Redifining edibility of feed content in aquaculture boosts food security

A shift away from using feed ingredients fit for humans could greatly improve resource efficiency in aquaculture, reduce environmental impacts and increase food security. A recent study on tilapia farming shows that while efficient in producing protein, much of the omega-3 fatty acids and essential micronutrients, such as vitamin B-12, calcium, iron, and zinc, are lost in the feed-to-fish conversion.

The study, published in the journal Food Security which analysed ten different tilapia production systems across eight countries, sheds light on the feed-food competition limiting global food production efficiency. Tilapia, the third most farmed finfish species globally, is raised in diverse systems ranging from low-input ponds to intensive land-based tanks.

“How we use food-grade resources more responsibly is a general challenge for the entire animal sector, not just aquaculture”, says co-author Max Troell.

Gaining protein but losing nutrients

Researchers focused on the human-edible nutrient conversion ratio (HeNCR), comparing the human-edible nutrients in feed inputs to those in the fish produced. While tilapia farming is generally a net producer of protein, the fish contained less omega-3s and micronutrients than the feed. The most efficient systems produced 2.5 times more human-edible protein than consumed, but the feed contained about seven times as many omega-3s and up to 175% more essential micronutrients.

The study also compared different tilapia aquaculture practices, finding that polyculture systems (farming tilapia mixed with other species) performed better in nutrient conversion efficiency. However, tilapia monoculture could be improved by prioritizing non-human-edible ingredients in feed.

Redifining “edible”

The study, led by Killian Chary of Wageningen University and co-authored by Patrik Henriksson and Max Troell of the Beijer Institute, analysed four scenarios with different definitions of feed and fish edibility. It found that redirecting edible feed resources like soy or fishmeal directly to human consumption resulted in more nutrients for people than consuming the fish itself, even when the entire fish was eaten.

Notably, certain feed ingredients such as soy and fishmeal are often classified as non-edible despite originating from edible resources.

“Up to 69% of the ingredients in tilapia feeds can be considered edible by humans, depending on how we define edibility,” the study highlights.

This suggests current definitions of “edible” may need to evolve to improve food system efficiency. This is easier said than done, since the notion of what is edible varies across cultures and regions and depends on markets, processing methods, and logistics.

Resource efficiency benefits the environment too

Using resources wisely is not only beneficial for human health but also essential for environmental sustainability. It reduces the need for additional agricultural land, minimizes the impact on biodiversity, and lowers greenhouse gas emissions.

“Transformative changes are needed to maximize food resource use, including changes in consumer food preferences and the way we define edibility,” the researchers conclude.

Read abstract

Reference: Chary, K., P.J.G. Henriksson, and M. Troell. 2024. Competition for human edible feed resources in aquaculture – looking at tilapia farming. Food Security 17:57-72.