Whenever nutrition is discussed, whether about livestock, humans, or bees, one must take into account the fact that actual absorption of nutrients is not directly correlated to the quantity nor quality of the foodstuffs consumed. For example:

Bees digested less of the protein in the PS [protein supplements] than the pollen. Our estimates were similar to Wang et al. who reported digestion of B. rapa pollen to be about 67 %. In contrast, bees digested only about 35 % of the protein in the PS. The differences might be that PS are difficult to digest because they contain soy or barley flour and eggs as protein sources, none of which are part of a bee’s natural diet.

Though protein digestion was lower for PS than rapini pollen, hemolymph protein titers did not differ. Others have reported no effects of protein stress on soluble protein titers. In our study, brood production did not differ between colonies fed PS or pollen possibly because it occurred in the winter when brood rearing rates are low. In a study comparing PS with pollen in summer, brood rearing was lower in those fed PS.

DeGrandi-Hoffman, G., Chen, Y., Rivera, R. et al. Honey bee colonies provided with natural forage have lower pathogen loads and higher overwinter survival than those fed protein supplements. Apidologie (2016) 47: 186. 

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