Evaluation of vitamin A gut loading in black soldier fly larvae ( Hermetia illucens )

Black soldier fly (BSF) larvae are potentially an excellent source of calcium for insectivores; however, previous studies have identified that they lack appreciable amounts of fat‐soluble vitamins (A, D 3 , and E). To make BSF larvae a more complete food item, fat‐soluble vitamins should either be provided via gut loading or with a multivitamin dusting supplement. The purpose of this study is to identify factors associated with gut loading vitamin A into BSF larvae and to develop feeding recommendations for a more consistent gut‐loading process. Factors that were addressed include the vitamin A concentration added to the diet, length of time given to gut load, moisture content of the diet, and density of larvae during feeding. Diets and larvae were analyzed for vitamin A concentration using high‐performance liquid chromatography. Larval vitamin A concentrations increased in a nonlinear fashion with increasing dietary vitamin A. Length of time ( F  = 150.818, p  < .001), moisture content of the diet ( F  = 41.436, p  < .001), and larval density ( F  = 78.407, p  < .001) were all found to be significant factors contributing to the larvae's gut‐loading capacity. On the basis of our results and vitamin A recommendations from the National Resource Council for rats and poultry, gut‐loading recommendations for BSF larvae when fed to insectivorous reptiles and amphibians are as follows: vitamin A concentration of diet between 16,000 and 20,000 mcg retinol equivalents/kg, gut‐loading time period of 24 h, moisture content of the diet approximately 60%, and larval density between 0.1 and 1 larvae per each gram of moist substrate.