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

Potential use of seaweed as a dietary supplement to mitigate enteric methane emission in ruminants

Seaweeds or marine algae exhibit diverse morphologies, sizes, colors, and chemical compositions, encompassing various species, including red, green, and brown seaweeds. Several seaweeds have received increased research attention and application in animal feeding investigations, particularly in ruminant livestock, due to their higher yield and convenient harvestability at present. Recent endeavors encompassing both in vitro and in vivo experiments have indicated that many seaweeds, particularly red seaweed (Asparagopsis taxiformis and Asparagopsis armata), contain plant secondary compounds, such as halogenated compounds and phlorotannins, with the potential to reduce enteric ruminal methane (CH4) emissions by up to 99 % when integrated into ruminant diets. This review provides an encompassing exploration of the existing body of knowledge concerning seaweeds and their impact on rumen fermentation, the toxicity of ruminal microbes, the health of animals, animal performance, and enteric ruminal CH4 emissions in both in vitro and in vivo settings among ruminants. By attaining a deeper comprehension of the implications of seaweed supplementation on rumen fermentation, animal productivity, and ruminal CH4 emissions, we could lay the groundwork for devising innovative strategies. These strategies aim to simultaneously achieve environmental benefits, reduce greenhouse gas emissions, enhance animal efficiency, and develop aquaculture and seaweed production systems, ensuring a high-quality and consistent supply chain. Nevertheless, future research is essential to elucidate the extent of the effect and gain insight into the mode of action.

Modeling the environmental impacts of Asparagopsis as feed, a cow toilet and slurry acidification in two synthetic dairy farms

Intensive dairy farming, particularly enteric fermentation and manure management, is a major contributor to negative impacts on the local and global environment. A wide range of abatement measures has been proposed to reduce livestock-related emissions, yet the individual and combined effects of these innovations are often unknown. In this study, we performed an attributional life cycle assessment of three innovative measures modeled in two synthetic German dairy farm systems: Feeding of the seaweed Asparagopsis, installing an in-house cow toilet system, and performing on-field slurry acidification. These measures were modeled both individually and in combination to account for single and cumulative effects and compared to a reference scenario under current practices. Our results showed that feeding high levels of Asparagopsis and the combination of all three measures were most effective at reducing global warming potential (20-30 %), while only the latter mitigated eutrophication (6-9%) and acidification potential (14-17 %). The cow toilet required additional adapted manure management (separated storage and injection of urine) to effectively reduce eutrophication (8-10 %) and acidification potential (19-23 %) and to decrease global warming potential (3-4%) and abiotic depletion (4-5%). Slurry acidification slightly affected all considered environmental impact categories. All three measures involved trade-offs, either between LCA impact categories (global warming potential vs. abiotic depletion), the location of impacts (off- vs. on-farm), or the emission reduction in individual gases (ammonia vs. nitrous oxide). Measure combinations could compensate for the observed trade-offs. Our study highlights the potential of novel abatement measures but also shows the interdependencies of measures in different stages. This calls for a revisiting of current priorities in funding and legislation, which often focus on single objectives and measures (e.g. ammonia reduction) toward the preferential use of measures that are effective without driving trade-offs or improving resource efficiency.

Forage peanut legume as a strategy for improving beef production without increasing livestock greenhouse gas emissions

The transformation of pastures from a degraded state to sustainable productivity is a major challenge in tropical livestock production. Stoloniferous forage legumes such as Arachis pintoi (forage peanut) are one of the most promising alternatives for intensifying pasture-based beef livestock operations with reduced greenhouse gas (GHG) emissions. This 2-year study assessed beef cattle performance, nutrient intake and digestibility, and balance of GHG emissions in three pasture types (PT): (1) mixed Palisade grass - Urochloa brizantha (Hochst. ex A. Rich.) R.D. Webster (syn. Brachiaria brizantha Stapf cv. Marandu) and forage peanut (A. pintoi Krapov. & W.C. Greg. cv. BRS Mandobi) pastures (Mixed), (2) monoculture Palisade grass pastures with 150 kg of N/ha per year (Fertilised), and (3) monoculture Palisade grass without N fertiliser (Control). Continuous stocking with a variable stocking rate was used in a randomised complete block design, with four replicates per treatment. The average daily gain and carcass gain were not influenced by the PT (P = 0.439 and P = 0.100, respectively) and were, on average, 0.433 kg/animal per day and 83.4 kg/animal, respectively. Fertilised and Mixed pastures increased by 102 and 31.5%, respectively, the liveweight gain per area (kg/ha/yr) compared to the Control pasture (P < 0.001). The heifers in the Mixed pasture had lower CH4 emissions (g/animal per day; P = 0.009), achieving a reduction of 12.6 and 10.1% when compared to the Fertilised and Control pastures, respectively. Annual (N2O) emissions (g/animal) and per kg carcass weight gain were 59.8 and 63.1% lower, respectively, in the Mixed pasture compared to the Fertilised pasture (P < 0.001). Mixed pasture mitigated approximately 23% of kg CO2eq/kg of carcass when substituting 150 kg of N/ha per year via fertiliser. Mixed pastures with forage peanut are a promising solution to recover degraded tropical pastures by providing increased animal production with lower GHG emissions.

Improving Human Diets and Welfare through Using Herbivore-Based Foods: 2. Environmental Consequences and Mitigations

Animal-sourced foods are important for human nutrition and health, but they can have a negative impact on the environment. These impacts can result in land use tensions associated with population growth and the loss of native forests and wetlands during agricultural expansion. Increased greenhouse gas emissions, and high water use but poor water quality outcomes can also be associated. Life cycle analysis from cradle-to-distribution has shown that novel plant-based meat alternatives can have an environmental footprint lower than that of beef finished in feedlots, but higher than for beef raised on well-managed grazed pastures. However, several technologies and practices can be used to mitigate impacts. These include ensuring that grazing occurs when feed quality is high, the use of dietary additives, breeding of animals with higher growth rates and increased fecundity, rumen microbial manipulations through the use of vaccines, soil management to reduce nitrous oxide emission, management systems to improve carbon sequestration, improved nutrient use efficacy throughout the food chain, incorporating maize silage along with grasslands, use of cover crops, low-emission composting barns, covered manure storages, and direct injection of animal slurry into soil. The technologies and systems that help mitigate or actually provide solutions to the environmental impact are under constant refinement to enable ever-more efficient production systems to allow for the provision of animal-sourced foods to an ever-increasing population.

Review: Biological consequences of the inhibition of rumen methanogenesis

Decreasing enteric CH4 emissions from ruminants is important for containing global warming to 1.5 °C and avoid the worst consequences of climate change. However, the objective of mitigating enteric CH4 emissions is difficult to reconcile with the forecasted increase in production of ruminant meat and milk, unless CH4 production per animal and per kilogram of animal product are decreased substantially. Chemical compound 3-nitrooxypropanol and bromoform-containing red algae Asparagopsis are currently the most potent inhibitors of rumen methanogenesis, but their average efficacy would have to be increased to mitigate enteric CH4 emissions to contain global warming to 1.5 °C, if the demand for ruminant products increases as predicted. We propose that it may be possible to enhance the efficacy of inhibitors of methanogenesis through understanding the mechanisms that cause variation in their efficacy across studies. We also propose that a more thorough understanding of the effects of inhibiting methanogenesis on rumen and postabsorptive metabolism may help improve feed efficiency and cost-effectiveness as co-benefits of the methanogenesis inhibition intervention. For enhancing efficacy, we examine herein how different inhibitors of methanogenesis affect the composition of the rumen microbial community and discuss some mechanisms that may explain dissimilar sensitivities among methanogens to different types of inhibitors. For improving feed efficiency and cost-effectiveness, we discuss the consequences of inhibiting methanogenesis on rumen fermentation, and how changes in rumen fermentation can in turn affect postabsorptive metabolism and animal performance. The objectives of this review are to identify knowledge gaps of the consequences of inhibiting methanogenesis on rumen microbiology and rumen and postabsorptive metabolism, propose research to address those knowledge gaps and discuss the implications that this research can have for the efficacy and adoption of inhibitors of methanogenesis. Depending on its outcomes, research on the microbiological, biochemical, and metabolic consequences of the inhibition of rumen methanogenesis could help the adoption of feed additives inhibitors of methanogenesis to mitigate enteric CH4 emissions from ruminants to ameliorate climate change.

Speciation of arsenic in milk from cows fed seaweed

BACKGROUND

Including seaweed in cattle feed has gained increased interest, but it is important to take into account that the concentration of toxic metals, especially arsenic, is high in seaweed. This study investigated the arsenic species in milk from seaweed-fed cows.

RESULTS

Total arsenic in milk of control diets (9.3 ± 1.0 μg As kg-1, n = 4, dry mass) was significantly higher than seaweed-based diet (high-seaweed diet: 7.8 ± 0.4 μg As kg-1, P < 0.05, n = 4, dry mass; low-seaweed diet: 6.2 ± 1.0 μg As kg-1, P < 0.01, n = 4, dry mass). Arsenic speciation showed that the main species present were arsenobetaine (AB) and arsenate (As(V)) (37% and 24% of the total arsenic, respectively). Trace amounts of dimethylarsinic acid (DMA) and arsenocholine (AC) have also been detected in milk. Apart from arsenate being significantly lower (P < 0.001) in milk from seaweed-fed cows than in milk from the control group, other arsenic species showed no significant differences between groups.

CONCLUSION

The lower total arsenic and arsenate in seaweed diet groups indicates a possible competition of uptake between arsenate and phosphate, and the presence of AC indicates that a reduction of AB occurred in the digestive tract. Feeding a seaweed blend (91% Ascophyllum nodosum and 9% Laminaria digitata) does not raise As-related safety concerns for milk. © 2024 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Effects of Bacillus subtilis on in vitro ruminal fermentation and methane production

The objective of this study was to evaluate the effect of a proprietary strain of a Bacillus subtilis on in vitro ruminal fermentation and methane production in batch culture serum bottles. One hundred forty-nine batch culture bottles were used in a complete randomized block design. The arrangement of treatments was a 3 × 3 × 4 factorial to evaluate the effects of inoculum, time, diet, and their respective interactions. There were three experimental runs total, where the run was used as block. Inoculum treatments were 1.85 mg/mL of microcrystalline cellulose (CON); 10 billion B. subtilis plus microcrystalline cellulose (A1); and 60 billion B. subtilis plus microcrystalline cellulose (A2). Diet treatments were 0.50 g of early lactation diet (E, 30% starch), mid-lactation diet (M, 25% starch), or dry cow diet (D, 18% starch). The combination resulted in total of nine treatments. Each treatment had five replicates, two of which were used to determine nutrient degradability at 24 and 48 h after inoculation, and three were used to determine pH, ammonia nitrogen (NH3-N), volatile fatty acids, lactate, total gas, and methane production at 3, 6, 24, and 48 h after inoculation. Fixed effects of inoculum, diet, and their interaction were tested using the GLIMMIX procedure of SAS. Significance was declared at P ≤ 0.05. We observed that, compared to control, the supplementation of B. subtilis, decreased the production of acetate and propionate, while increasing the production of butyrate, iso-butyrate, valerate, iso-valerate, and caproate within each respective diet. Additionally, the total methane production exhibited mixed responses depending on the diet type. Overall, the inclusion of B. subtilis under in vitro conditions shows the potential to reduce ruminal methane production when supplemented with a mid-lactation diet, constituting a possible methane mitigation additive for dairy cattle diets.

Identification of reproductive sex-biased gene expression in Asparagopsis taxiformis (lineage 6) gametophytes

The sub-tropical red seaweed Asparagopsis taxiformis is of significant interest due to its ability to store halogenated compounds, including bromoform, which can mitigate methane production in ruminants. Significant scale-up of aquaculture production of this seaweed is required; however, relatively little is known about the molecular mechanisms that control fundamental physiological processes, including the regulatory factors that determine sexual dimorphism in gametophytes. In this study, we used comparative RNA-sequencing analysis between different morphological parts of mature male and female A. taxiformis (lineage 6) gametophytes that resulted in greater number of sex-biased gene expression in tips (containing the reproductive structures for both sexes), compared with the somatic main axis and rhizomes. Further comparative RNA-seq against immature tips was used to identify 62 reproductive sex-biased genes (59 male-biased, 3 female-biased). Of the reproductive male-biased genes, 46% had an unknown function, while others were predicted to be regulatory factors and enzymes involved in signaling. We found that bromoform content obtained from female samples (8.5 ± 1.0 mg·g-1 dry weight) was ~10% higher on average than that of male samples (6.5 ± 1.0 mg·g-1 dry weight), although no significant difference was observed (p > 0.05). There was also no significant difference in the marine bromoform biosynthesis locus gene expression. In summary, our comparative RNA-sequencing analysis provides a first insight into the potential molecular factors relevant to gametogenesis and sexual differentiation in A. taxiformis, with potential benefits for identification of sex-specific markers.

Recent Advances in Enteric Methane Mitigation and the Long Road to Sustainable Ruminant Production

Mitigation of methane emission, a potent greenhouse gas, is a worldwide priority to limit global warming. A substantial part of anthropogenic methane is emitted by the livestock sector, as methane is a normal product of ruminant digestion. We present the latest developments and challenges ahead of the main efficient mitigation strategies of enteric methane production in ruminants. Numerous mitigation strategies have been developed in the last decades, from dietary manipulation and breeding to targeting of methanogens, the microbes that produce methane. The most recent advances focus on specific inhibition of key enzymes involved in methanogenesis. But these inhibitors, although efficient, are not affordable and not adapted to the extensive farming systems prevalent in low- and middle-income countries. Effective global mitigation of methane emissions from livestock should be based not only on scientific progress but also on the feasibility and accessibility of mitigation strategies.

A Review of Potential Feed Additives Intended for Carbon Footprint Reduction through Methane Abatement in Dairy Cattle

Eight rumen additives were chosen for an enteric methane-mitigating comparison study including garlic oil (GO), nitrate, Ascophyllum nodosum (AN), Asparagopsis (ASP), Lactobacillus plantarum (LAB), chitosan (CHI), essential oils (EOs) and 3-nitrooxypropanol (3-NOP). Dose-dependent analysis was carried out on selected feed additives using a meta-analysis approach to determine effectiveness in live subjects or potential efficacy in live animal trials with particular attention given to enteric gas, volatile fatty acid concentrations, and rumen microbial counts. All meta-analysis involving additives GO, nitrates, LAB, CHI, EOs, and 3-NOP revealed a reduction in methane production, while individual studies for AN and ASP displayed ruminal bacterial community improvement and a reduction in enteric CH4. Rumen protozoal depression was observed with GO and AN supplementation as well as an increase in propionate production with GO, LAB, ASP, CHI, and 3-NOP rumen fluid inoculation. GO, AN, ASP, and LAB demonstrated mechanisms in vitro as feed additives to improve rumen function and act as enteric methane mitigators. Enzyme inhibitor 3-NOP displays the greatest in vivo CH4 mitigating capabilities compared to essential oil commercial products. Furthermore, this meta-analysis study revealed that in vitro studies in general displayed a greater level of methane mitigation with these compounds than was seen in vivo, emphasising the importance of in vivo trials for final verification of use. While in vitro gas production systems predict in vivo methane production and fermentation trends with reasonable accuracy, it is necessary to confirm feed additive rumen influence in vivo before practical application.

- Invited Review - Translational gut microbiome research for strategies to improve beef cattle production sustainability and meat quality

Advanced and innovative breeding and management of meat-producing animals are needed to address the global food security and sustainability challenges. Beef production is an important industry for securing animal protein resources in the world and meat quality significantly contributes to the economic values and human needs. Improvement of cattle feed efficiency has become an urgent task as it can lower the environmental burden of methane gas emissions and the reduce the consumption of human edible cereal grains. Cattle depend on their symbiotic microbiome and its activity in the rumen and gut to maintain growth and health. Recent developments in high-throughput omics analysis (metagenome, metatranscriptome, metabolome, metaproteome and so on) have made it possible to comprehensively analyze microbiome, hosts and their interactions and to define their roles in affecting cattle biology. In this review, we focus on the relationships among gut microbiome and beef meat quality, feed efficiency, methane emission as well as host genetics in beef cattle, aiming to determine the current knowledge gaps for the development of the strategies to improve the sustainability of beef production.

Bioactive metabolites of Asparagopsis stabilized in canola oil completely suppress methane emissions in beef cattle fed a feedlot diet

Asparagopsis taxiformis (Asparagopsis) has been shown to be highly efficacious at inhibiting the production of methane (CH4) in ruminants. To date, Asparagopsis has been primarily produced as a dietary supplement by freeze-drying to retain the volatile bioactive compound bromoform (CHBr3) in the product. Steeping of Asparagopsis bioactive compounds into a vegetable oil carrier (Asp-Oil) is an alternative method of stabilizing Asparagopsis as a ruminant feed additive. A dose-response experimental design used 3 Asp-Oil-canola oil blends, low, medium, and high Asp-Oil which provided 17, 34, and 51 mg Asparagopsis derived CHBr3/kg dry matter intake (DMI), respectively (in addition to a zero CHBr3 canola oil control), in a tempered-barley based feedlot finisher diet, fed for 59 d to 20 Angus heifers (five replicates per treatment). On four occasions, live weight was measured and CH4 emissions were quantified in respiration chambers, and blood, rumen fluid, and fecal samples were collected. At the end of the experiment, all animals were slaughtered, with carcasses graded, and samples of meat and edible offal collected for testing of consumer sensory qualities and residues of CHBr3, bromide, and iodide. All Asp-Oil treatments reduced CH4 yield (g CH4/kg DMI, P = 0.008) from control levels, with the low, medium, and high Asp-Oil achieving 64%, 98%, and 99% reduction, respectively. Dissolved hydrogen increased linearly with increasing Asp-Oil inclusion, by more than 17-fold in the high Asp-Oil group (P = 0.017). There was no effect of Asp-Oil treatment on rumen temperature, pH, reduction potential, volatile fatty acid and ammonia production, rumen pathology, and histopathology (P > 0.10). There were no differences in animal production and carcass parameters (P > 0.10). There was no detectable CHBr3 in feces or any carcass samples (P > 0.10), and iodide and bromide residues in kidneys were at levels unlikely to lead to consumers exceeding recommended maximum intakes. Overall, Asp-Oil was found to be safe for animals and consumers of meat, and effective at reducing CH4 emissions and yield by up to 99% within the range of inclusion levels tested.

Enteric methane emission reduction potential of natural feed supplements in ewe diets

Research into the potential use of various dietary feed supplements to reduce methane (CH4) production from ruminants has proliferated in recent years. In this study, two 8-wk long experiments were conducted with mature ewes and incorporated the use of a variety of natural dietary feed supplements offered either independently or in combination. Both experiments followed a randomized complete block design. Ewes were offered a basal diet in the form of ad libitum access to grass silage supplemented with 0.5 kg concentrates/ewe/d. The entire daily dietary concentrate allocation, incorporating the respective feed supplement, was offered each morning, and this was followed by the daily silage allocation. In experiment 1, the experimental diets contained 1) no supplementation (CON), 2) Ascophyllum nodosum (SW), 3) A. nodosum extract (EX1), 4) a blend of garlic and citrus extracts (GAR), and 5) a blend of essential oils (EO). In experiment 2, the experimental diets contained 1) no supplementation (CON), 2) A. nodosum extract (EX2), 3) soya oil (SO), and 4) a combination of EX2 and SO (EXSO). Twenty ewes per treatment were individually housed during both experiments. Methane was measured using portable accumulation chambers. Rumen fluid was collected at the end of both experiments for subsequent volatile fatty acid (VFA) and ammonia analyses. Data were analyzed using mixed models ANOVA (PROC MIXED, SAS v9.4). Statistically significant differences between treatment means were considered when P < 0.05. Dry matter intake was not affected by diet in either experiment (P > 0.05). Ewes offered EO tended to have an increased feed:gain ratio relative to CON (P < 0.10) and SO tended to increase the average daily gain (P < 0.10) which resulted in animals having a higher final body weight (P < 0.05) than CON. Ewes offered EX1 and SO emitted 9% less CH4 g/d than CON. The only dietary treatment to have an effect on rumen fermentation variables relative to CON was SW, which enhanced total VFA production (P < 0.05). In conclusion, the A. nodosum extract had inconsistent results on CH4 emissions whereby EX1 reduced CH4 g/d while EX2 had no mitigating effect on CH4 production, likely due to the differences in PT content reported for EX1 and EX2. SO was the only dietary feed supplement assessed in the current study that enhanced animal performance whilst mitigating daily CH4 production.

Effect of residual methane emission on physiological characteristics and carcass performance in Japanese Black cattle

This study investigated the physiological characteristics and carcass performance associated with residual methane emissions (RME), and the effects of bull differences on CH4-related traits in Japanese Black cattle. Enteric methane (CH4) emissions from 156 Japanese Black cattle (111 heifers and 45 steers) were measured during early fattening using the sniffer method. Various physiological parameters were investigated to clarify the physiological traits between the high, middle, and low RME groups. CH4-related traits were examined to determine whether bull differences affected progeny CH4 emissions. Ruminal butyrate and NH3 concentrations were significantly higher in the high-RME group than in the low-RME group, whereas the propionate content was significantly higher in the low-RME group. Blood urea nitrogen, β-hydroxybutyric acid, and insulin concentrations were significantly higher, and blood amino acids were lower in the high-RME group than in the other groups. No significant differences were observed in the carcass traits and beef fat composition between RME groups. CH4-related traits were significantly different among bull herds. Our results show that CH4-related traits are heritable, wherein bull differences affect progeny CH4 production capability, and that the above-mentioned rumen fermentations and blood metabolites could be used to evaluate enteric methanogenesis in Japanese Black cattle.

Identification of Incomplete Annotations of Biosynthesis Pathways in Rhodophytes Using a Multi-Omics Approach

Rhodophytes (red algae) are an important source of natural products and are, therefore, a current research focus in terms of metabolite production. The recent increase in publicly available Rhodophyte whole genome and transcriptome assemblies provides the resources needed for in silico metabolic pathway analysis. Thus, this study aimed to create a Rhodophyte multi-omics resource, utilising both genomes and transcriptome assemblies with functional annotations to explore Rhodophyte metabolism. The genomes and transcriptomes of 72 Rhodophytes were functionally annotated and integrated with metabolic reconstruction and phylogenetic inference, orthology prediction, and gene duplication analysis to analyse their metabolic pathways. This resource was utilised via two main investigations: the identification of bioactive sterol biosynthesis pathways and the evolutionary analysis of gene duplications for known enzymes. We report that sterol pathways, including campesterol, β-sitosterol, ergocalciferol and cholesterol biosynthesis pathways, all showed incomplete annotated pathways across all Rhodophytes despite prior in vivo studies showing otherwise. Gene duplication analysis revealed high rates of duplication of halide-associated haem peroxidases in Florideophyte algae, which are involved in the biosynthesis of drug-related halogenated secondary metabolites. In summary, this research revealed trends in Rhodophyte metabolic pathways that have been under-researched and require further functional analysis. Furthermore, the high duplication of haem peroxidases and other peroxidase enzymes offers insight into the potential drug development of Rhodophyte halogenated secondary metabolites.

Anti-methanogenic potential of seaweeds and seaweed-derived compounds in ruminant feed: current perspectives, risks and future prospects

With methane emissions from ruminant agriculture contributing 17% of total methane emissions worldwide, there is increasing urgency to develop strategies to reduce greenhouse gas emissions in this sector. One of the proposed strategies is ruminant feed intervention studies focused on the inclusion of anti-methanogenic compounds which are those capable of interacting with the rumen microbiome, reducing the capacity of ruminal microorganisms to produce methane. Recently, seaweeds have been investigated for their ability to reduce methane in ruminants in vitro and in vivo, with the greatest methane abatement reported when using the red seaweed Asparagopsis taxiformis (attributed to the bromoform content of this species). From the literature analysis in this study, levels of up to 99% reduction in ruminant methane emissions have been reported from inclusion of this seaweed in animal feed, although further in vivo and microbiome studies are required to confirm these results as other reports showed no effect on methane emission resulting from the inclusion of seaweed to basal feed. This review explores the current state of research aiming to integrate seaweeds as anti-methanogenic feed additives, as well as examining the specific bioactive compounds within seaweeds that are likely to be related to these effects. The effects of the inclusion of seaweeds on the ruminal microbiome are also reviewed, as well as the future challenges when considering the large-scale inclusion of seaweeds into ruminant diets as anti-methanogenic agents.

Methane mitigation in ruminants with structural analogues and other chemical compounds targeting archaeal methanogenesis pathways

Ruminants are responsible for enteric methane production contributing significantly to the anthropogenic greenhouse gases in the atmosphere. Moreover, dietary energy is lost as methane gas without being available for animal use. Therefore, many mitigation strategies aiming at interventions at animals, diet, and microbiota have been explored by researchers. Specific chemical analogues targeting the enzymes of the methanogenic pathway appear to be more effective in specifically inhibiting the growth of methane-producing archaea without hampering another microbiome, particularly, cellulolytic microbiota. The targets of methanogenesis reactions that have been mainly investigated in ruminal fluid include methyl coenzyme M reductase (halogenated sulfonate and nitrooxy compounds), corrinoid enzymes (halogenated aliphatic compounds), formate dehydrogenase (nitro compounds, e.g., nitroethane and 2-nitroethanol), and deazaflavin (F420) (pterin and statin compounds). Many other potential metabolic reaction targets in methanogenic archaea have not been evaluated properly. The analogues are specifically effective inhibitors of methanogens, but their efficacy to lower methanogenesis over time reduces due to the metabolism of the compounds by other microbiota or the development of resistance mechanisms by methanogens. In this short review, methanogen populations inhabited in the rumen, methanogenesis pathways and methane analogues, and other chemical compounds specifically targeting the metabolic reactions in the pathways and methane production in ruminants have been discussed. Although many methane inhibitors have been evaluated in lowering methane emission in ruminants, advancement in unravelling the molecular mechanisms of specific methane inhibitors targeting the metabolic pathways in methanogens is very limited.

Stonefish (Synanceia spp.) Ichthyocrinotoxins: An ecological review and prospectus for future research and biodiscovery

Marine organisms possess a diverse array of unique substances, many with wide ranging potential for applications in medicine, industry, and other sectors. Stonefish (Synanceia spp.), a bottom-dwelling fish that inhabit shallow and intertidal waters throughout the Indo-Pacific, harbour two distinct substances, a venom, and an ichthyocrinotoxin. Stonefish are well-known for the potent venom associated with their dorsal spines as it poses a significant risk to public health. Consequently, much of the research on stonefish focusses on the venom, with the aim of improving outcomes in cases of envenomation. However, there has been a notable lack of research on stonefish ichthyocrinotoxins, a class of toxin that is synthesised within specialised epithelial cells (i.e., tubercles) and exuded onto the skin. This has resulted in a substantial knowledge gap in our understanding of these animals. This review aims to bridge this gap by consolidating literature on the ecological functions and biochemical attributes of ichthyocrinotoxins present in various fish species and juxtaposing it with the current state of knowledge of stonefish ecology. We highlight the roles of ichthyocrinotoxins in predator defence, bolstering innate immunity, and mitigating integumentary interactions with parasites and detrimental fouling organisms. The objective of this review is to identify promising research avenues that could shed light on the ecological functions of stonefish ichthyocrinotoxins and their potential practical applications as therapeutics and/or industrial products.

Rumen microbial degradation of bromoform from red seaweed (Asparagopsis taxiformis) and the impact on rumen fermentation and methanogenic archaea

BACKGROUND

The red macroalgae Asparagopsis is an effective methanogenesis inhibitor due to the presence of halogenated methane (CH4) analogues, primarily bromoform (CHBr3). This study aimed to investigate the degradation process of CHBr3 from A. taxiformis in the rumen and whether this process is diet-dependent. An in vitro batch culture system was used according to a 2 × 2 factorial design, assessing two A. taxiformis inclusion rates [0 (CTL) and 2% DM diet (AT)] and two diets [high-concentrate (HC) and high-forage diet (HF)]. Incubations lasted for 72 h and samples of headspace and fermentation liquid were taken at 0, 0.5, 1, 3, 6, 8, 12, 16, 24, 48 and 72 h to assess the pattern of degradation of CHBr3 into dibromomethane (CH2Br2) and fermentation parameters. Additionally, an in vitro experiment with pure cultures of seven methanogens strains (Methanobrevibacter smithii, Methanobrevibacter ruminantium, Methanosphaera stadtmanae, Methanosarcina barkeri, Methanobrevibacter millerae, Methanothermobacter wolfei and Methanobacterium mobile) was conducted to test the effects of increasing concentrations of CHBr3 (0.4, 2, 10 and 50 µmol/L).

RESULTS

The addition of AT significantly decreased CH4 production (P = 0.002) and the acetate:propionate ratio (P = 0.003) during a 72-h incubation. The concentrations of CHBr3 showed a rapid decrease with nearly 90% degraded within the first 3 h of incubation. On the contrary, CH2Br2 concentration quickly increased during the first 6 h and then gradually decreased towards the end of the incubation. Neither CHBr3 degradation nor CH2Br2 synthesis were affected by the type of diet used as substrate, suggesting that the fermentation rate is not a driving factor involved in CHBr3 degradation. The in vitro culture of methanogens showed a dose-response effect of CHBr3 by inhibiting the growth of M. smithii, M. ruminantium, M. stadtmanae, M. barkeri, M. millerae, M. wolfei, and M. mobile.

CONCLUSIONS

The present work demonstrated that CHBr3 from A. taxiformis is quickly degraded to CH2Br2 in the rumen and that the fermentation rate promoted by different diets is not a driving factor involved in CHBr3 degradation.

Microalgae as a Sustainable Source of Antioxidants in Animal Nutrition, Health and Livestock Development

Microalgae are a renewable and sustainable source of bioactive compounds, such as essential amino acids, polyunsaturated fatty acids, and antioxidant compounds, that have been documented to have beneficial effects on nutrition and health. Among these natural products, the demand for natural antioxidants, as an alternative to synthetic antioxidants, has increased. The antioxidant activity of microalgae significantly varies between species and depends on growth conditions. In the last decade, microalgae have been explored in livestock animals as feed additives with the aim of improving both animals' health and performance as well as product quality and the environmental impact of livestock. These findings are highly dependent on the composition of microalgae strain and their amount in the diet. The use of carbohydrate-active enzymes can increase nutrient bioavailability as a consequence of recalcitrant microalgae cell wall degradation, making it a promising strategy for monogastric nutrition for improving livestock productivity. The use of microalgae as an alternative to conventional feedstuffs is becoming increasingly important due to food-feed competition, land degradation, water deprivation, and climate change. However, the cost-effective production and use of microalgae is a major challenge in the near future, and their cultivation technology should be improved by reducing production costs, thus increasing profitability.

Effect of dietary seaweed (Ascophyllum nodosum) supplementation on milk mineral concentrations, transfer efficiency, and hematological parameters in lactating Holstein cows

This study investigated the effect of feeding seaweed (Ascophyllum nodosum) to dairy cows on milk mineral concentrations, feed-to-milk mineral transfer efficiencies, and hematological parameters. Lactating Holstein cows (n = 46) were allocated to 1 of 2 diets (n = 23 each): (1) control (CON; without seaweed) and (2) seaweed (SWD; replacing 330 g/d of dried corn meal in CON with 330 g/d dried A. nodosum). All cows were fed the CON diet for 4 wk before the experiment (adaptation period), and animals were then fed the experimental diets for 9 wk. Samples included sequential 3-wk composite feed samples, a composite milk sample on the last day of each week, and a blood sample at the end of the study. Data were statistically analyzed using a linear mixed effects model with diet, week, and their interaction as fixed factors; cow (nested within diet) as a random factor; and data collected on the last day of the adaptation period as covariates. Feeding SWD increased milk concentrations of Mg (+6.6 mg/kg), P (+56 mg/kg), and I (+1,720 μg/kg). It also reduced transfer efficiency of Ca, Mg, P, K, Mn, and Zn, and increased transfer efficiency of Mo. Feeding SWD marginally reduced milk protein concentrations, whereas there was no effect of SWD feeding on cows' hematological parameters. Feeding A. nodosum increased milk I concentrations, which can be beneficial when feed I concentration is limited or in demographics or populations with increased risk of I deficiency (e.g., female adolescents, pregnant women, nursing mothers). However, care should also be taken when feeding SWD to dairy cows because, in the present study, milk I concentrations were particularly high and could result in I intakes that pose a health risk for children consuming milk.

Life cycle assessment of greenhouse gas emission from the dairy production system - review

Climate change is altering ecological systems and poses a serious threat to human life. Climate change also seriously influences on livestock production by interfering with growth, reproduction, and production. Livestock, on the other hand, is blamed for being a significant contributor to climate change, emitting 8.1 gigatonnes of CO2-eq per year and accounting for two-thirds of global ammonia emissions. Methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2) are three major greenhouse gases (GHG) that are primarily produced by enteric fermentation, feed production, diet management, and total product output. Ruminants account for three-quarters of total CO2-equivalent (CO2-eq) emissions from the livestock sector. The global dairy sector alone emits 4.0% of global anthropogenic GHG emissions. Hence, dairy farming needs to engage in environmental impact assessment. Public concern for a sustainable and environmentally friendly farming system is growing, resulting in the significant importance of food-based life cycle assessment (LCA). Over the last decade, LCA has been used in agriculture to assess total GHG emissions associated with products such as milk and manure. It includes the production of farm inputs, farm emissions, milk processing, transportation, consumer use, and waste. LCA studies on milk production would assist us in identifying the specific production processes/areas that contribute to excessive greenhouse gas emissions when producing milk and recommending appropriate mitigation strategies to be implemented for a clean, green, and resilient environment.

Effect of fumaric acid in combination with Asparagopsis taxiformis or nitrate on in vitro gas production, pH, and redox potential

Reduction in enteric methane (CH4) emissions from cattle can be achieved through use of feed additives, which often results in increased emission of hydrogen (H2). The objective of this study was to investigate in vitro effects of a known hydrogen sink, fumaric acid, in combination with either of 2 methane inhibitors, the macroalga Asparagopsis taxiformis or nitrate, on CH4 and H2 production, feed degradability, pH, and redox potential. A corn silage (0.5 g; control) was incubated in buffered rumen fluid with the addition of 0.025 g of nitrate (Nit), 0.025 g of dried A. taxiformis (Asp), 0.025 g of nitrate + 0.025 g of fumaric acid (Nit+Fum), or 0.025 g of dried A. taxiformis + 0.025 g of fumaric acid (Asp+Fum). Accumulated gas production was determined using the AnkomRF system equipped with airtight gasbags. There were 9 replicates per treatment with 3 replicates per treatment stopped after 24, 36, and 48 h of incubation. The amount of undegraded feed was determined by filtration. Gas composition was determined by gas chromatography. Degradable dry matter, degradable organic matter, pH, redox potential, and gas production data were analyzed using a mixed model. Asp and Asp+Fum reduced CH4 production by 98% or greater at all incubation times, whereas Nit and Nit+Fum reduced CH4 production (mL of CH4/g of dry matter) by 52% to 63% compared with the control. Hydrogen was only detectable in gas from Asp and Asp+Fum treatments, with no difference in H2 production between the 2 treatments. The treatments had only minor effects on redox potential in the fermented rumen fluid, and pH was lowest for treatments including A. taxiformis. In conclusion, both A. taxiformis and nitrate reduced CH4 production. Fumaric acid in combination with A. taxiformis did not reduce H2 production, and treatments including nitrate did not result in any detectable levels of H2. Future dose-response in vitro studies will contribute to investigating the potential of fumaric acid as a hydrogen sink during CH4 mitigation.

Dietary Ruminant Enteric Methane Mitigation Strategies: Current Findings, Potential Risks and Applicability

This review examines the current state of knowledge regarding the effectiveness of different dietary ruminant enteric methane mitigation strategies and their modes of action together with the issues discussed regarding the potential harms/risks and applicability of such strategies. By investigating these strategies, we can enhance our understanding of the mechanisms by which they influence methane production and identify promising approaches for sustainable mitigation of methane emissions. Out of all nutritional strategies, the use of 3-nitrooxypropanol, red seaweed, tannins, saponins, essential oils, nitrates, and sulfates demonstrates the potential to reduce emissions and receives a lot of attention from the scientific community. The use of certain additives as pure compounds is challenging under certain conditions, such as pasture-based systems, so the potential use of forages with sufficient amounts of plant secondary metabolites is also explored. Additionally, improved forage quality (maturity and nutrient composition) might help to further reduce emissions. Red seaweed, although proven to be very effective in reducing emissions, raises some questions regarding the volatility of the main active compound, bromoform, and challenges regarding the cultivation of the seaweed. Other relatively new methods of mitigation, such as the use of cyanogenic glycosides, are also discussed in this article. Together with nitrates, cyanogenic glycosides pose serious risks to animal health, but research has proven their efficacy and safety when control measures are taken. Furthermore, the risks of nitrate use can be minimized by using probiotics. Some of the discussed strategies, namely monensin or halogenated hydrocarbons (as pure compounds), demonstrate efficacy but are unlikely to be implemented widely because of legal restrictions.

Algal Carotenoids: Chemistry, Sources, and Application

Recently, the isolation and identification of various biologically active secondary metabolites from algae have been of scientific interest, with particular attention paid to carotenoids, widely distributed in various photosynthetic organisms, including algal species. Carotenoids are among the most important natural pigments, with many health-promoting effects. Since the number of scientific studies on the presence and profile of carotenoids in algae has increased exponentially along with the interest in their potential commercial applications, this review aimed to provide an overview of the current knowledge (from 2015) on carotenoids detected in different algal species (12 microalgae, 21 green algae, 26 brown algae, and 43 red algae) to facilitate the comparison of the results of different studies. In addition to the presence, content, and identification of total and individual carotenoids in various algae, the method of their extraction and the main extraction parameters were also highlighted.

Maine organic dairy producers' receptiveness to seaweed supplementation and effect of Chondrus crispus on enteric methane emissions in lactating cows

Introduction

There is a growing interest in utilizing seaweed in ruminant diets for mitigating enteric methane (CH₄) emissions while improving animal health. Chondrus crispus is a red seaweed that grows in the Gulf of Maine (United States) and has shown to suppress CH₄ production in vitro. Organic dairy producers in Maine are currently feeding seaweed due to herd health promoting benefits. However, large-scale adoption depends on technical and financial factors, as well as validation from pilot studies.

Methods

A survey was developed to identify barriers and drivers towards the adoption of CH₄-reducing algal-based feeds. Concurrently, a randomized complete block design study was conducted to investigate the effect of C. crispus on enteric CH₄ emissions and milk production in a typical Maine organic dairy farm. Twenty-two organically certified Holstein and Jersey cows averaging 29 ± 6.8 kg of milk/d and 150 ± 69 days in milk, were blocked and randomly assigned to a control diet without C. crispus (0CC), or with 6% [dry matter (DM) basis] C. crispus (6CC). Samples were collected on the last week of the 2-wk covariate period, and wk 3, 5, 8, and 10 after initiation of treatments for a total of 12 weeks. Gaseous emissions were measured using a GreenFeed unit. Data were analyzed using the MIXED procedure of SAS with repeated measures over time.

Results

All survey respondents (n = 35; 54% response rate) were familiar with seaweeds as feed, and 34% were already users. Producers who were willing to pay 0.64 USD/cow/d on average for a CH₄-reducing algal-based feed, also stated the need for co-benefits in terms of cattle health and performance as a requirement for adoption. Feeding 6CC decreased enteric CH₄ production by 13.9% compared with 0CC (401 vs. 466 g/d). Further, milk yield (mean = 27.1 kg/d), CH₄ intensity (mean = 15.2 g of CH₄/kg of energy corrected milk), and concentrations and yields of milk fat and true protein were not affected by treatments.

Discussion

Producer receptiveness to CH₄-reducing algal-based feeds will not only be dependent on purchase price, but also on co-benefits and simplicity of integration into existing feed practices. Feeding C. crispus at 6% of the diet DM decreased CH₄ production in dairy cows by 13.9% without negative effects on milk yield and composition. Identifying the bioactive compounds in C. crispus is critical to understand the effect of this red seaweed on mitigating enteric CH₄ emissions in dairy cows.

Screening macroalgae for mitigation of enteric methane in vitro

This study investigated the effects of 67 species of macroalgae on methanogenesis and rumen fermentation in vitro. Specimens were analyzed for their effect on ruminal fermentation and microbial community profiles. Incubations were carried out in an automated gas production system for 24-h and macroalgae were tested at 2% (feed dry matter basis) inclusion rate. Methane yield was decreased 99% by Asparagopsis taxiformis (AT) when compared with the control. Colpomenia peregrina also decreased methane yield 14% compared with control; no other species influenced methane yield. Total gas production was decreased 14 and 10% by AT and Sargassum horneri compared with control, respectively. Total volatile fatty acid (VFA) concentration was decreased between 5 and 8% by 3 macroalgae, whereas AT reduced it by 10%. Molar proportion of acetate was decreased 9% by AT, along with an increase in propionate by 14%. Asparagopsis taxiformis also increased butyrate and valerate molar proportions by 7 and 24%, respectively, whereas 3 macroalgae species decreased molar proportion of butyrate 3 to 5%. Vertebrata lanosa increased ammonia concentration, whereas 3 other species decreased it. Inclusion of AT decreased relative abundance of Prevotella, Bacteroidales, Firmicutes and Methanobacteriaceae, whereas Clostridium, Anaerovibrio and Methanobrevibacter were increased. Specific gene activities for Methanosphaera stadtmane and Methanobrevibacter ruminantium were decreased by AT inclusion. In this in vitro study, Asparagopsis taxiformis was most effective in decreasing methane concentration and yield, but also decreased total gas production and VFA concentration which indicates overall inhibition of ruminal fermentation. No other macroalgae were identified as potential mitigants of enteric methane.

Effect of Pelagic Sargassum on In Vitro Dry Matter and Organic Matter Degradation, Gas Production, and Protozoa Population

This study determined the effect of pelagic Sargassum on in vitro dry matter and organic matter degradation, total gas production (TGP), and protozoa population. The treatments were different levels of Sargassum inclusion on a basal substrate (Stargrass hay; Cynodon nlemfuensis) as follows: T0 (control treatment based on Stargrass hay), T10 (90% Stargrass hay + 10% Sargassum), T20 (80% Stargrass hay + 20% Sargassum), and T30 (70% Stargrass hay + 30% Sargassum). Ruminal fermentation kinetics and protozoa population were determined during 72 h of in vitro incubations. Compared to control, dry matter degradability at 48 and 72 h and organic matter degradability at 24 and 48 h were higher in Sargassum treatments. TGP was lower with T20 at 48 h. The total population of protozoa and the concentration of Entodinium spp. were lower at T20 at 48 h and T30 at 72 h. Cl, S, Ca, K, and Zn (103, 5.97, 88.73, 285.70 g/kg, and 15,900 mg/kg) were high in Sargassum, reaching twice or even nine times higher than the contents in Stargrass (11.37, 1.60, 43.53, 87.73 g/kg, and 866.67 mg/kg). Overall, up to 30% pelagic Sargassum could be included in hay-based substrates from tropical grasses without negative effects on in vitro dry matter and organic matter degradability.

Comparative analysis of macroalgae supplementation on the rumen microbial community: Asparagopsis taxiformis inhibits major ruminal methanogenic, fibrolytic, and volatile fatty acid-producing microbes in vitro

Seaweeds have received a great deal of attention recently for their potential as methane-suppressing feed additives in ruminants. To date, Asparagopsis taxiformis has proven a potent enteric methane inhibitor, but it is a priority to identify local seaweed varieties that hold similar properties. It is essential that any methane inhibitor does not compromise the function of the rumen microbiome. In this study, we conducted an in vitro experiment using the RUSITEC system to evaluate the impact of three red seaweeds, A. taxiformis, Palmaria mollis, and Mazzaella japonica, on rumen prokaryotic communities. 16S rRNA sequencing showed that A. taxiformis had a profound effect on the microbiome, particularly on methanogens. Weighted Unifrac distances showed significant separation of A. taxiformis samples from the control and other seaweeds (p &lt; 0.05). Neither P. mollis nor M. japonica had a substantial effect on the microbiome (p &gt; 0.05). A. taxiformis reduced the abundance of all major archaeal species (p &lt; 0.05), leading to an almost total disappearance of the methanogens. Prominent fiber-degrading and volatile fatty acid (VFA)-producing bacteria including Fibrobacter and Ruminococcus were also inhibited by A. taxiformis (p &lt; 0.05), as were other genera involved in propionate production. The relative abundance of several other bacteria including Prevotella, Bifidobacterium, Succinivibrio, Ruminobacter, and unclassified Lachnospiraceae were increased by A. taxiformis suggesting that the rumen microbiome adapted to an initial perturbation. Our study provides baseline knowledge of microbial dynamics in response to seaweed feeding over an extended period and suggests that feeding A. taxiformis to cattle to reduce methane may directly, or indirectly, inhibit important fiber-degrading and VFA-producing bacteria.

Evaluating the effect of phenolic compounds as hydrogen acceptors when ruminal methanogenesis is inhibited in vitro – Part 2. Dairy goats

Most mitigation strategies to reduce enteric methane (CH₄) production in the rumen induce an excess of rumen dihydrogen (H₂) that is expelled and consequently not redirected to the synthesis of metabolites that can be utilised by the ruminant. We hypothesised that phenolic compounds can be potential H₂ acceptors when added to the diet, as they can be degraded to compounds that may be beneficial for the animal, using part of the H₂ available when ruminal methanogenesis is inhibited. We performed four in vitro incubation experiments using rumen inoculum from Murciano-Granadina adult goats: Experiment 1 examined the inhibitory potential of Asparagopsis taxiformis (AT) at different concentrations (0, 1, 2, 3, 4 and 5% of the substrate on a DM basis) in 24 h incubations; Experiment 2 investigated the effect of a wide range of phenolic compounds (phenol, catechol, resorcinol, hydroquinone, pyrogallol, phloroglucinol, gallic acid and formic acid) at different doses (0, 2, 4, and 6 mM) on rumen fermentation for 24 h; Experiment 3 evaluated the combined effect of each phenolic compound at 6 mM with AT at 2% DM in sequential batch cultures for 5 days; and Experiment 4 examined the dose-response effect of phloroglucinol at different concentrations (0, 6, 16, 26 and 36 mM) combined with AT in sequential batch cultures for 5 days. Results from Experiment 1 confirmed that AT at 2% DM substantially inhibited CH₄ production while significantly increasing H₂ accumulation and decreasing the acetate:propionate ratio. Results from Experiment 2 showed that phenolic compounds did not negatively affect rumen fermentation at any dose. In Experiment 3, each phenolic compound at 6 mM combined with AT at 2% DM inhibited CH₄ production. Phloroglucinol numerically decreased H₂ accumulation and significantly increased total gas production (TGP), volatile fatty acid (VFA) production and the acetate:propionate ratio. In Experiment 4, phloroglucinol at increasing doses supplemented with AT at 2% DM significantly decreased H₂ accumulation and the abundances of archaea, protozoa and fungi abundances, and increased TGP, total VFA production and the acetate:propionate ratio in a dose-dependent way. In conclusion, combined treatment with AT and phloroglucinol was successful to mitigate CH₄ production while preventing the accumulation of H₂, leading to an increase in acetate and total VFA production and therefore an improvement in rumen fermentation in goats.

Evaluating the effect of phenolic compounds as hydrogen acceptors when ruminal methanogenesis is inhibited in vitro – Part 1. Dairy cows

Some antimethanogenic feed additives for ruminants promote rumen dihydrogen (H₂) accumulation potentially affecting the optimal fermentation of diets. We hypothesised that combining an H₂ acceptor with a methanogenesis inhibitor can decrease rumen H₂ build-up and improve the production of metabolites that can be useful for the host ruminant. We performed three in vitro incubation experiments using rumen fluid from lactating Holstein cows: Experiment 1 examined the effect of phenolic compounds (phenol, catechol, resorcinol, hydroquinone, pyrogallol, phloroglucinol, and gallic acid) at 0, 2, 4, and 6 mM on ruminal fermentation for 24 h; Experiment 2 examined the combined effect of each phenolic compound from Experiment 1 at 6 mM with two different methanogenesis inhibitors (Asparagopsis taxiformis or 2-bromoethanesulfonate (BES)) for 24 h incubation; Experiment 3 examined the effect of a selected phenolic compound, phloroglucinol, with or without BES over a longer term using sequential incubations for seven days. Results from Experiment 1 showed that phenolic compounds, independently of the dose, did not negatively affect rumen fermentation, whereas results from Experiment 2 showed that phenolic compounds did not decrease H₂ accumulation or modify CH₄ production when methanogenesis was decreased by up to 75% by inhibitors. In Experiment 3, after three sequential incubations, phloroglucinol combined with BES decreased H₂ accumulation by 72% and further inhibited CH₄ production, compared to BES alone. Interestingly, supplementation with phloroglucinol (alone or in combination with the CH₄ inhibitor) decreased CH₄ production by 99% and the abundance of methanogenic archaea, with just a nominal increase in H₂ accumulation. Supplementation of phloroglucinol also increased total volatile fatty acid (VFA), acetate, butyrate, and total gas production, and decreased ammonia concentration. This study indicates that some phenolic compounds, particularly phloroglucinol, which are naturally found in plants, could improve VFA production, decrease H₂ accumulation and synergistically decrease CH₄ production in the presence of antimethanogenic compounds.

Effects on rumen microbiome and milk quality of dairy cows fed a grass silage-based diet supplemented with the macroalga Asparagopsis taxiformis

The objective was to determine the effects on rumen microbiome and milk quality of reducing the methane (CH4) produced from enteric fermentation by the addition of Asparagopsis taxiformis (AT) to the diets of dairy cows. Six Nordic Red cows at 122 ± 13.7 (mean ± SD) days in milk, of parity 2.7 ± 0.52 and producing 36 kg ± 2.5 kg milk per day at the start of the trial were divided into three blocks by milk yield and assigned to an extra-period Latin-square change-over design comprising two dietary treatments. An extra period of observation was added to the Latin-square change-over design to control for carry-over effects. The dietary treatments were a diet consisting of grass silage and a commercial concentrate mixture (60:40) either not supplemented or supplemented with 0.5% AT on an organic matter intake basis. On average, daily CH4 production, CH4 yield, and CH4 intensity decreased by 60%, 54%, and 58%, respectively, in cows fed the diet supplemented with AT. Furthermore, hydrogen gas emitted by cows fed diets supplemented with AT increased by more than five times compared with cows fed a non-AT-supplemented diet. Feed intake was decreased and milk production altered, reflecting a decreased yield of milk fat in cows fed an AT-supplemented diet, but feed efficiency increased. Rumen fermentation parameters were changed to promote propionate rather than acetate and butyrate fermentation. The most prominent change in milk quality was an increase in bromine and iodine when the diet was supplemented with AT. The reduction in CH4 was associated with a shift from Methanobrevibacter to Methanomethylophilaceae in the archaeal population and a lower relative abundance of Prevotella in the bacterial population. Changes in milk fat odd-numbered and branched-chain fatty acids in the current study of AT supplementation support observed differences in ruminal archaeal and bacterial populations.

Micro- and Macro-Algae Combination as a Novel Alternative Ruminant Feed with Methane-Mitigation Potential

This study was conducted to provide alternative high-quality feed and to reduce methane production using a mixture of the minimum effective levels of Euglena gracilis, EG, and Asparagopsis taxiformis, AT. This study was performed as a 24 h in vitro batch culture. Chemical analysis demonstrated that EG is a highly nutritive material with 26.1% protein and 17.7% fat. The results showed that the supplementation of AT as a feed additive at 1 and 2.5% of the diet reduced methane production by 21 and 80%, respectively, while the inclusion of EG in the diet at 10 and 25% through partially replacing the concentrate mixture reduced methane production by 4 and 11%, respectively, with no adverse effects on fermentation parameters. The mixtures of AT 1% with both EG 10% and EG 25% had a greater reductive potential than the individual supplementation of these algae in decreasing methane yield by 29.9% and 40.0%, respectively, without adverse impacts on ruminal fermentation characteristics. These results revealed that the new feed formulation had a synergistic effect in reducing methane emissions. Thus, this approach could provide a new strategy for a sustainable animal production industry.

Enteric Methane Emissions in Dairy Cows with Different Genetic Groups in the Humid Tropics of Costa Rica

Enteric methane (CH₄) is one of the main greenhouse gases emitted in livestock production systems with ruminants. Among the options to reduce such emissions, animal genetics is one of the factors that is taking relevance in recent years. The aim of the present study was to assess the emission of enteric CH₄ in dairy cows with different genetic backgrounds. Sixteen cows belonging to the following three genetic groups were selected for this study: seven F1 (50% Jersey × 50% Gyr), five Triple cross (50% Jersey × 31% Holstein × 19% Sahiwal) and four Jersey. Enteric CH₄ emissions were measured in all cows for 15 months, at the middle of each month, using the SF₆ technique. Enteric CH₄ emissions did not differ (p > 0.05) among genetic groups, although it varied with the stage of lactation, due to differences in milk yield and dry matter intake (DMI). Pasture DMI and the intensity of CH₄ emissions (g kg^-1 DMI) differed (p < 0.05) between dry and lactating cows, with higher DMI in the lactation period, while CH₄ emission intensity was higher for dry cows. Cows with the highest proportion of Bos taurus genes presented a higher annual mean methane conversion factor (Y_m), with 7.22, 7.05 and 5.90% for the Triple cross, purebred Jersey and F1, respectively. In conclusion, non-significant differences in enteric CH₄ emissions and Y_m were detected among dairy cows with different genetic backgrounds. However, F1 cows tended to show lower enteric CH₄ emission and Y_m, compared to those with more Bos taurus genes.

In vitro screening of anti-methanogenic additives for use in Australian grazing systems

Despite considerable effort to develop and optimise additives to reduce methane emissions from cattle, little information on additive effectiveness exists for cattle under grazing scenarios. As the majority of Australian cattle production occurs on grazing land it is pertinent to report on the use of additives under simulated conditions. The current study evaluated the addition of nine additives to Rhodes grass hay under in vitro conditions, to estimate their impact on methane (CH4), gas production, and rumen fermentation parameters (volatile fatty acids, rumen pH and in vitro dry matter digestibility [IVDMD]). Citral extract at 0.1% of rumen media decreased all CH4 production parameters, but reduced gas production and digestibility, compared to a 100% hay control. Similarly, Sandalwood essential oil decreased CH4 production at 48 h, IVDMD and gas production, compared to the control. Biochar + nitrates at 5 and 8% DM, and Biochar + Asparagopsis at 5% DM decreased cumulative CH4 production (15.6%, 25.9%, 23.8%, respectively; P &lt; 0.01), compared to the control. No changes in IVDMD and gas production were observed. As such, the biochar additives were considered the most promising additives from those evaluated with a substrate designed to replicate Australian grazing systems.

Performance and enteric methane emissions from housed beef cattle fed silage produced on pastures with different forage profiles

Methane (CH₄) produced by ruminants is a significant source of greenhouse gases from agriculture in the United Kingdom (UK), accounting for approximately 50% of the emissions in this sector. Ration modification is linked to changes in rumen fermentation and can be an effective means of CH₄ abatement. In temperate climate countries, forage silage represents a major feed component for cattle during the housing period. The objective of this study was, therefore, to compare enteric CH₄ emission from cattle offered silage produced from different types of grassland. Beef cattle, steers (n = 89) and heifers (n = 88) with average liveweight (LW) of 328 ± 57.1 kg were evaluated during two housing seasons (2016-2017 and 2017-2018) from November to April, at the Rothamsted Research North Wyke Farm Platform (UK). The treatments corresponded to three diet types, comprising silage harvested from three different pastures: MRG, monoculture of perennial ryegrass (PRG, Lolium perenne L.cv. AberMagic), bred to express the high-sugar phenotype; RG-WC, a mixed sward comprised of the same perennial ryegrass cultivar with white clover (Trifolium repens L.) with a target clover proportion of 30% as land cover; and permanent pasture (PP) dominated by PRG and a small number of non-introduced species. MRG and PP received 160-200 kg N/ha/year. Cattle were weighed every 30 days, and the enteric CH₄ emission was determined using GreenFeed automated systems. No significant differences in enteric CH₄ emission per head or per kg LW were observed between treatments. However, emission expressed per average daily gain (ADG) in LW was greater (P < 0.001) for MRG compared with RG-WC and PP, at 270, 248 and 235 g CH₄/kg ADG, respectively. This related to a lower ADG (P = 0.041) for the animals fed MRG silage compared with RG-WC and PP which were similar, with respective values of 0.67, 0.71 and 0.74 kg/day. The forages compared in this study showed little or no potential to reduce enteric CH₄ emission when fed as silage to growing beef cattle during the winter housing period.

Inclusion of Red Macroalgae (Asparagopsis taxiformis) in Dairy Cow Diets Modulates Feed Intake, Chewing Activity and Estimated Saliva Secretion

The current study assessed the effects of red macroalgae Asparagopsis taxiformis (AT)-included as an enteric methane inhibitor-in dairy cow diets on feed intake and eating-rumination behaviour. Fifteen early lactating Norwegian Red dairy cows were offered ad libitum access to drinking water and a total mixed ration (TMR) composed of 35% concentrate feed and 65% grass silage on a dry matter (DM) basis. The experiment lasted for 74 days with the first 22 days on a common diet used as the covariate period. At the end of the covariate period, the cows were randomly allocated into one of three dietary treatments: namely, 0% AT (control), 0.125% AT and 0.25% AT in the TMR. The TMR was offered in individual feed troughs with AT blended in a 400 g (w/w) water-molasses mixture. Eating-rumination behaviour was recorded for 11 days using RumiWatchSystem after feeding the experimental diets for 30 days. The 0.25% AT inclusion significantly reduced the DM intake (DMI). Time (min/d) spent on eating and eating in a head-down position increased with the increasing AT level in the diet, whereas rumination time was not affected. The greater time spent on eating head-down with the 0.25% AT group resulted in a significantly higher chewing index (min/kg DMI). Estimated saliva production per unit DMI (L/kg DMI, SE) increased from 10.9 (0.4) in the control to 11.3 (0.3) and 13.0 (0.3) in the 0.125% and 0.25% AT groups, respectively. This aligned with the measured ruminal fluid pH (6.09, 6.14, and 6.37 in the control, 0.125% AT and 0.25% AT groups, respectively). In conclusion, either the level of the water-molasses mixture used was not sufficient to mask the taste of AT, or the cows used it as a cue to sort out the AT. Studies with relatively larger numbers of animals and longer adaptation periods than what we used here, with varied modes of delivery of the seaweed may provide novel strategies for administering the additive in ruminant diets.

Galyean appreciation club review: a holistic perspective of the societal relevance of beef production and its impacts on climate change

This article provides a science-based, data-driven perspective on the relevance of the beef herd in the U.S. to our society and greenhouse gas (GHG) contribution to climate change. Cattle operations are subject to criticism for their environmental burden, often based on incomplete information disseminated about their social, economic, nutritional, and ecological benefits and detriments. The 2019 data published by the U.S. Environmental Protection Agency reported that U.S. beef cattle emitted 22.6% of the total agricultural emissions, representing about 2.2% of the total anthropogenic emissions of CO2 equivalent (CO2e). Simulations from a computer model developed to address global energy and climate challenges, set to use extreme improvements in livestock and crop production systems, indicated a potential reduction in global CO2e emissions of 4.6% but without significant enhancement in the temperature change by 2030. There are many natural and anthropogenic sources of CH4 emissions. Contrary to the increased contribution of peatlands and water reservoirs to atmospheric CO2e, the steady decrease in the U.S. cattle population is estimated to have reduced its methane (CH4) emissions by about 30% from 1975 to 2021. This CH4 emission deacceleration of 2.46 Mt CO2e/yr2 might be even more significant than reported. Many opportunities exist to mitigate CH4 emissions of beef production, leading to a realistic prospect of a 5% to 15% reduction in the short term after considering the overlapping impacts of combined strategies. Reduction strategies include feeding synthetic chemicals that inactivate the methyl-coenzyme M reductase (the enzyme that catalyzes the last step of methanogenesis in the rumen), red seaweed or algae extracts, ionophore antibiotics, phytochemicals (e.g., condensed tannins and essential oils), and other nutritional manipulations. The proposed net-zero concept might not solve the global warming problem because it will only balance future anthropogenic GHG emissions with anthropogenic removals, leaving global warming on a standby state. Recommendations for consuming red meat products should consider human nutrition, health, and disease and remain independent of controversial evidence of causational relationships with perceived negative environmental impacts of beef production that are not based on scientific data.

Effects of incremental increases in grass silage proportions from different harvest years on methane emissions, urinary nitrogen losses, and protein and energy utilisation in dairy cows

Dairy cows, methane and global warming have become publicly related terms. However, appropriate dairy cow management may in fact be part of the climate solution when viewed as part of the biogenic carbon cycle. Accordingly, governments and consumers are encouraging more sustainable, locally produced, climate friendly dairy production that often includes grassland-based feeding. However, this system is presumed to result in greater methane emissions compared to corn silage- or concentrate-based diets. An increase in urine nitrogen, associated with increased ammonia and nitrous oxide emission potential, questions the environmental usefulness of this strategy pertaining to global warming. This study is the first to compare the effects of incremental increases of grass silage proportion on enteric methane production as well as N and energy losses in dairy cows. Twenty-four mid- to end-lactation dairy cows were each fed one of 24 different diets, from two different harvest years, gradually increasing in grassland-based feeds (grass silage and hay) from about 500 to 1000 g/kg and concomitantly decreasing in corn silage. Each cow underwent a 7-day total collection period and was housed for 48 h in respiration chambers. Incremental data were subjected to an approved parametric regression analysis approach. The dietary increase in grassland-based feeds did not impair milk yield, N and energy utilisation. Simplified regression equations revealed that, contrary to current assumptions, there was a decline in methane production from 373 to 303 g/day when increasing grassland-based feeds from 500 to 1000 g/kg diet, and there was a trend for a decline in emission intensity from 20.6 to 17.6 g/kg of energy-corrected milk. However, urine nitrogen emissions clearly increased even when related to nitrogen intake; the latter from 260 to 364 g/kg when increasing grassland-based feeds from 500 to 1000 g/kg. Methane and urine nitrogen emissions were not affected by year of harvest.

Bioprospecting essential oils of exotic species as potential mitigations of ruminant enteric methanogenesis

The inclusion of essential oils (EOs) in the diet of ruminants is one of the strategies used to alter ruminal microbial fermentation, improving feed efficiency, while simultaneously reducing enteric methane (CH4) production. This study aimed to evaluate the effects of three new EOs from plants exotic to the Azores, Pittosporum undulatum (PU), Hedychium gardnerianum (HG), and Cryptomeria japonica (CJ), on biogas production kinetics and in vitro CH4 production. Three levels of EOs (40, 80, and 120 μL/g dry matter (DM) were added to the basal diet to evaluate ruminal fermentation using the in vitro gas production technique. Added 800 mL of rumen inoculum with 5 g DM of the basal diet (BD) to all experimental units for 96 h, except for the blanks, to which only the inoculum was added. The total gas and CH4 produced by treatment incubation were recorded every hour after incubation until 96 h. The results showed that the gas production decreased significantly (P < 0.001) at 24 and 96 h after incubation, in the medium and high levels, with the essential oils PU, CJ, and HG treatment, when compared to the control treatment. The same significant differences (P < 0.001) were observed in in vitro CH4 production. The greatest reduction was noted with the addition of PUEO at the highest concentration (120 μL), which allowed a reduction in CH4 production at 24 h of 47% (P < 0.01). There was an interaction effect between EOs and concentration levels for all variables (P < 0.001). A decrease in total volatile fat acid (VFA) concentration (P < 0.05) was recorded compared to control, as well as the insoluble fraction and the potential degradation of the BD when EOs were included in the diet. In conclusion, the addition of EOs to the BD effectively reduced total enteric gas emissions and mitigated CH4 production. The most significant reduction of CH4 (47% in 24 h of incubation) occurs when 120 μL PUEO is added to each gram DM. The inclusion of OEs in the BD also affected the gas production kinetics and fermentation parameters.

Effect of brown and green seaweeds on diet digestibility, ruminal fermentation patterns and enteric methane emissions using the rumen simulation technique

Inclusion of the red seaweed Asparagopsis taxiformis as a feed additive, has led to significant reductions in methane (CH4) production from ruminants. However, dietary supplementation with this seaweed is negatively associated with health and environmental concerns mainly due to its bromoform content, a compound with potential carcinogenic properties. Thus, there is renewed focus on ascertaining the anti-methanogenic potential of locally grown brown and green seaweeds, which typically do not contain bromoform. The objective of this study was to investigate the effects of selected brown and green seaweeds on diet digestibility, ruminal fermentation patterns, total gas (TGP) and CH4 production in vitro, using the rumen simulation technique system. In experiment 1, Pelvetia canaliculata (PEC) was examined. In experiment 2, Cystoseira tamariscifolia (CYT), Bifurcaria bifurcata (BIB), Fucus vesiculosus (FUV), Himanthalia elongata (HIM) and Ulva intestinalis (ULI) were analysed. Ascophyllum nodosum (ASC) was included in both experiments. A diet containing A. taxiformis (ASP1; ASP2) and an unsupplemented diet (CON) were included as positive and negative controls, respectively in both experiments. All seaweeds were included at a rate of 10 g/kg dry matter (DM) into a control diet of 50:50 (w:w) forage:concentrate. The seven brown and green seaweeds assessed failed to affect absolute CH4 emissions or alter fermentation patterns. In experiment 1, seaweed treatment had no effect on diet digestibility, CH4%, CH4 mmol/d or CH4 L/d (P&gt;0.1), however ASP1 reduced CH4 mmol/g DOM by 49% (P&lt;0.01) relative to the control. Both ASC and ASP1 tended to increase TGP (P&lt;0.1) relative to the control. In addition to this, the inclusion of seaweed in experiment 1 reduced the production of NH3-N (P&lt;.0001) compared to the control. In experiment 2, seaweed treatment had no effect on diet digestibility or TGP. Both ASP2 and FUV reduced CH4% (P&lt;0.01) but only ASP2 significantly reduced CH4 mmol/d, CH4 L/d and CH4 mmol/g DOM (P&lt;0.05). Daily mMol butyrate was reduced by ASP2 relative to the control and most other seaweeds (P&lt;.0001). In both experiment 1 and 2, seaweed inclusion had no effect on daily total VFA, acetate or propionate production or the acetate:propionate ratio relative to the control. To conclude, including the bromoform-free brown and green seaweeds at 10g/kg DM has no negative effects on diet digestibility or fermentation patterns but also failed to reduce the production of enteric CH4in vitro.

Provision of High-Quality Molasses Blocks to Improve Productivity and Address Greenhouse Gas Emissions from Smallholder Cattle and Buffalo: Studies from Lao PDR

Large ruminant production in developing countries is inefficient with low growth rates and likely high greenhouse gas emissions per unit of meat or milk produced. Trials conducted in Lao PDR from 2017 to 2020, studied ad libitum supplementation for 12 weeks with 20 kg high-quality molasses nutrient blocks (Four Seasons Pty Ltd., Brisbane, Australia), that were either non-medicated; fenbendazole-medicated (Panacur100®, Coopers Australia, 5 g/kg); triclabendazole-medicated (Fasinex®, Novartis Australia, 5 g/kg or 10 g/kg, respectively); or formulated with urea (8% or 10% urea, respectively). Average daily gains were determined for access to all molasses blocks and compared with access to control blocks, no supplementation, or previously determined free-grazing baseline average daily gains (55−84 g in cattle; 92−106 g in buffalo). Productivity was significantly improved following access to all molasses blocks. Average daily gains following access to 8% urea and control blocks were calculated for three age cohorts of cattle: young calves <8 m (238−298 g), growing cattle (143−214 g) and lactating cows (179−191 g). Modelling using IPCC Inventory software model V 2.69 of published data demonstrated a conservative net abatement of 350 kg CO2e was achievable over a 200-day feeding period. An additional trial of Emissions control blocks (n = 200) distributed to farmers (n = 60) and two educational institutions were conducted. Consumption rates (156 g/day) and farmer and institutional acceptance of these blocks were similar to our published findings with other molasses blocks, confirming all formulations of blocks improved animal productivity and body condition score, with healthier animals that were easier to manage. Modelling of changes in greenhouse gas emissions intensity identified an abatement of 470 kg CO2e per Emissions control blocks consumed, delivering a total project emissions abatement of 94 t CO2e. Provision of high-quality molasses blocks significantly improved smallholder large ruminant productivity and addition of greenhouse gas reducing agents is likely to achieve impressive abatement of greenhouse gas emissions due to improved efficiency of rumen fermentation and productivity.

Red seaweed extracts reduce methane production by altering rumen fermentation and microbial composition in vitro

A series of in vitro batch culture incubations were carried out to investigate changes in rumen fermentation characteristics, methane (CH4) production, and microbial composition in response to supplementation with five different red seaweed species (Amphiroa anceps, AANC; Asparagopsis taxiformis, ATAX; Chondracanthus tenellus, CTEN; Grateloupia elliptica, GELL; and Gracilaria parvispora, GPAR). Prior to the incubations, the total flavonoid and polyphenol content of the red seaweed extracts was quantified. The incubated substrate consisted of timothy hay and corn grain [60:40 dry matter (DM) basis]. Treatments were substrate mixtures without seaweed extract (CON) or substrate mixtures supplemented with 0.25 mg/mL of red seaweed extract. Samples were incubated for 6, 12, 24, 36, and 48 h. Each sample was incubated in triplicates in three separate runs. In vitro DM degradability, fermentation parameters (i.e., pH, volatile fatty acids, and ammonia nitrogen), total gas production, and CH4 production were analyzed for all time points. Microbial composition was analyzed using 16S rRNA amplicon sequencing after 24 h of incubation. The highest CH4 reduction (mL/g DM, mL/g digested DM, and % of total gas production) was observed in ATAX (51.3, 50.1, and 51.5%, respectively, compared to CON; P &lt; 0.001) after 12 h of incubation. The other red seaweed extracts reduced the CH4 production (mL/g DM; P &lt; 0.001) in the range of 4.6–35.0% compared to CON after 24 h of incubation. After 24 h of incubation, supplementation with red seaweed extracts tended to increase the molar proportion of propionate (P = 0.057) and decreased the acetate to propionate ratio (P = 0.033) compared to the CON. Abundances of the genus Methanobrevibacter and total methanogens were reduced (P = 0.050 and P = 0.016) by red seaweed extract supplementation. The linear discriminant analysis effect size (P &lt; 0.05, LDA ≥ 2.0) showed that UG Succinivibrionaceae, Anaeroplasma, and UG Ruminococcaceae, which are associated with higher propionate production, starch degradation, and amylase activity were relatively more abundant in red seaweed extracts than in the CON. Our results suggest that supplementation with red seaweed extracts altered the microbiota, leading to the acceleration of propionate production and reduction in CH4 production.