Foregut and hindgut fermentation efficiency in mammalsSamantha Bray

Foregut fermenting mammals are more efficient than hindgut

fermenting mammals at extracting energy from a similar diet because

of their different digestive morphologies.

Predictions

• Foregut fermenting mammals should be able to extract more energy and nutrients from their diet compared to hindgut fermenters.

• Hindgut fermenting mammals are less efficient than foregut fermenting mammals because their guts are less specialized.

Comparative digestive anatomy

Hindgut Fermenter• Single chambered

stomach• Adapted to digesting

cellulose• Fermentation occurs

after digestion in the stomach in the enlarged caecum and large intestine

Foregut Fermenter (Ruminant)• Multi-chambered stomach• Adapted to digesting

cellulose• Fermentation occurs

before digestion in the stomach in a specialized rumen (1st stomach chamber).

Normal GIT• Not adapted to

digesting cellulose.

• No fermentation chamber.

Microbial Fermentation in Mammals

Main Products:• Volatile Fatty Acids (VFA’s)• Proteins

• Took 3 hindgut and 3 foregut fermenting primates and fed them a test diets of 15% acid detergent fiber (ADF).

• Acid Detergent Fiber (ADF): The least digestible plant components, including cellulose and lignin. ADF values are inversely related to digestibility, so forages with low ADF concentrations are usually higher in energy.

• Collected fecal samples daily to analyze for dry matter, digestive energy intake, gross energy, ADF, etc.

Experiment by Edwards and Ullrey

Hindgut Fermenters Foregut Fermenters

Alouatta carayaAlouatta v.

palliata

Alouatta s. sara

Colobus g. kikuyeunsis Pygathrix n.

namaeus

Trachypithecus f. francoisi

Alouatta caraya

Alouatta v. palliata

Alouatta s. sara

Colobus g. kikuyeunsis

Pygathrix n. namaeus

Trachypithecus f. francoisi

0

50

100

150

200

250

300

0 1 2 3 4 5 6 7

Dig

est

ible

En

erg

y In

take

(kc

al/k

g)

Number of Primate Subjects

Hindgut Fermenters

Foregut Fermenters

Figure 1. Digestible energy intake for 6 primates, 3 hindgut fermenting Alouatta spp., and 3 foregut fermenting colobine primates when fed at 15ADF (Acid Detergent Fiber) diet.

Results

Edwards and Ullrey Conclusion

• Hindgut and foregut fermenting mammals are both more efficient at digesting plant fiber than ‘normal’ mammals because of their specialized digestive tract.

• Colobines (foregut fermenters) demonstrate that they are more well suited to consume a diet containing plant fiber compared to Alouattaspecies (hindgut fermenters).

• Hindgut fermenters (Alouatta spp) are less efficient digestive fermenters than foregut fermenters (colobines).

• The reduced digestive efficiency in hindgut fermenters is related to the lack of specializations before gastric digestion in the stomach.

• Hindgut fermenters have smaller absorptive area further down the tract from the site of fermentation.

Explanation for differences in digestive efficiency

Picture from:http://www.fao.org/ag/agp/AGPC/doc/Publicat/PUB6/P617.htm

• Hindgut fermenters have their fermentation site positioned posterior to the stomach. Thus they lose the opportunity to exploit VFA’s and proteins synthesized by the microbes.

Explanation for differences in digestive efficiency

Questions?

References

Rasby R., and J. Martin. Understanding feed analysis. Retrieved from https://beef.unl.edu/learning/feedanalysis.shtml

Edwards M.S., and D.E. Ullrey. 1999. Effect of dietary fiber concentration on apparent digestibility and digesta passage in non-human primates. II. Hindgut- and foregut-fermentation foliovores. Zoo Biology. 18: 538-549

Sherwood L., H. Klandorf, and P.H. Yancey. 2013. Animal physiology from genes to organisms 2nd edition. 704-714.