Beef Steers and Enteric Methane: Reducing Emissions by Managing Forage Diet Fiber Content

Abstract

Understanding the methane (CH4) emissions that are produced by enteric fermentation is one of the main problems to be solved for livestock, due to their GHG effects. These emissions are affected by the quantity and quality of their diets, thus, it is key to accurately define the intake and fiber content (NDF) of these forage diets. On the other hand, different emission prediction equations have been developed; however, there are scarce and uncertain results regarding their evaluation of the emissions that have been observed in forage diets. Therefore, the objectives of this study were to evaluate the effect of the NDF content of a forage diet on CH4 enteric emissions, and to evaluate the ability of models to predict the emissions from the animals that are consuming these forage diets. In total, thirty-six Angus steers (x¯ = 437 kg live weight) aged 18 months, blocked by live weight and placed in three automated feeding pens, were used to measure the enteric CH4. The animals were randomly assigned to two forage diets (n = 18), with moderate (<50%, MF) and high (>50%, HF) NDF contents. Their dry matter intake was recorded individually, and the CH4 emissions were measured using the SF6 tracer gas technique. For the model evaluation, six prediction equations were compared with 29 studies (n = 97 observations), analyzing the accuracy and precision of their estimates. The emission intensities per unit of DMI, per ADG, and per gross energy intake were significantly lower (p < 0.05) in the animals consuming the MF diet than in the animals consuming the HF diet (21.7 vs. 23.7 g CH4/kg DMI, 342 vs. 660 g CH4/kg ADG, and 6.7% vs. 7.5%, respectively), but there were no differences in the absolute emissions (p > 0.05). The best performing model was the IPCC 2006 model (r2 = 0.7, RMSE = 74.04). These results show that reducing the NDF content of a forage diet by at least 10% (52 g/kg DM) reduces the intensity of the g CH4/kg DMI by up to 8%, and that of the g CH4/kg ADG by almost half. The use of the IPCC 2006 model is suitable for estimating the CH4 emissions from animals consuming forage-based diets.

Silvopastoral systems as a strategy to reduce GHG emissions and restore natural areas in livestock systems in the Amazonian foothills of Caquetá, Colombia

“…Similar values were found by Santander et al (2023), by reducing the NDF of the diet by at least 10%. Gaviria et al (2020) also found lower emissions in animals consuming grass after a regrowth period of 45 days compared to those observed after a regrowth period of 65 days.…”

Evaluation of Two Species of Macroalgae from Azores Sea as Potential Reducers of Ruminal Methane Production: In Vitro Ruminal Assay

“…This in vitro study is the first to consider the total production of gas and CH 4 using different percentages of red macroalgae from the Azores (Terceira Island) and using exclusively pasture-based feed (substrate), which was chemically characterised ( Table 1 ), emphasising the fibre content. This aspect is crucial to understand due to the observed positive correlation between fibre content and enteric methane production [ 31 ].…”

Designing a More Sustainable and Environmentally Friendly Food Supply: A Roadmap for Future Food and Agricultural Research

“…171 For instance, increasing the amount of dietary fiber in the feed of beef steers increases enteric methane production. 172 Consequently, reducing the dietary fiber levels in feeds may have beneficial effects in terms of GHG emissions. However, the impact of changing an animal's diet or using feed additives on its health, productivity, and nutritional quality also needs to be considered.…”

“…Researchers have also shown that the nature of the feed given to livestock animals impacts their GHG emissions . For instance, increasing the amount of dietary fiber in the feed of beef steers increases enteric methane production . Consequently, reducing the dietary fiber levels in feeds may have beneficial effects in terms of GHG emissions.…”