Apparent digestibility in honeybee (Apis mellifera L.): titanium dioxide (TiO2) as an inert marker.

LEDESMA GONZÁLEZ MATÍAS FRANCISCO; FERNÁNDEZ LETICIA A.; TOURN ELIAN; REYNALDI FRANCISCO JOSÉ

Santiago de Chile

Congreso; 48° Congreso Internacional de Apicultura; 2023

Apimondia

Digestibility refers to the extent to which feedstuff and its nutrients are absorbed in the digestive tract of an animal and utilized by the body. Apparent digestibility is a widely used method for measuring nutrient and feedstuff digestibility. This method requires an inert marker such as titanium dioxide (TiO₂). TiO₂ had never been used in apparent digestibility studies in domestic honeybee. Thus, the aim of this work was to evaluate, for the first time, the behavior of TiO₂ as inert marker for apparent digestibility studies in A. mellifera under in vitro conditions. Two experiments were carried out: TiO₂ in sucrose syrup and TiO₂ in bee pollen, with five treatments each: 0 (control) - 0.1 - 0.25 - 0.5 - 0.75 % TiO₂ weight by weight based on dry mass basis. Eight replicates were used per treatment. A randomized complete block design was used with half of the replicates of both experiments on two dates (November 2021 and December 2021). We measured consumption variables (water, sucrose and pollen consumption and sucrose mobilization), apparent digestibility, mortality rate and body parts weight. The results revealed that sucrose consumption and mobilization, mortality rate and body parts weight did not differ between the different concentrations of inert marker used in both experiments. However, when concentration of TiO₂ increased, water consumption was reduced in both feeds provided. Apparent digestibility was 94,22% (±2,2) for sucrose syrup and 48,61 % (±10,4) for bee pollen. Like water consumption, apparent digestibility decreased as the inert marker concentration augmented. The use of TiO2 as an inert marker for digestibility studies in A. mellifera is viable. The decline of water consumption and apparent digestibility with the increase of TiO₂ concentration in the feeds could be associated with a toxic effect on bee physiology. Inert marker concentration and apparent digestibility relation could also be explained to the analytical procedure. Based on these results, we selected a TiO₂ concentration of 0.1 % weight by weight for further apparent nutrient digestibility studies.