Summary
This experimental study quantified urination patterns and urine nitrogen characteristics in penned sheep (n=6) across 193 urination events, addressing a data gap in ruminant excretion physiology. Daily nitrogen excretion and urine nitrogen concentration were significantly higher on improved pasture (26.7 g N sheep⁻¹ d⁻¹; 7.0 g N L⁻¹) than semi-improved pasture (16.7 g N sheep⁻¹ d⁻¹; 5.5 g N L⁻¹), though actual urine patch nitrogen loading varied inversely due to differences in urine-to-soil contact area. The authors provide an updated recipe for artificial sheep urine and demonstrate that site- and season-specific urine composition should be incorporated into experimental and modelling assessments of nitrogen losses from grazed grasslands.
UK applicability
The findings are directly applicable to United Kingdom pastoral systems, as the study was conducted on UK grasslands under typical British grazing conditions. The quantified parameters for nitrogen excretion and urine composition will inform more accurate modelling of reactive nitrogen pollution from sheep-grazed grasslands in the UK, supporting improved farm management and environmental regulation.
Key measures
Urination frequency (events per day); urine volume (mL per event); daily urine production (L per sheep per day); daily urine nitrogen excretion (g N per sheep per day); urine nitrogen concentration (g N per L); urine patch nitrogen loading (L per m²); urine chemical composition; metabolomic profile
Outcomes reported
The study quantified urination frequency (8–11 times daily), mean urine volume (289 ± 14 mL per event), daily urine production (2.77 ± 0.15 L per sheep per day), and nitrogen excretion rates in sheep grazing improved and semi-improved pastures. Urine chemical composition and metabolomic profiles were characterised seasonally and by site, and an updated artificial sheep urine recipe was developed for experimental use.
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