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Despite a surge in interest in plant-based foods, and the widely acknowledged fact that richer countries consume too much red meat, global consumption of animal products is predicted to rise over the coming decades, driven by an increasing demand from the developing world. In addition to the widely acknowledged challenge of curbing the greenhouse gases produced by livestock, farmers using manure and other organic fertilisers on their pastures need to control the ammonia and greenhouse gas emissions associated with their storage and use, and to minimise the risk of polluting water courses. Further issues arise from the drugs routinely given to livestock to prevent them falling to terrible worm and bacterial infections.


Alison Carswell

“Livestock farms are incredibly diverse. Production of animal-based products can range from systems that produce both the animal feed and the animal product on-farm, to those which import all nutrition into the farm, such as fully housed systems. Under all systems the environmental and societal impact of the agrochemicals imported into the farm must be considered as part of the whole chain analysis of livestock products, of which excreta has an important role.

“Animal excreta can be used as fertiliser in a variety of forms, such as manures and slurries, and can be further processed to create pellets, composts and digestate. These fertilisers contain both macro- and micro-nutrients, which, like chemical fertilisers, must be carefully managed in a way that minimises ammonia and greenhouse gas emissions, and the transfer of pollutants to receiving waters. So, farmers need to take account of the nutritional content of organic fertilisers and that of their soils to optimise fertiliser use, in addition to using best practice methods to minimise environmental and societal impacts associated with fertiliser storage and land application. These include covering stores, capturing runoff from farmyards, and band spreading or injecting slurries.”

Andrew Cooke

Resisting the urge to overuse

“Antibiotics and anthelmintics are used widely by sheep and cattle farmers. They play an important role in preventing losses from diseases, which would otherwise have environmental, welfare, and economic costs. For example, without benzimidazoles, sheep in the west of the UK could be at severe risk from liver parasites and ultimately death.

“However, such drugs are not without their own impact. In addition to the costs associated with their production, they can be passed through dung and urine where they can be toxic to invertebrates. Furthermore, they create a selection pressure on pathogens, promoting drug resistance which can diminish the efficacy of these drugs in both animals and humans.

“These negative effects are most pronounced when blanket treatment is applied to the whole-herd or flock - but by only treating animals most at risk and only when needed, the rate at which resistance spreads is slowed. This technique also provides non-toxic dung for invertebrates to utilise. Above all of this, the primary objective should always be to minimise the exposure of animals to pathogens and thus the need for drugs. This can be achieved through grazing strategies, genetic selection, monitoring, forecasting, and promoting high standards of health and welfare elsewhere.”