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After a previous in-depth presentation of the honey bee’s carbohydrate nutrition, in this article we will analyze the protein requirements of the honey bee. While the nectar (or sugar as supplemental food) represents the primary energy source for the bee, pollen, through its composition, contributes to the development of the colony with a series of vital elements.
As we all know, there are many approaches and recipes for replacing and supplementing pollen when there isn’t enough available or its quality is low. Without the intention of causing any disputes, some of these approaches reveal the lack of basic knowledge with regards to the composition of pollen and the bee’s protein requirements. Without further ado, let’s first see what pollen is and understand how we can successfully supplement it.
The main element provided by pollen is protein. Alongside protein, pollen also ensures a series of other substances that are important to the normal development of the bee colony: fat, vitamins and minerals.
The protein percentage of pollen that is necessary to the honey bee is at least 20-25%. These numbers were confirmed by numerous studies (linked at the end of the article).
It is also true the fact that the honey bee can survive by consuming pollen with lower protein concentration, but it was also proved that worker bees longevity is greatly increased when consuming pollen with a high protein percentage (25 – 30%) when compared to lower quality pollen (less than 20% protein). Brood rearing is also reduced when only low protein pollen is available.
A plausible explanation comes from D. Anderson’s 1997 study which revealed that for every 10 grams of bioavailable protein a quantity of 48 grams of pollen with 30% protein need to be metabolized by the colony. For 20% pollen, the same colony needs 72 grams of pollen in order to get the same 10 grams of protein. Using the results of the study, we can see that a colony consuming 3 kg of pollen with 20% protein will obtain the same amount of protein as in the case of consuming 2 kg of pollen with 30% protein. This reveals the importance of higher protein percentage with regards to the colony’s effort in consuming and metabolizing pollen. Another conclusion is that the quantity of pollen consumed by a colony largely depends upon its protein percentage and several factors like brood area and population. In the case of medium quality pollen the conversion ratio pollen:bee is 1:1 (1kg of pollen is needed for producing 1kg of bee); this means that the consumption depends greatly on the quality of pollen and then the other factors come into play. This explains the great variation of pollen consumption during one year (from 25 to 55 kg). The latest research also show that these numbers are actually higher as the pollen consumed by newly hatched bees (needed to form their fat bodies) wasn’t taken into account.
If protein percentage was the only concern when performing supplemental feeding, things would be very simple. But aside from the protein percentage, we must also take into account a key aspect: amino acid profile. Amino acids are the bits that form protein and their ratio is extremely important. As we already said it in a previous article, after analyzing various pollen samples, it was concluded that even though the quantity of every amino acid varies, their ratio remains constant. It was then possible to come up with a profile of amino acids that is optimal for the honey bees:
|Amino Acid||Bee requirements (g/16 g N)|
Measuring every amino acid was carried out similarly to measuring the quantity of crude protein in a substance – by reporting the numbers of grams of one amino acid to 16 grams of Nitrogen. To better understand the importance of amino acid ratio, let’s look at the following example: changing the Isoleucine and Valine ratio from 4:4 to 3:4 led to a 25% decrease in the efficiency of metabolizing protein from supplemental food. This makes the total protein percentage of supplemental food even more important as it is highly unlikely that the bees will use 100% of the protein, especially if amino acid ratio and bioavailability are not taken into account.
Apart from amino acids, in creating a protein supplement for pollen we must also consider fat. Even though the importance of fat in honey bees’ nutrition wasn’t extensively studied, we do know that a small amount of cholesterol is used in brood rearing. The percentage is very small at 0.01% in dry substance and can be supplied from the nurse bees. Other two important conclusions were that certain types of fat from pollen are very attractive for the bee and certain fatty acids have very important antimicrobial properties.
While the role of fat with regards to palatability was easily determined (by supplementing pollen and other substitutes with different amounts of fat it was revealed that bees prefer the ones with higher fat content), there is still much to be done in the case of the antimicrobial role of fat. What we do know for certain is that linoleic acid prevents the development of two bacteria that could cause European foulbrood (Melissococcus pluton) and American foulbrood (Paenibacillus larvae subsp. larvae).
Another particular group of fatty acids – Decanoic (Capric) acid, Lauric acid, Myristic acid – has proven antimicrobial properties. Thus the addition of a fat source like canola oil or corn oil can produce a significant antimicrobial effect. However, an overdose of these substances can be detrimental; Rob Manning has showed that an increase of more than 6% in Linoleic Acid can lead to brood rearing restriction.
Regarding the vitamin and mineral necessities of the honey bee, there are very little conclusive studies. It is a known fact that vitamin B is very important for the majority of insects and it was assumed that it is the same for the honey bees.
What we do know for certain is that by adding mineral to protein supplements the content of ash will increase (ash is the residue that remains after a substance is burned at 180 degrees Celsius). Pollen has a content of 2 to 4% ash depending on the source. A high content of ash found in pollen or protein supplements have led to a reduction in brood rearing. Ideally, the ash content should be around 2% or less. The components of a protein patty already have vitamins and minerals, thus they contain ash. Therefore, we must be very careful when adding a multitude of supplements that contain vitamins and minerals that are intended to help with the brood rearing. The ash content will increase and the intervention will have the opposite effect. The same goes for adding vitamins and minerals to sugar syrup. We won’t go into great detail, but these vitamins and minerals should be bioavailable in order to be of any use to the bee. Any additional residues will only make the product more difficult to digest, which goes against one of the defining characteristics of a supplement: it should be easy to digest and should’t include substances that are toxic to the bee.
All these aspects must be taken into account prior to conceiving a protein supplement suitable for the bee. Often times, despite our good intentions, we make more damage than good by not being correctly informed. And this is particularly true in case of supplemental feedings. We’ve said on previous occasions as well: if we don’t know for certain that our intervention will be beneficial, it’s best to not do it at all.
We’ve already presented a detailed formula of protein patties that accounts for the bees’ protein requirements. A protein supplement cannot replace pollen, but only supplement it during periods when it is not available as a natural source or its quality is low (low protein percentage, disproportionate amino acids ratio). We’ve seen that pollen availability doesn’t necessarily means it meets the requirements of the honey bee. An example is sun-flower pollen. Further more, one of the causes of the massive drops in population of the colonies after the sun-flower nectar flow is the quality of the pollen. There are other causes as well, like the use of neonicotinoides and other stress inducing factors as we will see in future articles.
Finally, here is the analysis of several types of pollen:
Crude protein: 22.8%, 26.1%, 23.8%, 23.6% (4 analyzed sources) | Fat: 7.3%, 6.9%, 1.8%, 6.8%
Crude protein: 13.8%, 12.9% (2 analyzed sources) | Fat: 1.4%, 1.1%
Crude protein: 19.4% (one analyzed source) | Fat: 2.9%
Crude protein: 20%, 24.1% (2 analyzed sources)
Crude protein: 14.8%, 20% (2 analyzed sources)
Crude protein: 22%, 22.3%, 22.4% (3 analyzed sources) | Fat: 5.7%, 6.4%, 5.4%
Crude protein: 25.9%, 22.5%, 22.6%, 23.1%, 24.9%, 25.4%, 25.1%, 25.6%, 24.7% (9 analyzed sources) | Fat: 2.5%
Crude protein: 13.9% (one analyzed source) | Fat: 2.04%
Crude protein: 14.9% (one analyzed source) | Fat: 1.8%
Crude protein: 26.2% (one analyzed source) | Fat: 1.8%
- Haydak, MH; Dietz, A (1972). Cholesterol, pantothenic acid, pyridoxine and thiamine
requirements of honeybees for brood rearing. Journal of Apicultural Research. 1(2):
- Herbert, EWJ (1979). A new ash mixture for honeybees maintained on a synthetic diet.
Journal of Apiculture Research. 18(2): 144-147.
- Herbert, EW Jr; Shimanuki, H (1977). Brood-rearing capacity of caged honey bees fed
synthetic diets. Journal of Apicultural Research. 16(3): 150-153.
- Kleinschmidt, G; Kondos, A (1976). The influence of crude protein levels on colony
production. The Australasian Beekeeper. 78(2): 36-39.
- Kleinschmidt, G; Kondos, A (1977). The effect of dietary protein on colony performance.
Proceedings of the 26th International Apicultural Congress, Adelaide 357-361.
- Kleinschmidt, G; Kondos, A (1979). Colony management for low quality pollens. The Australasian Beekeeper. 81: 5-6.
- Kleinschmidt, GJ (1984). Nutritional management of colonies on the basis of body protein of
bees. Honeybee Research and Development Council. Project No. QAC–1H.
- Doug Somerville – Fat bess, skinny bees