Wilmer Cuervo

CH₄ emissions from cattle are a major contributor of greenhouse gases in the world. Finding additives to mitigate CH₄ production is essential to achieve sustainable livestock operations. MgO may reduce carbon dioxide (CO₂) production under anaerobic conditions and, theoretically, can decrease CH₄ synthesis. To evaluate the effects of MgO on CH₄ production and dry matter digestibility (DMD) using an in vitro ruminant model, two experiments were conducted. The first experiment evaluated the combined effect of replacing sodium bicarbonate (NaHCO₃) with MgO and of CO₂ flushing (as a C source) on CH₄ production and fermentation parameters. The second experiment evaluated the addition of three MgO sources (A, B, and C at 50 mg/g of DM) to one of three substrates (100% corn, 50:50 corn/forage, or 100% forage) in three independent incubations. In both experiments, CH₄ concentration and production, gas production, pH, and DMD were individually determined in each bottle per incubation. Data for Experiment 1 were analyzed under a completely randomized design with a 2 × 2 factorial arrangement; for Experiment 2, data were analyzed using the MIXED procedure from SAS following a randomized complete block design with a 3 × 4 factorial arrangement. In Experiment 1, replacing NaHCO₃ with MgO reduced gas production and CH₄ concentration while increasing pH. In contrast, CO₂ flushing increased CH₄ concentration and decreased pH. In Experiment 2, increasing forage inclusion reduced CH₄ production and gas production, which is potentially associated with the reduced DMD in forage. Supplementation of MgO at 50 mg/g of DM reduced gas production and CH₄ yield without significantly affecting DMD. Source A reduced CH₄ production per gram of incubated dry matter by 44.6% relative to the non-supplemented control and reduced CH₄ yield per gram of DMD. Overall, MgO modified fermentation responses and reduced in vitro CH₄ production without significantly affecting DMD. Source A seemed to mediate an aggressive CH₄ yield reduction in forage-based substrate. Despite these promising results, further studies measuring fermentation products and evaluating animal responses are needed to clarify the mechanisms and practical applications of MgO addition in cattle diets.

(1) Background: Beef cattle production is essential for Montana’s economy. These operations rely on fibrous diets promoting enteric methane (CH₄) emissions, resulting in dietary energy inefficiency and environmental impacts. Concurrently, noxious weeds invade approximately 10% of state rangeland. Yet, some species produce plant secondary metabolites (PSMs) that could be repurposed for CH₄ mitigation strategies. (2) Methods: This study evaluated seven invasive weeds from South-Central Montana using in vitro incubations with ruminal fluid from cannulated Angus Cows (590 ± 18 kg). Experiment 1 screened whole plants added at 20% of incubated dry matter (IDM) against a control (hay), then, experiment 2 evaluated ethanolic extracts from leaves and inflorescences from top candidates identified in experiment 1. (3) Results: In the screening phase, common burdock (BURD) and Curly dock (DOCK) modified fermentation dynamics. BURD leaf extract achieved a 25.2% reduction in CH₄ yield (mL/g fermented organic matter) without compromising in vitro organic matter digestibility (IVOMD) or ammonia (NH₃-N). Conversely, DOCK extracts demonstrated the strongest CH₄ volume reduction but at the cost of a dramatic reduction in IVOMD and NH₃-N depletion. Bioactivity of PSM remained consistent across anatomical structures. (4) Conclusions: Specific weeds (BURD, DOCK) represent a biochemical repository with potential as a feed additive for roughage-based diets. Leaves from BURD exhibited optimal potential to mitigate CH₄ emission without impairing diet digestibility.

Enteric methane emissions (EMEs) from grazing dairy systems in tropical regions remain poorly quantified, increasing uncertainty in national greenhouse gas inventories. This study aimed to quantify EMEs using electronic spirometry masks (ESMs) in dairy cows in the Colombian high tropics during two precipitation seasons in two adjacent milk production management systems. Six cows of a high-milk-yield management system (HMYMS; >30 L/d) and six cows of a low-milk-yield management system (LMYMS; Cenchrus clandestinus) and supplemented with concentrate feed were monitored by EMEs, exhaled air volume, feed intake, milk yield and composition. Data were analyzed in a 2 × 2 factorial arrangement (season × production system). Season affected kikuyu chemical composition (p < 0.05) but not dry matter intake (DMI), milk production, quality, nor EMEs (p > 0.05). However, the absence of seasonal effects on these variables may be due to the sample size. Although HMY cows had a higher DMI (kg DM/d; p < 0.01) and EME (g/d, L/d; p < 0.05), they exhibited a lower methane intensity (both, L/L milk yield and L/kg fat-corrected milk) and gross energy intake lost as methane (p < 0.05). Positive correlations were found between EMEs and total dry matter intake (r = 0.638) and milk production (r = 0.726). The observed methane yield was comparable to previous studies for tropical kikuyu-based systems but lower than reports from temperate regions, suggesting seasonal-driven kikuyu quality does not translate into EME changes in high tropic regions. Animal productivity level was a key driver of EME magnitude and efficiency.

Enteric methane emissions (EME) from grazing dairy systems in tropical regions remain poorly quantified, increasing uncertainty in national greenhouse gas inventories. This study aimed to quantify EME using electronic spirometry masks (ESM) in dairy cows in Colombian high tropics during two precipitation seasons. Six high milk yield (HMY; >30 L/d) and six low milk yield (LMY; Cenchrus clandestinus) and supplement with concentrate feed were monitored by EME, exhaled air volume, feed intake, milk yield and composition. Data was analyzed in a 2 × 2 factorial arrangement (season × production level). Season affected Kikuyu chemical composition (P< 0.05) but not dry matter intake (DMI), milk production, quality, nor EME (P > 0.05). Despite HMY cows having a greater DMI (kg DM/d; P < 0.01) and EME (g/d, L/d; P < 0.05) exhibited lower methane intensity (g / kg fat-corrected milk) and gross energy intake lost as methane (P < 0.05). Positive correlations were found between EME and total dry matter intake (r = 0.638) and milk production (r = 0.726). The observed methane yield was comparable to previous studies for tropical kikuyu-based systems but lower than reports from temperate regions, suggesting seasonal-driven kikuyu quality does not translate into EME changes in high tropic regions. Animal productivity level was a key driver of EME magnitude and efficiency, effectively measured by ESM which may represent a practical tool for narrowing EME estimates for tropical pasture-based dairy systems.

Residual feed intake (RFI) is a measure of feed efficiency (FE) independent of growth and body weight (BW), calculated as the difference between actual and expected feed intake (FI) based on mean metabolic weight (MW) and weight gain. We hypothesized that bulls with contrasting RFI differ in plasma concentration of different compounds. RFI was evaluated in 302 bulls from 3 different ranches. After adaptation, bulls consumed the same diet for 56 d, individual FI was daily recorded, BW was measured every 2 weeks, and blood samples were taken at d 0 and 56. The bulls were ranked as low RFI (LRFI) and high RFI (HRFI), and the top and bottom 30 were used for metabolomic, hormone, and isotope analysis. Multivariate and pathway analysis were conducted with MetaboAnalyst, and univariate analysis was conducted with SAS using Mixed procedures. Additionally, for Biomarker analysis, Receiver Operating Characteristic (ROC) curves were constructed with MetaboAnalyst. Sparse Partial Least Squares–Discriminant Analysis (sPLSDA) showed partial cluster separation evidenced by acceptable R² values. The model showed poor predictive power, reflected by low Q² values. For LRFI animals (more feed efficient), the most abundant metabolites (P = 0.05) at d 0 were Cer(d18:1/24:1), TG(20:2_32:1), SM (OH) C22:1, SM (OH) C22:2, SM C24:0, TG(20:2_34:3), GCA, Choline, TG(20:2_34:4), and Hex2Cer(d18:1/14:0), while at d 56 were Cer(d18:1/18:0), Cer(d18:1/23:0), TG(14:0_34:2), C16:2, HexCer(d18:1/20:0), C16:1, lysoPCaC16:0, TG(18:3_38:5), C9, SM C24:1, SM C16:0, Carnosine, Cer(d18:2/12:0), SM C18:0, and Cer(d18:1/24:0). Primary bile acid biosynthesis pathway was enriched at d 0 (P = 0.008) and sphingomyelin metabolism at d 56 in LRFI (P = 0.041). Compounds that were identified as variable importance of projection (VIP) and were also statistically different in the univariate analysis, were used to construct ROC curves to identify their potential as biomarker for RFI. With an Area Under the Curve (AUC) value > 0.7 and p-value < 0.05 as the criteria for diagnostic potential, choline was identified as biomarker of RFI at d 0, and Cer(d18:1/23:0) and TG(18:1_30:0) were identified as biomarkers of RFI at d 56. Although multivariate model showed a poor predictive value, further exploration of individual metabolites could provide insights into the mechanisms contributing to FE differences. Feed efficiency is an important trait in cattle production because it influences the amount of feed required to achieve growth and therefore impacts both production costs and environmental sustainability. One way to measure feed efficiency is through residual feed intake (RFI), which compares an animal’s actual feed intake to what would be expected for its body size and growth. Animals with low RFI are considered more efficient because they eat less food than expected while maintaining growth. In this study, we evaluated 302 young bulls to identify blood compounds linked to differences in feed efficiency. The most efficient and least efficient animals were compared for a wide range of blood metabolites and hormones. Our results showed that efficient and inefficient bulls had different patterns of certain blood compounds, especially those related to lipid metabolism and bile acid production. We also identified a few specific compounds, including choline and some types of fats, which may serve as biomarkers to predict feed efficiency. While the overall predictive models were limited, these findings highlight the potential to use blood tests to better understand and eventually improve cattle feed efficiency.

Direct-fed microbials (DFM) have been used to improve livestock production efficiency and reduce environmental impact. Spore-forming bacteria such as Bacillus spp. present handling and processing advantages for use as a DFM; however, more information is needed about their effects in beef cattle. The objective of this study was to evaluate the effect of a DFM composed of a mixture of B. subtilis and B. licheniformis on growth performance, nutrient utilization, enteric methane (CH4) emissions, microbiome of ruminal fluid and feces, and metabolome of plasma and ruminal fluid. Angus crossbred heifers (n = 108; 318 ± 40 kg of body weight) were used in a generalized randomized block design. Heifers were fed a sorghum silage-based diet containing the following treatments: 1) control (CTL, no additive), or 2) Bacillus-based DFM (BOV, 310 mg/kg of diet dry matter [DM]), to provide an average of 3 g/animal/d. No effect of treatment (P > 0.05) was observed for DM intake, average daily gain, or gain-to-feed ratio. The DFM inclusion did not affect (P > 0.05) the apparent total tract digestibility of nutrients or CH4 emissions. Alpha and beta diversity of fecal and ruminal microbiome did not differ with supplementation (P > 0.05). Multivariate analysis indicated minimal impact of the DFM on ruminal and plasma metabolomes. In ruminal fluid, supplementation with the DFM reduced the abundance of three metabolites after false discovery rate (FDR) correction (FDR < 0.05), and pathway analysis indicated that the ubiquinone biosynthesis pathway was enriched by DFM supplementation (P ≤ 0.05). In plasma, two metabolites were differentially abundant between treatments, with proline being more abundant and serine less abundant in heifers supplemented with the DFM than in control heifers (P ≤ 0.05). In summary, supplementation with a Bacillus-based DFM did not affect growth performance, efficiency of feed utilization, nutrient digestibility, or CH4 emissions in beef heifers under the experimental conditions of this trial. Minimal changes were observed in the ruminal and fecal microbiomes and the ruminal and plasma metabolomes, suggesting a limited microbial or systemic impact. Further research is needed to clarify the conditions and mechanisms by which Bacillus-based DFM may exert beneficial effects in beef cattle.

Ruminal methanogenesis represents considerable energy loss within the fermentative processes mediated by microbial populations, by means of which up to 12% of gross energy intake is driven away from microbial protein synthesis (MPS). This review explores the relationship between methane (CH₄) synthesis and emission with MPS in beef cattle, focusing on the nutritional, biochemical, and microbial factors modulating these processes. The synthesis of CH₄ by ruminal archaea is essential for maintaining redox balance during the fermentation of carbohydrates. This process diverts metabolic H₂ from energy-efficient pathways like propionate synthesis, which could otherwise enhance microbial growth. Dietary factors, including carbohydrate fermentability, N synchronization, and passage rate, modulate MPS. Diets based on roughage might enhance CH₄ synthesis while impairing MPS efficiency by reducing diet digestibility and promoting microbial shifts towards methanogenic populations. Potential mitigation strategies, including plant secondary metabolites, CH₄ inhibitors, and controlled forage-to-concentrate ratios, demonstrate the potential to reduce CH₄ emissions while enhancing nutrient utilization. This review underscores the need for integrated approaches combining dietary strategies, advanced feed additives, and improved prediction models to optimize ruminal fermentation, enhance MPS, and reduce the environmental footprint of beef cattle systems.

Global beef demand will rise by 40 million tons in 30 years, increasing methane (CH₄) emissions. Pigweed (Amaranthus spinosus), an invasive weed abundant in southeastern U.S. pastures, may mitigate CH₄. Yet, its potential as a feed additive remains unexplored. The aim of this study was to evaluate the influence of pigweed and its extracts on ruminal fermentation and CH₄ production. For Exp 1, ruminal fluid from three American Aberdeen steers was incubated with 0, 2.5%, 5%, or 10% of diet dry matter (DM) of roots, stems, leaves, seeds, or the whole pigweed plant (WHO). In Exp 2, extracts from the leaves and WHO were incubated under the same conditions. For the first experiment, 2.5% of the roots, 5% of the leaves, and 10% of the WHO decreased acetate and butyrate concentrations (p < 0.01). In contrast, the WHO, leaves, and seeds at 2.5% of DM increased propionate concentration (p = 0.05). Increasing levels of WHO, leaves, and seeds quadratically reduced CH₄ (p < 0.001). The addition of 2.5 and 5% of leaves and WHO reduced in vitro CH4 production per gr of organic matter fermented (p < 0.01). In Exp 2, based on their CH₄ mitigation, the leaves and WHO were extracted, and their phenol (3.2 and 1.1 mg/g of DM, respectively) and flavonoid (19.7 and 1.9 mg/g of DM, respectively) contents were determined. Extracts from WHO (2.5%) decreased acetate and CH₄ (p < 0.05), while 5% inclusion decreased gas production and increased ruminal pH (p < 0.03). Leaf extracts (2.5%) increased propionate and reduced acetate: propionate (p < 0.05). The leaves and WHO extracts did not affect IVOMD at either inclusion level (p > 0.4). Extracts at 5% from WHO were more effective than that from leaves in reducing CH₄ (27% vs. 4%). The evidence suggests that the inclusion of 2.5 to 5% of WHO extracts shifts ruminal fermentation towards propionate-producing impairing methanogenesis, representing a sustainable strategy to mitigate CH₄. This hypothesis must be further assessed under in vivo supplementation of the extracts to beef cattle.

Supplementation of low-protein diets with non-protein nitrogen (NPN) increases ruminal degradable protein and improves rumen fermentation and microbial growth. The objective of this experiment was to evaluate the effect of supplementing urea-biuret (UB) and urea-biuret-nitrate (UBN) mixtures relative to urea (U) on rumen fermentation and microbial N outflow in growing steers. Twelve American Aberdeen steers were used in a replicated and balanced 3 × 3 Latin square design (LSD) with 3 periods of 35 d each. Steers were housed in pens and consumed a corn silage-based diet. Steers were stratified by body weight and randomly allocated to 1 of the 3 NPN supplementation treatments. Treatments were supplementation with U, UB, and UBN, adjusted to the amount of N provided by U when included at 1% of the diet on a dry matter (DM) basis. Intake and feeding behavior were individually recorded throughout the experiment. In each period, steers were adapted to increasing levels of NPN during the first 8 days. From days 19 to 23, feed and fecal samples were collected to assess nutrient digestibility. Samples of blood, rumen contents, and omasal digesta were collected on days 20 to 23. On day 24, rumen evacuation was performed, and subsequently steers were dosed with Co-EDTA and YbCl3 to determine the passage rate of digesta flow. Rumen fluid collection was conducted on days 24 and 25. Steers did not receive NPN supplementation from days 26 to 35 during the washout period. Microbial N flow was estimated for each animal within periods. Intake, digestibility, digesta flow, and microbial N flow were analyzed using a 3 × 3 LSD, while blood and rumen fermentation parameters were analyzed using a 3 × 3 LSD with repeated measures. Steers supplemented with UB tended (P < 0.07) to consume more DM and organic matter (OM) than those supplemented with UBN; however, animals supplemented with UBN tended (P = 0.051) to digest more acid detergent fiber in the total tract. Steers supplemented with U and UB showed greater (P < 0.05) DM and OM flow throughout the omasum than those with UBN. Microbial N flow, microbial efficiency, and the concentration of total volatile fatty acids were not different (P > 0.10) among NPN-supplemented treatments. Steers supplemented with UBN showed lesser (P < 0.05) concentration of ammonia than those with U and UB. In conclusion, novel NPN mixtures have the potential to modify ruminal fermentation without affecting microbial protein outflow.

By 2050, the U.S. beef industry must produce an extra 40 million tons of beef to satisfy the global demand. Such an increase in inventory will undoubtedly enhance methane (CH₄) production from livestock, which should be reduced by over 20%. The addition of plant secondary metabolites, such as anacardic acid present in cashew nutshell extract (CNSE), has shown promising results in reducing CH₄ yield, although its effects seemed to be diet dependent. This study evaluated the addition of CNSE to a high-grain diet (85:15 Grain: forage) on in vivo CH₄ emissions, nutrients digestibility, performance, feeding behavior, and ruminal fermentation parameters of beef steers. Sixteen Angus crossbred steers [599 ± 40 kg of bodyweight (BW)] and six ruminally cannulated crossbred steers (490 ± 51 kg of BW) were utilized in a crossover design with 2 experimental periods of 56 d each, composed by 14 d of adaptation, 35 d of measurement, and 7 d of washout. Following adaptation, steers were sorted by BW, and assigned to receive no additive (CON) or CNSE at 5 g/steer/d. Data were analyzed using the MIXED procedure of SAS. Inclusion of CNSE increased (P < 0.05) propionate concentration and molar proportion (MP; mol/100 mol), tended to decrease acetate MP (P = 0.10), reduced the acetate: propionate (A:P) ratio (P = 0.05), and MP of branched chain volatile fatty acids (P < 0.01). Neither in vitro organic matter digestibility nor in vitro CH₄ yield were affected by CNSE inclusion (P > 0.05). Steers receiving CNSE exhibited greater (P < 0.05) final BW, dry matter intake (DMI), and average daily gain (ADG) but lesser (P < 0.05) in vivo CH₄ emission rate (g/d), yield (g/kg of DMI), and intensity (g/kg of ADG). Meal length, bunk visit duration, and apparent total tract digestibility of DM increased (P < 0.05) after CNSE addition. Considering CNSE-supplemented steers spent more time in the feedbunk and exhibited higher DMI, CH₄ mitigation was unlikely associated with intake reduction. The addition of CNSE to a high-grain diet in beef steers demonstrated significant improvements in animal performance and reduced CH₄ emissions, as the result of shifts in ruminal fermentation patterns, favoring propionate instead acetate concentration, leading to a reduction in the A:P ratio. CNSE shows promise as a strategy to enhance beef industry sustainability.