I.G. Georgiev
Department of Non-ruminant Animals and Special Branches, Faculty of Agriculture, Trakia University, Stara Zagora, Bulgaria
(Manuscript received 05 June 2025; accepted for publication 04 August 2025)

Abstract. The present study evaluated the effect of autumn feeding with different protein sources on the development of the fat body in worker bees (Apis mellifera L.). The experiment involved 28 bee colonies, divided into seven groups – one control and six experimental. The experimental groups were fed with diets containing different protein sources: soy isolate, brewer’s yeast, spirulina, pea protein, bee pollen and a combined diet with several protein sources. The results showed that bee pollen was the most effective source of protein, with the group fed with it registering the highest percentage of bees with a well-developed fat body (41.7% with grade 5). The combined feed (bee pollen, brewer’s yeast and spirulina) and brewer’s yeast as a single protein source showed good results with 35.0% and 29.2% with grade 5, respectively. The control group, which did not receive additional protein but was fed carbohydrates, showed 34.2% of bees with grade 5, which highlights the role of energy sources in autumn feeding. Alternative protein sources (soy isolate, spirulina and pea protein) were less effective, but still suitable for supporting the development of the fat body. Based on the results obtained, showing the positive effect of the application of alternative protein sources supplementing or replacing bee pollen, we recommend their application in the beekeeping practice to ensure good fat body development in worker bees during the autumn period. This will lead to a more successful wintering and sufficient energy resources for good spring development of the bee colonies.