The fiber of forages

Relative feeding value, neutral detergent fiber, lignin.  These are all terms that can be found on any hay or grass analysis.  But what do they mean and how are they determined? 

Let's start at the beginning.  Sending in your forage to be analyzed is very important when developing a feeding plan for any species.  The values you get back tell you how the forage is lacking so that you can fill in the gaps without overfeeding nutrients that the animal won't be able to utilize.

In this post I'm going to focus on the fiber portions of forage analysis.  We'll get to protein and energy later.  Fiber in this sense refers to the structural portions of the plant cells.  The compounds that make plant cell walls rigid.  These are also the least digestible compounds in forages, thus they are important in indicating how well animals can use the nutrients in the forage.

The big three fiber categories are neutral detergent fiber (NDF), acid detergent fiber (ADF), and lignin.  NDF and ADF refer to several types of fiber and the names come from how they are analyzed.  The forage sample is 'washed' in a detergent solution, that solution is either of a neutral pH or an acid because of the chemicals used in each 'wash'.   Each of these procedures removes a set or components from the plant material, leaving only specific fiber types.  But what do they represent?

Plant cell components (image from University of Minnesota)

The neutral detergent removes soluble carbohydrates, sugars, etc.  This leaves us with only the cell wall components, lignin+cellulose+hemicellulose.  NDF value is a general indicator of intake ability.  As NDF increases voluntary intake generally goes down.

The ADF procedure removes hemicellulose, leaving only cellulose and lignin.  It is a general indicator of digestibility.  Cellulose is not digested by any mammalian enzymes, only by the microbes in the rumen of cattle and sheep or the hindgut of horses, rabbits, etc.  As ADF increases digestibility goes down.

Finally lignin, which is almost completely indigestible.  As lignin increases so does ADF and NDF, which means that both intake and digestibility go down.

Generally fiber can also be used a general indicators of maturity.  As plant age (maturity) increases the percent lignin and cellulose go up, decreasing the quality of the forage. 

That's fiber in a nutshell, what portions of nutrition do you want to hear about next?

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Goats on Statten Island?

An illustration of the future Fresh Kills Park. (Photo credit: Wikipedia)

Yes indeed, there are goats on Statten Island.  In Freshkills park to be precise.   This park used to be the largest land fill in the world.  It was closed in 2001 and is now being developed into a 2,200 acre park.  The development will be on going for the next 30 years, but it's getting started now.

A large portion of the park is being developed into a  wetlands area.  The only problem?  That area is currently overrun by the invasive plant phragmites.

Phragmites. (Photo credit: Maryland Dept. of the Environment)

Pharagmites is an extremely long lived plant that grows up to 18 feet tall.  Unfortunately, it's also not easy to get rid of.  Freshkills park is trying to avoid using herbicides to kill these plants, so they are trying something a bit different.

Enter the goats.  Twenty Anglo-Nubians.  They will be at the park for 6 weeks this summer, munching as much phragmites (and anything else they find) as they can. 

 Using goats to tackle difficult plants isn't anything new.  This technique is call targeted or prescribed grazing.  Many animals have been used to deal with excessive, unwanted vegetation; from Asian carp in overgrown streams, to cattle grazing kudzu.  Growing up in Georgia, we had kudzu all over the farm.  It always amazed me to see how the cattle would choose to eat it over the grass at times.  Horses didn't seem to like it though.  But, kudzu is a story for another day.

For now, if you are in the area, go see the goats at Freshkills park and admire some truly natural weed control at work.

An Anglo-Nubian goat attempts to eat their prize ribbon at a Scottish fair. (Photo credit: Wikipedia)

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In Defense of GM Plants

Not long ago, this came across my facebook wall:

I've long been an advocate for GM crops, but this claim was new to me.  Fortunately I have a wide range of friends, in various disciplines, to turn to when topics are not in my realm of expertise.  This time, I didn't even have to ask as a link to this article came from a plant pathologist friend not much later.

Go, read it.  I'll wait here while you do.

Complex right?  These issues are rarely as simple as we'd like.  We can accept that there may be some side affect of using GM crops.  Or we can go back to using pesticides and herbicides at very high levels, with known, worse, negative effects.

Now, I know what you are saying.  "But why can't we use non-GM crops and no herbicides, etc?"  Well, we can, but you are going to pay more for your food and get less of it.  These techniques allow farmers to grow more food more easily.  I think the telling statement in this article about weed control in corn production is this:

"There was no feasible way to establish an untreated level of
control without complete loss of yield due to weed competition."

So, the corn has to be treated with something.  What that something is is up to the farmer and decided based on their land, variety, and marketing desires.  Sure there are organic herbicides out there, but they require frequent application, typically in larger amounts.  They are also non-specific.  They kill everything, meaning application must be done carefully.


As with most things in life, there is no one answer, no perfect solution.   At least not yet.

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• GM crops good for environment, study finds

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Deadly cyanide...

One of my mother's friends posted this CBS article to Facebook recently, and the story seems to be quickly making the rounds of many blogs and news agencies.

This article makes a couple claims, which I am going to go through separately, then give a quick "big picture".

1) Claim "The grass is a genetically-modified form of Bermuda known as Tifton 85"

       Tifton 85 is the name of the grass, right off the bat I can tell you that is was developed in 1985 at the UGA experiment station in Tifton, GA.  That's the easy part.  A little bit of looking brought me to the UGA site on Tifton 85.  The page says that Tifton 85 is a hybrid variety of grass produced from cross-breeding a South African Grass with a bermudagrass.  Personally, I would not consider this a GMO, it was not produced via gene splicing or other techniques in a lab, but rather by normal, everyday breeding.  Similar to crossing a horse and donkey to get a mule.

     Tifton 85 is a sterile pentaploid. While sterility can be caused by chemicals and lab techniques (these are used to produce those seedless watermelons we all love), Tifton 85 is naturally sterile (like a mule) because it's a crass between two genera with differing chromosome numbers.  Basically, it can't reproduce naturally as it has an odd number of chromosomes, so gametes (sperm and eggs) are unstable.  So, mutation isn't impossible, but I'd say extremely unlikely.  It is much more likely that a gene that is normally lowly expressed was up-regulated due to adverse conditions such as drought or heat.

2) Claim: "Preliminary tests revealed the Tifton 85 grass, which has been here for years, had suddenly started producing cyanide gas, poisoning the cattle."

      Many common plants are cyanogenic.    It is produced naturally as a part of plant nutrient metabolism.  Cyanide functions as an anti-herbivory agent in plants.  The cyanide is typically stored as cyanic glucoside (cyanide sugars).  When the plant matter is damaged (chewed/digested) glucosidase enzymes break down these sugars releasing hydrogen cyanide gas (HCN).  This process can also occur naturally in the plant during stress conditions (i.e. drought, frost, wilting) or naturally occurring damage to the plant(i.e. trampling, bruising, etc).  High levels of nitrogen fertilizer can also increase HCN production in plants.

     If the cyanide sugars and enzymes are high enough in the plant before or during ingestion by the animal then the level of cyanide production can be very high natural.  Considering the very hot summer so far (especially in Texas) I would guess that this pasture was just producing very high levels of cyanide.  Cattle and other animals can handle very small amounts of cyanide, as they have evolved with these plants.  But they have also learned to avoid them.  It's when the levels are too high that there is a problem.
 
     Cyanide production has been known to be a problem in several species of grasses commonly planted (Johnson grass, Sudan grass, clovers, etc), though most reports I have found indicate that Tifton 85 has very low natural production.  For species with known high natural cyanide production it is recommended that livestock not graze them unless they are fully mature or dried as hay (cyanide is volatile and will dissipate when the dried plant is exposed to air).  This is not the first instance of cyanide poisoning occurring from a plant not generally believed to be a high producer.

Big picture: Tifton 85 is a naturally bred hybrid grass, not a lab-devloped GMO.  Plants produce cyanide naturally, especially when growing under drought conditions.  While Bermudagrass isn't know to have high levels of cyanide production, apparently in this case condition were just right.

Fescue: Basics

Considering that my PhD research is all about fescue, I'm likely to mention it a fair bit here.  So, I thought I'd make sure we were all on the same page.

Step one:  Raise your hand if you know what fescue is.  

No cheating!

For some of you, this was a silly question. But, I recently gave a presentation about fescue to a local agriculture magnet high school.  I asked who knew what fescue was and for less than 10% of the students raised their hands.  I was reminded then and there that not everyone has the base of knowledge I do.

From Texas A&M's website

So, fescue is a grass.  It's a cool season bunch-grass to be precise.  That meas that it grows best in spring and fall (cool season) and grown in clumps, as opposed to spreading out like a sod-grass.

There are about  300 species in the fescue genus.  I am particularly interested in Festuca arundinacea.  That's tall fescue.  Tall fescue came to the US from Europe in the 1800s.  But it wasn't widely planted until the 1940s after the KY-31 variety was developed right here at the University of Kentucky.

KY-31 was developed and released as a drought tolerant, trample resistant grass that would grow where other cool season grasses failed.  During the dust bowl KY-31 and other tall fescue were widely planted to help with land reclamation.  It makes a great pasture or lawn grass and is still one of the most popular vareties in the south-east US.


The interesting thing about tall fescue is that is has a symbiotic relationship with a fungal endophyte called Neotyphodium coenophialum.  This little guy produced alkaloids that give the plant drought and insect resistance.  Great right?

For the plant, yes.  Unfortunately, when these alkaloids are consumed by animals they cause a wide range of physiological problems.  Ranging from reduced conception rates, dystocia (difficulty giving birth), and aglactia (reduced milk production) to elevated body temperature and low growth rates.  Cattle, horses, sheep, goats, and even some wildlife such as deer have been reported to show these problems and more.

Fabulous image from the University of Tennessee.  

The steer in the front is the same age as the one in the back, but he's been on a fescue pasture.








That covers the basics of fescue.  My research deals with understanding exactly how the alkaloids are causing problems in the animal.  I'm happy to talk fescue all day any day, so please email or ask here if you have any questions.