Amino acid intro

Question 1

How is Crude protein measured?

Answer 1

Measured using Kjeldahl rxn
*measures nitrogen

Question 2

What does Kjeldahl rxn assume?

Answer 2

Assumes that all the proteins are 16% Nitrogen or Nitrogen x 6.25= protein

Question 3

Issues with Kjeldahl rxn

Answer 3

1. tells you nothing about the amino acid content of a diet
2. not all of the nitrogen measured is from amino acids= non-protein nitrogen
   *allowing for the contamination of feeds
   eg. melamine
   eg. ammonia- preservative

Question 4

Nitrogen and protein eqn

Answer 4

N=crude protein x 6.25

**%= g/100g
**g/kg= g/1000g

To convert 10x %inclusion = g/kg

Question 5

Protein requirements with age

Answer 5

Youngest animals need higher protein per weight of feed because growth demands
**but small stomach (so need more in less food)

Question 6

Animal protein demands

Answer 6

-don’t need nitrogen, need amino acids for protein synthesis
*only some amino acids can be synthesized by the body

Question 7

Essential amino acids

Answer 7

Amino acids that can’t be synthesized by animals of cannot be synthesized in sufficient amounts to maximize production

Question 8

Non essential amino acids

Answer 8

Amino acids that can be synthesized in amounts that meet their requirements to maximize production

Question 9

Conditionally essential amino acids

Answer 9

-essential in some species but not all
-essential in some life stages
-can partially replace the requirement for an essential amino acid

Question 10

What are the essential amino acids?

Answer 10

Question 11

Essential amino acid differences in humans vs.cats vs. trout/salmon

Answer 11

Humans: don’t need histidine

Cats: don’t need glutamine and taurine BUT need high levels of methionine, arginine, leucine

Trout/salmon: require taurine

Question 12

Taurine synthesis

Answer 12

Beta-sulfonic amino acid that is synthesized from Cysteine and indirectly from Methionine
*only found in animal products so need to be added for vegetarian products

Question 13

Taurine and grain free diets for dogs

Answer 13

Dogs: grain free diets have increased plant products (typically peas) which means increased plant protein in the diet. Means that producers were able to decrease the amount of animal proteins (taurine only from animals)… means that they are not getting enough taurine. Likely taurine is also conditionally essential in dogs (especially when being fed a lot of plant protein)

Question 14

Glycine dietary requirements in broiler chickens

Answer 14

Conditionally essential amino acids at certain stages in life
-required in first 2-4 weeks after hatch

Question 15

How are cysteine and tyrosine considered amino acid sparing?

Answer 15

Cysteine and tyrosine are conditionally essential because they meet 50% of methionine and phenylalanine requirements

*cys=Met therefore requirement for Met given as Met+Cys
*Tyr=Phe

Question 16

Why not just feed essential amino acids?

Answer 16

Because need both carbon skeleton and amino groups for synthesis
**but main source of amino groups for non essential amino acids are from other non essential amino acids

Question 17

Daily gain based on total amino acids

Answer 17

Higher total will result in a greater avg daily gain
*decreased total is less daily gain