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Investigations of feed for honey bees and the analysis of possible residues of lithium chloride in bee products and their influence on bee behaviour
Project
Project code: BfR-SiN-08-1322-731
Contract period: 01.01.2019
- 31.12.2019
Purpose of research: Experimental development
Keywords: Apis mellifera, hydroxymethylfurfural, lithium chloride, varroosis control measures, food chain
The honeybee (Apis mellifera) is one of the most important livestock. In addition to their pollination activity, it also produces bee products such as honey, wax and propolis. Hydroxymethylfurfural, also called 5-hydroxymethyl-2-furaldehyde, is a contaminant in the food chain which can arise through heat effects. The heating of carbohydrate- or sugar-containing food and feed leads to increased formation of hydroxymethylfurfural (HMF). HMF is formed by the thermal degradation of sugars (Maillard reaction) or by acid-catalyzed dehydration of hexoses (Kuster 1990, Teixidó et al., 2006). HMF can arise from all hexoses, but is preferably formed by fructose. The HMF concentration rises with increasing temperature. Besides temperature, the type of sugar and the pH value are crucial for HMF formation. Industrially produced feed for honey bees are generally used for the wintering period to replace the honey with an equivalent feed. Feed syrup is a compound feed based on beet sugar. The composition of industrially produced feed syrups for honey bees is based on the sugar spectrum of nectar and honey. Fructose, glucose and sucrose make up about one third of a suitable ratio of these sugars in the syrup. Directly after the preparation of the feed syrup for honey bees, the HMF levels in the feed syrup are generally between 15 and 25 mg/kg (information sheet). The sugar composition and the HMF content of the feed syrup change depending on time and temperature. Especially the temperatures during transport and storage are crucial for the increased formation of HMF. The HMF content of feed syrup can increase from normal low levels of 25 mg/kg to more than 350 mg/kg (information sheet). Various studies indicate that increased levels of HMF are toxic to honey bees, especially when a long-term feeding period (wintering period) causes long-term exposure to HMF. Currently available studies show different results on dose-dependent effects of HMF on honey bee mortality. Nevertheless, the studies show that increasing HMF content leads to increased mortality in honey bees (Jachimowicz & El Sherbiny 1975, LeBlanc et al., 2009, Lüken D.J. & van der Ohe, W. 2016). To avoid increasing HMF levels in the feed syrups, the recommendations for trade, transport and storage of feed syrup are to avoid a long storage period, direct sunlight and temperatures above 25 °C (information sheet). However, in literature storage studies are scarce. One aim of the project is to generate sufficient data based on standardized storage conditions (parameters: temperature, duration) to get information about the time- and temperature-dependent increase of HMF content and the safety of feed syrup for honey bees. A particular threat to Western honeybees is the infestation by the mite Varroa destructor, also known as varroosis. This mite can transmit viruses such as the Deformation Wing Virus, which is associated with colony losses. To date, there are only a few veterinary medicines (VM) approved in the EU for the treatment of varroosis. These involve risks, so the use of the organophosphate Coumaphos or the amidine Amitraz leads to residues in honey and wax. Organic acids such as formic acid and oxalic acid are difficult to handle and do not lead to complete varroa losses. A study published by the University of Hohenheim in January 2018 now presents lithium chloride as an effective salt for the treatment of varroosis. This salt is freely available for sale, but is not approved as VM for bees. Beekeepers are likely to use this salt, as beekeepers' enquiries to bee institutes have shown. So far no data are available on possible residues of salt in bee products. Another aim of the project is to investigate a possible transfer of lithium chloride into bee products. Therefore, bee colonies, established at the BfR, will be treated with different amounts of lithium chloride at different times within the bee year. A possible transfer of lithium chloride into honey and bee bread is to be analysed. Therefore, an analytical method for the quantification of lithium chloride in honey and bee bread needs to be developed. A further aim is to investigate the effect of lithium chloride on bee behaviour by means of classical conditioning tests. In summary, these research approaches should provide important insights into the transition of lithium chloride into the food chain. They can form the basis for a later risk assessment.
Section overview
Subjects
- Beekeeping and health
- Toxicology
