Dried Distillers’ Grains with Solubles in Ruminant Diets: Effects on Enteric Methane Emissions and Production Responses—A Systematic Review

Abstract

Simple Summary Ruminants release methane (CH4) during digestion, which contributes to climate change and represents a loss of feed energy that could otherwise support animal production. Dried distillers’ grains with solubles (DDGSs), a feed ingredient produced during ethanol manufacturing, are increasingly used in livestock diets because they provide protein, energy, and other nutrients. This review examined published research to determine whether including this ingredient in ruminant diets can reduce CH4 emissions while maintaining animal performance. Seventeen studies (9 in vivo, 5 in vitro, and 3 integrated in vivo–in vitro studies) were evaluated. The findings showed that DDGS did not consistently reduce total CH4 production. However, they often improved the efficiency with which animals converted feed into milk or meat, resulting in lower CH4 emissions per unit of product. Moderate DDGS inclusion levels were frequently associated with improved feed efficiency and animal performance, although these responses were not consistent across all studies. Higher inclusion levels generally produced more variable responses and, in some cases, reduced fiber digestibility. The effects varied depending on the amount included in the diet, the source of the ingredient, and the type of feed being replaced. These findings suggest that DDGSs can support more efficient livestock production and may help reduce the environmental impact of ruminant farming when used appropriately.