Valuing leftover streams through livestock: impact of livestock system and productivity level

The role of livestock in sustainable food systems is heavily debated nowadays. Recent studies, however, show that livestock can significantly contribute to global nutrition security by converting leftover streams – products humans cannot or do not want to eat – into nutritious animal-source food (ASF). They conclude that feeding livestock on only leftover streams can provide 7-27 g of animal protein per capita per day. Where these studies clearly underpin livestock’s role in global food security, the current study aims to identify which combination of livestock systems, differing in production level, can optimally convert leftover streams into protein. To this end, we developed an optimization model containing a variety of livestock systems (pigs, dairy cattle, beef cattle, laying hens and broilers), differing in production level (low, mid and high), to enable better utilisation of the various (low quality) leftovers. Included leftover streams consist of food waste and food processing co-products related to the current food consumption in the EU – according to FAO’s food balance sheets – and currently available grazing resources in the EU.
Optimal conversion of leftovers results in a protein supply of 39 g/cap/day – 60% of daily protein requirements – from ASF (mainly milk). This protein supply is higher than found in previous studies (7-27 g/cap/day) due to high assumed availability of coproducts and the inclusion of waste and grazing resources from arable land. Maintaining current animal product ratios reduces the amount of animal protein available to 26 g/cap/day, due to the use of relatively inefficient livestock systems that are unable to value grass. This study, therefore, illustrates that using leftover streams optimally improves the role of livestock in nutrition security. This does, however, require livestock systems to shift to dairy production under various productivity levels.