Fine-tuning livestock diets to reduce greenhouse gas emissions

Photo: Zerihun Sewunet (ILRI)

Of all livestock, beef and dairy cattle are the biggest source of greenhouse gas emissions from livestock globally, accounting for 77% of the total. So it is useful to study variations in their emissions and what causes them. A recent assessment by the International Livestock Research Institute (ILRI) and its partners, working under CCAFS, did just that.

The results show that animals in the developing world require far more food to produce a kilogramme of protein than animals in wealthy countries, and that greenhouse gas emissions vary widely depending on the animal and the quality of its diet. In the developing world, 75% of livestock emissions come from cattle and ruminants such as cows, sheep and goats, which is higher than in developed countries.

“We’re providing a set of detailed, highly location-specific analyses so we can get a fuller picture of how livestock in all these different regions interact with their ecosystems and what the real trade-offs are in changing these livestock production systems in future.” Philip Thornton, CCAFS Theme Leader

The most important results relate to the amount of feed consumed to produce a kilogramme of protein (feed efficiency), and the amount of greenhouse gases released for every kilogramme of protein produced (emission intensity). Ruminants require up to five times more feed to produce a kilogramme of protein as meat than a kilogramme of protein as milk, and the quality of an animal’s diet has a big effect on feed efficiency and emission intensity. Cattle scrounging for food in arid areas can release the equivalent of 1000 kilogram of carbon for every kilogramme of protein they produce. In many parts of the developed world, the emission intensity is around 10 kilogram of carbon per kilogramme of protein.

Cattle scrounging for food in arid lands can release the equivalent of 1000 kilogram of carbon for every kilogram of protein they produce

The new data will greatly help to assess the sustainability of different livestock production systems. But no single measure should be used as an absolute indicator of sustainability. For example, most animals in sub-Saharan Africa subsist largely on vegetation inedible by humans, especially by grazing on marginal land and on crop residues. This means low livestock feed efficiencies and high emission intensities. Changing the production system may mean trade-offs.

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