Get reliable science

Nitrogen is one of the constituents found in mammalian feces. Fecal nitrogen can be monitored to indicate forage diet quality or potential re-deposition of nitrogen into an ecosystem. Near infrared spectroscopy (NIRS) is a non-invasive, non-destructive analytical method used to determine fecal nitrogen. Multi-species NIRS calibrations have been developed for forage quality and composition but it is not known how well fecal NIRS calibrations might apply across herbivore species. We applied NIRS to determine fecal nitrogen in a temporo-spatially diverse calibration derived from multiple ruminant herbivore species (i.e. cattle, bison, deer, elk, goats, and sheep). Fecal samples collected fresh from the ground representing a herd or flock composite were shipped frozen or chilled to our laboratory via 2-d priority mail. Upon arrival, samples were processed for NIRS (400 to 2498 nm). Predictive calibrations�and validations were developed using partial least squares regression for: 1) all samples, 2) cattle only, 3) all except bison, 4) all except deer, 5) all except elk, 6) all except goats, and 7) all except sheep. All multiple coefficient of determination values for fecal nitrogen calibrations were ? 0.97. Corresponding standard error of cross validation values were ? 0.13. Validation results include simple coefficient of determination and standard error of prediction for each alternate species (3-7 above) using the cattle derived calibration ranged from 0.76 to 0.84, and 0.28 to 0.5 respectively. Similar values for the sequential species leave-one-out validation for fecal nitrogen were 0.67 to 0.89, and 0.17 to 0.47 respectively. Multi-species fecal NIRS calibrations for fecal nitrogen will facilitate real-time monitoring for pollution mitigation, precision application of soil amendments, livestock supplemental feeding, or wildlife habitat evaluation within appropriate guidelines. Our multi-species calibration results should be considered a preliminary evaluation of the technique.