Midterm - Lecture 4

Question 1

Cell walls of plants can be digested by bacteria in herbivore GI tracts. How can we quantitate it in feed?

Answer 1

Van Soest method for fiber characterization

Question 2

How does the Van Soest method work?

Answer 2

it attempts to subdivide the CHO of forages - particularly cell wall components - into readily digestible and less well digested fraction

Question 3

What do herbivores utilize cell wall CHO for?

Answer 3

energy, monogastrics mostly do not

Question 4

What is the first step of the Van Soest method?

Answer 4

feed sample is boiled in water containing a neutral pH detergent

Question 5

What happens to the to the feed sample in the first step of the Van Soest method?

Answer 5

the cell cytosol contents are dissolved - sugars, starches, most proteins, non-protein nitrogen, lipids, and some pectin

Question 6

What is the material that goes into the solution in the first step?

Answer 6

the neutral detergent soluble fraction

Question 7

What is the material that does not dissolve in the neutral detergent soluble fraction?

Answer 7

the neutral detergent fiber (NDF)

Question 8

What is the NDF?

Answer 8

all cell wall components; cellulose, hemicellulose, lignin, cutins, some silica and other minerals, and any heat damaged protein

Question 9

What happens to the NDF in the 2nd step of the Van Soest method?

Answer 9

the residue is boiled in acid detergent

Question 10

What does the acid detergent do?

Answer 10

hemicellulose is solubilized

Question 11

What is the insoluble residue from second step of the Van Soest method?

Answer 11

acid detergent fiber (ADF) = cellulose, lignin, cutins

Question 12

NDF - ADF =

Answer 12

hemicellulose

Question 13

What is the 3rd step of the Van Soest method?

Answer 13

the ADF is exposed to 72% sulfuric acid

Question 14

What does the sulfuric acid do to the ADF?

Answer 14

it solubilizes the cellulose leaving just the lignin

Question 15

What is NFC?

Answer 15

non-fibrous CHO

Question 16

How is NFC calculated?

Answer 16

100 - % protein - % NDF - % fat - % ash

Question 17

Why do we use NDF, rather than ADF when calculating the non-fibrous CHO (NFC) content of a forage intended for a herbivore?

Answer 17

because we cannot measure sugar and starches in the lab, without the NDF, the emicellulose is not included

Question 18

What are plant cell walls made out of?

Answer 18

cellulose, hemicellulose, lignin, pectins

Question 19

The more lignin there is in a plant the _____ _____ the plant is

Answer 19

less digestible

Question 20

What description of energy requirement and feedstuff energy supplied is most accurate?

Answer 20

NE