Crickets Are Not a Free Lunch, Protein Conversion Rates May Be Overestimated
Some practitioners of entomophagy believe that raising insects for consumption by humans will help solve world hunger problems. Crickets and other insects, they say, are able to convert plant matter into protein more efficiently than animals such as cattle, pigs, or chicken. For example, the Food and Agriculture Organization of the United Nations states on its website that “crickets need six times less feed than cattle, four times less than sheep, and twice less than pigs and broiler chickens to produce the same amount of protein.”
However, new research from the University of California, Davis suggests that these numbers — at least for chickens — may be exaggerated. Mark Lundy, an agronomy advisor, and Michael Parrella, an entomologist, have found that house crickets (Acheta domesticus) fed a poultry-feed diet showed little improvement in protein conversion efficiency. Their research appears in the journal PLOS ONE.
“Everyone assumes that crickets — and other insects — are the food of the future given their high feed conversion relative to livestock,” Dr. Parrella said. “However, there is very little data to support this, and this article shows the story is far more complex.”
“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,” Dr. Lundy said. “However, 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.”
Dr. Lundy, who has a background in nutrient cycling in agroecosystems and in crop-livestock integration, became curious about the feed-conversion ratios of various livestock after an entomologist friend told him that crickets were known to be more efficient than other animals.
“I guess what made me do the study is that I was hoping crickets were a free lunch, and I wanted to quantify it more thoroughly,” he said.
He and Dr. Parrella raised crickets on five different diets of varying quality in order to specifically quantify the relationship between feed quality and cricket growth. Crickets that received the highest-quality feed grew the largest and fastest. Those fed an ensiled combination of poultry manure, wheat straw, and rice straw fared the worst.
“The unprocessed and lower-quality organic side-streams tested in this study could not support adequate growth and survival of cricket populations,” they wrote. “Therefore, the potential for crickets to supplement the global supply of dietary protein appears to be more limited than has been recently suggested.”
“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,” Dr. Lundy said. “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. Moving forward, the imperative will be to design cost-effective processes that enable large populations of insects to capture protein from underutilized organic waste and side streams.”
The authors note that, in addition to crickets, many other insects are also being considered as possible food and feed sources, and that some — such as the black soldier fly (Hermetia illucens) — may be better suited for converting low-quality, organic materials into protein.
“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,” they wrote.
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