# Benefit of Hind Gut Fermentation



## Balboa (Apr 9, 2011)

It seems to me that a large part of the argument for not "over-feeding" torts comes from the knowledge that they are hind gut fermenters. They can hold food for weeks and extract every last bit of energy from it. Therefore, to simulate wild conditions and allow them to utilize their hind gut fermentation, we need to hold back some on the food, otherwise they flush it out before its fully digested, etc..

While this does seem a valid argument, I've been thinking about a potential hole in the logic.

What IS the real benefit of allowing the hind gut fermentation to run its course?

Does this yield more vitamins, minerals, truly essential dietary elements? I suspect this actually just yields more carbs, something not really crucial at all.

It seems to me that hind gut fermentation falls more in line with brumation. Its a survival trick that torts can use to stay alive through non-ideal conditions, not something that is actually necessary to exercise for their health.

I'm sure I'll be able to turn up some information with research, but decided to go ahead and pop this one out there to see if any of you already have knowledge on the subject.


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## Tom (Apr 9, 2011)

Are they true hind gut digesters? I don't think so, but I could be wrong. I think they are most like a horse digestion wise and horses are not hind gut digesters. Rabbits and rats are hind gut digesters.


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## onarock (Apr 10, 2011)

Balboa said:


> It seems to me that a large part of the argument for not "over-feeding" torts comes from the knowledge that they are hind gut fermenters. They can hold food for weeks and extract every last bit of energy from it. Therefore, to simulate wild conditions and allow them to utilize their hind gut fermentation, we need to hold back some on the food, otherwise they flush it out before its fully digested, etc..
> 
> While this does seem a valid argument, I've been thinking about a potential hole in the logic.
> 
> ...


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## Madkins007 (Apr 10, 2011)

Heck, not only are they hind-gut fermenters, they can also route a fruit-heavy meal though faster since they don't need to break down the fiberous walls and cellulose as much. 

I believe that the hindgut method helps allow the tortoises to thrive in places where there is simply not much high-quality food around- just as it does for animals like goats and desert rabbits. Most of our favorite species live in places that are either low in plants, period, or low in plants with good levels of nutrients- like the typical forest species.


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## Balboa (Apr 10, 2011)

Ok been doing some reading, interesting stuff.

Just a terminology mix-up for Tom. Cows and Sheep are Fore-Gut fermentors, Horses, rabbits, torts and PEOPLE are hind gut fermentors.

With the foregut fermentors in simple terms, they aren't living on the plant material they eat directly, they actually live on the microbes in their guts that eat the plant material. Pretty cool huh?

With us hind-gut types most of the nutrients are absorbed up front. The hind-gut for the most part only provides us with energy, in horses a large portion of their energy, humans relatively little (10%).

Vitamin B and K and some proteins are produced in fermentation, but here's the catch. You only get benefit from that if you eat the poop and run it through again. Apparently animals that do this regularly make different poops. Soft ones that need to be run through again, and hard ones that have already gone through twice.

What does this tell me?

Yes, hind gut fermentation is useful for torts to get by on little food. They'll obviously run everything through multiple times and get everything they can from it during the non-growing season.

In captivity how much chance or need do they get to run it through twice? Not much, we go and snatch that yummy poop from them every chance we get.

In reality, we're just robbing them of vitamins b,k and some calories. Might as well give them a twinkie with some vitamins dusted on.

Given plenty of nutritious food there is no need for extended digestion like this from what I see. Fresh food will have the calcium, vitamins, etc that will benefit them more than the calories in their poop.


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## dmarcus (Apr 10, 2011)

I learn something new on this forum every day.


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## onarock (Apr 11, 2011)

I was talking with a forum member tonight about the behavior of my male gpb. I was sharing with him the behavior of my males durring the peak breeding season (my males are always ready to go, but more active durring certain times of the year). I don't know if this is everyones experience who has a breeding group, but when my males are in full "Rutt" they don't eat much, preferring to spend most of their days chasing females. The females eat regardless, usually unaffected by the males advances and success . This got me thinking about hindgut fermentation of all things. I would say that in my groups case of leopards, hindgut fermentation is probably less necessary in females, but a necessity with the males as they tend to eat alot less durring their more active breeding times. 

I also have some thought about hindgut fermentation as it pertains to commercially formulated diets. In particular the benefits and detriments of hindgut fermentation in relation to commercial diets fed to tortoises both male and female and the effects they may have on totoises durring breeding or seasonal change.


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## John (Apr 11, 2011)

Great thread Brett,I'm lagging behind on this subject had no time to research yesterday,and my heads still full with the topic we were on two days ago.I have found some info that puts it into perspective when dealing with captive animals,Vetter references a study by Hailey (1997) which I now have to find and read for myself since Vetter states that on average food passes through in 3-8 days.Whereas Fife states that store bought greens pass in 3-8 days while grasses and such will take 16-28 days,so a tort that is being fed store greens is passing faster and not getting the benifit of recycling its poop the double whammy.


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## ISTortoiseLover (Apr 11, 2011)

Wow..this is most interesting. Wouldn't that mean they'd be defecating alot less? Maybe once every 7 days? I'm sure they'd urinate alot less too if food intake is reduced. Well unless there's a water dish available 24/7..


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## John (Apr 11, 2011)

onarock said:


> I was talking with a forum member tonight about the behavior of my male gpb. I was sharing with him the behavior of my males durring the peak breeding season (my males are always ready to go, but more active durring certain times of the year). I don't know if this is everyones experience who has a breeding group, but when my males are in full "Rutt" they don't eat much, preferring to spend most of their days chasing females. The females eat regardless, usually unaffected by the males advances and success . This got me thinking about hindgut fermentation of all things. I would say that in my groups case of leopards, hindgut fermentation is probably less necessary in females, but a necessity with the males as they tend to eat alot less durring their more active breeding times.
> 
> I also have some thought about hindgut fermentation as it pertains to commercially formulated diets. In particular the benefits and detriments of hindgut fermentation in relation to commercial diets fed to tortoises both male and female and the effects they may have on totoises durring breeding or seasonal change.



So lets here it,what are your thoughts on commercial diets?



ISTortoiseLover said:


> Wow..this is most interesting. Wouldn't that mean they'd be defecating alot less? Maybe once every 7 days? I'm sure they'd urinate alot less too if food intake is reduced. Well unless there's a water dish available 24/7..



unfortunately if they eat every day they should aslo defecate everyday.


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## HLogic (Apr 12, 2011)

I believe we have stumbled into the zone of misunderstanding...

Coprophagy (coprophagia - the consumption of feces) is practiced by young torts to establish intestinal flora necessary for the digestion of food materials particularly cellulose. Typically, adult torts do not consume their own or other torts (of the same species) feces. They will consume other animals feces as a protein or nutrient source and just to gross out their owners!

The 'double-whammy' or 'recycling', otherwise known as caecotrophy, is the production of partially digested pseudo-fecal (caecal) pellets which are excreted and immediately consumed. It is limited to a few high metabolism organisms like rabbits, hampsters and certain other small mammals. The digestive product of caecal pellets are feces which are not consumed. This mechanism evolved to eliminate prolonging the digestive process necessary for fiber fermentation, reducing the load in the digestive tract and still be able to utilize the nutrients generated by the shorter fermentation. True caecotrophs will starve to death if prevented from consuming the caecal pellets.

Cellulose is a structural constituent of plant cell walls. In certain parts and types of plants the cellulose serves as 'armor'. Vertebrates are incapable of producing cellulase (notice the "A"), the enzyme responsible for breaking down (digesting) cellulose. Certain microbes in the intestinal flora of many animals, even termites, can produce cellulase and in most herbivores are harbored within the intestines for this purpose.

Fiber (cellulose) itself is not absorbed during digestion. It is actually a barrier to digestion. The purpose of chewing, foregut fermentation by ruminants, acid hydrolysis in the stomach and hindgut fermentation in many higher animals; is an attempt to release and/or convert released nutrients from within the plant cells and convert some of the cellulose (via microbial action) into useable nutrients.

Tortoises, in general, have a rather slow digestive process. The purpose of the slow digestion is to allow time for the microbial digestion of the plant cell walls so as to release the nutrients within and the production of additional nutrients by the microbes themselves for absorption in the colon like certain B vitamins, vitamin K and fatty acids. The amino acids, proteins and certain other nutrients generated by these microbes are mostly lost as there is no means for them to be absorbed in the posterior (distal) colon.

Overall, hindgut fermentation does not generate great quantities of nutrients responsible for energy production. Although up to 30% may occur in the anterior (proximal) and mid colon, the majority occurs in the small intestines and 'functional' caecum (an eccentric dilation of the anterior colon in tortoises). The relatively low energy available precludes hindgut fermentation from providing long-term sustenance. In almost all cases, prolonged activity during periods of extended fasting is fueled by fat reserves.

The research that demonstrates a direct correlation between fiber content and digesta retention time simply illustrates that low fiber (greens, fruits, flowers, shoots, etc.) diets, similar to our own, do not require substantial cellulose fermentation whereas higher fiber (grasses, sedges, twigs, etc.) diets do. Higher fiber diets reduce the average digestibility (the amount utilized vs. the amount eaten) as well - the expected scenario for most tortoises. Tortoises, among others, are able to modify the rate at which digesta move through the colon, including reverse peristalsis in some instances, thereby maximizing the efficiency of the fermentation by retaining the materials in the digestive tract longer.

Eating daily does not equate to exreting daily necessarily. Once digested, the large masses of material are reduced considerably in volume - most food items are largely composed of water which is absorbed. The utilized components of the diet comprise a surprisingly small percentage of the total mass consumed. Depending upon the food materials consumed defecation may occur from once every several days to multiple times per day.


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## ALDABRAMAN (Apr 12, 2011)

I agree Art, lol. I wish I was as smart as you guys! Impressive.


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## Neal (Apr 13, 2011)

HLogic - good post, it will take me a bit of time to "digest" (no pun intended) your words, but let me see if I am understanding correctly as someone with no scientific or biological background. You're saying that because high fiber foods take a longer time to digest and extract nutrients, the benefit of hind gut fermentation is that it basically keeps the food in the tortoises system longer to extract the necessary nutrients? So really, hind gut fermentation has nothing to do with surviving in low food availability conditions, it's just necessary to handle the high fiber dietary requirements of certain tortoises, correct?


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## Madkins007 (Apr 14, 2011)

Art, I once again stand in awe of your knowledge and research!


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## brymanda (Apr 18, 2011)

Like Art said, very few things are actually absorbed from the colon, most are absorbed higher up in the small intestine, but interestingly, the fatty acids produced by the bacteria in the colon theoretically provide 100% of the metabolizable energy for the turtle. (I'm not actually sure if this reference to turtles includes tortoises, but this is what my veterinary nutrition book said. I'll try and track down the actual source). Admittedly this seems a little hard to believe. By comparison the cow receives 70% of its metabolizable energy from the fatty acids produced by bacteria in it's rumen. 

(Metabolizable energy is defined as the amount of energy available from pet food once the energy from feces, urine, and combustible gases has been subtracted.)

This seems to imply that nutrient absorption that occurs prior to the colon isn't as relevant.... Which would be counterintuitive given that most absorption occurs in the small intestine.... 


Great thread btw, and bear in mind that I'm just a student, this is not an expert opinion 




HLogic said:


> Tortoises, in general, have a rather slow digestive process. The purpose of the slow digestion is to allow time for the microbial digestion of the plant cell walls so as to release the nutrients within and the production of additional nutrients by the microbes themselves for absorption in the colon like certain B vitamins, vitamin K and fatty acids. The amino acids, proteins and certain other nutrients generated by these microbes are mostly lost as there is no means for them to be absorbed in the posterior (distal) colon.
> 
> Overall, hindgut fermentation does not generate great quantities of nutrients responsible for energy production. Although up to 30% may occur in the anterior (proximal) and mid colon, the majority occurs in the small intestines and 'functional' caecum (an eccentric dilation of the anterior colon in tortoises). The relatively low energy available precludes hindgut fermentation from providing long-term sustenance. In almost all cases, prolonged activity during periods of extended fasting is fueled by fat reserves.


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