Livestock farming is sometimes criticised for creating competition between feed and food production. However, the animals fulfil an important function by recycling plant by-products and thus closing nutrient cycles.
While the importance of animals in the recycling of plant by-products from food production is generally known, the amounts actually recycled per animal category have never been quantified in detail. In particular, the question arises as to which animal species contribute significantly to the recycling of the main by-products. In this study, we established the contribution of the different animal species to the recycling of by-products. The amount of by-products was calculated from the raw produce processed domestically and the respective food yield, while the (compound) feed consumption of the animals was obtained from the livestock numbers. Finally, the characteristics of the by-products enabled the maximum possible proportion of by-products in compound feed to be determined.
Origin of by-products
On average, the processing of a tonne of bread wheat in a flour mill generates around 200 kg of mill by-products. With around 650,000 t of bread cereals processed for human consumption in Switzerland every year, flour milling alone produces over 140,000 t of by-products. There are also residues from the extraction of edible oils, the pressing of fruit to make juice, and from beer and sugar production. These are only used to a very small extent in human nutrition. However, by feeding these residues to livestock, in particular as ingredients of compound feed, they can still be used for food production.
Pigs and poultry as significant recyclers
Throughout Switzerland, a total of around 365,000 t of plant by-products are generated each year during the processing of primary produce in the food industry. In terms of weight, the by-products of flour milling are the most important (see graph). The annual quantity of compound feed amounts to 629,000 t of pig feed and 367,000 t of poultry feed. Given the maximum percentages of by-products in compound feed, 196,000 t of by-products can be recycled by these two categories of animals, of which 138,000 t can be fed to pigs and 58,000 t to poultry.
Recycling by cattle also necessary
However, not all by-products, particularly mill by-products, can be fully recycled via pig and poultry feed. Almost half of all by-products, i.e. around 170,000 t, must be recycled via cattle feed. Due to their nutrient content, these by-products are defined as concentrated feed. Thus, in terms of the practicable use of by-products, it is necessary to include a certain amount of concentrated feed in cattle rations. With 570,000 dairy cows as the most important ‘consumers’ in the Swiss cattle sector, a minimum consumption of 300 kg of by-products per cow is needed.
- Every year, the Swiss food processing industry produces around 365,000 t of vegetable by-products which are used in the feeding of livestock.
- About half of these by-products can be recycled via poultry and pig feed. The other half goes into cattle feed, which is why a minimum consumption of concentrated feed is necessary and practicable for cattle.
- Viewed across all animal species, Swiss compound feed consists on average of 20 percent by-products from domestic food production. Compound feed thus makes a significant contribution to closing nutrient cycles.
- If livestock holdings in Switzerland were to decline significantly, it would no longer be possible to ensure that the by-products produced were fully recycled in animal feed.