Honey Bee Nutrition: what carbohydrate source should we use for supplementary feeding?

Honey Bee Nutrition: what carbohydrate source should we use for supplementary feeding?

This post is also available in: Spanish

When we started the series Beekeeping from Passion to Profession, we wanted to address five essential topics: breeding and selection (rearing queens), honey bee nutrition, diseases, working techniques and management.

The reason behind this approach was to offer all the support to other beekeepers that want to make one step further towards professionalism. At least in Romania, one of the main causes that make practicing professional beekeeping a difficult task is the lack of useful, quality information and also the lack of a work methodology. Obtaining good financial results every step of the way is vital.

Unfortunately, information that is backed by scientific proof is often replaced by myths and pseudo-science. And this can be very confusing for a beginner.

Topics that include nutrition and treatments for diseases are by far the ones with the most contradictory information. One of the reasons for this is not putting enough resources into this field as in the case of the genetics of the honey bee. Therefore, there were many opinions concerning supplementary feeding and treatments that proved to be detrimental to the honey bee.

We will present a review of all the information regarding nutrition and supplementary feeding that are actually science based. We will also show that many of the supplements and treatments considered to be less harmful just because they are natural can actually do much damage to the honey bee.

The nutritional elements the honey bee needs for survival and development are: proteins (amino-acids), carbohydrates (sugar), minerals, lipids (fat), vitamins and water.

In order to satisfy these nutritional needs, the honey bees harvest three substances: water, nectar and pollen. When the quality or the quantity of one of these three elements is not in line with the colony’s needs, an imbalance can occur (reduction in population, reduction in the bee’s longevity, disease predisposition and even the death of the colony).

In order for the beekeeper to be able to help the colony and thus avoid the so called nutritional stress, he should know how to evaluate the nutritional state of the colony and also to have a good understanding of the role of water, nectar and pollen; it’s also important to know what are the best options for supplementing these substances. According to Randy Oliver, the effects of nutritional stress (caused by the absence of one or more of these substances) can only be observed two months after it has occurred, thus making the role of the beekeeper even more important for maintaining the colony prepared for the important nectar flows. When the colony is dealing with a major shortage in pollen or nectar, it is extremely difficult to recover. Please note that we are not referring to the survival of the colony, but to the perspective of maximizing the results.

Without further ado, let’s take an in-depth look at the available information regarding the carbohydrate nutrition of the honey bee. Nectar is the primary source for energy; it is mainly composed of sucrose (with various degrees of humidity), but also contains enzymes and minerals. These enzymes, together with the ones added by the bees will turn sucrose into glucose and fructose. The humidity is also reduced down to a percentage that varies between 12% and 21% (depending on the nectar source and environmental conditions). Honey that has a humidity of more than 21% will ferment and it is very harmful to the bees. The ratio of glucose and fructose varies and is highly dependent on the nectar source. At the moment there isn’t any scientific data to show how this ratio affects the colony. For this reason, it is our opinion that sucrose (sugar) is the best option for supplementary feeding with carbohydrates. When there isn’t enough information about a certain substance one must not take any chances in administrating a product that could potentially harm the colony. We are obviously talking about the scenario in which we cannot use honey that was previously capped. Honey with more than 21% humidity can cause significant damage, definitely a lot more than sugar syrup. A comparative study performed by Roy J. Barker and Yolanda Lehner for the USDA in Tucson, Arizona, showed that feeding with honey syrup or high fructose corn syrup showed no advantage when compared to sugar syrup. The honey bees that were fed sugar syrup also survived the longest. Here is how the study went and what it concluded:

The honey bees shaken from frames with brood were put into twelve small cages (24x24x8 cm). Every cage contained 1200 bees and a fixture on which were placed two wooden sticks (25 cm long) with a 2×2 cm comb foundation in the middle. A caged queen was then placed near the foundation. After 48 hours the bees settled on the bar and started building comb. Then the bees and the caged queen were released inside a larger cage (56x56x43 cm). The temperature inside the cage was kept at 28 degrees Celsius, while the humidity was maintained at 20%. To prevent the bees from settling in the top part of the cages when the lights were turned on for inspection, aluminum foils mounted on a rack were used below the ceiling lights.

When the first dead bees appeared, they were removed from the cages and counted for a period of 60 days. The dead bees were also checked for Nosema spores.

For the carbohydrate feedings were used the following substances:

  • High fructose corn syrup
  • Grape syrup
  • Sucrose (table sugar)
  • Honey (unfiltered, unhealed, mixed flora, less than 1 year old)

Water was added in order for the above mentioned substances to reach a humidity of 50% (measured via a refractometer). Groups of 3 cages were fed with one of the four types of syrup placed inside inverted recipients with perforated lids. Water was supplied separately and the recipients with syrup were changed daily and the consumption was measured by weighing the recipients.

The following data was recorded: the number of dead bees for each day, the quantity of syrup, quantity of wax produced, quantity of syrup stored in the new comb, number of cells and sealed cells of honey, size of cells. The study, along with all the scientific methods used can be viewed here.

The results are summarized in the table below:

MeasurmentSucroseHoneyHFCSGrape syrup
Life span56.3 ± 8.131.3 ± 2.537.7 ± 2.113.3 ± 1.2
Mg consumption per day59.0 ± 6.966.3 ± 13.760.1 ± 3.231.8 ± 8.1
Mg of honey produced per day10.4 ± 1.413.4 ± 5.810.3 ± 1.20.6 ± 0.7
Mg of wax produced per day0.73 ± 0.100.73 ± 0.150.69 ± 0.050.23 ± 0.08
honey produced / syrup consumption ratio0.177 ± 0.0170.195 ± 0.0450.171 ± 0.0130.016 ± 0.016
wax produced / syrup consumption ratio0.012 ± 0.0060.011 ± 00.011 ± 0.0070.08 ± 0.007

The bees from the cages that were fed grape syrup quickly showed signs of dysentery. Nosema examination was negative except for a few bees from the honey group. The number was less than 15 spores per bee, so the disease wasn’t the problem. This only goes to show (again) that dysentery isn’t the same thing as Nosema and that bees that don’t exhibit dysentery can have Nosema (and the other way around).

The largest life span was observed for the group that was fed sugar syrup. The differences were significant. Survival rate was worst for the group fed with grape syrup. Longevity for HFCS and honey were very similar.

This study clearly concludes that the best carbohydrate source for supplementary feeding is sucrose (sugar) syrup. The honey bee’s digestive system is perfectly adapted to deal with this substance.

The theory which states that inverted sugar syrup helps with prolonging the longevity of the bees is therefore false and isn’t backed by any reliable scientific source. Moreover, in many cases were thermal means are used to produce inverted sugar, harmful compounds are created and they are toxic for the bees.

Another important conclusion is that excess minerals are harmful for the honey bee and will shorten the longevity. Honey contains large amounts of minerals that are not beneficial to the bees when used in supplementary feedings. This phenomenon is even more obvious when grape syrup is being used. Moreover, according to a study carried out in Germany (Horn, H., 1985: The causes of paralysis in honeybees during a honeydew flow), the large amounts of Potassium and Phosphorus are associated with paralysis of the adult bees. This is definitely something to consider when supplying large quantities of minerals and vitamins; they can do more harm than good. We will further expand this topic in our next articles. Here is the typical mineral content of different types of honey (Petrov 1970):

MineralDark honey (mg/kg)Light honey (mg/kg)
Ca227107
Cu11
K1241441
Mg13240
Mn101
Na23251
P123129
Zn23

Even though it is clear that from a practical and scientific point of view, sugar syrup represents the best alternative for supplementary feeding, lots of beekeepers prefer to use honey or high fructose corn syrup, hoping that they will hep the bees by doing so.

We can also conclude the importance of the hibernating state of the bees during winter, leading to less food consumption and wear. Basically, when the bee was kept active, even when there was no brood rearing, the bee didn’t survived more than 33 days (when honey was used for feeding). Sucrose was a better option, but even in this situation the life span was 64 days. So feeding during winter, that increase the activity within the colony, should only be carried out when there are no food reserves. Otherwise, they are not beneficial to the colony. Enough food reserves should be present before winter. When the brood rearing is started the effort and wear are even more pronounced. Early stimulation with supplemental food can only be made for the large colonies that have enough population to sustain the initial loss until more young bee is produced. Small colonies are at great risk of collapsing if brood rearing is being forced.

In our next article we will continue to explore the topic of honey bees nutrition and diseases. As it’s the case with the present article, we will only present information that is backed by scientific proof and experiment. It is vital that our actions are based of knowledge and proven facts; if we don’t have enough data about a certain a practice, it is best to avoid doing it as it can cause more harm than good.

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