Graham Alison, Thorn Camilla, McDonagh Michael, O'Donnell Caroline, Nolan Stephen, Kirwan Stuart F, O'Connor Sandra, Nzeteu Corine O, Montoya Alejandra C V, Bartle Andrew, Hall Alison, Abberton Cathy, Friel Ruairi, Waters Sinead M, O'Flaherty Vincent
Microbial Ecology Laboratory, Microbiology, School of Biological and Chemical Sciences and Ryan Institute, University of Galway, University Road, Galway, H91 TK33, Ireland.
GlasPort Bio, Unit 204, Business Innovation Centre, Galway, Co. Galway, H91 TK33, Ireland.
Sci Total Environ. 2025 Feb 1;963:177598. doi: 10.1016/j.scitotenv.2024.177598. Epub 2025 Jan 13.
Ruminant livestock contribute significantly to global methane production and mitigation of which is of utmost importance. Feed additives represent a cost-effective means of achieving this. A potential target for such additives is rumen Oxidative Reduction Potential (ORP), a parameter which influences CH production rates, with methanogenesis occurring optimally at ORPs below -300 mV. Thus, a controlled elevation of rumen ORP represents a potentially benign means of methanogen suppression. This research involved assessing a range of oxygen-releasing compounds for their ability to increase rumen ORP and inhibit methanogenesis, using the in-vitro rumen simulation technique (RUSITEC). Seven potential CH inhibitors were tested in a 21-day trial monitoring biogas volume, CH content, ORP, digestibility, ammonia, and volatile fatty acids concentration. The additives evaluated included: liquid peroxide (HO) and urea hydrogen peroxide (UHP), as well as slower reacting species (calcium and magnesium peroxide), in addition to encapsulated liquid HO for controlled, slow release. Consistent CH reductions of >50 % were observed from all additives. Reduced neutral detergent fibre (NDF) digestibility and a reduction in total volatile fatty acids (VFAs) was observed for some treatments, but MgO and encapsulated HO reduced CH volume by 62 % and 58 %, respectively, and had no detrimental effects on digestibility (p > 0.05) or on VFA production. Ex-situ ORP measurements demonstrated significant increases in ORP upon addition of the additives, with MgO and encapsulated HO inducing a more moderate effect suggesting a controlled additive release was achieved with the slow-release format of encapsulated liquid HO. Thus, potential slow-release forms deemed suitable to progress to bolus or pellet format in-vivo were identified and could enable a longer-lasting suppression of methanogens within the rumen, facilitating application in both intensive and pasture-based production systems.
