Reduction of ammonia emissions from dairy cubicle housing by sloped floors for rapid urine drainage

Rapid urine drainage from floors reduces ammonia (NH 3 ) formation and release. This study investigated the NH 3 emission mitigation potential in cubicle loose dairy housing with a solid floor with 3% slope, a urine-collecting gutter, and a manure removal scraper (‘solid floor with slope’) compared to the reference system of solid floors without a slope at full scale. Two spatially separated housing compartments enabled case-control measurements under comparable conditions (e.g. climate). A tracer-ratio method with artificial tracer gases was applied to quantify emissions under natural ventilation. Measurements taken over three seasons showed that the solid floor with slope reduced NH 3 emissions by 17% in summer, 37% in the transition season, and 21% in winter, compared to the reference system without slope, considering manure removal frequencies of three and 12 times per day in both compartments. A linear mixed-effects model identified the following influencing variables on NH 3 emissions: floor type ( p < 0.001), outside air temperature ( p < 0.001), wind speed in the housing ( p < 0.01), and milk urea content ( p < 0.001), as well as the interaction between manure removal frequency and floor type ( p < 0.001). Annual NH 3 emission values for both floor types with 12 manure removals per day were obtained using a model-based calculation with a broader Swiss database (temperature, milk urea content) differentiating between regions. NH 3 emissions per animal per year were 8.2–9.5 kg and 11.8–12.8 kg for cubicle loose housing with a sloped solid floor and a solid floor without a slope, respectively.