Edible insect potential hinges on identifying optimal diet, say researchers

By Elaine Watson

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Mark Lundy: 'Sustainability gains associated with cultivating crickets as an alternative source of protein will depend, in large part, on what they are fed'
Mark Lundy: 'Sustainability gains associated with cultivating crickets as an alternative source of protein will depend, in large part, on what they are fed'

Related tags Food waste Agriculture

If edible insects such as crickets are to deliver on their promise of providing a more environmentally-friendly source of protein, they may need to be put on a different diet, suggests a new study.

Crickets have been heralded as more sustainable protein source due to the rate at which they convert food into body mass. However, new data suggests that they are no more efficient at converting poultry feed (the typical diet given to crickets) to protein than chickens.

In a study​ published in the journal PLOS ONE, University of California Davis agronomist Mark Lundy and horticultural entomologist Michael Parrella measured the biomass output and feed conversion ratios of crickets (Acheta domesticus​) reared on a range of foods from chicken feed to municipal food waste.

And compared to the industrial-scale production of chickens, “crickets fed a poultry feed diet showed little improvement in protein conversion efficiency, a key metric in determining the ecological footprint of grain-based livestock protein," ​they found.

A diet derived from underutilized organic waste and side streams would significantly improve their green credentials, of course, but only if it can deliver good feed conversion ratios, said Lundy et al.

‘Some of the sustainability claims on this topic have been overstated’

“Crickets fed the solid filtrate from food waste processed at an industrial scale via enzymatic digestion were able to reach a harvestable size and achieve feed and protein efficiencies similar to that of chickens. However, crickets fed minimally-processed, municipal-scale food waste and diets composed largely of straw experienced >99% mortality without reaching a harvestable size.

“Therefore, the potential for Adomesticus to sustainably supplement the global protein supply, beyond what is currently produced via grain-fed chickens, will depend on capturing regionally scalable organic side-streams of relatively high-quality that are not currently being used for livestock production.”

They concluded: "While there is potential for insect cultivation to augment the global supply of dietary protein, some of the sustainability claims on this topic have been overstated.

“Our study demonstrates that the sustainability gains associated with cultivating crickets as an alternative source of protein will depend, in large part, on what the crickets are fed and which systems of livestock production they are compared to.”

Study details

In a controlled-environment greenhouse at the University of California, Davis, 15 experimental units were organized in randomized complete blocks with five treatments and three replications per treatment.

From 14 days after hatching until they were harvested or died, the crickets were given the following five feed treatments ad libitum:

1) POULTRY FEED:​ 5:1 ratio of non-medicated poultry starter feed and rice bran.

2) FOOD WASTE FROM ANAEROBIC DIGESTOR​: Solid, pasteurized, post-process filtrate from aerobic enzymatic digestion process that converts grocery store food waste into 90% liquid fertilizer and 10% solids.

3) MUNICIPAL FOOD WASTE:​ minimally-processed, post-consumer food waste from municipalities in the Bay area.

4) CROP RESIDUE:​ 1:1 ratio of wheat and maize silage prepared at an industrial scale as dairy cow rations and containing approximately 50% straw.

5) CROP RESIDUE:​ 2:1:1 ratio of poultry manure, wheat straw and rice straw silage.

They observed: “Even if global demand for crickets were to exist at a much greater scale than it does at present, a novel protein source with little or no protein conversion efficiency improvement compared to chicken is unlikely to justify the investments required to produce crickets at a scale of global significance.

“Further, the same global forces driving the recent and projected increases in conventional livestock prices will also increase the cost of crickets fed these same diets."

Therefore, they conclude: “In order for insect cultivation to sustainably augment the global supply of protein, more work is needed to identify species and design processes that capture protein from scalable, low-value organic side-streams, which are not currently consumed by conventional livestock​.”

Source​: PLOS ONE​ Published: April 15, 2015 DOI: 10.1371/journal.pone.0118785

Crickets Are Not a Free Lunch: Protein Capture from Scalable Organic Side-Streams via High-Density Populations of Acheta domesticus

Authors​: Mark E. Lundy and Michael P. Parrella

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