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

• Published in: Animals (Basel) Vol. 14; no. 4; p. 568
• Main Authors: Hodge, Ian, Quille, Patrick, O’Connell, Shane
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 08.02.2024
• Subjects: Analysis; Animal feeding and feeds; Antibiotics; Ascophyllum nodosum; Asparagopsis; Bacteria; bacterial communities; Carbohydrates; Carbon dioxide; Carbon footprint; Carbon offsets; Cattle; chitosan; Costs (Law); Dairy cattle; Diet; dose response; Ecological footprint; Emissions; enteric methane; enzymes; essential oils; Fatty acids; feed additives; feed supplementation; Feeds; Fermentation; garlic; Gram-positive bacteria; Greenhouse gases; Infrared radiation; Investigations; Lactobacillus plantarum; Lipids; Livestock; Livestock industry; meta-analysis; Methane; methane production; mitigation; Natural gas; nitrates; oils; Oxidation; Productivity; propionic acid; Rumen fermentation; rumen protozoa; volatile fatty acids; meta-analysis; rumen fermentation; mitigation; enteric methane; feed supplementation
• ISSN: 2076-2615; 2076-2615
• DOI: 10.3390/ani14040568

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.