Can insect proteins replace soybeans in pig feed?

Soy is often cited as one of the main contributors to greenhouse gas (GHG) emissions from pig farms.

With all livestock sectors now facing moral and governmental pressure to reduce their GHGs, many producers are now looking to move away from soybeans and replace them with low-emitting protein sources.

To date, alternatives have been limited. However, there is strong belief that insect proteins could now help fill this gap.

This was highlighted at the Insects as Food and Feed conference (April 26-27, 2022), organized by the Royal Society of Entomology (RES).

So what are the prospects, opportunities and potential barriers for insect proteins in pig feed?

See also: How a laying hen producer reduces his carbon footprint with maggots


Arnold van Huis of Wageningen University and Research in the Netherlands recently published an entomological research paper on the challenges and prospects of edible insects.

He says most of the insect production goes to the pet food industry. However, growth is expected for pig (and poultry) feed in the coming years.

Although a few species can be used as a source of protein, the one that shows the most promise for animal feed markets is the black soldier fly.

Broadly, this insect can be fed as protein meal to adult flies or larvae.

According to Professor van Huis, soybean meal accounts for around 85% of the protein supplements given to pigs, and the black soldier fly has the potential to partially replace this.

Black soldier fly larvae can be reared on a wide range of cheap food sources and substrates – including food scraps – and require much less space to grow than more traditional protein sources.

Slaughterhouse products, manure, catering waste and supermarket products containing meat or fish may not be used when rearing insects for animal feed, in accordance with legislation on food hygiene.


Developments in insect genetics, improved animal health through insect protein feeding, and the ability to use insect by-products – such as droppings, insect larval waste insects – in agriculture at large are among the potential opportunities.

Production of insects

Breeding insects suitable for commercial production is a key goal for Desmond Cave of genetics company Beta Bugs, based at the Roslin Innovation Center in Scotland.

He has been working on the development of the black soldier fly for two and a half years.

While the black soldier fly has been commercially cultivated for some time, Cave says genetic improvement to enable large-scale production has not always been enough.

“We are focused on improving this by selectively breeding the black soldier fly. Our larvae are heavier than the standard fly and grow faster, and the adult flies produce more eggs.

One gram of eggs from a standard fly, cultured for a year, could produce about 104 kg of larvae.

In comparison, one gram of genetically enhanced eggs could produce around 226 kg of larvae per year.

Beta Bugs also aims to improve the mass, development time, hatch rate and number of eggs laid by the adult fly, he adds.

Swine health

Various studies have shown beneficial health effects when animals are fed the black soldier fly and/or its larvae, says Prof. van Huis. They include:

  • Less diarrhea, better immune response and better small intestine morphology – which is linked to good gut health (Choi et al, 2020)
  • An antimicrobial effect on gram-positive bacteria due to lauric acid present in black soldier flies (Spranghers et al, 2018)
  • Digestibility and growth of similar amino acids compared to soy and fishmeal (Veldkamp and Vernooij, 2021)
  • Reduced tail biting when fed live black soldier fly larvae (Ipema et al, 2021)

Other research has shown that feeding black soldier fly larvae can also potentially reduce ammonia pollution from livestock manure, he adds.


Legislation and cost were the two main barriers highlighted at the conference.

Under EU law, insect-processed animal protein (PAP), including black soldier fly, has been allowed in pig (and poultry) feed since 2021.

This is not yet the case for UK farmers, says Rachael O’Connor, senior partner at law firm Michelmores.

She says what is now UK domestic law reflects a “snapshot” of what EU law looked like on 31 December 2020 and does not encompass the changes that have been made in the EU since then.

These include changes to the feed ban rules, which now allow the use of insects as feed in European pig and poultry production.

“While not yet applicable to UK farmers, this decision reflects the direction we could and should be taking,” she adds.

The World Wide Fund for Nature (WWF) is among the non-governmental organizations campaigning to change that.

In his 2021 Roadmap to fast-track insect protein in UK food (PDF), WWF is urging the UK government to introduce legislation that allows the use of insect meal in pig and poultry feed and expands the range of raw materials that can be used for insect farming .

It also indicates that the pork and poultry sectors must advocate for the legislative changes required.

Feeding black soldier fly larvae is, however, permitted for pig feed under current UK legislation (see ‘Understanding black soldier fly’).

Professor van Huis adds that the cost of insect meal is currently even higher than the comparable price of soybeans. This presents another challenge to its widespread adoption.

Understanding the Black Soldier Fly

The black soldier fly is native to South America. An adult fly measures around 30mm, while larvae are around 15-20mm long.

The larvae are currently of most interest to UK farmers as they can be fed to poultry, pigs, trout and salmon.

The larvae can also be dried, processed and fed as a protein powder, which can be used as a substitute for soy. However, under current legislation insect protein meals cannot be fed.

A large volume of feed is required to grow the larvae, and this is converted primarily into protein, along with oil and carbohydrates.

Growth from 1mm to 15mm takes about 14 days – depending on feed, temperature etc.

Constant temperatures of 28°C are required and larval growth can be done in a number of ways, including trays, barrels and long tubs.

Many insect breeders feed supermarket produce that has passed its best before date or spent grain from breweries or distilleries, for example.

Regardless of the feed source, consistency is essential to ensure consistent larval production.

Source: Desmond Cave