Protein quality

Question 1

Energy sources of protein diet

Answer 1

-Relatively insufficient energy source
-high E loss in urine/gases AND high heat increment

Question 2

What is protein energy expensive?

Answer 2

Energy needed for:
-protein metabolism
-nitrogen excretion
-heat increment
-conversion of protein to fat

Question 3

What is using high protein diets bad for finishing animals?

Answer 3

high energy cost to convert protein into fat COMPARED with carbohydrates and fatty acids into fat

Question 4

What are the two things that determine the nutritional quality of a protein?

Answer 4

1. the AA content of the protein relative to the needs of the animal
2. The digestibility of the amino acids in protein

Question 5

Locations of absorption and digestion

Answer 5

1. Absorption in the small intestines (no AA absorption in large intestines)
2. Digestion in stomach and small intestines
3. Any undigested feed proteins in digested by microbes in large intestines and turned into microbial protein

Question 6

How is microbial protein excreted?

Answer 6

In feces

Question 7

Digestible AA

Answer 7

The % of AA that are absorbed from the gut
*different than total AA

Therefore diet formulations based on total levels of AA are inaccurate

Question 8

Define Absorption

Answer 8

The amount of a dietary component passing across the gut
*hard to measure

Question 9

Define digestibility

Answer 9

The amount of a dietary component removed from the digesta
*easier to measure
*assume that AA that are digested are also absorbed but this is not always true

Question 10

Apparent Fecal digestibility

Answer 10

Digestibility when the AAs found in the feces is subtracted from AA in the feed, apparently digested amount can be calculated

Question 11

Apparent fecal digestibility (AFD) equation

Answer 11

Question 12

Microbial metabolism of protein in the gut

Answer 12

Bacteria in the ceca and large intestines can convert 1 amino acid to another through deamination and transamination

*can impact the apparent fecal digestibility

Question 13

True digestibility

Answer 13

Takes into account the losses from feces and bacterial metabolism from total ingested AA

Question 14

Microbial distribution

Answer 14

-highest in the cecum/large intestine; more diverse

Question 15

What methods can be used to bypass the microbial metabolism effects?

Answer 15

Ileal cannulation= Capture the digestive fluids at the distal ileum (less bacteria in small intestine) and determine what is exiting at that point to determine more accurate amount of what was given to animal

*digestibility coefficient based on disappearance of amino acids prior to distal ileum

Question 16

Apparent Ileal digestibility coefficient (AID) equation

Answer 16

Question 17

Endogenous losses of AAs

Answer 17

-AAs are constantly lost from digestive enzymes, enterocytes, bile, mucus, and other
-AAs secreted into the lumen of small intestines; some are not reabsorbed and end up in the digesta captured at the distal ileum

Question 18

True Ileal digestibility coefficient eqn

Answer 18

-used if AID is corrected for the endogenous losses

Question 19

How do you measure endogenous losses?

Answer 19

Measured by capturing the digestive fluids at the distal ileum after a nitrogen free diet has been fed

Question 20

Digestibility eqn/measurement summary

Answer 20

Question 21

AA requirements of monogastrics

Answer 21

-Require AAs not protein
-Lean meat= H2O and protein… want as much lean meat as possible deposited

Question 22

What does all of nothing protein synthesis mean?

Answer 22

Means you need all AA to be available at the same time

Question 23

What factors affect AA requirements?

Answer 23

-species
-age
-production level
-genetics (determines animals lean meat deposition capacity AND AA requirements)
-nutrition (determines genetic capacity)