Influence of Protein supplements on thermoregulation of stingless bees
Description
The research hypothesis was that protein-rich supplementation would improve the nutritional status of Tetragonula iridipennis, reflected by increased free amino acid content in honey and worker-bee tissue, and would enhance brood-chamber thermoregulation through an indirect, treatment-mediated pathway. The study tested six plant-protein formulations against a sugar control using 21 colonies, with three colonies per treatment. The experiment ran for 121 days, from 1 December 2025 to 31 March 2026. Brood-chamber temperature and relative humidity were recorded daily at seven daytime intervals, while honey and pooled worker-bee samples were collected at Day 0 and at 30-day intervals up to Day 120. Total free amino acids were quantified using the ninhydrin colorimetric method and expressed as L-leucine equivalents. The data support the hypothesis strongly for biochemical responses but only partially for thermoregulation. Protein supplementation significantly affected brood-chamber temperature and relative humidity, but the biological magnitude was small. The total difference among treatments was only 0.65 °C. The chickpea plus wheat-germ formulation, T6, produced the highest brood-chamber temperature, 30.39 °C, and the highest thermal differential, +4.31 °C, compared with 29.74 °C and +3.65 °C in the sugar control. The treatment effect was strongest under higher thermal load and became smaller as ambient temperature approached the preferred range. The strongest response occurred in free amino acid content. By Day 120, T6 increased honey free amino acids to 43.9 mg LE/100 g, approximately 2.4 times its baseline value. Worker-bee tissue reached 18,185 µg LE/g fresh weight, approximately 2.2 times baseline. Treatment, sampling time and their interaction were significant in both matrices, showing progressive and treatment-dependent enrichment. Feed disappearance also supported the superior performance of T6. It recorded 10.54 g colony⁻¹ week⁻¹, the highest among the solid formulations. The evaporative control indicated that differences in feed disappearance were not explained by moisture loss alone. A notable finding was the strong positive association between free amino acids and thermoregulatory parameters, reaching r = +0.953 for honey free amino acids and ΔRH at Day 120. However, treatment-adjusted correlations were weak and non-significant. This indicates that the strong overall correlation arose mainly because both responses changed according to the dietary treatment, rather than because increased free amino acids directly controlled thermoregulation. Therefore, the data support an indirect effect of protein supplementation on nest climate, while the biochemical response is the stronger and more consistent outcome.
Files
Institutions
- University of Agricultural Sciences RaichurKarnataka, Rāichūr