and the CH4 EF for animal manure was higher than the IPCC default values. The current study's estimates will be helpful in the creation of the national methane inventory. In case more detailed data are collected to improve population data, subcategories may be expanded, and subgroups may vary by region.

Analysis of milk production and greenhouse gas emissions as a function of extreme variations in forage production among French dairy farms

Bromoform effectively reduces enteric methane in livestock; however, its effects in late gestation and early lactation cows in a conventional grazing system and the subsequent impact on the progeny is not well understood. This study evaluated the effect of bromoform supplementation on greenhouse gas emissions, health and performance of late gestation Angus cows and their progeny. Cows were allocated to either a control (CON; n = 40) or bromoform (BRO; n = 40; 0.69 mg of bromoform/kg body weight/day) diet based on body weight. GreenFeed systems were used to quantify methane and carbon dioxide emissions. Body weights of both the cows and calves were collected at Calving, Day 7 and 21, with blood samples also collected on Day 7. Additionally, the calves were weighed at Day 150. There was an interaction between week and treatment for methane (P&amp;lt; 0.01), where it was reduced in the BRO group between 49.5% and 77.0% between Week 1 and 8. The estimated dry matter intake of the BRO cows was reduced by 1.56 kg/day (P = 0.010) with no change in cow body weight between groups over the trial period (P = 0.983). Additionally, there was no carry over effect of dam supplementation of bromoform (P = 0.847) on progeny growth from birth to Day 150 post-birth. Base excess concentration in blood of the BRO cows at Day 7 post-calving was 21.0% higher than the CON group (P = 0.027). These findings highlight the opportunity to effectively use bromoform in breeding cows in extensive systems to achieve significant reductions in methane emissions but also highlights possible areas of concern with changing dosage rates or long-term supplementation.

We evaluated the effects of mineral salt supplement on enteric methane emissions, ruminal fermentation and methanogen community of dairy cows over a whole lactation period. Ten Holstein cows fed a total mixed ration (TMR) diet were randomly allocated into two groups, one supplied with mineral salts as the treatment group and the other as the control group. The methane measurement showed that the ingestion of mineral salts lowered enteric methane emissions significantly (P<0.05), with an average of 10.5% reduction over the whole lactation period. Ruminal fermentation analysis showed the mineral salt intake could significantly decrease the acetate:propionate ratio (P<0.05). Real-time PCR assay showed that rumen methanogen abundance significantly reduced in the treatment group (P<0.05) but was not significantly influenced by mineral salt intake over the whole lactation period. Intergroup methanogen community composition was influenced slightly by mineral salt intake; however, significantly different intragroup profiles were apparent throughout the whole lactation period, according to denaturing gradient gel electrophoresis analysis. In conclusion, these results suggested that the effective mitigation of enteric methane emissions by mineral salt intake could be attributed to decreased density of methanogenic archaea and that fluctuations in methane emission over the lactation period might be related to Methanobrevibacter diversity.