Livestock Production: Part 3 – A Modeller’s Perspective

It’s never easy explaining to anybody what you do at university, regardless of what you study. When I studied Mathematics for my bachelor's degree, people would always ask what that entailed, and would then proceed to get incredibly confused or uninterested when I tried to explain. This has lessened since studying Environmental Modelling, probably because the environment is something that almost all of us can identify with, or at least respect its importance (except maybe Donald Trump and the Tories). However, I still get asked the same question all the time: “what actually is environmental modelling?”

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A model, in general, is a simulation of a real-life system for the purpose of understanding that system better. For example, you can use models to forecast future behaviour (without having to wait for time to unfold), and develop projections based on changes in the system (without having to tamper with the real-life system). However, to do this first requires assumptions about our system (parameters), boundary and initial conditions, and an understanding of the model and inter-connected relationships within it. Then, we can construct a model using field observation, laboratory experiments, mathematical equations, statistics, logic, and computation to best predict the system in the simplest way necessary.

In an environmental modelling context, these systems are highly variable. The whole Earth as a system is used for many different models, such as weather forecasting, fluctuations in sea surface temperatures and climate change. Alternatively, some models can focus on specific localised regions, like ecological models/population dynamics, hydrological systems, etc. We can even use models to simulate livestock systems!

But, why should we do that? Well, instead of using trial and error on the parameters of the model to increase productivity or predict environmental damage, models allow us to use computers, which is more cost-effective, faster and can avoid unnecessary environmental damage. However, predicting systems is incredibly difficult, which can sometimes make environmental models fairly unreliable. To avoid them going pear-shaped, we need to highlight the most vital parameters in our model and portray them as accurately as possible.

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Here are some examples of livestock production models:

Global Livestock Environmental Assessment Model (GLEAM)

This model, produced by the FAO, does exactly what it says on the tin: assesses the environmental impacts of global livestock production, which include greenhouse gas emissions, land use, land degradation and forestry, feed, water use and species interaction, as well as determine possible adaptation and mitigation strategies on a regional and global scale.

The main elements of the model are as follows:

• Systematic, global coverage of meat and milk from cattle, sheep, goat and buffalo, meat and eggs from chicken, and meat from pigs.
• Spatial distribution models of livestock, climate data and feed yields to identify driving factors, environmental consequences and mitigation strategies
• Approximations of carbon dioxide, methane and nitrous oxide (GHG emissions) at each stage of production, and from fermentation and manure management

The outputs of the model are:

• ·    Spatial distribution and quantity of cattle, sheep, goats, buffaloes, chickens and pigs
•      Amount and management of manure
•      Volume, composition and quality of feed
•      Emissions emitted at each stage of production
•      Commodities produced by livestock

Integrated Model to Assess the Global Environment (IMAGE)

This model has been developed by the PBL Netherlands Environmental Assessment Agency to measure the environmental impacts of global human activity, including livestock production systems. This aspect of IMAGE is similar to GLEAM as it measures the impact of livestock production on greenhouse gas emissions, air and water pollutants, and land use.

European Livestock Policy Evaluation Network (ELPEN)

The purpose of ELPEN is to measure or predict the outcomes of policy change in the livestock industry. The model incorporates bio-geographical data (including climate, land cover, soil, water, topography), statistical data, economic, social, environmental and technical features of livestock systems, to produce conclusions based on social, economic and environmental effects of policy change.

Livestock Development Planning System, Version 2 (LDPS2)

The LDPS2 is a computer model to aid livestock development planners in decision-making for livestock systems, including those of cattle, sheep, goats, buffaloes, pigs and poultry.

The main features are:

• Calculating the size, composition and feed of livestock herds needed for a given demand of livestock products, including meat, milk, eggs, skin, wool, manure and power supply
• Measuring the growth of herds to find the “growth constraint” to meet demand
• Compares these estimates with the amount of resources available

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