Substituting fishmeal with plant ingredients

 

by Wesley Malcorps, PhD student, The Institute of Aquaculture, University of Stirling, UK and Björn Kok, MatureDevelopment BV, The Netherlands

 

Currently, more than 50 percent of shrimp supply originates from aquaculture. The shrimp industry is one of the dominant consumers of fishmeal in the aquaculture sector.

However, in order to meet the demand for a growing industry in the face of a finite supply of marine ingredients, feed manufacturers have decreased the inclusion of fishmeal in commercial diets.

In 2000, 19-40 percent fishmeal was included in shrimp feed, however, that fell to 11-23 percent in 2014.

Over the years, and in response to fishmeal price increases, fishmeal has been increasingly substituted by plant ingredients. This approach is widely recognised as being more environmentally friendly due to the reduced pressure on the marine environment.

However, substituting fishmeal in aquaculture feeds with plant ingredients may not be as beneficial for the environment as many people think, according to a new study.

This research was conducted by an international and multidisciplinary team of experts and academics from the aquaculture industry and beyond, including; MatureDevelopment BV (The Netherlands); Institute of Aquaculture, University of Stirling (UK); Research Institute for Agriculture, Fisheries and Food (Belgium); Mexico Aquaculture Research Inc (Mexico); Association of International Seafood Professionals (Australia); Aquaculture without Frontiers (USA); Universidad Tecnológica del Mar de Tamaulipas (Mexico); IFFO, The Marine Ingredients Organisation (UK); Utrecht University (The Netherlands); University of Zürich (Switzerland); and Harper Adams University (UK).

The study assessed the impact on marine and terrestrial resources, such as fish, land, freshwater, nitrogen and phosphorus by modelling incremental fishmeal substitution, from 20-30 percent to zero, by plant ingredients.

This includes ingredients, such as soybean meal concentrate, rapeseed meal concentrate, pea protein concentrate and corn gluten meal, commonly included in modern shrimp feeds for the two main shrimp species produced globally, whiteleg shrimp (Litopenaeus vannamei) and black tiger shrimp (Penaeus monodon).

The results show that complete fishmeal substitution by plant ingredients could lead to an increasing demand for freshwater (up to 63 percent), land (up to 81 percent), and phosphorus (up to 83 percent). These are significant increases, as only a share of 20–30 percent of the feed is actually substituted.

This is mainly caused by the inclusion of resource-intensive crops and their derived ingredients to meet nutritional requirements, such as soybean meal concentrate, rapeseed meal concentrate and pea protein concentrate.

These ingredients caused a considerable rise in freshwater, land and phosphorus use.

However, nitrogen demand remained relatively stable in most scenario's, which is caused by crops requiring little to no nitrogen fertiliser, due to their ability to fix nitrogen from the atmosphere.

Nevertheless, some of these crops use relatively more phosphorus, explaining the increase in demand of this valuable resource, already heavily strained under existing agricultural demand.

 

Complex dietary requirements

Additionally, it must be noted that complete substitution of fishmeal and fish oil with plant-based ingredients, without affecting shrimp performance, is very difficult.

This is caused by the complex dietary requirements of shrimp species.

Therefore, a small percentage of fish oil remains in the diet when all fishmeal is substituted, explaining the remaining demand for fish in the feed formulation.

Increasing dependency on plant ingredients could lead to competition for agricultural crops from a terrestrial system and its essential resources, which are already under pressure to meet global demand for food, feed, biofuels and bio-based materials.

These additional pressures on essential agricultural resources could lead to socio-economic and environmental implications, which may affect the resilience of the global food system. Additionally, increasing dependency on plant ingredients for aquafeed could also affect the nutritional value of farmed seafood.

An excessive dependency on the use of plant ingredients for aquaculture could lead to deleterious effects on the environment and indirectly impact human health by altering the nutritional value of the aquaculture products, likely underestimating the impacts of this feed transition.

Consequently, even though the production of shrimp feed (or aquafeed in general) utilises only a small percentage of the global crop production, a shift from fishmeal to plant ingredients should not be taken for granted as a sustainable solution, to meeting a rapidly expanding (shrimp) aquaculture industry.

 

The potential to improve

There is much potential to improve the sustainability of feed for (shrimp) aquaculture.

First, fishmeal can be used more strategically in various aquafeed formulations. This requires more research and innovation in order to optimise its value in relation to alternative ingredients.

Strategic management and utilisation of fish by-products shows potential for higher resource use efficiency of valuable marine resources. Additionally, improvement of feed conversion ratios, side streams up to 30–40 percent of the global food system, and novel protein sources might allow acceptable solutions to supplement high quality fishmeal.

Promising supplements include the innovative use of by-products and novel ingredients, such as microbial biomass, insect meal, yeasts, micro/macroalgae and macrophytes.

All these options should be explored further.

As well as innovative production systems, such as integrated multi-trophic aquaculture (IMTA), biofloc systems and aquamimicry, reducing feed use and its embodied resources.

Such a feed strategy would contribute to the Sustainable Development Goals (SDGs) of the United Nations. This would enable the shrimp farming industry to operate and contribute in a sustainable manner to global food security and the economy, providing the much needed highly nutritionally valuable seafood.

The paper, 'The Sustainability Conundrum of Fishmeal Substitution by Plant Ingredients in Shrimp Feeds' is available at the open access journal 'Sustainability'.

Malcorps, W.; Kok, B.; van 't Land, M.; Fritz, M.; van Doren, D.; Servin, K.; van der Heijden, P.; Palmer, R.; Auchterlonie, N.A.; Rietkerk, M.; Santos, M.J.; Davies, S.J. The Sustainability Conundrum of Fishmeal Substitution by Plant Ingredients in Shrimp Feeds. Sustainability 2019, 11, 1212.

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