How much animal-source food can we produce while avoiding feed-food competition?

Livestock directly contribute to food supply by providing essential nutrients to humans, and indirectly support cultivation of food crops by providing manure and draft power. Livestock, however, also consume humanedible food or graze on land suitable for cultivation of food crops. As we face the challenge of feeding 9.7 billion people by 2050, preferably without expanding the amount of agricultural land, there is an increasing need to avoid competition for land between animals and humans. We performed a review on studies that provide insight into the amount of animal-source food (ASF) produced without feed-food competition. So called default livestock are only fed with co-products, food-waste, crop-residues, or biomass from grazing land. Results showed, that between 7 g and 27 g of animal source protein per person per day can be produced from default livestock. On average, it is recommended to consume about 57 g of protein from ASF or plant-origin per person per day. Although ASF from default livestock does not fulfil the current global animal protein consumption of 32 g per person per day, about one third of the protein each person needs can be produced without competition for land between feed and food production. Default livestock, therefore, can have an important contribution to the future nutrition supply.