This document discusses and compares the digestive systems of herbivores that ferment cellulose. Foregut fermenters, like ruminants, have a compartment called the rumen before the stomach where microbes break down cellulose. This produces short-chain fatty acids which provide energy and microbes as a protein source. Hindgut fermenters ferment cellulose in chambers after the stomach and intestine. They absorb fatty acids but do not digest microbes, relying solely on diet for protein. Foregut fermentation allows for greater energy and protein extraction from plant materials.

1. Assorted Digestive Systems

2. Carnivores

3. Herbivores
• Fermentation of cellulose by gut bacteria
• Short chain fatty acids (scfa)(aka volatile fatty acids)
produced by bacteria provide and energy source for the
herbivore
• Foregut fermenters v’s hindgut fermenters
• Foregut fermenters/ruminants
1) Fermentation vat (rumen) comes before the “stomach”
2) Food is entirely processed by microorganisms
3) SCFA are absorbed straight through rumen walls
This is how ruminants get their energy!
4) True stomach is used to digest excess microorganisms

4. Foregut fermenters/ruminants
1) Fermentation vat (rumen) comes before the
“stomach”
2) Food is entirely processed by microorganisms
3) SCFA’s are absorbed straight through rumen
walls. This is how ruminants get their energy!
4) True stomach is used to digest excess
microorganisms. This is how ruminants get their
protein.

5. Foregut Fermentation: Ruminant

6. Foregut Fermenters

7. Hindgut Fermentation
1) Fermentation chamber(s) comes after the
“stomach” and the small intestine. Enlarged hindgut
or pouches called “cecae”
2) Microorganisms get what the animal doesn’t use
Better if your diet is of higher quality
3) VFA’s are absorbed straight through hindgut walls
4) Excess microorganisms are defecated
Hindgut fermenters miss out on microbial protein

8. Hindgut Fermenters

9. Comparing fermentation strategies
Characteristics Foregut /Ruminants Hindgut
Where are the
microbes?
Before stomach After stomach
Are microbes digested? Yes No
Source of energy Volatile fatty acids Food and VFA
Source of protein microbes diet