Greenhouse gas, animal performance, and bacterial population structure responses to dietary monensin fed to dairy cows

Effects of monensin supplementation on rumen fermentation, methane emissions, nitrogen balance, and metabolic responses of dairy cows: A systematic review and dose-response meta-analysis

To investigate the effects of supplemental monensin administration on the metabolic responses of dairy cows, a systematic review and dose-response meta-analysis were conducted. Initially, 604 studies were identified through comprehensive database searches, including Google Scholar, Scopus, Science Direct, and PubMed, using key words related to dairy cows, monensin, and metabolic outcomes. After a 2-stage screening process, 51 articles with a total of 60 experiments were selected for meta-analysis based on criteria such as study implementation date between 2001 and 2022, presence of a control group that did not receive monensin supplementation, reporting of at least 1 outcome variable, and presentation of means and corresponding errors. The meta-analysis used the 1-stage random-effects method, and sensitivity analyses were performed to assess the robustness of the results. The results showed that the administration of monensin at a dosage of 19 to 26 mg/kg was inversely related to methane emissions and that the administration of monensin at a dosage of 18 to 50 mg/kg resulted in a significant decrease in dry matter intake. Administration of monensin at doses of 13 to 28 and 15 to 24 mg/kg also resulted in a significant decrease in ruminal acetate proportion and an increase in propionate proportion, respectively, with no effects on ruminal butyrate, NH3, or pH levels. We found no effects on blood parameters or nitrogen retention, but a significant negative correlation was observed between monensin supplementation and fecal nitrogen excretion. Based on the analysis of all variables evaluated, the optimal dose range of monensin was estimated to be 19 to 24 mg/kg.

Enteric Methane Emissions Prediction in Dairy Cattle and Effects of Monensin on Methane Emissions: A Meta-Analysis

Greenhouse gas emissions, such as enteric methane (CH₄) from ruminant livestock, have been linked to global warming. Thus, easily applicable CH₄ management strategies, including the inclusion of dietary additives, should be in place. The objectives of the current study were to: (i) compile a database of animal records that supplemented monensin and investigate the effect of monensin on CH₄ emissions; (ii) identify the principal dietary, animal, and lactation performance input variables that predict enteric CH₄ production (g/d) and yield (g/kg of dry matter intake DMI); (iii) develop empirical models that predict CH₄ production and yield in dairy cattle; and (iv) evaluate the newly developed models and published models in the literature. A significant reduction in CH₄ production and yield of 5.4% and 4.0%, respectively, was found with a monensin supplementation of ≤24 mg/kg DM. However, no robust models were developed from the monensin database because of inadequate observations under the current paper's inclusion/exclusion criteria. Thus, further long-term in vivo studies of monensin supplementation at ≤24 mg/kg DMI in dairy cattle on CH₄ emissions specifically beyond 21 days of feeding are reported to ensure the monensin effects on the enteric CH₄ are needed. In order to explore CH₄ predictions independent of monensin, additional studies were added to the database. Subsequently, dairy cattle CH₄ production prediction models were developed using a database generated from 18 in vivo studies, which included 61 treatment means from the combined data of lactating and non-lactating cows (COM) with a subset of 48 treatment means for lactating cows (LAC database). A leave-one-out cross-validation of the derived models showed that a DMI-only predictor model had a similar root mean square prediction error as a percentage of the mean observed value (RMSPE, %) on the COM and LAC database of 14.7 and 14.1%, respectively, and it was the key predictor of CH₄ production. All databases observed an improvement in prediction abilities in CH₄ production with DMI in the models along with dietary forage proportion inclusion and the quadratic term of dietary forage proportion. For the COM database, the CH₄ yield was best predicted by the dietary forage proportion only, while the LAC database was for dietary forage proportion, milk fat, and protein yields. The best newly developed models showed improved predictions of CH₄ emission compared to other published equations. Our results indicate that the inclusion of dietary composition along with DMI can provide an improved CH₄ production prediction in dairy cattle.

Effects of monensin supplementation on lactation performance of dairy cows: a systematic review and dose-response meta‑analysis

The aim of this study was to conduct a comprehensive review with meta-analysis to determine the effects of the dose-response relationship between monensin supplementation and dairy cow performance and milk composition. Results from 566 full-text articles and 48 articles with 52 studies were meta-analyzed for pooled estimates. Monensin supplementation up to 23 ppm increased milk production, with the optimal dose being 12.6 ppm. Monensin supplementation at doses ranging from 16 to 96 ppm increased milk production in the prepartum phase (- 28 to 0 day relative to calving). From 60 to 150 DIM, monensin supplementation up to 21 ppm had a significant positive effect on this outcome, while supplementation in the 37 to 96 ppm range caused a decrease in this variable. At 0 to 60 and > 150 DIM, monensin supplementation had no effect on milk yield. At dosages of 22 to 96 ppm, 12 to 36 ppm, and below 58 ppm and 35 ppm, respectively, monensin supplementation resulted in significant decreases in dry matter intake (DMI), milk protein percentage, milk fat percentage, and milk fat yield. Overall, based on the results of this meta-analysis and considering all variables, the recommended optimal dose of monensin could be about 16 ppm.

Dosage-dependent effects of monensin on the rumen microbiota of lactating dairy cattle

We examined the dose-dependent effects of feeding lactating dairy cows a standard diet supplemented with monensin at 175, 368, or 518 mg cow^-1 day^-1 on the rumen microbiota. For each dosage, 3 animals were randomly assigned into groups and fed the same basal total mixed ration diet supplemented with monensin, at the respective dose. After 20 days, rumen samples were taken and the effect on the microbiota was examined by 16S rRNA gene sequence analysis and qPCR. At the lowest dose no significant change in 16S rRNA gene sequences associated with any bacterial phyla was observed; however, at the medium and high dosages, we observed significant reductions in sequences associated with gram-positive bacteria and significant increases in those associated with gram-negative bacteria that were dosage dependent. All dosages reduced the levels of sequences associated with methanogenic archaea in the rumen, with the medium dosage showing the largest decline. No significant difference was observed for the 18S rRNA gene sequences associated with protozoa in any of the libraries. Our results indicate that with this diet the medium dosage of monensin was most efficacious for the reduction in methanogenic archaea in the rumen of lactating dairy.

Response of surface GHG fluxes to long-term manure and inorganic fertilizer application in corn and soybean rotation

This study was conducted to investigate the impacts of dairy manure and inorganic fertilizer on soil surface greenhouse gases (GHG) [carbon dioxide (CO₂), nitrous oxide (N₂O) and methane (CH₄)] fluxes from soils managed under corn (Zea mays L.)-soybean (Glycine max L.) rotation. The experiment was established on a silty loam soil, and the treatments included three manure application rates [phosphorus based recommended rate (low manure, LM), nitrogen based recommended rate (medium manure, MM) and two times recommended nitrogen rate (high manure, HM)], two inorganic fertilizer levels [recommended fertilizer (medium fertilizer, MF) and high rate of fertilizer (HF)], and control (CK) replicated four times. Soil GHG fluxes were monitored once a week during the growing season for 2015 and 2016. Data from this study showed that there were not any significant impacts from manure and inorganic fertilizer applications on the annual CH₄ fluxes in 2015 and 2016. However, annual soil surface CO₂ fluxes were increased by manure treatments compared to inorganic fertilizer treatments in both the years. In contrast, manure treatments decreased N₂O fluxes, but significantly increased net GWP than the fertilizer treatments in 2016. In general, higher manure and fertilizer rates resulted in higher annual GHG emissions compared to lower manure and fertilizer rates in both years. Data from this study showed that HF application in crops can be detrimental for the environment by emitting higher GHG emissions, therefore, improved application strategies for manure and fertilizer management need to be explored to avoid any negative environmental impacts.

Dietary Nitrate for Methane Mitigation Leads to Nitrous Oxide Emissions from Dairy Cows

Nitrate supplements to cattle diets can reduce enteric CH emissions. However, if NO metabolism stimulates NO emissions, the effectiveness of dietary NO for CH mitigation will be reduced. We quantified NO emissions as part of a dairy cow feeding experiment in which urea was substituted in nearly iso-N diets with 0, 5, 14 or 21 g NO kg dry matter (DM). The feeding experiment was a Latin square with repetition of Period 1. Each period lasted 4 wk, with CH emission measurements in Week 4 using respiration chambers. During Period 3, NO concentrations in chamber outlet air were monitored semicontinuously during 48 h. High, but fluctuating, NO concentrations were seen at the two highest NO levels (up to between 2 and 5 μL L), and dynamics were linked with recent feed intake. In Periods 4 and 5, NO concentrations and feed intake were determined from all four respiration chambers during two 7-h periods. Emissions of NO coincided with feed intake, again with NO concentrations in the microliter per liter range at the two highest NO intake levels. Neither feed nor excretion of NO via urine were significant sources of NO, indicating that emissions came from the animals. Leakages due to rumen fistulation could also not account for NO emissions. The possibility that NO is produced in the oral cavity is discussed. Nitrous oxide emission factors ranged between 0.7 and 1.0% except in one case at 21 g NO kg DM, where it was 3.4%. When accounting for NO emissions at the highest NO intake level, the overall GHG mitigation effect in two different animal-diet combinations changed from -47 to -40%, and from -19 to -17%, respectively, due to NO emissions.

CH4 and N2O emissions from China's beef feedlots with ad libitum and restricted feeding in fall and spring seasons

Accurately quantifying methane (CH4) and nitrous oxide (N2O) emissions from beef operations in China is necessary to evaluate the contribution of beef cattle to greenhouse gas budgets at the national and global level. Methane and N2O emissions from two intensive beef feedlots in the North China Plain, one with a restricted feeding strategy and high manure collection frequency and the other with an ad libitum feeding strategy and low manure collection frequency, were quantified in the fall and spring seasons using an inverse dispersion technique. The diel pattern of CH4 from the beef feedlot with an ad libitum feed strategy (single peak during a day) differed from that under a restricted feeding condition (multiple peaks during a day), but little difference in the diel pattern of N2O emissions between two feeding strategies was observed. The two-season average CH4 emission rates of the two intensive feedlots were 230 and 198gCH4animal(-1)d(-1) and accounted for 6.7% and 6.8% of the gross energy intake, respectively, indicating little impact of the feeding strategy and manure collection frequency on the CH4 conversion factor at the feedlot level. However, the average N2O emission rates (21.2g N2Oanimal(-1)d(-1)) and conversion factor (8.5%) of the feedlot with low manure collection frequency were approximately 131% and 174% greater, respectively, than the feedlot under high frequency conditions, which had a N2O emission rate and conversion factor of 9.2g N2Oanimal(-1)d(-1) and 3.1%, respectively, indicating that increasing manure collection frequency played an important role in reducing N2O emissions from beef feedlots. In addition, comparison indicated that China's beef and dairy cattle in feedlots appeared to have similar CH4 conversion factors.

Methane oxidation and abundance of methane oxidizers in tropical agricultural soil (vertisol) in response to CuO and ZnO nanoparticles contamination

There is worldwide concern over the increase use of nanoparticles (NPs) and their ecotoxicological effect. It is not known if the annual production of tons of industrial nanoparticles (NPs) has the potential to impact terrestrial microbial communities, which are so necessary for ecosystem functioning. Here, we have examined the consequences of adding the NPs particularly the metal oxide (CuO, ZnO) on CH4 oxidation activity in vertisol and the abundance of heterotrophs, methane oxidizers, and ammonium oxidizers. Soil samples collected from the agricultural field located at Madhya Pradesh, India, were incubated with either CuO and ZnO NPs or ionic heavy metals (CuCl2, ZnCl2) separately at 0, 10, and 20 μg g(-1) soil. CH4 oxidation activity in the soil samples was estimated at 60 and 100 % moisture holding capacity (MHC) in order to link soil moisture regime with impact of NPs. NPs amended to soil were highly toxic for the microbial-mediated CH4 oxidation, compared with the ionic form. The trend of inhibition was Zn 20 > Zn 10 > Cu 20 > Cu 10. NPs delayed the lag phase of CH4 oxidation to a maximum of 4-fold and also decreased the apparent rate constant k up to 50 % over control. ANOVA and Pearson correlation analysis (α = 0.01) revealed significant impact of NPs on the CH4 oxidation activity and microbial abundance (p < 0.0001, and high F statistics). Principal component analysis (PCA) revealed that PC1 (metal concentration) rendered 76.06 % of the total variance, while 18.17 % of variance accounted by second component (MHC). Biplot indicated negative impact of NPs on CH4 oxidation and microbial abundance. Our result also confirmed that higher soil moisture regime alleviates toxicity of NPs and opens new avenues of research to manage ecotoxicity and environmental hazard of NPs.

Anti-methanogenic effects of monensin in dairy and beef cattle: a meta-analysis

Monensin is a widely used feed additive with the potential to minimize methane (CH4) emissions from cattle. Several studies have investigated the effects of monensin on CH4, but findings have been inconsistent. The objective of the present study was to conduct meta-analyses to quantitatively summarize the effect of monensin on CH4 production (g/d) and the percentage of dietary gross energy lost as CH4 (Ym) in dairy cows and beef steers. Data from 22 controlled studies were used. Heterogeneity of the monensin effects were estimated using random effect models. Due to significant heterogeneity (>68%) in both dairy and beef studies, the random effect models were then extended to mixed effect models by including fixed effects of DMI, dietary nutrient contents, monensin dose, and length of monensin treatment period. Monensin reduced Ym from 5.97 to 5.43% and diets with greater neutral detergent fiber contents (g/kg of dry matter) tended to enhance the monensin effect on CH4 in beef steers. When adjusted for the neutral detergent fiber effect, monensin supplementation [average 32 mg/kg of dry matter intake (DMI)] reduced CH4 emissions from beef steers by 19±4 g/d. Dietary ether extract content and DMI had a positive and a negative effect on monensin in dairy cows, respectively. When adjusted for these 2 effects in the final mixed-effect model, monensin feeding (average 21 mg/kg of DMI) was associated with a 6±3 g/d reduction in CH4 emissions in dairy cows. When analyzed across dairy and beef cattle studies, DMI or monensin dose (mg/kg of DMI) tended to decrease or increase the effect of monensin in reducing methane emissions, respectively. Methane mitigation effects of monensin in dairy cows (-12±6 g/d) and beef steers (-14±6 g/d) became similar when adjusted for the monensin dose differences between dairy cow and beef steer studies. When adjusted for DMI differences, monensin reduced Ym in dairy cows (-0.23±0.14) and beef steers (-0.33±0.16). Monensin treatment period length did not significantly modify the monensin effects in dairy cow or beef steer studies. Overall, monensin had stronger antimethanogenic effects in beef steers than dairy cows, but the effects in dairy cows could potentially be improved by dietary composition modifications and increasing the monensin dose.

Greenhouse gas and ammonia emissions from an open-freestall dairy in southern idaho

Concentrated dairy operations emit trace gases such as ammonia (NH), methane (CH), and nitrous oxide (NO) to the atmosphere. The implementation of air quality regulations in livestock-producing states increases the need for accurate on-farm determination of emission rates. Our objective was to determine the emission rates of NH, CH, and NO from the open-freestall and wastewater pond source areas on a commercial dairy in southern Idaho using a flush system with anaerobic digestion. Gas concentrations and wind statistics were measured and used with an inverse dispersion model to calculate emission rates. Average emissions per cow per day from the open-freestall source area were 0.08 kg NH, 0.41 kg CH, and 0.02 kg NO. Average emissions from the wastewater ponds (g m d) were 6.8 NH, 22 CH, and 0.2 NO. The combined emissions on a per cow per day basis from the open-freestall and wastewater pond areas averaged 0.20 kg NH and 0.75 kg CH. Combined NO emissions were not calculated due to limited available data. The wastewater ponds were the greatest source of total farm NH emissions (67%) in spring and summer. The emissions of CH were approximately equal from the two source areas in spring and summer. During the late fall and winter months, the open-freestall area constituted the greatest source area of NH and CH emissions. Data from this study can be used to develop trace gas emissions factors from open-freestall dairies in southern Idaho and other open-freestall production systems in similar climatic regions.

Gas emissions from dairy cows fed typical diets of Midwest, South, and West regions of the United States

Gas emissions were determined for dairy cows fed three diets formulated to represent feed ingredients typical of the Midwest, South, or West regions of the United States. Dairy cows were housed and monitored in 12 environmentally controlled rooms (4 cows diet). Two experiments were performed, representing two lactation stages (initial days in milk were 115 ± 39 d in Stage 1 and 216 ± 48 d in Stage 2). The results demonstrated that the combination of different dietary ingredients resulted in different gas emissions while maintaining similar dry matter intake (DMI) and milk yield (MY). Diet effect on ammonia (NH) emissions was more prominent in Stage 1. During Stage 1, cows fed the Midwest diet had the highest daily NH emission, corresponding to the highest crude protein (CP) concentration among the three regions. The differences in NH emissions (39.0%) were much larger than the percent difference in CP concentrations between diets (6.8%). Differences in N intake, N excretion, or milk urea N alone may not serve as a strong indicator of the potential to reduce NH emissions. Lower emissions of methane (CH) per unit DMI or per unit MY were observed for cows offered the South diet during Stage 1 as compared with that from cows offered the Midwest or West diets. No diet effect was observed for hydrogen sulfide (HS) emission per unit S intake, nor for nitrous oxide (NO) emission. The measured NH and CH emissions were comparable, but the NO emissions were much higher than those reported for tie-stall dairy barns in the literature.

Construction and Operation of a Ventilated Hood System for Measuring Greenhouse Gas and Volatile Organic Compound Emissions from Cattle

Simple Summary

We describe the construction and operation of a unique system for measuring gaseous emissions that arise from the rumen and metabolism of cattle. This system allows for the collection of high quality data that can be used to improve emission inventories at the regional and national level. Additionally, the system can be used to test various emission mitigation techniques.

Abstract

Recent interest in greenhouse gas emissions from ruminants, such as cattle, has spawned a need for affordable, precise, and accurate methods for the measurement of gaseous emissions arising from enteric fermentation. A new head hood system for cattle designed to capture and quantify emissions was recently developed at the University of California, Davis. The system consists of two head hoods, two vacuum pumps, and an instrumentation cabinet housing the required data collection equipment. This system has the capability of measuring carbon dioxide, methane, ethanol, methanol, water vapor, nitrous oxide, acetic acid emissions and oxygen consumption in real-time. A unique aspect of the hoods is the front, back, and sides are made of clear polycarbonate sheeting allowing the cattle a full range of vision during gas sampling. Recovery rates for these slightly negative pressure chambers were measured ranging from 97.6 to 99.3 percent. This system can capture high quality data for use in improving emission inventories and evaluating gaseous emission mitigation strategies.

Emissions of ammonia, methane, carbon dioxide, and nitrous oxide from dairy cattle housing and manure management systems

Concentrated animal feeding operations emit trace gases such as ammonia (NH₃), methane (CH₄), carbon dioxide (CO₂), and nitrous oxide (N₂O). The implementation of air quality regulations in livestock-producing states increases the need for accurate on-farm determination of emission rates. The objective of this study was to determine the emission rates of NH₃, CH₄, CO₂, and N₂O from three source areas (open lots, wastewater pond, compost) on a commercial dairy located in southern Idaho. Gas concentrations and wind statistics were measured each month and used with an inverse dispersion model to calculate emission rates. Average emissions per cow per day from the open lots were 0.13 kg NH₃, 0.49 kg CH₄, 28.1 kg CO₂, and 0.01 kg N₂O. Average emissions from the wastewater pond (g m(-2) d(-1)) were 2.0 g NH₃, 103 g CH₄, 637 g CO₂, and 0.49 g N₂O. Average emissions from the compost facility (g m(-2) d(-1)) were 1.6 g NH₃, 13.5 g CH₄, 516 g CO₂, and 0.90 g N₂O. The combined emissions of NH₃, CH₄, CO₂, and N₂O from the lots, wastewater pond and compost averaged 0.15, 1.4, 30.0, and 0.02 kg cow(-1) d(-1), respectively. The open lot areas generated the greatest emissions of NH₃, CO₂, and N₂O, contributing 78, 80, and 57%, respectively, to total farm emissions. Methane emissions were greatest from the lots in the spring (74% of total), after which the wastewater pond became the largest source of emissions (55% of total) for the remainder of the year. Data from this study can be used to develop trace gas emissions factors from open-lot dairies in southern Idaho and potentially other open-lot production systems in similar climatic regions.

Greenhouse gas and alcohol emissions from feedlot steers and calves

Livestock's contributions to climate change and smog-forming emissions are a growing public policy concern. This study quantifies greenhouse gas (GHG) and alcohol emissions from calves and feedlot steers. Carbon dioxide (CO) methane (CH), nitrous oxide (NO), ethanol (EtOH), and methanol (MeOH) were measured from a total of 45 Holstein and Angus steers and 9 Holstein calves representative of four different growth stages commonly present on calf ranches and commercial feedlots. Individuals from each animal type were randomly assigned to three equal replicate groups of nine animals per group. Steers were fed a high concentrate diet and calves a milk replacer and grain supplement. Cattle and calves were housed in groups of three animals in an environmental chamber for 24 h. The CO, NO, EtOH, and MeOH concentrations from the air inlet and outlet of the chamber were measured using an INNOVA 1412 monitor and CH using a TEI 55C methane analyzer. Emission rates (g head h) were calculated. The GHGs were mainly produced by enteric fermentation and respiration and differed across life stages of cattle. Compared with dairy cows, feedlot steers produce relatively less GHG. In general, ethanol and methanol, the most important volatile organic compound (VOC) group in the dairy sector, were below the lower limit of detection of the gas analyzer. The present data will be useful to verify models and to enhance GHG emission inventories for enteric fermentation, respiration, and fresh excreta for numerous cattle life stages across the beef industry.