Study examines pasture mix, defoliation, and ruminal methane

A new paper in Animals looks at a practical question for pasture-based ruminant systems: whether changing the pasture mix, and how often it’s defoliated, can shift ruminal fermentation, methane output, and ammonia production. The study, by Isidora P. Ruiz-Tagle-Renner, Juan Pablo Keim, and Óscar Balocchi, evaluated monoculture, binary, and multispecies pastures under two defoliation frequencies, focusing on forage systems relevant to southern Chile. (scielo.cl)

That question lands in a research area with real momentum. A 2025 review of enteric methane mitigation research in Chile said one of the field’s central challenges is that most methane-mitigation work globally has been developed in confined animals on total mixed rations, not in grazing systems. The review argued that pasture-based countries need evidence built around their own forage species, grazing patterns, and seasonal conditions, because those factors can materially alter rumen fermentation and methane responses. (scielo.cl)

The new study builds on earlier work from the same Chilean research community. A 2013 paper from Keim and colleagues reported that botanical composition affected nutritive value and in vitro fermentation characteristics of perennial pastures in southern Chile, even when methane production itself did not always differ across pasture and regrowth treatments. More recent Chilean pasture research has also shown that multispecies systems can outperform simpler ryegrass-clover systems for dry matter production and compositional stability, and that defoliation management can shape which species persist and dominate over time. (doi.org)

Taken together, that gives the new Animals paper a clear practical frame: it’s testing whether pasture diversity and harvest timing might help move fermentation in a more favorable direction without relying solely on feed additives. That idea is consistent with other in vitro forage-mixture work showing that some multispecies combinations can reduce methane relative to ryegrass monocultures, although effects vary by species and proportion. Reviews of grazing management and methane mitigation have also suggested that pasture structure, quality, and intake dynamics can meaningfully influence emissions intensity in pastoral systems. (mdpi.com)

Expert commentary in this niche has been cautious rather than sweeping. The Chile methane review emphasized that mitigation approaches for grazing cattle need local validation, especially because improvements seen in vitro or in housed systems may not hold under grazing. Likewise, broader reviews of rumen methanogenesis have noted persistent constraints around cost, practical delivery in grazing animals, and limited data on animal health, productivity, and field-level consistency. In other words, pasture-based methane mitigation is promising, but veterinary and production teams still need evidence that connects fermentation markers with outcomes in the paddock. (scielo.cl)

Why it matters: For veterinary professionals, this is less about a single methane number and more about decision-making at the herd level. If pasture composition and defoliation frequency can shift ammonia production alongside methane, that could affect nitrogen-use efficiency, rumen function, and the nutritional profile of grazed forage. Those are issues that intersect with production medicine, transition planning in seasonal dairy systems, and advisory work on sustainable herd management. It also reinforces that methane discussions in ruminant practice increasingly involve forage agronomy, not just animal nutrition. (scielo.cl)

For mixed and food-animal practices, the broader takeaway is that pasture design may become a more important part of climate and efficiency planning, especially in regions where grazing dominates. Multispecies swards have been associated in recent studies with better resilience and, in some cases, favorable fermentation or emissions signals, but responses are species-specific and management-dependent. That means veterinarians may need to work more closely with nutritionists and pasture specialists when producers ask about methane reduction strategies that won’t compromise intake, performance, or forage persistence. (mdpi.com)

What to watch: Watch for full-text details on which pasture combinations and defoliation schedules performed best, and for follow-up in vivo trials measuring methane, intake, milk or meat output, and nitrogen partitioning under commercial grazing conditions. (scielo.cl)