Simulating grazing beef and sheep systems

A - Papers appearing in refereed journals

Wu, L., Harris, P., Misselbrook, T. H. and Lee, M. R. F. 2022. Simulating grazing beef and sheep systems. Agricultural Systems. 195, p. 103307.

AuthorsWu, L., Harris, P., Misselbrook, T. H. and Lee, M. R. F.

Ruminant livestock makes an important contribution to global food security by converting feed that is unsuitable for human consumption into high value food protein, demand for which is currently increasing at an unprecedented rate because of increasing global population and income levels. Globally, ruminant livestock will be important for the foreseeable future and demonstrating the sustainability of production will become increasingly important. Factors affecting production efficiency, product quality, and consumer acceptability, such as reduced animal fertility, health and welfare, will ultimately define the sustainability of ruminant production systems. These more complex systems can be developed and analysed by using models that can predict system responses to environment and management.
We present a framework that dynamically models, using a process-based and mechanistic approach, animal and grass growth, nutrient cycling and water redistribution in a soil profile taking into account the effects of genotype, climate, feed quality and quantity on livestock production, greenhouse gas emissions, water use and quality, and nutrient cycling in a grazing system.
A component to estimate ruminant animal growth was developed and integrated with the existing components of the SPACSYS model. Intake of herbage and/or concentrates and partitioning of the energy and protein contained in consumed herbage and/or concentrates were simulated in the component. Simulated animal growth was validated using liveweight data collected from over 200 finishing beef cattle and 900 lambs collected from the North Wyke Farm Platform (NWFP) in southwest England, UK, between 2011 and 2018. Simulated annual nitrous oxide (N2O), ammonia, methane and carbon dioxide emissions from individual fields were examined.
Results and Conclusions
A series of statistical indicators demonstrated that the model could simulate liveweight gain of beef cattle and lamb. Simulated nitrogen cycling estimated N input of 190 to 260 kg ha-1, of which 41 – 58% was removed from the fields either as silage or animal intake, 6 – 15% was lost through surface runoff or lateral drainage and 1.5% was emitted to the atmosphere as N2O. About 12% of the manure applied to the NWFP and excreta nitrogen deposited at grazing was lost via ammonia volatilisation.
The extended model has the potential to investigate the responses of the system on and consequences of a range of agronomic management and grazing strategies. However, modelling of multi-species swards needs to be validated including the dynamics of individual species in the swards and the impact on animal growth and nutrient flows.

KeywordsSPACSYS; North Wyke Farm Platform; Grazing; Modelling; Liveweight
Year of Publication2022
JournalAgricultural Systems
Journal citation195, p. 103307
Digital Object Identifier (DOI)
Open accessPublished as ‘gold’ (paid) open access
FunderBiotechnology and Biological Sciences Research Council
Funder project or codeS2N - Soil to Nutrition - Work package 2 (WP2) - Adaptive management systems for improved efficiency and nutritional quality
The North Wyke Farm Platform- National Capability [2017-22]
Publisher's version
Accepted author manuscript
Supplemental file
Output statusPublished
Publication dates
Online08 Nov 2021
Publication process dates
Accepted29 Oct 2021
PublisherElsevier Sci Ltd

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