CELLULAR BIOLOGY - Ruminant Digestion and Metabolism

Question 1

List the three main carbohydrates found in the ruminant diet

Answer 1

Cellulose
Hemi-cellulose
Polysaccarides

Question 2

List the three kinds of microbes found in the rumen?

Answer 2

Bacteria
Fungi
Protozoa

Question 3

What are the two main classes of carbohydrate digesting bacteria found in the rumen?

Answer 3

Cellulocytic bacteria
Amylolytic bacteria

Question 4

Which carbohydrates are digested by cellulocytic bacteria?

Answer 4

Cellulose
Hemi-cellulose

Question 5

Which carbohydrates are digested by amylocytic bacteria?

Answer 5

Polysaccharides

Question 6

Which type of carbohydrate digesting bacteria is predominately found in a ruminant fed a forage based diet?

Answer 6

Cellulocytic bacteria

Question 7

Which type of carbohydrate digesting bacteria is predominately found in a ruminant fed a grain based diet?

Answer 7

Amylolytic bacteria

Question 8

How does cellulolcytic bacteria digest carbohydrates?

Answer 8

Cellulolcytic bacteria produces cellulase which cleaves the cellulose and hemi-cellulose beta 1,4-glycosidic bonds to produce glucose

Question 9

How does amylolcytic bacteria digest carbohydrates?

Answer 9

Amylolcytic bacteria produces amylase which cleaves the polysaccharide alpha 1,4-glycosidic bonds to produce glucose

Question 10

Can glucose be absorbed by the rumen?

Answer 10

No, glucose cannot be absorbed by the rumen

Question 11

How are volatile fatty acids produced?

Answer 11

Volatile fatty acids are produced from the anaerobic microbial fermentation of glucose in the rumen

Question 12

What are the three main volatile fatty acids produced in the rumen?

Answer 12

Propionate
Acetate
Butyrate

Question 13

How are volatile fatty acids absorbed from the rumen lumen into the bloodstream?

Answer 13

Volatile fatty acids are absorbed by the rumen papillae and into the bloodstream

Question 14

Why is it essential there a continuous absorption of volatile fatty acids from the rumen into the bloodstream?

Answer 14

To prevent an excessive decrease in the rumen pH

Question 15

How does the length of the luminal papillae differ depending on the ruminant diet?

Answer 15

Long papillae: high volatile fatty acid concentration
short papillae: nutritional deprivation, low volatile fatty acid concentration

Question 16

What is the function of propionate?

Answer 16

Propionate enters gluconeogenesis in the liver and contributes to glucose production

Question 17

What are the functions of acetate and butyrate?

Answer 17

Acetate and butyrate are converted to acetyl CoA which can be directed to the citric acid cycle for ATP production or fatty acid synthesis for storage

Question 18

In which two tissue types do acetate and butyrate undergo fatty acid synthesis?

Answer 18

Adipose tissue
Mammary glands

Question 19

Which of the volatile fatty acids can be converted into ketone bodies?

Answer 19

Butyrate can be converted into ketone bodies

Question 20

Which volatile fatty acid is seen most predominately in ruminants fed forage based diets?

Answer 20

Acetate is seen predominately in ruminants fed forage based diets

Question 21

Which volatile fatty acid is seen most predominately in ruminants fed grain based diets?

Answer 21

Propionate is seen predominately in ruminants fed grain based diets

Question 22

How does increased acetate concentrations affect milk composition in ruminants?

Answer 22

Increased acetate concentrations lead to an increased butterfat percentage in the milk

Question 23

How does increased propionate concentrations affect milk composition in ruminants?

Answer 23

Increased propionate concentrations lead to an increased protein percentage in the milk

Question 24

Why is there less blood glucose fluctuation in ruminants compared to non-ruminants?

Answer 24

There are less blood glucose fluctuations as ruminants eat more continuously so microbial fermentation is continually producing volatile fatty acids to be used in continuous gluconeogenesis

Question 25

What are the three main lipids found in the ruminant diet?

Answer 25

Triacyglycerols (TAGs)
Glycolipids
Phospholipids

Question 26

Which enzyme breaks down triacyglyerols (TAGs) into fatty acids and glycerol in the ruminant?

Answer 26

Microbial lipase breaks down triacyglycerols (TAG) into fatty acids and glycerol

Question 27

In the rumen, what happens to the glycerol released from the breakdown of triacylglycerols?

Answer 27

Glycerol undergoes microbial fermentation into propionate

Question 28

In the rumen, what happens to the unsaturated fatty acids released from the breakdown of triacylglycerols?

Answer 28

Unsaturated fatty acids undergo biohydrogenation by the ruminal microbes to form saturated fatty acids

Question 29

Why do fatty acids in the rumen undergo biohydrogenation?

Answer 29

Because too many unsaturated fatty acids can be toxic to the microbes in the rumen

Question 30

What is the main site of saturated fatty acid absorption in the ruminant digestive system?

Answer 30

Small intestine is the main site of saturated fatty acid absorption

Question 31

In which physiological state are ruminants most likely to experience ketosis and why?

Answer 31

Ruminants are most likely to suffer from ketosis during early lactation as the high energy demand causes intense gluconeogenesis which removes oxaloacetate from the citric acid cycle, preventing acetyl CoA from entering the citric acid cycle and instead being converted into ketone bodies in the liver

Question 32

How can ruminants survive on a poor protein diet?

Answer 32

Because the ruminant can use microbial rumen content as a source of protein