Concentrate type improved milk output and methane intensity in grazing cows

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A new study in Frontiers in Veterinary Science suggests that the right concentrate strategy can help grazing dairy cows produce more saleable milk while lowering methane intensity. In late-lactation cows on summer pasture, high-starch and mixed starch-fiber concentrates increased fat- and protein-corrected milk by 16% versus no supplementation, while daily methane production remained unchanged. That translated into a 13% to 14% reduction in methane per unit of milk. (frontiersin.org)

The work fits into a long-running question for pasture-based dairying: can supplementation improve environmental efficiency, not just output. Grazing systems rely heavily on fresh herbage, but pasture quality and supply often decline in summer, making concentrates a common tool to support intake and production. Researchers have been studying methane effects of concentrate supplementation in grazing cows for years, and earlier work has also found that supplementation can reduce methane intensity mainly by lifting milk production rather than by sharply lowering total methane emissions. (frontiersin.org)

In the new trial, researchers assigned 72 multiparous Holstein-Friesian × Jersey cows, averaging about 206 days in milk, to one of four treatments: no concentrate, 5 kg/day of high-starch concentrate, 5 kg/day of high-fiber concentrate, or a 50:50 mix. Methane was measured over 36 days using GreenFeed units, with 60 cows included in the final methane analysis based on visit data. Milk was recorded daily, milk composition weekly, and feeding behavior through collar-based monitoring. The mixed and high-starch treatments delivered the clearest production response, while the high-fiber group was intermediate. (frontiersin.org)

That pattern is broadly consistent with the underlying biology described in prior literature. A 2022 Frontiers review concluded that carbohydrate type can affect methane through differences in rumen fermentation, including shifts tied to rapidly fermentable carbohydrates and rumen pH. The same research group has also reported chamber-based findings in herbage-fed late-lactation cows showing lower methane per unit of milk in concentrate-fed animals, again driven largely by stronger milk output rather than a large drop in absolute methane production. (frontiersin.org)

Industry-facing research has framed this as an efficiency story. Teagasc has noted that higher milk solids output can lower methane intensity in grazing dairy systems, even when total methane output does not fall proportionally. Separate recent AgResearch-linked work in early-lactation cows fed cut herbage likewise found that increasing concentrate levels reduced methane yield and intensity, and explicitly flagged the need to test whether late-lactation cows respond differently because dry matter intake declines as lactation progresses. This new paper helps fill part of that gap for grazing cows in late lactation. (teagasc.ie)

Why it matters: For veterinary professionals advising dairy clients, the study reinforces that methane metrics need context. A ration may not lower daily methane output, yet still improve environmental performance per kilogram of milk solids. That distinction is important as farms, processors, and regulators increasingly focus on emissions intensity benchmarks. It also means ration decisions should be evaluated alongside milk response, pasture substitution, animal behavior, and whole-herd economics, not methane alone. The study does not suggest a one-size-fits-all methane fix, but it does support concentrate formulation as a practical lever in pasture systems when late-lactation production is slipping. (frontiersin.org)

There are still limits to keep in mind. The study was conducted in late-lactation cows in a specific grazing setting, and the methane benefit came from dilution through greater milk production, not from a clear reduction in absolute methane per cow. That means results may vary with pasture quality, substitution effects, milk price, concentrate cost, and stage of lactation. Economic response to concentrate feeding at grass can be modest under some conditions, according to Teagasc guidance, which makes on-farm context critical. (frontiersin.org)

What to watch: The next step is whether researchers can translate these findings into stage-specific feeding recommendations, including how concentrate type and feeding rate perform in early, mid, and late lactation, and whether methane intensity gains hold up in commercial herds over longer periods. (sciencedirect.com)