Citation: Vargas, J.; Ungerfeld, E.; Muñoz, C.; DiLorenzo, N. Feeding Strategies to Mitigate Enteric Methane Emission from Ruminants in Grassland Systems. Animals 2022, 12, 1132. https://doi.org/ 10.3390/ani12091132 Academic Editor: Donald C. Beitz Received: 18 March 2022 Accepted: 15 April 2022 Published: 28 April 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). animals Review Feeding Strategies to Mitigate Enteric Methane Emission from Ruminants in Grassland Systems Juan Vargas 1 , Emilio Ungerfeld 2 , Camila Muñoz 3 and Nicolas DiLorenzo 1, * 1 Department of Animal Sciences, North Florida Research and Education Center, University of Florida, Marianna, FL 32443, USA; jvargasmartinez@ufl.edu 2 Centro Regional de Investigación Carillanca, Instituto de Investigaciones Agropecuarias, Temuco 4880000, Chile; emilio.ungerfeld@inia.cl 3 Centro Regional de Investigación Remehue, Instituto de Investigaciones Agropecuarias, Osorno 5290000, Chile; camila.munoz@inia.cl * Correspondence: ndilorenzo@ufl.edu Simple Summary: Ruminants under grazing conditions play an important role, especially in devel- oping countries. Enteric methane emissions from ruminants are greater with pasture-based diets; however, it is not clear which abatement practices are effective to reduce methane emissions under grazing conditions. The objective of this review was to identify and describe enteric methane abate- ment practices for ruminants that are applicable under grazing conditions. Decreasing the pre-grazing herbage mass reduced methane emissions per unit of product. Other grazing management practices such as increased stocking rate, decreased forage maturity, rotational stocking, and incorporating tannin-containing or non-tannin-containing legumes showed inconsistent results. Nitrogen fertil- ization or silvopastoral systems did not modify methane emissions, although they may alter carbon sequestration in a system. Supplementation in grazing conditions shows inconsistent responses on methane emissions. However, lipid supplementation showed promising results. Identifying and implementing grazing strategies and supplementation practices under grazing conditions is required to increase efficiency and reduce the environmental impact of these systems. Abstract: Ruminants produce approximately 30% of total anthropogenic methane emissions globally. The objective of this manuscript was to review nutritional enteric methane abatement practices for ruminants that are applicable under grazing conditions. A total of 1548 peer-reviewed research articles related to the abatement of enteric methane emissions were retrieved and classified into four categories: non-experimental, in vitro, in vivo confined, and in vivo grazing. The methane abatement strategies for grazing systems were arranged into grazing management and supplementation prac- tices. Only 9% of the retrieved papers have been conducted under grazing conditions. Eight grazing management practices have been evaluated to reduce methane emissions. Decreasing the pre-grazing herbage mass reduced the methane emission per unit of product. Other grazing management prac- tices such as increased stocking rate, decreased forage maturity, rotational stocking, and incorporating tannin-containing or non-tannin-containing feeds showed contradictory results. Nitrogen fertilization or silvopastoral systems did not modify methane emissions. Conversely, supplementation practices in grazing conditions showed contradictory responses on methane emissions. Lipid supplementation showed promising results and suggests applicability under grazing conditions. Identifying and implementing grazing strategies and supplementation practices under grazing conditions is required to increase efficiency and reduce the environmental impact of these systems. Keywords: diet supplementation; grassland systems; grazing management; methane emission; secondary compounds tannin-containing legume Animals 2022, 12, 1132. https://doi.org/10.3390/ani12091132 https://www.mdpi.com/journal/animals