During the survey (see also DAW-100A), 73 different fatty acids were identified from all pollen samples. Only five of these fatty acids: palmitic, stearic, oleic, linoleic and linolenic were common to all 577 pollens sampled.

European honeybees have evolved with plant species that have pollen that contain higher concentrations of lipid, particularly linolenic acid where concentrations are higher than Australian native plant pollen which were found in this research to be typically higher in the other essential fatty acid linoleic acid (e.g. Eucalyptus).

A second part of the research focussed on two of the five commonly found fatty acids, namely oleic and linoleic by supplementing them in varying concentrations into a low fat pollen collected from Corymbia calophylla (Marri; Redgum). This feedstuff was fed to honey bees to determine if there were any effects on longevity or physiological aspects such as nutrient levels and hypopharyngeal gland development within the honey bee.

The research is important from the point of view of flower resources that the bee industry rely when drought and climate change make it difficult for beekeepers to procure sufficient pollen flows that sustain and grow bee colonies. Artificial means of supplying protein and minerals to colonies needs to occur to retain maximum population levels that stem from young bees being able to fully develop hypopharyngeal glands, that supply the abundant worker jelly required to feed the hundreds of larvae that hatch from eggs laid each day by the queen.

Who is the report targeted at?
The report is targeted to scientific researchers who are interested in adjusting and testing current feeding practices with the new knowledge gained from this research. For the curious beekeepers the research will only add to their own interest in this field as many do make and test their own supplementary feeds often without scientific basis.

Background
In times of drought or when apiaries are in environments that lack floral abundance of nectar and pollen, many beekeepers maintain their colonies by supplying artificial feedstuffs to colonies of bees.

The artificial ingredient of choice is the high protein soya beans. Soya bean flour is available in a range of products that differ in fat content and have never undergone scientific testing in hives for longevity and physiological effects. These were tested in the same way as the fatty acid (oleic and linoleic) enhanced pollen diets. Lupin flour was also tested as a possible import replacement for soya bean flour.

No studies of the fatty acid content of Australian plant pollen have been conducted until the RIRDC funded three research projects (DAW 91A, DAW100A & DAW 105A). The knowledge is essential if studies on honey bee nutrition are to be conducted and artificial diets are to be formulated.

Aims/Objectives
The objectives were to conduct an extensive literature review of the fatty acid composition of pollen and honey bee body tissue, then carry out a comprehensive Australia-wide survey of bee-collected pollens for their fatty acid composition. A second objective was to determine the effect of an antimicrobial fatty acid (linoleic) and a common lipid, oleic on honey bee longevity and hypopharyngeal gland activity. A third objective was to use cage experiments to ascertain the influence of high or low fats in soya bean flours on honey bee performance.

Methods used
Beekeepers utilise plants from the genus eucalyptus as their major source of honey. Two of the common fatty acids (oleic and linoleic) were added to a low-lipid eucalypt pollen that was beecollected from Corymbia calophylla (redgum, marri). This diet was fed to honeybees confined in cages (mini colonies containing 1,400 bees) to ascertain their effect on longevity and hypopharyngeal gland development. Soy flour and lupin diets were tested in the same way.

Longevity was assessed over six weeks by measuring daily mortality and hypopharyngeal gland development was by measuring head weight which was verified using histological sectioning of the head. The value of the diets was assessed by weekly measurements (with gut removed) of the bees’ body for protein, lipid, fatty acids and minerals.

Results/Key findings
Honeybees that were fed diets of redgum pollen had the greatest longevity of the 22 diets tested and those bees fed diets of pure sugar had the shortest life. Honeybees fed a protein concentrate (low fat) from soya bean flour had the longest life of the flours tested.

The addition of fatty acid (oleic and linoleic) to pollen at different concentrations caused significant differences in longevity but did not increase longevity over the controls (pollen only). However, the addition of oleic acid to pollen greater than 2% caused bees’ longevity to decrease, a poor head weight response and a failure of the queen to lay eggs. The addition of linoleic acid greater than 6% to pollen diets had a similar response. As the percentage of oil was increased in both fatty acid additions, total consumption of the diet decreased.

In dietary comparisons, defatted and full-fat soya bean flours gave similar longevities and despite large differences in fat content, the response to diet of head weight was negligible and no response was elicited by the queen to lay eggs. Adding pollen to the flour diets improved longevity whereas the addition of pollen to lupin flour caused an increase in honeybee mortality.

Honeybees fed flour diets (soya bean, lupin) failed to accumulate linoleic acid in their body, which was in contrast to honeybees fed pollen diets. Manganese was another element that was poorly accumulated by honeybees fed both soya bean and lupin flour diets when compared with pollen diets. Bees fed sugar diets increased body fat, however, linoleic acid, was not accumulated.

Observations of honeybee behaviour inside the cages indicate that emerged honeybees, only a few days old, reorganise themselves into a caste sequence that differed to that normally followed by a colony where its repertoire follows from being a nurse bee to field bee.

Implications for relevant stakeholders
The development of artificial feedstuffs is dependent on more research into the effect on physiological aspects of bees viz hypopharyngeal gland development of the various elements that feedstuffs are composed. There are many ‘successful’ commercial feedstuffs in the market place, ‘successful’ only in that the honey bees are seen to consume the product supported by very little science-based evidence.

The associated effects on the hypopharyngeal gland and nutrient accumulation in the bee’s body are not known. Several proprietary brands of feedstuffs (including overseas product) should be scientifically tested/evaluated here in Australia.

The research process is typically a lengthy analysis of experimental work and longer term thinking in this area of nutrition by beekeepers (drivers of research) should be always be contemplated.

Recommendations
Further research into adding linoleic acid and manganese into feedstuffs to elevate body levels of these elements to be within normal limits attained when bees are fed on pollen. Further research should also test the other common fatty acids such as linolenic acid, palmitic acid, stearic acid and some of the less common fatty acids.