Estimating sectoral livestock biomass and stock value using data from national diseases eradication programmes: a case study based on the Irish cattle herd from 2011 to 2021

Emma-Jane Murray^1,2*Eoin Ryan³Jonathan Rushton²Jamie Alexander Tratalos⁴Jonas Brock⁵Elaine Tarrant³Sharon Walshe³David A Graham⁵Damien J Barrett³Tim Geraghty^6,7Conor G McAloon⁴

• ¹School of Veterinary Medicine, College of Health and Agricultural Sciences, University College Dublin, Dublin, Ireland
• ²Global Burden of Animal Diseases, The Roslin Institute, University of Edinburgh, Easter Bush Campus, Midlothian, Edinburgh, United Kingdom
• ³Government of Ireland Department of Agriculture Food and the Marine, Dublin, Ireland
• ⁴Centre for Veterinary Epidemiology and Risk Analysis, University College Dublin School of Veterinary Medicine, Dublin, Ireland
• ⁵Animal Health Ireland, Carrick-On-Shannon, Ireland
• ⁶Glenythan Vet Group, Ellon, United Kingdom
• ⁷Dunnydeer Veterinary Group, Muiryheadless Road, Insch, Aberdeenshire, United Kingdom

Livestock biomass is a denominator for a wide range of important production metrics, including productivity, environmental impact, greenhouse gas emissions, and antimicrobial usage. Accurate biomass estimates allow cross-sectoral and international comparisons for these important indices across a range of high-priority areas, which can then inform policy risk assessments and decision-making. Similarly, accurate estimates of the value of livestock are needed to monitor economic efficiency and productivity and understand the costs associated with animal health policy decisions. Previous methods to estimate biomass have relied on assigning an average liveweight for a given species and multiplying this by the number of individual animals of that species in a region. However, without taking into account the population's demographics and structure, these approaches cannot be relied upon to accurately represent the cattle population. Using data from the Irish cattle herd as a case study, this study developed liveweight and value models and applied these models to a cattle registration and movement database to estimate the biomass (kg) and economic stock value (€) of each animal and herd, aggregated by herd type based on a herd classification tree model, and explored trends in biomass and stock value over time. The Irish cattle sector biomass increased from 2,924,800 tonnes in 2011 to 3,317,100 tonnes in 2021, and the cattle sector stock value increased from €6,323.7m in 2011 to €8,792.3m in 2021. Furthermore, this study demonstrated the biomass and stock value within-year and between years. We illustrate a novel approach using real-time movement data for dynamic estimates of biomass and stock value at animal-, herd-and national-level that can be applied in countries with existing animal registration and movement tracing systems.