Thermal processing effect on element absorption from honey bee (Apis mellifera) feed

Recently it was shown that micronutrient deficiency in honey bees may be associated with the widespread chalkbrood disease [1], caused by the fungus Ascosphaera apis. To address this, we have begun exploring the use of yellow mealworm larvae (Tenebrio molitor L.) flour as a potential substitute for pollen in bee diets. Our current focus is to determine how thermal processing of this food, affects the absorption of essential elements by the bees. Honey bees were divided into two groups consisting of five cages each, with about 100 bees per cage. They were kept in an incubator at 35° C and RH 70%. All 10 cages were supplied with a piece of drawn-out comb, tap water and 35 g of specific patty partially enveloped with plastic wrap to prevent drying. First group of five cages (NT) were supplied with patties with non-autoclaved mealworm flour for 8 days, those patties were than replaced with patties with autoclaved mealworm flour for next 10 days. Second group of five cages (AT) were supplied with patties with non-autoclaved mealworm flour during whole experiment (18 days). After 18 days gut (midgut and rectum) was rapidly removed using tweezers. Element concentrations were done separately from the gut and rest of body. About 100 mg of freeze-dried and homogenized sample was digested in an ultraCLAVE IV microwave digestion system using 5 mL of concentrated HNO3. Each digestion was accompanied by three digestion blanks (5 mL conc. HNO3) and three reference materials BOVM-1 “Bovine muscle powder”. Element concentrations were determined using ICPMS. NA group of bees was first kept on non-autoclaved patties for the first 8 days of bee rearing, because soon after emergence young bees start to consume protein rich food (beebread). Afterword it was replace so as to observe whether nutrition in first days of life has a long-term impact honey bee nutrition status and body composition. Significantly higher concentration of K, B, Rb, Ba, Ag and Pb was detected in bodies of AT group in comparison to NT group of bees. There was no statistically significant difference in other tested elements, except for Fe that was to only element that was higher in NT group in comparison to AT group. Only element that was detected in significantly higher concentration in the gut NT bees was Pb, there were not significant differences between other tested elements. At the same time Pb is lower in NT group. This confirms that Pb is more efficiently absorbed from autoclaved food in comparison to non-autoclaved food.