"When the BSF larvae were mashed, calcium digestibility increased to 88%. The high calcium content of the larvae is the main selling point for use in reptiles and amphibians. If the calcium is poorly digestible, the larvae will still require calcium dusting or gut loading to meet the consumer's physiological requirements. Previous literature has identified that the larvae's high calcium content is due to calcium carbonate impregnated within the exoskeleton matrix (Johannsen, 1922). When the exoskeleton is disrupted, such as occurred with the mashed diet, the calcium, as well as other nutrients, become more available to the consumer. The authors' theorized that animals with an alternative feeding strategy, chewing prey versus swallowing whole (as is the case with many frog species), may cause enough disruption to the exoskeleton to improve digestibility.
Unfortunately, Dierenfeld and King also identified another potential issue for using these larvae as a main diet staple. The live larvae actually produced negative digestibilities for fiber, sodium, copper, iron, and molybdenum, indicating a loss of these body nutrients. When the larvae were mashed, these nutrients became much more bioavailable, with the exception of sodium."...
https://digitalcommons.lsu.edu/cgi/viewcontent.cgi?article=5934&context=gradschool_theses
Also..."The live larvae actually produced negative digestibilities for fiber, sodium, copper, iron, and molybdenum, indicating a loss of these body nutrients. When the larvae were mashed, these nutrients became much more bioavailable, with the exception of sodium."
Unfortunately, Dierenfeld and King also identified another potential issue for using these larvae as a main diet staple. The live larvae actually produced negative digestibilities for fiber, sodium, copper, iron, and molybdenum, indicating a loss of these body nutrients. When the larvae were mashed, these nutrients became much more bioavailable, with the exception of sodium."...
https://digitalcommons.lsu.edu/cgi/viewcontent.cgi?article=5934&context=gradschool_theses
Also..."The live larvae actually produced negative digestibilities for fiber, sodium, copper, iron, and molybdenum, indicating a loss of these body nutrients. When the larvae were mashed, these nutrients became much more bioavailable, with the exception of sodium."