Exam 4 (Lecture 46) - Fermentative Digestion

Question 1

Fermentative digestion occurs in specialized compartments positioned either _______ or ________ to the stomach and small intestine.

Answer 1

Cranial; caudal

Question 2

Foregut fermentation compartment name?

Answer 2

Rumen

Question 3

Hindgut fermentation compartment name?

Answer 3

Cecum

Question 4

Foregut and hindgut digestive structures support fermentative digestion by providing and environment for ________.

Answer 4

Microbes

Question 5

What do the redox (Eh) conditions in the digestive tract of animals determine?

Answer 5

Whether aerobic oxidation or anaerobic fermentation of nutrients will occur.

Question 6

In normal conditions, ruminal microbes are _______ with a markedly ________ redox potential, reflecting the absence of ________.

Answer 6

anaerobic; negative; oxygen

Question 7

Why is a negative redox potential important?

Answer 7

It impacts the digestion, absorption, and metabolism of nutrients

Question 8

Describe the microbial ecosystem of fermentative digestion.

Answer 8

Mostly bacterial; but also contains a large number of protozoa and smaller numbers of fungi

Question 9

Protozoa are beneficial in the rumen because of the ingestion of ________. Why are protozoa beneficial in the rumen?

Answer 9

Bacteria

Important in ingestion of:
- Large numbers of bacteria to maintain bacterial numbers
- Smaller protozoa
- Particles of starch and protein

Slows the digestion of rapidly fermentable substrates

Protects from bacterial action

Question 10

Why is digestion so slow?

Answer 10

Because of the complex structure and organization of plant fibers

Question 11

All cell wall molecules that are CHOs will be digested with _________ (hydrolytic enzymes) produced by the _________. Cellulases release ________ and _________ from the complex CHOs of cell walls. Release saccharides are ________ available for absorption by the animal and are metabolized by _________.

Answer 11

Cellulases; microbes

Monosaccharides; oligosaccharides

Not directly; microbes

Question 12

Is lignin digestible or indigestible?

Answer 12

Indigestible

Question 13

Almost all _______ and ________ are subject to _________ digestion. What do CHOs and proteins provide for the microbes?

Answer 13

CHOs; proteins; fermentative

CHOs = Substrates for energy and growth of microbes

Question 14

Insoluble CHOs require the _______ attachment of bacterial to the surface of the plant particle. Where are the enzymes located?

Answer 14

Physical

Enzymes are located on the surface coating of the bacteria

Question 15

_________ enters a glycolytic pathway to produce VFAs. VFAs provide _________% energy for herbivores.

Answer 15

Glucose

70%

Question 16

List the three VFAs.

Answer 16

1) Acetate

2) Proprionate

3) Butyrate

Question 17

Total amount of VFA produced with a high _______ diet is usually much higher than that produced with a high _______ diet.

Answer 17

Starch; fiber

Question 18

Ruminants depend on _________ produced by ________ as the source of dietary protein. Microbial crude protein reaches the abomasum and small intestine (absorption of protein) when microbes are washed out of the rumen. The majority of bacteria have surface ________ which catabolize ________ to ________. _________ is a major source of ____________ required for ____________.

Answer 18

Microbial crude protein; microbes

Proteases; RDP; peptide

NH3; nitrogen; microbial growth

Question 19

Describe how microbial crude protein (MCP) can be synthesized in the rumen from nonprotein nitrogen (NPN) sources.

Answer 19

If sufficient glucose is available most rumen microbes can synthesize microbial protein from NH3

Question 20

Describe the NPN sources that are used for microbial protein production.

Answer 20

NH3, Nitrates, Urea (NH3 > Urea occurs in liver)

Question 21

Describe the two sources of hepatic urea production.

Answer 21

1) Nitrogen arising from the deamination of endogenous amino acids (occurs in liver) and converted to urea

2) Nitrogen absorbed as NH3 from the rumen

Question 22

The microbial growth rate depends on the supply of nutrients and the rate at which microbes are washed from the rumen. The overall reaction in the rumen can be evaluated using what equation? Understand what the variables in the equation represent.

Answer 22

Glucose + Peptide = MCP + VFA + NH3 + CH4 + CO2

Question 23

Describe what happens to MCP when glucose and peptide availability are well matched.

Answer 23

These conditions favor MCP synthesis

Question 24

Describe what happens to MCP when the availability of glucose > peptide.

Answer 24

Decreased MCP synthesis

Question 25

Describe what happens to MCP when peptide > glucose.

Answer 25

Decreased MCP synthesis

*Both are decreased because in order for synthesis to occur, glucose and peptide HAVE to be balanced