Journal Articles

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    Plantain-mixed pasture collected in different climatic seasons produced less methane and ammonia than ryegrass–white clover pasture in vitro
    (CSIRO Publishing, 2025-06-23) Sivanandarajah K; Donaghy D; Molano G; Horne D; Kemp P; Navarrete S; Ramilan T; Pacheco D; Jonker A
    Context Plantain (PL) is recognised for reducing nitrate leaching and nitrous oxide emissions in pastoral systems. Evidence has shown that cows fed pure PL produced less methane (CH4) than cows fed ryegrass. However, it is unclear if the CH4 reduction can be achieved with PL in mixed pasture. Aim The study evaluated the in vitro rumen fermentation profiles of ryegrass–white clover (RWC) and medium-level PL (PLM, containing ~40% PL) pasture collected during different climatic seasons, to determine whether this inclusion level influences CH4 and rumen ammonia (NH3) production. Methods Substrates were selected from samples with various proportions of PL. Samples were categorised into three climatic seasons (i.e. spring, summer and autumn) and two pasture types (PLM and RWC). Representative samples for these scenarios were tested in an automated in vitro rumen batch culture system for gas, CH4 (mL/g DM) and NH3 (mM/g DM) production. Key results In summer samples, PLM produced approximately 8%, 14% and 19% less CH4 at 12 h, 24 h and potential CH4 production (PCH4), respectively. Although gas production (GP) was similar at 12 and 24 h, PLM had 13% lower potential GP than RWC (P < 0.05). In spring samples, PLM had approximately 11% greater GP and CH4 production at 12 h. For the autumn samples, GP and CH4 production were similar between PLM and RWC (P > 0.05). Net NH3 production from PLM substrates was significantly lower in spring (27%) and autumn (17%) samples, with no differences in summer, despite higher crude protein levels in the selected PLM. Conclusions Compared with RWC, PLM changed rumen fermentation parameters that could translate to potential environmental benefits: PLM produced less net NH3 in spring and autumn samples (27% and 17%, respectively), and up to 19% less CH4 production in summer samples. Implications Incorporating ~40% PL into RWC pasture showed a promising reduction of CH4 emissions and nitrogen losses in vitro. If the in vitro results translate to cows grazing pasture, this could offer greater environmental benefits with minimal input costs. In vitro results suggest that PLM’s potential to mitigate CH4 emissions can be influenced by seasonal variations in pasture quality compared with RWC. However, further animal studies are needed to fully comprehend the CH4 mitigation potential of this forage.
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    Evaluation of methane prediction equations for Australian feedlot cattle fed barley and wheat-based diets
    (CSIRO Publishing, Clayton, Victoria, Australia, 2025-03-13) Almeida AK; McMeniman JP; Van der Saag MR; Cowley FC; Dougherty J
    Context. Accurately predicting baseline methane (CH4) emissions from beef cattle is of utmost importance for the beef industry and governments alike. It serves as a vital component for accounting as part of national GHG inventories and enables the development and implementation of greenhouse gas (GHG) mitigation strategies. Aims. The aim of this study was to evaluate equations in the literature for predicting CH4 emissions of beef cattle when fed barley and wheat-based diets typical of the Australian feedlot industry. Then, propose the best prediction equation to accurately reflect CH4 emissions of feedlot cattle under Australian conditions. Methods. As part of the project, a large database of methane measurements performed in respiratory calorimeters taken from beef cattle fed a range of feedlot diets was assembled. The dataset included a wide range of factors that are known to impact CH4 production, such as dry matter intake (DMI), ether extract (EE), crude protein (CP), and cell wall components, amongst others. The database contained 713 individual measurements, from 175 animals and 12 studies. Key results. The equation currently utilised by the Australian National Inventory Report had poor accuracy, with mean bias overprediction of 115 g/day (P < 0.01), along with significant linear bias (P < 0.01) and poor precision (r2 = 0.05). The mean bias was 144% of average observed CH4 production. All evaluated equations lacked accuracy and precision in predicting CH4 emissions for the diets fed in this study. Roughage concentrations (DM basis) ranged from 5.54 to 43.0% with a mean of 20.5 ± 11.1%. Given these findings, two specific equations were developed, (1) a CH4 yield equation based on DMI: CH4 (g/day) = 9.89 ± 1.54 × DMI (n = 384; P < 0.01; root mean square error (RMSE) = 32.6 g/day; r2 = 0.85); and (2) an equation based on DMI, neutral detergent fibre (NDF) and EE: CH4 (g/day) = 5.11 ± 1.58 × DMI − 4.00 ± 0.821 × EE + 2.26 ± 0.125 × NDF (n = 384; P < 0.05; RMSE = 22.2 g/day; r2 = 0.91). When validated, the second equation yielded a mean bias of 6.10 g overprediction, with no linear bias, and better fit than any of the literature equations. Conclusions. Based on a thorough model evaluation, our findings support the need to revise current methods to predict CH4 for barley and wheat-based diets. Implications. This study contributes to developing accurate estimations of enteric CH4 emissions for cattle fed barley and wheat-based diets.
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    C3 and C4 grass species: who can reduce soil nitrous oxide emissions in a continental arid region?
    (MDPI AG, 8/09/2020) Ning J; He XZ; Hou F
    In order to relieve grazing pressure, drought-tolerant grass species are widely cultivated in arid regions. However, soil N emission is largely neglected while pursuing forage yield. We carried out a randomized block study to investigate whether and how the C3 and C4 grass species differ in soil N emission in a typical salinized field with temperate continental arid climate in the northwest inland regions, China. We quantified soil N2O flux from two C3 (barley and rye) and two C4 grass species [corngrass and sorghum hybrid sudangrass (SHS)] in fields during the growing season (from May to September) by using the static box method, and then determined the relationships between soil N2O fluxes and forage yield and soil properties. Results show that soil available nitrogen, soil temperature, pH, soil organic carbon, and total nitrogen were correlated, but soil water was anti-correlated with soil N2O fluxes. In addition, N2O flux increased significantly faster with soil temperature in C4 than in C3 grass fields. Although the lower total N2O emission fluxes were detected for C3 species, the lower yield-scaled N2O was detected for C4 species. Our study provided insights into the determination of grass species and the understanding of mechanisms regulating N2O fluxes in C3 and C4 species in the continental arid regions.