Prussic Acid Misconceptions – Dr. Ted McCollum

Dr. Ted McCollum, Extension Beef Cattle Specialist with Texas A&M AgriLife Extension Service, explains that prussic/cyanide levels when there is a frost/freeze event is one of the most confusing and misleading statements in most extension and popular press articles.  Here’s the skinny on the actual facts brought to you by thee Dr. McCollum:

“The cyanide(prussic acid) in plants does not exist in a free, liberated state.  The cyanide is part of a larger molecule called a cyanogenic glycoside. In members of the sorghum family this compound is Dhurrin; in chokecherries, wild cherries, mountain mahogany, among others, and the kernels of almonds, peaches,  apricots and apples this is Amygdalin (laetrile) and Prunasin; in cassava, white clover, flax and lima beans this is Linamarin.  These compounds themselves are harmless; the breakdown and liberation of the cyanide is the insult.  

A hand grenade represents a “potential” explosion.  As long as the pin is in place and the lever (trigger) has not been released that “potential” is not realized; the grenade is harmless.  But when the pin is pulled and the trigger is released and the fuse activates and catalyzes the explosion, the potential is realized and potential harm ensues.  The cyanogenic glycoside is like the hand grenade.   As long as the cyanogenic glycoside remains intact there is only the potential for toxicity; this is sometimes referred to as “cyanide potential”.  In order for the potential to be realized, something has to trigger the enzymatic action to liberate the cyanide molecule from the glycoside.   The beta-glucosidase enzymes that liberate cyanide from the parent glycoside are found in the plant tissue. In the intact plant tissue, the cyanogenic glycosides are found in vacuoles while the enzymes are found in the cytosol.  In order for the cyanide to be released the plant tissue must be damaged so that the glycosides and the enzymes come together. The enzymes are also produced by ruminal microbes.  Cutting, crimping, mastication, trampling, hail damage, and frost/freeze disrupt cellular structure and allow the glycosides and enzymes to mix and liberate cyanide from the parent glycoside.  Introduction into the ruminal environment presents the glycosides to the microbial enzymes and releases cyanide. 

So back to the grenade, the cyanogenic glycoside is the grenade and represents “potential toxicity”.  The damage to the plant tissue or introduction to the ruminal environment pulls the pin and releases the trigger.  The subsequent mixing of the glycoside with the enzymes activates the fuse and catalyzes the release of cyanide and a possibly toxic insult.  

Back to the freeze/frost — 

First, freeze/frost causes tissue damage and will indeed result in an increase in the “free” cyanide present in plant tissue (In fact, when analyzing cyanide in the lab, the forage samples are first frozen in order to release all of the cyanide; simply analyzing cyanide on fresh samples only indicates what is “free” in the tissue).  But remember, when the animal bit, chewed and swallowed that same forage into the ruminal environment just hours before the freeze or frost, the same cascade of events occurred as when the standing forage was exposed freeze/frost a few hours later.  The potential for toxicity was always there, different events pulled the pin and released the trigger. So, in order for a freeze/frost to increase toxicity for ruminants (more later) as is stated in the many pubs, the freeze/frost would have to actually stimulate dhurrin (cyanogenic glycoside) synthesis by the plant.  In other words, the freeze/frost would have to stimulate the plant to make more hand grenades. I have searched for research to prove that freeze/frost increases dhurrin synthesis (specifically dhurrin since that is the glycoside in sorghums, sudans, johnsongrass) in the plant.  It is not there.  I recently contacted Dr. Ros Gleadow from Australia who works in the area of cyanogenensis in plants and her response to my query was quote “Dhurrin is not synthesised in response to frost.” 

So, the plant does not make more hand grenades in response to frost/freeze which goes back to Dr. Halliburton’s comment which I have reworded with my interpretation of his meaning – The potential toxicity after the freeze was the same as the day before the freeze.

I think some of the misinterpretation and source of information in the pubs stems from studies of long ago where the researchers collected plant samples before and after a freeze and analyzed the cyanide content of the forage tissue.  However, they did not freeze the samples before they analyzed them.  So, they did not release all of the cyanide before analyses.  They found that the amount of “Free” cyanide was higher after the freeze.  This is indeed true. BUT, they did not measure “cyanide potential” which is the real concern and as far as I have discerned, if they had measured cyanide potential they would have found no difference before and after the freeze.

We typically deal with ruminants in these grazing forage situations.  Ruminants are typically more susceptible to cyanide toxicity because (1) ruminal microbial beta-glucosidase activity, (2) ruminal pH near neutrality – the optimum pH for beta-glucosidase activity.

What about nonruminants?  Typically less susceptible to cyanide toxicity (1) no microbial activity in the first stage of digestion (2) acid pH in first stage of digestion slows/eliminates beta-glucosidase activity in ingested forages.  So when the nonruminant is ingesting forage with “cyanide potential”, they have some protection because the enzymatic activities that release cyanide are suppressed or absent.

BUT, following a freeze/frost, the possibility for toxicity in a nonruminant may increase.  The frost or freeze has liberated the cyanide and the animal will be ingesting free cyanide.  The other “protective” mechanisms – no microbial digestion, acid pH in stomach – have been circumvented.”


Texas Section Society for Range Management Youth Range Workshop

From June 26th – July 1st, I had the privilege of meeting some pretty cool kids.  Not just any kids…RANGE KIDS!  At Range Camp, 25 youth from 8th-12th grade learned about prescribed burning, stocking rates, grazing management, brush control, public speaking, and most importantly, STEWARDSHIP.  This fine group of kids blew me away with the yes ma’ams, no ma’ams, and a special creativity and magic that only kids possess.  Range Camp is always hectic, always moving, and with very little sleep so it’s not something I get super excited for, but this year’s kids went above and beyond to make it a memorable experience for the directors, TSSRM leaders, and for one another. I am pleased to announce that even though our society and this generation is driven by technology, social media, name-brands, and a urbanized way of life, for one week at Range  Camp, the world paused and we remembered that our job is to be stewards.  Stewards of the land and stewards for the youth.

Virgil Epperson and Franklin Buchholz…you two were my favorites.  Remember what you learned.  And definitely remember how to carry a drip torch.


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More than just wildfire

Today, as the grass grows, the days get warmer, and we begin summer my mind drifts to what is to come.  I promise I am not a negative or pessimistic person. However, I do believe that we as land stewards, managers
of all things range, we have an obligation to be proactive in what is sure to be an impressive fire year.  Three years ago on June 28th, the Yarnell Hill Fire wreaked havoc and heartache on the west side of highway 89 in Arizona.  Fast-forward to June 8th, 2016 the Tenderfoot Fire burned over 4,000 acres on the east side of the Yarnell Hill Fire scar on the opposite side of highway 89 forcing another evacuation of Yarnell, Arizona.  As Texans, you are probably wondering what the hell does this have to do with us.  Easy…it could happen to us.  Impressive spring precipitation was a blessing, but fast-forward a couple of weeks and our outlook will change tremendously.

As we ramp up for summer prescribed burns and wildfires.  Please, take the time to read “Honor the Fallen – The Big Lie” by Mark Smith.  Whether you belong to an agency, burn association, or you just like to carry a torch, please take a moment to honor and learn from those making the same high-risk decisions you make everyday.

On another note, Dad (in the feature picture) has decided to keep fighting the good fight this summer and is on a Type 2 IMT in Idaho, Jake, my brother, helps out when needed for Type 2 crews and engines in Arizona.

These are the men that I honor.  They are apart of our fire community…even in Texas.


Dormant Season Burns Paired with Abundant Spring Rainfall – Did you Do that?

If you were one of the lucky landowners that burned during early/late winter, I am sure you are pleasantly pleased with the post-fire results you are seeing from these spring/early summer rains! The opportunities that fire reveals are not only inspiring, but make for gorgeous and productive rangelands! Hats off to you landowners that light the match out of faith and reap the blessings and bounty soon after!01b5ccef040adeb235a2c902f8f9e9b834c4b3f8e5 01cdebb89768087e1dfa187df49e6f0a778ee9e76e 01fee7e543eac40f34a2654e497449c433b0827477 016eda4e5cc20112f561dcc1163235fbff6508faba 0105a2e1b4f36ec2abd022fcd8b4b320d86f8567b7

Fire Appreciation Day

A HUGE thank you to Dr. Dale Rollins for organizing Fire Appreciation Day at the Rolling Plains Quail Research Ranch on May 24th!  We had over 80 participants and a healthy mix of stakeholders, agencies, and Prescribed Burn Association members!  Thank you to Dr. Robin Verble-Pearson, Zac Wilcox, Lloyd LaCoste, Matt McEwen, Mark Moon, Chris Ellis, Kent Mills, Barrett Koennecke, Brad Kubecka, Seth Pearson, Ethan McJames and all the other others who helped put this show on!  Thank you for your support in prescribed burning! Click here for more information on the talks presented at Fire Appreciation Day! And check out this link for the radio broadcast presented by Texas Farm Bureau!

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Strike First with Prescribed Fire

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Last week I had the opportunity to participate in Fire Appreciation Day at the Rolling Plains Quail Research Ranch (blog post coming soon on that!) organized by Dr. Dale Rollins.  What a fantastic way to celebrate and learn more about fire effects!  You will find summaries and abstracts of the day’s events under the tab Resources.  I was blown away by the numerous stakeholders we were able to bring together, County Judges, Commercial and Insured Prescribed Burn Managers, producers, Prescribed Burn Associations, Texas Tech University, Texas A&M AgriLife Extension, Texas Parks and Wildlife, USDA-NRCS, County Extension Agents, National Grazing Lands Coalition, and many others!  As a result of these efforts, Gary Joiner from the Texas Farm Bureau covered the event and wrote a tremendous story on prescribed burning (which you find here). It’s days like these and stories like these that help tip the fire scale a little bit closer to proactive prescribed burning!  #EveryDayisABurnDay #HappinessIsSmokeOntheHorizon

Managing Heat for Wildlife on Texas Rangelands

I am a really, really lucky Range Specialist!  I get to have one of the most amazing jobs and work across the hall from a very intelligent Wildlife Specialist!  We decided to combine forces and have recently published “Managing Heat for Wildlife on Texas Rangelands”.  You can find the publication here.  Check it out and download it!  It’s free!

100 Years at Sonora

In case you haven’t heard, Sonora is having a party! Well, technically, Field Day first and party afterwards.  Dr. Butch Taylor has decided to retire and go out with a bang at the Sonora Celebration.

This Saturday we celebrate one individual and one Experiment Station that have been inseparable for 44 years.  One man.  One Career.  One location.  Pretty amazing and definitely not something you see everyday.  The Sonora Experiment Station is a magical place to start with.  This is probably the only place in the United States where producers advocated and helped purchase land and facilities to be solely utilized for applied research that producers NEED.  Match that research station with a very dedicated and determined individual and you have the perfect combination of research and outreach.  Here you will find an invitation to the Celebration and all the information you need to know to attend, including directions and a list of hotels.

If you have only heard of Dr. Butch Taylor, please come to the Sonora Celebration and shake the man’s hand.  Butch has done more for Texas rangelands and for Fire Ecology than any other scientist or Aggie for that matter.  But, you would never know that just by talking to him.  He is humble, gracious, kind, and truly in the business of education. I promise to keep a straight face, tear free, on Saturday, and can’t wait to applaud one hell of an amazing man. To learn more about Dr. Taylor’s story and tenure at Texas A&M University click here.


Please come celebrate Sonora with me this Saturday, April 23rd.  More importantly, come meet the man behind the station.

5 Thing I Loved about the Eldorado-Divide Range Contest April 16, 2016

Last Saturday I had the pleasure of watching our District 6 and 7 4-H’ers complete the Range Contest in Eldorado, Texas.  These kids represent the very best of the best and as I watched them calculate stocking rates, forage production, and identify range plants I realized that I am so very blessed to learn from them.  I had the time of my life last Saturday because they #1) actively pursue learning about rangelands EVEN ON SATURDAY, #2) take pride in agriculture, livestock, and ranching, #3) are some of THEE most polite and well-mannered kids I have ever been around, #4) keep me on my A-Game, these kiddos are sharp, stubborn, and smart and they are not afraid to stand up for what they believe, and #5) reminded me why I am a Range Specialist 🙂

I encourage all of you to get your kids, grandkids, nieces, nephews, pretty much all kids, into a 4-H program and point them the direction of Rangeland Management, because we all know it starts in the pastures!

Congratulations to all the winners!  We will see you all again in Ozona on May 21st and Junction April 27th!

Ring-Fire Ignition

Click here for a fantastic short YouTube video of drone footage on a prescribed burn!  This 70-acre RX Fire was conducted by Conservation Fire Team south of San Angelo.  Thank you to all who helped make this happen!