Ruminant Nutrition Exam 2

Fall 2026 Gressley ANFS454 University of Delaware

Neutral Detergent Solubles (NDS)

Non-structural carbohydrates and Pectin (highly digestible/fermentable) are released

Neutral Detergent Fiber (NDF)

Hemicellulose, Cellulose, and Lignin stay in

What is the first step in the Detergent System of Analysis?

Boil feed in neutral (pH 7) detergent (soapy solution) with amylase to get NDS and NDF

What is the second step in the Detergent System of Analysis?

Boil NDF residue in acid (pH 4) detergent (soapy solution)

Acid Detergent Fiber (ADF)

Cellulose and Lignin

What happens to hemicellulose after Step 2 of the DSA?

Hemicellulose goes into solution
NDF-ADF= hemicellulose

What is the third step in the Detergent System of Analysis?

Treat ADF Residue with strong acid (72% pure sulfuric acid)

What is the final residue of the DSA?

Lignin

What happens to Cellulose in step 3 of the DSA?

Cellulose goes into solution,

ADF-lignin=cellulose

“High Quality” forage → DSA

high NDS, moderate NDF, low ADF, low ADL

“Low Quality” forage → DSA

Low NDS, high NDF, ADF, and ADL

What is dietary NDF associated with?

Intake

What is dietary ADF associated with?

Digestibility

What is step 1 of the rumen carbohydrate fermentation?

Access: Break down complex carbs into mono, di, and oligosaccharides

What is step 2 of the rumen carbohydrate fermentation?

Energy: Ferment monosaccharides into pyruvate to yield energy

What is step 3 of the rumen carbohydrate fermentation?

Reducing Equivalent Regeneration (And sometimes additional ATP)

What is reducing equivalent regeneration?

NADH → NAD+ to allow glycolysis to continue

What are some extra products of step 3 of rumen carb fermentation?

Some pathways generate additional ATP

Pyruvate is converted to VFAs and other products

Which of the following is a component of neutral detergent fiber but not acid detergent fiber?

hemicellulose

Which acid is produced by Lactobacillus buchneri and inhibits yeast growth in silages?

acetic acid

Which of the following has the lowest pKa?

Lactic acid

Diets high in starch tend to increase the molar proportion of

Propionic Acid

Diets high in fiber tend to increase the molar proportion of

Acetic Acid

The acrylate and oxaloacetate/succinate pathways lead to the production of

Propionic Acid

The pKa of acetic acid is 4.8. If the pH is 5.8, then

more of it will be in the ionic form (CH3COO-)

The bacterial glycocalyx is used for:

attaching bacteria to feed particles

Which fiber digesting bacteria has the greatest ability to attach and degrade fiber, even at undamaged areas other fiber digesting bacteria cannot typically attach?

Fibrobacter succinogenes

Why is it important for starch fermenting rumen bacteria to have proteolytic activity?

provide amino acids or to access the starch (break away prolamins)

What is the difference between expressing volatile fatty acids as concentration vs. molar proportion?

concentration is the actual concentration; molar proportion is relative to all of the VFA

(proportion of 100%)

If amylase was not added during the detergent analysis process, then

NDF would be overestimated

ADF contains

Cellulose and lignin

Which would you expect to provide the most energy to an animal?

1 lb hemicellulose

Which is NOT produced during glycolysis?

NAD+

Production of which results in a net use of hydrogen?

Propionate

Which has 3 carbons?

Propionate

Which is the most common pathway for propionate generation?

Oxaloacetate/succinate pathway

What is the structure that fibrolytic bacteria use to attach to cellulose?

glycocalyx

Which fibrolytic bacteria is the best at breaking down hard-to-digest fiber?

Fibrobacter succinogenes

Which fibrolytic bacteria is motile?

Butyrivibrio fibrisolvens

Which fibrolytic bacteria was named for its white appearance?

Ruminococcus Albus

High fiber diets tend to increase the molar proportion of what in the rumen?

acetate

The total concentration of VFAs in the rumen increases with diets that are higher in

Concentrates

What should go into solution following boiling in neutral detergent?

Pectin

Which should NOT be present in ADF?

hemicellulose

Which is digestible by mammalian enzymes and fermentable by rumen microbes?

Starch

Which occurs during glycolysis?

NAD+ is converted to NADH

True/False: Rumen microbes use VFAS like acetate, propionate, and butyrate as energy sources

false

Which product of microbial fermentation does NOT provide energy to the host animal?

methane

Which one has 2 carbons?

acetate

Production of methane and what results in a theoretical net utilization of hydrogen?

Propionate

True/False: all organisms in the rumen can make butyrate

False

Which of the following would you expect to be true when comparing a high fiber diet to a high concentration diet?

the high fiber diet should have a greater proportion of acetate

If a diet has more energy, which of the following would you expect to find?

higher rumen VFA concentration

Fiber digestion should increase with ______________.

decreased passage rate out of the rumen

Where in the rumen do we expect to find the largest particles?

top (dorsal)

Other than water, what is the most important component of ruminant saliva?

sodium bicarbonate

The amount of saliva produced per day ____________ when the particle size of a diet increases.

Increases

Which ingredient would you expect to provide the greatest concentration of physically effective fiber?

alfalfa silage

If corn silage is chopped too long, what is a potential negative consequence when fed to dairy cows?

decreased milk production

Which of the following is NOT a component of NDF?

pectin

Where in the ruminant digestive tract is the extent of starch digestion the greatest?

rumen

At which rumen pH would we expect to see the greatest rate of fiber degradation?

7.0

If we want to increase the energy density of a ruminant diet, we should increase the percentage of

Concentrates

True or false: Cobalt helps convert propionate into glucose

True

What is the requirement for cobalt?

0.11

Why is cobalt essential for ruminants?

It is required by rumen microbes to synthesize vitamin B12

True or false: Cobalt deficiency can lead to reduced growth and poor body condition in ruminants

True