Bill, thanks for the reference on how bees digest protein.  It’s not an explanation for how they digest pollen, which involves getting through that nearly indigestible pollen wall, but it  is just as important.

The Hive and the Honey Bee states that the amount of protein collected from different plants by bees ranges from 8% to 40%.  One would suppose that bees stuck with pollen that provides poor protein are worse off now than bees in the same situation 50 years ago, given that the total protein in all these plants is on the decline.   I noticed this statement in the paper Bill posted:  “The percentage of protein in the food for the young larvae depends not only on the age of the larvae but is also subject to seasonal fluctuations:  during 1 summer a decline from more than 50% (protein of dry weight) to less than 30% was demonstrated in 2 colonies investigated in parallel (Kunert and Crailsheim, 1987).”  It seems clear that if there is a poor season, and bees collect less than 30% protein proportional to carbs in their food, that if we then add the recently documented decades-long decline in protein to this bad scenario the “poor years” will be really bad, whilst the “good years” might not show any colony effect.  This calls to mind the earlier comment by Gene that crude protein is not the same as amino acid requirements.  Obviously at different seasons there will be different amounts of protein available, but the question is are all the amino acids they need present in adequate amounts?  Summer bees, winter bees have different physiologies, and that is another factor to reckon with.

Lunden (1954) showed that 10 essential amino acids (for honeybees) are always present in all pollens in about the same quantity, suggesting to me that the large fluctuations of protein content in pollen due to seasonal variations may not be uniform among constituent amino acids.  This begs the question:  As a consequence of the CO2 driven decrease in protein content in plant matter, do the 10 essential amino acids decline to the same extent as the non-essential ones, or not?  I went back to Loladze’s paper and found that he didn’t report on this.  I went to the Kislyak paper (goldenrod study) and they also only looked at total protein.

 “The nutritive value of pollen stored (…as bee bread…) is higher than that of laboratory-stored pollen”  “…. honey bees lived longer on pollen removed from the combs than on pollen collected in traps”, suggesting that there is some nutritive advantage to the bee bread. (Beutler et al, 1949; Van Der Vorst and Jacobs, 1980).  I have always understood that bee bread is more nutritious to bees than raw pollen….although recently in this discussion some seem to have been saying otherwise, and that surprises me.   Perhaps “laboratory-stored pollen” has been degraded in some way?  (Again I wonder why people buy raw pollen as a “nutritional supplement”.)

10 AAs are required by bees, they are called “essential amino acids” (work by Groot in 1953).  I put together a table of AAs and compared bee to human:

Largest requirements were for leucine, isoleucine, and valine.

Essential AA

Bee

Human

Arginine

Essential

Conditionally essential

Histidine

Essential

Essential

Lysine

Essential

Essential

Tryptophan

Essential

Essential

Phenylalanine

Essential

Essential

Methionine

Essential

Essential

Threonine

Essential

Essential

Leucine

Essential

Essential

Isoleucine

Essential

Essential

Valine

Essential

Essential

Cysteine



Conditionally essential

Glycine



Conditionally essential

Glutamine



Conditionally essential

Proline



Conditionally essential

Tyrosine



Conditionally essential




Loladze was more concerned with the diminishment of mineral nutrients than he was about the diminishment of amino acids.  As he points out, the “junk food” effect of CO2 on plant growth is a simple dilution of the minerals in the plant matter such that more has to be eaten before sufficient is ingested.   According to Hive and the Honey Bee, K, Ph, Ca, Mg, and Fe are the most common minerals in pollen.  Nation and Robinson in 1971 found K, Na, Ca, Mg, Cu, Mg, and Zn in various pollens.  Too much of a given mineral is toxic, as Jerry noted earlier. I’ve often thought that bees seek out minerals on their own, but have no proof of this.  I have been watching bees recently where I go swimming….there are many hundreds of them just now all over the mosses and seaweeds along the shore.

So none of this has helped me figure out if I can alter my fall management practice in some way to ensure maximum nutritional state and best health for my hives going into winter.  It’s really not even clear that mineral/AA deficiency is a problem except during poor years when pollen protein content drops significantly.  I suspect that if bees have a low pathogen/toxin load, they can better tolerate suboptimal nutrition.  But as pathogen and chemical stressors accumulate, they will have to have the best possible nutritional state to stay alive….and nutritional supplementation is about the only available tool we have to combat viruses and Nosema, not to mention all the “-cides”.

Christina


             ***********************************************
The BEE-L mailing list is powered by L-Soft's renowned
LISTSERV(R) list management software.  For more information, go to:
http://www.lsoft.com/LISTSERV-powered.html