New research has reopened the question of how plantain cuts nitrogen losses from grazing animals — and whether the effect is unique to plantain at all. A Canterbury study published in the Journal of Animal Science compared eight plantain, chicory and ryegrass treatments, including the commercial Ecotain blend, across three autumn runs with 120 young sheep.

Plantain has been the centre of DairyNZ's plantain potency and practice programme, most of it using Ecotain, a blend of the Ceres Tonic and Agritonic cultivars. DairyNZ has suggested that secondary compounds in plantain may reduce rumen ammonia production. The new experiment found no biologically meaningful evidence that those compounds increased urine production or further diluted urinary nitrogen.

What the study did support is the dilution effect: forages with lower dry matter content led to more water intake, more urine and lower urine nitrogen concentration. Dry matter in the Tonic control plantain varied substantially between the three runs, and urine output moved with it — evidence, the authors said, that dry matter rather than a fixed cultivar effect drives urine volume. Plantain-fed sheep did partition a smaller share of excreted nitrogen into urine than ryegrass-fed sheep, though plantain's nitrogen concentration is not necessarily lower than ryegrass or chicory under commercial conditions.

DairyNZ senior project manager Kate Fransen said the trial had limits — non-lactating sheep and seven-day measurements against DairyNZ's multi-season farmlet trials — but agreed it confirmed plantain moves more nitrogen into faeces and less into urine, and that dilution driven by high water intake is the mechanism. It did not measure nitrate leaching, which DairyNZ's four-year Lincoln farmlet trial cut by about 33 per cent in pastures with 17 per cent plantain dry matter.

The paper follows last year's scientific dispute in which a review questioned the evidence for secondary compounds and soil-nitrogen mechanisms; DairyNZ rejected most of that review but accepted low dry matter as the dominant, best-documented effect. Fransen said chicory-fed animals in the new study had high nitrogen intake and urinary losses, with no comparable farm-scale leaching evidence for chicory, and confirmed DairyNZ has not run farm-scale head-to-head comparisons of Ecotain, chicory and other low-dry-matter forages. "Our confidence in recommending plantain is based on a substantial body of evidence showing that it can reduce nitrate leaching through several mechanisms, not urine dilution alone," she said.

Source: Farmers Weekly NZ