Crickets are not all that they’re cracked up to be as an alternative, global source of protein in the human diet to supplement or replace livestock consumption, according to newly published research at the University of California, Davis.

Worldwide, statistics show that crickets are the most widely cultivated insects for the human diet and are considered the “gateway bug” for people who choose to eat insects. Crickets are touted as highly nutritious and much better for the planet — environmentally and financially — than livestock, due to the comparatively efficient rate at which they convert feed into body mass. 

But the issue is far more complex than that, say UC Cooperative Extension agronomist Mark Lundy and horticultural entomologist Michael Parrella, a professor and chair of the UC Davis Department of Entomology and Nematology, in research published April 15 in the journal PLOS ONE, published by the Public Library of Science.

"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,” said Lundy, who headed the research at UC Davis while seeking his doctorate in agronomy. “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.”

“Insect cultivation is more likely to contribute to human nutrition at a scale of economic and ecological significance if it does not rely on a diet that competes with conventional livestock, but more innovation is needed for this to become a reality,” Lundy said. The goal will be to design cost-effective processes to feed large populations of insects on underutilized organic waste and side streams, he said.

Crickets efficient at converting feed

It's widely assumed that crickets and other insects are efficient in converting feed to protein compared to conventional livestock, Parrella said. However, there is very little data to support this, and the story is far more complex, he said.

The researchers measured the biomass output and feed conversion ratios of crickets (Acheta domesticus) that were reared on foods ranging from grain-based to high in cellulose.

They found that the biomass accumulation was strongly influenced by the quality of the diet.

The measurements were made at a much greater population scale and density than any previously reported studies. For populations of crickets that survived to a harvestable size, the feed conversion ratios were less efficient than those reported from studies conducted at smaller scales and lower population densities.

Crickets fed a poultry-feed diet showed little improvement in protein conversion efficiency compared to the industrial-scale production of broiler chickens.

Crickets fed on processed food waste grew to harvestable size with conversion efficiency similar to broiler chickens. But crickets fed on minimally processed, municipal-scale food waste and diets composed largely of straw had more than a 99 percent mortality before reaching a harvestable size.

High-quality feed sources needed

Bringing crickets into the global protein supply will depend on collecting and using relatively high-quality waste side-streams that are not currently being used for livestock production, the researchers said.

Lundy, who received his doctorate in agronomy from UC Davis in 2013 and his master’s degree in international agricultural development from UC Davis in 2010, admitted to eating some of his experimental subjects — after weighing them for the research, of course. He dusted them with cornmeal and Cajun seasoning and fried them in olive oil. He has also snacked on protein bars made with cricket flour.

“I'm all for exploring alternatives, and I am impressed by the amount of innovation that has sprung up around insect cultivation and cuisine in the last few years,” Lundy said. “However, I also think we need to be clear-eyed about what the sustainability gains are and aren’t, and focus our innovative efforts and limited resources to where they will have the most lasting impact.”

Crickets are readily available in pet stores as food for turtles, frogs and other pets. Part of many human diets, they are considered delicacies or snacks in many countries. Cricket flour is now commonly found in protein bars, baked goods and protein powders.