Nutritive Value of Fibre

Question 1

What are some examples of fibre?

Answer 1

Sugar beet, grass pellets, alfalfa, hay, grass, haylege, oat feed, wheat feed, nutritionally improved straw.

Question 2

Define FIBRE

Answer 2

Fibre is a dietry material containing substances such as cellulose, lignin and pectin that are resistant to the action of digestive enzymes. It is comprised of beta glucose and is a structural carbohydrate.

Question 3

What are cell walls composed of?

Answer 3

• the middle lamella contains pectins
• the primary cell walls contain cellulose and hemicelluose
• the secondary cell wall contains lignin, which is matured cellulose. Once it has matured, it is harder to break down - older grass (hay) is harder to digest

Question 4

In what ways can fibre be measured?

Answer 4

• crude fibre analysis
• neutral detergent fibre
• acid detergent fibre (should have a low ADF)

Question 5

What other nutrients are found in forages?

Answer 5

• proteins (found in cell walls). As the plant ages, the protein content decreases
• fat (very small amount). Amount decreases with age
• minerals
• vitamins

Question 6

In what ways can the nutritive value of fibre be altered?

Answer 6

As the plant ages, the nutritive value of the plant decreases (more lignin and less protein).

Question 7

Define the TCA CYCLE

Answer 7

The TCA cycle is a series of chemical reactions used to release stored energy.

Question 8

Define ATP

Answer 8

Adenosine triphosphate. It is a nucleotide that can store and transport energy within cells.

Question 9

How is the consumption of fibre linked to the horse’s health?

Answer 9

• fibre consumption is key to a horse’s health
• should consume a minimum of 1%/LW of fibre per day, with 2% being normal
• essential for digestive health - chewing, saliva production etc.
• in the wild they would be eating for up to 14 hours a day

Question 10

What should fibre/roughage be assessed on?

Answer 10

• nutrient content
• digestibility
• anti-nutritional factors
• palatability
• storage quality

Question 11

What are the percentage of fibre turned to VFAs in the hindgut?

Answer 11

70% becomes acetate, 20% becomes propionate, 10% becomes butyrate. These are metabolised in the TCA cycle.

Question 12

How much ATP does each VFA produce?

Answer 12

Acetate - 10 ATP
Propionate - 17 ATP
Butyrate - 25 ATP