NUTRITIONAL REQUIREMENTS OF HONEY BEES

Honey bees, like all animals, require a balanced diet of sugar, protein, vitamins and minerals. Water is also a vital nutritional requirement.

Nectar/Energy

Nectar is bees' energy source and is extremely important for growth, breeding, flying and keeping warm.

In a supplementary feeding program, sugar is a most effective bee feed, because it stimulates the bees into breeding, foraging for pollen, and metabolising stored honey and protein. Sugar feeding can kick start bees into action. It can be used to capitalise on out-of-season honey flows, to prepare bees for pollination, start bees breeding earlier in the spring and to prepare hives for queen breeding. However, feeding sugar only is a stimulus to the bees and not a balanced diet.

Stored honey is a very good energy source, but bees are reluctant to use it unless they really need it. They use it only when there is no fresh nectar available, such as during a drought or in winter. It does not stimulate bees to breed, except in the spring when natural brood expansion occurs.

Pollen/Protein

Pollen is the bees' main source of protein, and is required for muscle growth in brood and young adult bees. Bees need pollen with at least 20% protein. Spotted gum pollen is 25% to 33% protein so is regarded as very good for hive build-up. Pine tree pollen is only 5% to 7% protein, so is a poor food source for bees.

Bees obtain pollen from flowers or from pollen stored in the combs. They can also draw on body-protein when they are protein-stressed, such as occurs in a spring build-up or a heavy honey flow. They consume body-protein to create royal jelly to feed their brood. This is similar to a cow using body tissue to produce milk for a calf.

Protein and Amino-acids

Protein is not just protein. Protein is made up of separate parts called amino-acids.

Building up body muscle with protein is a bit like building a house. The protein can be likened to the "building materials" as a whole. The amino-acids are like the individual kinds of building materials, such as timber studs, bricks, window glass, nails and roofing iron. However, in the case of protein, most amino-acids can be reconstituted from other amino-acids.

In digesting the protein, the animal can manufacture some of the required amino-acids from other amino-acids that may be surplus.

This is like a builder using a surplus stud for making noggins or a door frame, or some flooring for a brace, or rafters for floor joists. There is a degree of flexibility in how building materials may be used.

However, there are some specific building materials, such as nails or glass or roofing iron or tiles, that cannot be reconstituted from other items.

Not only are these essential building materials needed, they are needed in specific quantities in order to construct the building according to the plans.

It is the same with protein and amino-acids. Some amino-acids cannot be reconstituted from other amino-acids. These amino-acids are called essential amino-acids.
 

Essential Amino-acids

Some amino-acids are an essential part of the protein digested by the bees, while others are reconstituted from surplus non-essential amino-acids. Essential amino-acids are required in definite proportions of the protein digested as protein.

In 1953 Dr. A. De Groot studied the amino-acid and protein requirements of honey bees and found that they need ten (10) essential amino-acids, at levels ranging from 1% to 4.5% of the protein digested. These results are listed in Table 1.

Table 1: Essential amino-acids for honey bees

 
Amino-acid
Minimum required % of amino-acid in protein digested
Threonine
3.0
Valine
4.0
Methionine
1.5
Leucine
4.5
Iso-leucine
4.0
Phenylalanine
2.5
Lysine
3.0
Histidine
1.5
Arginine
3.0
Tryptophan
1.0

  If one of these essential amino-acids is not present in the amount required by the bees, then the bees cannot fully digest as protein all the protein they have eaten. For instance, if one of the amino-acids is required at 4% and is only available at 3%, then only three-quarters of the total protein consumed can be utilised by the bees, as body-building protein.

Analysis of pollen protein has indicated that most of these essential amino-acids are at satisfactory levels. However, Iso-leucine and on a few occasions Valine are below these desired levels.

Iso-leucine

De Groot (1953) found that the amino-acid iso-leucine is required by honey bees at 4% of the digested protein. Analysis of pollen samples for this book found that iso-leucine contained in the pollen protein was usually below this 4%, in a range of 2.7% to 4%. This observation was recorded in Victorian eucalypts by Lynn Muss (Muss 1996), and also by Ryner and Landridge (1985), and in Queensland pollens by Kleinschmidt (1984).

Studies carried out at Wollongbar N.S.W. on iso-leucine (Stace and White 1994) found that a response to supplementary iso-leucine can be observed when bees are breeding rapidly but have only limited amounts of pollen. The supplementary iso-leucine allowed the bees to fully digest as protein, all the protein in the pollen consumed.

This indicates that, when there is a protein deficiency with bees foraging on Australian plants, it is most likely that the essential amino-acid, iso-leucine is the major limiting factor.

The practical application of this information is that bee feed supplements should have over 4% iso-leucine. This will allow the feedstuff to be a true supplement, in that it supplies both additional protein and additional iso-leucine. The additional iso-leucine allows for a better utilisation of the field-collected pollen.

Bee body-protein

Bees store protein in their body, and use it to make wings, muscles and other body organs. The higher the level of protein in their bodies, the stronger the bees are and the longer they can live.

Bees can have a very high body-protein of over 60% crude protein, at which time they are strong, long-lived bees, with the ability to collect lots of honey. Or at the other extreme they can have low body-protein of less than 30% (Kleinschmidt 1988). When bees have low body-protein they will live only a short time, suffer from diseases like European brood disease (EBD) and nosema, and be very poor honey producers.

High body-protein bees are essential in autumn, so the bees can combat nosema, overwinter in strong condition, and have plenty of body-protein to use for hive build-up in the spring. Bees with a low body-protein in the autumn will generally not overwinter well, will be susceptible to nosema and "spring dwindles" and possibly have restricted breeding in the spring.

Bee body-protein is reduced by honey production, cold or hot weather, wax production, and an increase in breeding, especially during the spring build-up period.

Bee body-protein will increase if the bees are getting plenty of pollen with more than 20% digestible crude protein, especially if they are not stressed by heavy honey production and extremes in weather.

Bee body-protein is a good measure of the hives' ability to survive winter, collect good honey crops, and overcome many of the bee diseases, like European brood disease or chalk brood. The higher the body-protein level, the better the bees will be able to collect economic yields of honey, pollinate crops, and produce queen bees.

Protein and stress

Bees require protein at different rates, according to the level of stress they are under.

By understanding the concept of bee stress, beekeepers are able to make better management decisions about bee nutrition.

Low stress

Low stress hives show little activity. The bees may be breeding at a constant rate, there is little or no honey to gather, the air temperature is warm (above 20oC) and their needs are small. Under such conditions, bee hives will increase their body-protein, and maintain or slowly increase their populations if they can collect pollen at 12% to 15% crude protein. Under such conditions hives will develop to a reasonable strength in six to eight weeks. This can be observed when bees are collecting ground flora such as flatweed (false dandelion). During nutrition trials at Wollongbar Agricultural Institute in 1993, hives foraging only on flatweed increased their body-protein from 40% to 60% in six weeks. The hives did not store honey or increase in size. However, the low stress allowed the hives to develop high body-protein (Stace personal observation).

High stress situations

Honey bees in a high stress situation require surplus pollen with a digestible crude protein level greater than 20%. The higher the stress the greater their need for protein.

High stress in beehives occurs when:

. the bees are on a honey flow. The heavier the honey flow the greater the stress.

. the bees are increasing their breeding rate or brood area, as occurs in spring or during a high nectar stimulated breeding program. (Stace 1994)

. it is too cool or too hot (below 20°C or over 35°C) and the bees are working hard for their pollen and nectar (eg. a white box winter honey flow, or lucerne in summer).

Examples of high stress are:

White box stress

White box, which flowers in the winter, is known to be hard on bees. The crude protein of it's pollen is 17% to 20% and the essential amino-acid iso-leucine is 3.7% to 3.8% of the crude protein. This would give a digestible protein of 16% to 19%. This is below the desirable 20%. The bees are highly stressed because the temperature is low, the honey flow is good, the wax production is high, and they are stimulated to breed. Honey bees working white box often produce 20 to 40 kg of honey, then the hive populations collapse, usually due to protein stress.
 

Lucerne stress

The crude protein of lucerne pollen is 20% to 24% (table 2). This should be sufficient for the bees to maintain hive numbers and body-protein, but this appears not to be the case. Beehives tend to become weak and inactive when working lucerne only. The cause is a shortage of one of the amino-acids (iso-leucine) that comprise the pollen protein.

Table 2: Protein and amino-acid ratios Lucerne

 
Amino-acid
Minimum % of Amino-Acid from De Groot (1953)
1989 Dubbo
1989 Dubbo
Threonine 3 3.6 3.3
Valine 4 4.0 3.3
Methionine 1.5 1.6 1.4
Leucine 4.5 5.4 5
Iso-leucine 4 3.1* 2.7*
Phenylalanine 2.5 3.3 3.1
Lysine 3 5.5 5.6
Histidine 1.5 2.9 3.2
Arginine 3 5.2 4.5
Tryptophan 1 1.4 1.6
Crude protein - 24.1% 20%
 

* Low level of this amino-acid

The level of iso-leucine is around the 2.7% to 3.1% of the crude protein which is only three-quarters of the 4% which bees need. This shortage means bees can use only three-quarters of all the protein, so the available protein is equivalent to a pollen of 15% to 18% crude protein.

When bees are foraging on lucerne flowers, they are under high stress. This is because they are usually collecting good crops of honey and are breeding rapidly, and it is usually hot and dry. Also, the lucerne flower kicks the bee when the anther is tripped, causing extra stress.
 

Stress management : supplementary protein

A possible management strategy for bees working stress-creating flora like white box and lucerne would be to feed the bees a supplementary protein which has a high level (greater than 4%) of the amino-acid iso-leucine, as well as additional protein. A good example would be a soyflour based feedstuff (Table 3).

The supplement may be fed as a patty in the hive, or if the bees will collect it, in an open feeding station. The soyflour based feedstuff should be fed at 150 to 200 grams per hive per week. Warren Jones (personal comment) from Dubbo has had good results with this strategy.

Table 3: Protein and amino-acid Soyflour

 
Amino-acid
Minimum % of Amino-Acid from De Groot (1953)
Riverland oil seed
Continental grain
W.A.I. chem lab
Threonine 3.0 3.9 4.2
Valine 4.0 5.1 4.5 4.5
Methionine 1.5 1.4 1.3 1.6
Leucine 4.5 7.6 7.4 7.7
Iso-leucine 4.0 5.6** 4.4** 4.5**
Phenylalanine 2.5 5.1 4.8 5.0
Lysine 3.0 6.4 6.1 6.2
Histidine 1.5 2.4 2.8 2.8
Arginine 3.0 7.1 7.1 8.2
Tryptophan 1.0 - -
Crude protein 20% 50% 47.9% 42.8% 
** Beneficial excess of Iso-leucine.

Both defatted soyflour and expeller press soyflour appear to be ideal supplementary feed for bees. They contain over 4% iso-leucine, plenty of protein, and the bees consume it reasonably well. (Stace and Hayter 1994). However, it is important to dilute the soyflour with sugar, irradiated honey, pollard or pollen to reduce the percentage of crude protein to about 30%. This appears to help the bees digest the soyflour.
 
 

Stress management : suitable pollen source

Natural food in the form of pollen and nectar is the very best food for bees. The ideal food source is plenty of pollen which contains more than 20% digestible crude protein, and a surplus of nectar. Examples of these desirable food sources would be: Broad-leaved stringy bark (Eucalyptus calignosa) Faba beans (Vicia faba), Tea-tree (Melaleuca quinquenervia), and Blakelys red gum (Eucalyptus blakelyi). However the best example on the N.S.W. north coast is Spotted gum (Eucalyptus maculata).

Spotted gum is a pollen source which supplies all bees' nutritional requirements. The crude protein level of 24% to 31%, the iso-leucine is only slightly below 4% total protein, and the high volume of pollen and high crude protein content supply all the bees protein requirements. Spotted gum also has adequate supplies of nectar for energy, so the bees obtain a balanced ratio of protein and energy. The trees usually flower for six to eight weeks in summer, when there is little temperature stress, but during this time the bees may store only two to three boxes of honey, which means they are not working hard. Bees breeding on spotted gum produce strong, high protein and high population hives. Spotted gum does not yield pollen and nectar in severe drought conditions. However bees may collect pollen and nectar in wet times. This is possibly due to the flowers hanging upside down and not allowing the rain to wash the nectar and pollen away.

Table 4: Spotted gum Eucalyptus maculata

 

 
Amino-acid
Minimum % of Amino-Acid from De Groot (1953)
Date and location of sample collected
   
Nymboida Autumn 88
Tabulam Nov 88
Casino Nov 88
Tabulam Dec 88
Grafton Mar 91
Threonine 3.0 3.9 4.3 4.0 4.0 3.0
Valine 4.0 4.4 4.8 4.3 4.4 4.5
Methionine 1.5 2.2 2.4 2.2 2.5 2.9
Leucine 4.5 6.8 7.1 6.9 6.9 4.8
Iso-leucine 4.0 3.5* 3.6* 3.3* 3.5* 3.4*
Phenylalanine 2.5 3.9 5.1 4.4 4.3 3.6
Lysine 3.0 6.7 6.8 6.3 6.9 4.9
Histidine 1.5 2.4 3.0 2.9 5.0 2.0
Arginine 3.0 9.1 9.5 9.2 8.7 7.0
Tryptophan 1.0 1.4 - - - -
Crude protein - 31.4% 26.8% 24.7% 27.3% 28.8%

 

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