Most beekeepers in the Atlantic region are currently feeding their bees in preparation for a successful winter. Last week we started to discuss some considerations around the quality of the feed we provide our bees. Feed quality is directly linked to bee longevity and therefore overwintering survival. Let's explore this further in this weeks blog.
Feed Quality - Part 2
There is a body of research indicating that poor quality
feed negatively impacts honey bee health and longevity3,4,5. The
repeated conclusion of researchers is that the best quality feed for bees is
honey6, second is sucrose syrup.
The implications for overwintering success are clear, poor-quality feed
will increase winter mortality! It may
be intuitive to think that direct and clear signs of poor-quality feed, such as
dysentery and the bees reluctance to consume, are important. Bees may consume degraded feed at the same,
or perhaps an even faster, rate as good syrup7. Dysentery can be caused by a number of things
and should not be relied on as a determination of feed quality. The more subtle indicator of poor-quality
feed may be increased winter losses as a result of changes in pH and increased hydroxymethylfurfural (HMF). The increase in HMF in sugar syrup is used as
a direct marker of quality deterioration8. The
levels of this toxin will build over time, increase with temperature and in the
presence of acid. The final catalyst for
HMF formation, acid, is worth discussing further.
Honey contains approximately 75% simple sugars such as
fructose and glucose9 with only a relatively small proportion of
sucrose (a more complex sugar). The simple sugars are a nutritionally available
energy source for the bees and the sucrose will be broken down further. This reduction of the complex sugars by the
bees, called inversion, is achieved using an enzyme (invertase). This enzymatic inversion of more complex, disaccharide
sugar (sucrose) to monosaccharide sugars (fructose and glucose) is part of the
natural process of making honey from nectar.
Inversion of sucrose can also be achieved artificially by using acid
instead of the enzyme invertase. These
two different processes are referred to as enzyme hydrolysis or acid
hydrolysis. The later process will
result in HMF as a by-product of inversion.
 |
| Feeding sucrose syrup with a in frame feeder. |
The increase in HMF in sugar syrup due to the addition of
acid is something that beekeepers should understand. Outdated practices to include acid as an
additive for feed are thought to extend shelf life and convert sucrose to
simpler sugars. Although this will be a
catalyst for inversion, this is no longer recommended due to the resulting
increase in HMF. It is also worth noting
that recipes for homemade fondant generally include some form of acid (citric
acid, acetic acid). The acid along with
heating of the sugar syrup inverts the sucrose into simple sugars. The acid and the heating will both increase
HMF levels. Good quality commercially
available fondants will use enzymatic hydrolysis. If you read the marketing information on Hive
Alive® fondant, as an example, it states “produced using enzymatic hydrolysis
without the use of acids or heat processing, thereby avoiding the introduction
of harmful HMF”.
When using and storing sugar syrup there are some things
that beekeepers should consider. Store
your syrup in airtight, sealed containers with as little ‘headspace’ as
possible. Low temperature storage will
slow down degradation, which is almost arrested at 4˚C but increases greatly
above 20˚C. Also, heavy syrup (67%
sucrose) will keep longer. There are currently no preservatives which have
proven to effectively extend the life of sugar syrup and are also safe for bees.
The use of any acid-based additives or preservatives can be harmful. So understanding that the indicators of poor
quality (e.g. MHF, changes in pH) increase with storage time, monitoring and
testing of syrup is advised.
A couple of final points!
If taking risks with sugar syrup, dilute any questionable feed as much
as possible with fresh. Fall is the time
bees are most at risk from tainted feed.
Ensure that your syrup and feed have low toxicity (i.e HMF) and
understand the link between age, storage temperature, pH and toxification. Feeding the freshest and highest quality syrup
available will always be best practice.
References
3. Frizzera, D., Del Fabbro, S., Ortis, G., Zanni, V.,
Bortolomeazzi, R., Nazzi, F. and Annoscia, D., 2020. Possible side effects of
sugar supplementary nutrition on honey bee health. Apidologie, 51, pp.594-608.
4. El-Seedi, H.R., Ahmed, H.R., El-Wahed, A.A.A., Saeed, A.,
Algethami, A.F., Attia, N.F., Guo, Z., Musharraf, S.G., Khatib, A., Alsharif,
S.M. and Naggar, Y.A., 2022. Bee stressors from an immunological perspective
and strategies to improve bee health. Veterinary Sciences, 9(5),
p.199.
5. EFSA Panel on Contaminants in the Food Chain (CONTAM),
Schrenk, D., Bignami, M., Bodin, L., Chipman, J.K., del Mazo, J., Grasl‐Kraupp,
B., Hogstrand, C., Hoogenboom, L., Leblanc, J.C. and Stefano Nebbia, C., 2022.
Evaluation of the risks for animal health related to the presence of
hydroxymethylfurfural (HMF) in feed for honey bees. EFSA Journal, 20(4),
p.e07227.
6. Quinlan, G., Döke, M.A., Ortiz-Alvarado, Y.,
Rodriguez-Gomez, N., Koru, Y.B. and Underwood, R., 2023. Carbohydrate nutrition
associated with health of overwintering honey bees. Journal of Insect Science,
23(6), p.16.
7. Polinsky, M., 2024. Personal Communication, Aug 29.
8. Solayman, M., Shapla, U.M. and Khalil, I., 2023. Furfural
and Hydroxymethylfurfural. Honey: Composition and Health Benefits, pp.152-166.)
. This compound is toxic to bees and
shortens their lives.
9. da Silva, P.M., Gauche, C., Gonzaga, L.V., Costa, A.C.O.
and Fett, R., 2016. Honey: Chemical composition, stability and
authenticity. Food chemistry, 196, pp.309-323.
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