Lecture Three

Question 1

What is the importance of amino acids?

Answer 1

Amino acids are essential for protein synthesis, amino acid metabolism and nitrogen losses from the body

Question 2

What is an essential amino acid?

Answer 2

One that is not made within the diet and must be consumed

Question 3

What is a non-essential amino acid?

Answer 3

One that is synthesised by transamination and is not required in the diet

Question 4

Rank the following in terms of greatest need to the lowest need for protein in the diet: carnivorous fish, members of the feline family, camelids, Llamas and Alpacas:

Answer 4

Carnivorous fish = very high
Feline family = high
Camelids, Llamas and alpacas = low

Question 5

What are the potential fates of dietary protein within monogastrics?

Answer 5

• Used as energy
• Used for protein synthesis- retained in tissues (muscle, organs) and eggs + milk
• Excreted as urinary nitrogen
• Excreted as faecal nitrogen

Question 6

What is the dietary fate of rumen microbes?

Answer 6

• Rumen microbes ferment dietary nitrogen and there is a high efficiency of recycling through saliva and conversion to absorbable amino acids

Question 7

What are the two key sources of amino acids (metabolisable) in the small intestine of the ruminant?

Answer 7

• Microbial protein

- Undegraded dietary fibre (UDF)

Question 8

What are the three main factors that will influence the level of rumen degradability?

Answer 8

• Variation between feedstuffs
• With level of intake and rumen transit time (More feedstuffs in rumen = more escape from the rumen)
• Processing

Question 9

What rate is microbial protein capacity capped at?

Answer 9

About 14% of crude protein

Question 10

How can protein be supplied to an animals diet to meet requirements of ruminants in different physiological states?

Answer 10

• select food with a high undergradable protein content
• process the food to increase the undergradable protein content (grinding, chemical treatment, heating)
• increase the level of feeding (reduces the ruminal resistance time and increases the ruminal outflow (escape))

Question 11

What are the three basic factors that determine the protein value of a ration?

Answer 11

1. Amount of protein (QUANTITY)
2. Mix of essential amino acids relative to target protein (QUALITY)
3. Digestibility of the protein (QUALITY)

Question 12

What are the weaknesses of crude protein as a measure of protein accuracy?

Answer 12

• Crude protein will not accurately predict true protein and does not give an indication of protein quality

Question 13

What is meant by the term rate limiting amino acid and what is the most common one?

Answer 13

• essential amino acid that determines the efficiency of other amino acids
• refers to the amino acid that is in greatest deficit compared to target protein
• lysine - rate limiting amino acids in most systems

Question 14

What is the “ideal protein” method of expressing amino acids?

Answer 14

• expressing everything relative to lysine