Digestion in Ruminants

1. Digestion in Ruminants
Herbivores such as cows, sheep and goats are ruminants.

2. The problem with cellulose
• Herbivore food contains a lot of cellulose e.g.grass
• Mammals cannot produce cellulase
• Ruminants have a large storage chamber called a
rumen
• The rumen contains a large number of bacteria
which do produce cellulase
• The bacteria and the ruminant both benefit from
this relationship
• This is known as mutualism

3. What is the difference between cellulose and starch?
H2O
C
C
H
H
 glucose
Condensation of 2  glucose molecules
O
OH
OH
OH
OH
O
H
H

4. H2O
H
 glucose
Condensation of 2  glucose molecules
O
H
OH
O
C
OH
C
O
H
H
Glycoside bond

5. Food chewed a second time 4
3
reticulum
1 Chewed grass
2 rumen
Grass is ground up by chewing
It is swallowed and passes into the rumen

6. Food chewed a second time 4 =chewing the cud
Abomasum
‘true stomach’
5
6
duodenum

7. Food chewed a second time 4
Abomasum
‘true stomach’
5
6
3
duodenum reticulum
The pathway the grass takes
2 rumen
1 Chewed grass

8. What happens in the rumen
•Bacteria in the rumen secrete cellulase
•Cellulose is hydrolysed to glucose by cellulase
•Providing energy for growth of bacteria
•Glucose is used by the bacteria for anaerobic respiration
cellulase
cellulose
glucose

9. •
•
•
•
•
Bacteria absorb glucose
Glucose used in anaerobic respiration
Fatty acids and methane produced as waste product
Fatty acids absorbed by ruminant
Provides energy for ruminant
glucose
methane
fatty acids
absorbed by ruminant and
used in respiration

10. Fermentation in the rumen
e.g. C6H12O6
2CH3COOH + CO2 + CH4
e.g. C6H12O6
Hexose sugar
2CH3COOH + CO2 + CH4
e.g. C6H12O6
2CH3COOH + CO2 + CH4
Ethanoic
methane
acid

11. How cattle can survive on a diet low in protein?
•Nitrogen may be taken that is not part of protein e.g.urea
•Some bacteria in the rumen use urea as a source of
nitrogen to make protein
•This protein is used for bacteria reproduction
•Some bacteria are swallowed with the chewed cud
•The bacterial protein is then digested in the abomasum and
duodenum as in other mammals
•Amino acids produced are absorbed in the small intestine
and used to make cow protein
•The bacteria have converted the waste urea into
protein to supplement their diet

12. Nitrogen metabolism in the ruminant
Some urea from deamination is recycled
Saliva + urea
Liver
Deamination
of amino
acids
rumen
urea
urine

13. grass+saliva+urea
rumen
cellulose
glucose
cellulase
urea+grass protein
bacteria
bacteria grow
methane+CO2+fatty acid
abomasum+
duodenum
fatty acids
absorbed
+respired
some protein
excess bacteria
protein
peptides
amino acids
absorbed +made
into protein

14. Now have a go at these
1. What is likely to be the main respiratory
substrate of a cow?
(1)
2. Explain how it is possible for cows to survive on a
diet poor in protein.
(2)
3. Give three ways in which the rumen of a cow is like
an industrial fermenter used to produce enzymes. (3)
4. What are the sources of non-protein nitrogen the
bacteria in the rumen may use to produce protein? (2)
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check your answer
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15. 1. Fatty acids – waste products from the bacterial respiration
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2. Bacteria in the rumen use non protein nitrogen to
make protein for growth; Some of these bacteria are
passed to the abomasum, along with the partially
digested grass ;
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16. 3.
•Temperature is controlled in both
•pH is kept constant in both
•The contents of both are kept moving
4.
Any 2 from Urea; ammonia; nucleic acids;
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