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A crude post on crude protein

During my research into honey bee nutrition, I kept running into statements about the crude protein content of different pollen types. According to a University of Florida Extension Bulletin, the crude protein content of pollen ranges from 6% to 30% of the dry weight, depending on the floral source. Furthermore, the article claims that larval and newly emerged honey bees require a diet containing 20% to 25% crude protein.

Then the question came to me: what the heck is crude protein? How is it different from regular old protein?

According to various dictionaries, “crude” can mean unrefined, lacking finish or polish, lacking culture or refinement, rudimentary, natural, raw, or blunt.

But crude protein isn’t any of those. Instead, it is an estimated protein level. The estimate is derived from a chemical analysis of the amount of nitrogen in the pollen. The amount of nitrogen is then multiplied by a constant (usually 6.25-6.38) which yields an estimate of total protein.

But nitrogen is also found in other parts of the pollen grain, not just the protein. This other nitrogen throws off the estimate and creates the difference between true protein and crude protein. Fortunately, there usually isn’t too much of this other nitrogen, so the estimates are fairly good.

However, when it comes to nutrition, not all protein is usable by honey bees. Protein is made up of amino acids. There are many different protein-building amino acids, but only ten of them are needed by honey bees. The ten they need are: threonine, valine, methionine, leucine, iso-leucine, phenylalanine, lysine, histidine, arginine, and tryptophan. The others are known as non-essential.

The problem with the crude protein estimate is that it includes nitrogen from all sources including the non-essential amino acids. So, when evaluating pollen as a food source, you need to know it’s amino acid profile, not just the crude protein level.

Dandelion pollen, for example, can have a crude protein content of 22.69 (Jivan, A. et. al. 2011) but it is deficient in four of the essential amino acids: arginine, isoleucine, leucine, and valine.

The bottom line is that honey bees need a variety of pollen types in their diet to assure they get all the essential amino acids. Crude protein is an estimate of protein content, but it certainly does not tell the whole story.

Rusty
HoneyBeeSuite

On a quest for protein. Pixabay photo.
On a quest for protein. Pixabay photo.

Comments

Glen B
Reply

The nutrient analysis for flowers is fascinating, (at least for us pollinator nerds). Already I was in awe of those who can i.d. pollen by its microscopic appearance. What published materials do you recommend so as to be better informed? Willow, maple, dandelion, dahlia, … are bees nourishing themselves, or just gorging on filled cream puffs and M&M’s.

Rusty
Reply

Glen,

I’ve heard that Fat Bees, Skinny Bees published by the Australian government is very good. Their plants are different, but plants within the same genus have comparable pollen (so I’m told) so you can get an idea of which ones are best for bees. It’s a free download. I’ve got it on my computer, but haven’t read it yet.

Craig
Reply

To make things worse, protein seems to be the only thing people ever talk about, when it comes to this subject.

This could easily give some folks the idea that protein is all that bees need.

I’ve seldom read anything which mentions the need for carbs, sugars, vitamins and minerals. When I HAVE seen it mentioned, it’s been in the middle of some rather complicated article… the kind that most people won’t read or can’t follow.

A beginning beek, with no knowledge/background of nutrition, biology, zoology or animal husbandry, could easily start thinking that protein is all that matters.

Rusty
Reply

Craig,

I think the same holds true in the human diet, or at least the North American diet, where protein is way over-rated. We don’t need nearly as much as we’re getting.

Craig
Reply

Yeah. I think that’s the result of the American fascination with fad diets. Everybody is looking for an easy way to lose weight.

Heaven forbid you point out that the only thing anybody ever permanently lost on a fad diet was the money they spent on the book. lol

jeff
Reply

Good Rusty. What is really needed is the amino acid content of pollen sources, which is really scarce out there for information. For a botanist or entomologist could be a great masters thesis.

Rusty
Reply

You are right, Jeff. Really good sources of this information are hard to find.

willowcreekhoney
Reply

It never ceases to amaze me, the research, the knowledge that you come up with. While the rest of us are watching our bees bring in different colors of pollen, you are analyzing such things as protein content. Wow! One day I hope to be able to do such things as get out a microscope and look at pollen, understand what I am looking at, even checking for different disease causing microbes.

This being said, I am furthering my education through schooling. The three-part course offered by the University of Montana has been very educational. (UMT.EDU/BEE) I am now a certified apprentice beekeeper (not that a certificate means anything, it’s the education) and will soon bee enrolled for the journeyman beekeeper. These are not just the simplified courses in beekeeping but are in-depth into the life, history, and science of honey bees. (Honeybees).

Rusty
Reply

Ken,

You will soon get there. The University of Montana has a great certification course. In the Journeyman course, you will get to count those microbes.

Ruby
Reply

Hi Rusty,

I have a question. Do you know how to get rid of wax moths? Had to re-queen a hive this year because of the wax moths. I would prefer not to use pesticides. Put new supers and frames in the hive. I live in Albuquerque, NM so it does get cold enough to kill the moths, but not if they are in the hive. Brought some frames of honey in the house and noticed wax moths again.

Rusty
Reply

The conventional wisdom says that a strong hive can take care of wax moths. I think it is more likely that a weak queen allowed the wax moths to take over rather than the wax moths caused a weak queen.

Also, keep your hives the right size for the colony without a lot of extra space. Freeze any combs that you take from the hive immediately. Other than that, it is really hard to kill an insect in an insect’s home.

Ruby
Reply

Thanks for the information. We did re-queen the hive this year, so I hope everything goes well. Thanks again for the information and I love reading your posts.

R

Kim
Reply

I love that you explain “crude protein”! It’s so important to understand that the test includes all nitrogen, including non-protein nitrogen (including melamine! ack!). However, I think that an “essential” amino acid is one that cannot be synthesized from scratch by the organism, and must be taken in through diet. I don’t think essential amino acids are the only amino acids the organism needs or uses. For example, taurine is essential for cats so it must be in their food, but dogs can synthesize it so it’s not typically in their food, but they still need it and can use it if it is in their food. Please correct me if I’m wrong. Thanks for an extremely informative article!

Rusty
Reply

Kim,

You are most probably right about the definition of essential amino acids. I will look into it further and appreciate the clarification. I added it to to my scary-long list of things to investigate!

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