Soybean flour

Soybean flour, or soyflour, is being used within the beekeeping industry as a substitute for pollen, or as a pollen extender. Soyflour is acceptable as a protein feed for bees, but excessive feeding of soyflour by itself has been reported to have detrimental effects on bees.

There are two forms of soyflour. First : defatted soyflour. This comes from soybeans which have had the soy oil removed by solvent extraction methods. It has approximately 2% oil still in the flour. Second : expeller press or cold press soyflour. This comes from soybeans which have been pressed only to obtain the soy oil. The residue protein flour has 6% to 8% soy oil. Bees will consume both products, but prefer expeller or cold press soyflour (Stace and Hayter 1994).

Soyflour is soymeal which has been ground into flour. It must be able to pass through a 200 micron sieve.

Soyflour contains 47% to 50% crude protein and the amino-acid profile is acceptable for bee metabolism. The amino-acid iso-leucine is well represented, and will give extra supplementation to the bees feeding on it. (Stace and White 1994).

The crude protein and amino-acid profile for soyflour, from three tests (from Wollongbar Agricultural Institute Chemistry Laboratory, from "Continental Grain Product Data", and from Riverland Oil Seed Product Data) are contained in Table 41.

This high concentration of protein in soyflour can cause protein toxicity in bees. It is recommended to dilute the soyflour with pollen, pollard, sugar or sterilised honey, so the mix is less than 30% crude protein.

On occasions bees are reluctant to eat soyflour-based feeds, especially in the autumn. The use of irradiated pollen, pollard and/or irradiated honey within the mix will encourage bees to eat the soyflour.

From field observations by beefarmers and Kleinschmidt (1986) bees fed non-pollen protein like soyflour for short periods are unlikely to have serious problems. Long term feeding (longer than six weeks), when pollen is very scarce, is not good for the bees. This is due to the lack of vitamins, minerals, and enzymes in the soyflour, as well as the high levels of protein found in the flour.

When feeding bees who are working deficient pollen honey flows like mugga or Caley's ironbark the recommendation would be to use soyflour as a pollen extender and not by itself.

Table 41: Analysis of soyflour

Minimum % of Amino-Acid from De Groot (1953)
Continental grain
Riverland oil seeds
Threonine 3 4.2  3.9 
Valine 4 4.5  4.5  5.1 
Methionine 1.5 1.6  1.3  1.4 
Leucine 4.5 7.7  7.4  7.6 
Iso-leucine 4 4.5** 4.4** 5.6**
Phenylalanine 2.5 4.8  5.1 
Lysine 3 6.2  6.1  6.4 
Histidine 1.5 2.8  2.8  2.4 
Arginine 3 8.2  7.1  7.1 
Tryptophan 1 - - -
Crude protein   42.8% 47.9% 50% 

** Beneficial excess of Iso-leucine.

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