@article{Vibart_Pacheco_2024, title={Adequacy of equations used to calculate urinary nitrogen contribution to total nitrogen excreted by ruminants}, volume={86}, url={https://nzgajournal.org.nz/index.php/JoNZG/article/view/3695}, DOI={10.33584/jnzg.2024.86.3695}, abstractNote={<p>Nitrogen (N) concentration in the diet is the best sole predictor of the contribution of urinary N to total N in excreta. A large database was compiled containing feed and excreta variables from dairy cattle, beef cattle, sheep and deer, to evaluate the predictive ability of five linear models and four non-linear models to calculate the contribution of urinary N to total N in excreta. Species-specific linear models for beef cattle and sheep did not result in better predictions than those obtained from a generic linear model developed for all ruminant species. The predictive ability of a non-linear dairy cattle model was noticeably better than that of a linear model. The poor performance of a linear model along with a smaller number of observations from deer studies points to the merit of the construction of a new deer-specific model. This study provides support for the robustness of N partitioning towards urinary N in the animal sub-model of OverseerFMâ„¢ for a comprehensive range of diets with varying N concentration for beef cattle and sheep. In the future, the use of more sophisticated modelling approaches that involve partitioning of data for model development and evaluation may be required.</p>}, journal={Journal of New Zealand Grasslands}, author={Vibart, Ronaldo Eduardo and Pacheco, David}, year={2024}, month={Oct.}, pages={179â€“187} }