Evaluation and prediction of nitrogen use efficiency and outputs in faeces and urine in beef cattle

A - Papers appearing in refereed journals

Angelidis, A., Crompton, L., Misselbrook, T. H., Yan, T., Reynolds, C.K. and Stergiadis, S. 2019. Evaluation and prediction of nitrogen use efficiency and outputs in faeces and urine in beef cattle. Agriculture, Ecosystems & Environment. 280, pp. 1-15. https://doi.org/10.1016/j.agee.2019.04.013

AuthorsAngelidis, A., Crompton, L., Misselbrook, T. H., Yan, T., Reynolds, C.K. and Stergiadis, S.
Abstract

Beef cattle production is valuable to food security, contributing meat of high nutritional value. However, beef cattle are rather inefficient in utilising dietary nitrogen (N), thus excreting substantial amounts of N in their urine and faeces and imposing an environmental burden. The aim of this study was to evaluate the main dietary factors affecting N use efficiency (NUE) in beef cattle and develop prediction models for N excretion in manure, faeces and urine. This knowledge is essential for the development and evaluation of cost-effective N mitigation strategies. A database of 289 treatment means was constructed from 69 published studies and 1194 animals. Data included diet contents of N, dry matter (DM), organic matter (OM), neutral-detergent fibre (NDF), acid-detergent fibre (ADF), ether extract, starch, ash, gross energy (GE), metabolisable energy (ME), and outputs of N in manure (MNO), in urine (UNO) or in faeces (FNO). Regression equations to predict MNO, UNO and FNO, as well as various NUE indicators, were developed using residual maximum likelihood analysis. Evaluation of new and existing models was performed using the mean prediction error (MPE) to describe prediction accuracy. MNO, UNO and FNO were predicted with improved accuracy (MPE from 0.557 to 0.162; from 0.764 to 0.208; and from 0.458 to 0.177, respectively) when DM or OM digestibilities, and/or diet contents of N, NDF, ADF, Starch, OM, GE, ME, and/or forage proportion in the diet were added as predictors in different equations already containing either DM intake, N intake or body weight as primary predictor. New and existing models displayed an under-prediction of N outputs at the highest range of actual N outputs (when MNO > 207 g/d, UNO > 109 g/d). However, some of the new equations had improved overall accuracy (best MPE for MNO, UNO and FNO being 0.162, 0.208 and 0.177, respectively) and, when DM digestibility, and contents of N, NDF, Starch and ME were added as predictors in different equations, the extent of this under-prediction was also reduced (occurring when MNO > 208 g/d, UNO > 132 g/d). The regression models for NUE, demonstrated that diets which are more digestible and contain less N and fibre and more ME, may reduce N excretions, but mitigation strategies will also need to account for the potential effect on animal productivity and health.

KeywordsNitrogen; Efficiency; Beef; Urine; Faeces; Prediction; Validation
Year of Publication2019
JournalAgriculture, Ecosystems & Environment
Journal citation280, pp. 1-15
Digital Object Identifier (DOI)https://doi.org/10.1016/j.agee.2019.04.013
Open accessPublished as non-open access
FunderBiotechnology and Biological Sciences Research Council
Funder project or codeSoils to Nutrition
Output statusPublished
Publication dates
Online25 Apr 2019
Publication process dates
Accepted23 Apr 2019
PublisherElsevier Science Bv
ISSN0167-8809

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