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Considerations in Selecting Sugars for Feeding to Honey Bees
by ROY J. BARKER
U. S. Dept. of Agriculture, Bee Research Laboratory
2000
E. Allen Road,
Tucson,
Arizona
85719
ABSTRACT
Sugars which poison honey bees, and impurities in commercial
sugars which are harmful are discussed.
COST is
a primary consideration in agricultural feeds. But, the
sweetness of cheapness can be quickly forgotten with a
bitter taste of the short-comings of a cheap product. High
costs of table sugar (sucrose) and a good market for honey
prompted beekeepers to test cheaper bee feeds. Some
substitutes for table sugar were consistently disappointing;
others were successful. The factors limiting the
effectiveness of carbohydrates in bee nutrition are not
explainable with trademarks; they need to be better
understood. Certain sugars, which are nutritious to mammals,
can poison honey bees. Considerations of toxins in sugars
should provide insight into some problems of honey bee
nutrition.
Sugars
which poison bees when fed at low levels in sucrose syrup
include galactose, arabinose, xylose, melibiose, mannose,
raffinose, stachyose, and lactose (Barker and Lehner, 1974b;
Barker 1976a). Pectin, agar, and many gums are toxic or can
hydrolyze to toxic sugars. On the other hand, glucose,
fructose, maltose, sucrose, melezitose, and trehalose are
safe and nutritious. The reasons some sugars are
poisonous at low dosages are unknown; conflicting theories
have been published. Even important biochemical processes
which produce honey from nectar remain cloaked in ignorance.
Why invert syrup is suggested for honey bee feeding—
Honey, which is mostly fructose and glucose, did not
sustain caged worker bees as long as did sucrose syrup
(Barker and Lehner, 1973). Nevertheless, many beekeepers
consider honey to be an ideal food for bees in spite of the
risks of spreading disease with it. Consequently, table
sugar that has been hydrolyzed to
invert syrup containing
glucose and fructose is often fed to bees. Justification for
this practice is not based upon nutritional data but on an
assumption that hydrolysis aids digestion. Syrups are
convenient to feed, and hydrolysis reduces granulations in
syrup. Also, robbing may be less of a problem with inverted
sugar because glucose and fructose become less attractive
than sucrose when bees reach foraging age (Barker and Lebner,
1974c). But all this applies to
invert syrup made
from sucrose (table sugar). Although the inverted sugar
tastes sweeter to man, it is no more attractive than sucrose
to bees.
Doull
(1974) fed 3 syrups produced by hydrolysis of wheat starch.
These invert syrups were detrimental to bees in confinement.
Doull suspected undigested polysaccharides, particularly
starch, to be harmful. He obtained better results with
sucrose than with his invert syrups.
"Formose,"
a sugar mixture synthesized from formaldehyde, caused growth
inhibition and death of worker bees (Mizuno et al., 1973).
Refined
beet and cane sugar are pure sucrose and, of course,
are safe and nutritionally equivalent. Unrefined sugars have
poisoned bees. The toxic factors in molasses and in
brown
sugars have not been identified. Bailey (1966) found
that semi-refined cane sugar was harmless but that
semi-refined beet sugar decreased the life of bees. So,
impurities in his unrefined beet sugar must be toxic. Crude
beet sugar may be toxic because of pectins or galactosides
in it (Barker, 1976a). Bailey also found that 8-year-old
honey had dysenteric effects much like poisonous sugars: an
absorption peak matching hydroxymethyl furfural correlated
with toxicity of old honey and of acid-hydrolyzed syrups.
Recent tests (Jachimowicz and El Sherbiny 1975; Barker
197Gb) show that hydroxymethyl furfural can be toxic when
fed in glucose plus fructose at dosages found in some
samples of acid-hydrolyzed or heated syrup and old or heated
honey.
Sugar refuse such as mill sweepings or surplus candy
sometimes furnishes an inexpensive source of sucrose, but
salt or flour in it may be harmful. Piskovoi et al. (1964)
found that common table salt, sodium chloride, in levels as
low as 0.125% in sugar syrup, caused dysentery and mortality
in caged bees. Bees in overwintering colonies with honey
stores containing 0.35 to 1.16% salt were dying prematurely.
Refuse high in flour or dextrins, when added to water,
ferments and kills bees. The toxicity should be influenced
by the microorganisms which happen to be present. Toxicity
of flour and of dextrins is sometimes attributed to
indigestibility and compaction in the rectum of bees. This
seems unreasonable. We routinely feed powdered cellulose
without harm to caged bees. Furthermore, many pollen walls
are indigestible but harmless.
Sugars which have poisoned bees are acceptable in rations if
they are sufficiently diluted with sucrose. Bailey
demonstrated that his samples of acid-inverted sugars had no
deleteriotis effect when diluted 8 to 1 with sucrose.
Honey and nectars contain traces of toxic sugars such as
raffinose, mannose, and galactose (Percival 1961; Siddiqui,
1970). Sublethal levels of these sugars in pollen, honey, or
nectar could modify effects of sugars in supplementary
diets. Conversely, generous stores of safe sugars could
dilute toxins in supplemental feeds. We agree with the
ancient philosopher, Paracelcus, who admonished that
poisoning is a consequence of quantity, not substance.
"Toxic" simply means too much.
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