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Why does animal feed matter so much to the environment?

Last year I took a module in ruminant nutrition (i.e. what you feed cows, sheep and goats) as part of my masters in Sustainable Agriculture. I was a bit taken aback when I saw the main essay title for the module was ‘How can ruminant diets save the world?’

I started the module with the vague idea that cow farts are bad for the environment, and that feeding grass is good for the environment, but almost immediately learnt that neither of these things is quite true. For one thing – dinner party fact alert! - cows burp methane rather than fart it out.

The question of whether feeding cows and goats grass is ‘good’ for the environment is debateable. It is certainly true that by eating grass, farm animals are not directly competing with humans for food. You have probably heard the argument that in eating a dairy or meat product you are also essentially ‘eating’ all the cereal and grain that the animals producing it ate themselves, and that this energy conversion is not very efficient. Humans can’t eat grass of course, so when a grazing animal eats pasture grown on land unsuitable for crops or vegetables, or wildflower meadows grown for biodiverse habitats, it allows this low value fibre to enter the human food chain as high quality protein.

And this is where goats, sheep and cows really come into their own: consuming things which humans would never be able to eat and turning it into nutritious food. They evolved their rumens exactly for the purpose of turning very poor quality fibre such as leaves, woody shrubs and grass, into protein – ingeniously, they source their own protein from the bacteria in their rumen. Because of their rumens and the soup of microbes living within it, they can digest parts of plants that we just can’t: seed husks, tough stems, fibrous outer layers, cellulose, lignin….

However – and this is where it gets more complicated – when it comes to methane emissions, grass alone is less obviously the environmentally friendly choice. Methane emissions are a natural by-product of a cow, sheep or goat’s digestion and make up large part of their carbon footprint. Feeding them at least some starch or fat, rather than pure grass alone, is proven to be far less methane emitting.

Unfortunately damaging environmental impacts can come from some of the ‘typical’ components of livestock diets. One of the top culprits is soya, popular with farmers because it supplies two very important amino acids which are much harder to source in other feedstuffs in the appropriate proportions. The British climate is not well-suited to growing soya, which prefers tropical climates, and as a result rainforest land has too often been deforested to make way for soya plantations, destroying an important habitat and major carbon sink. 90% of the soya imported into Europe goes into animal feed, the remaining 10% being eaten by humans.

Yet in the modern world, we actually have various sources of starchy and protein-rich by products available which are no use to humans but which goats, sheep and cows absolutely love. Our goats, for example, have 80% of the ‘concentrate’ part of their diet derived from by-products of flour, bioethanol and (edible) oil manufacturing, all human inedible. Their hay is cut from wildflower meadows, grown and managed by our landlord, the environmental charity Earth Trust, to be species rich and biodiverse.

To be fair, British retailers and farmers are already a long way along with addressing this issue: Waitrose, for example, does not allow farmers in its dairy supply chain to use soya in their rations, and animal feed suppliers have worked hard to identify appropriate alternative blends. We went soya free in our goats’ ration in 2021.

The question of how environmentally friendly a farmed cow or goat is lies almost entirely in the question of what they are fed. At worst, they compete with humans for land and cereal crops, emitting methane and indirectly causing deforestation. But at best, they have the potential to mop up our leftovers, turning the low grade, inedible fibre and by-products in the land and industries around us into protein in the form of meat and milk. Of course, they also provide natural fertiliser to enrich the soils used to grow crops for human consumption reducing the need for artificial fertiliser, which has its own huge carbon footprint.

It would be asking too much of ruminants to ‘save the world’ but they are extraordinary recyclers and upcyclers in animal form, and their zest for eating things that we just can’t stomach is one of the things I find most fascinating about them.


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