Exam 1 protein quality/ requirements

Question 1

Biological value is

Answer 1

portion of digestible N that is retained. i.e. (intake - feces and urine)/ intake - feces. inversely related to waste energy

Question 2

Why is total tract digestibility not appropriate for AA ?

Answer 2

BC Microbiota ferments AA to amines and ammonia, and microbial protein, changing the AA profile, yielding a distorted profile that is not representative of the undigested feed protein

Question 3

what are the 2 main types of cannulas?

Answer 3

T cannula is less invasive, still allow for proper gut movement but can only take samples and not collect all digesta.
Re-entrant cannula allows for total collection of the digesta but suffers from blockage as it cuts a fraction of the intestine and destroys neural connections so there is loss of myoelectrical impulses needed for proper motility

Question 4

what are the 7 methods to determine endogenous losses of AA?

Answer 4

Direct (NFD), regression, completely digested protein, enzyme hydrolyzed protein, N isotope dilution, Feeding labeled protein and guanidination

Question 5

Net protein utilization (NPU) is

Answer 5

BV * digestibility, or (N in carcass of animals - N in carcass of NFD animals) / intake

Question 6

Protein efficiency ratio (PER)

Answer 6

Weight gain per unit protein consumed, for rat growth, does not account for maintenance

Question 7

Net protein ratio (NPR)

Answer 7

Corrects PER to maintenance by measuring the weight loss in NFD animals (then weight gain in test group is added to NFD and divided by protein intake). Overestimates poor quality protein

Question 8

Essential AA score

Answer 8

assumes all EAA are equally essential, so it calculates the mean ratio of concentration of each EAA in the test ingredient compared to a standard. Does not account for digestibility

Question 9

AA bioavailability

Answer 9

proportion of an AA from an ingredient tha can be absorbed and utilized for a specific metric, requires linear response, lack of curvature and common intercept

Question 10

AA score is

Answer 10

ratio of first limiting EAA in the ingredient compared to a standard. Does not consider digestibility and informs from only one AA

Question 11

Protein digestibility corrected AA score (PDCAAS) is

Answer 11

AA score multiplied by the protein digestibility of the ingredient, maximum is 100%, only use 1 digestibility value for all AA

Question 12

Digestible indispensable AA Score (DIAAS) is

Answer 12

the true or standardized digestible AA in the protein of the ingredient / standard. is the ability of a protein to supply available AA if that protein food was the sole source of dietary protein

Question 13

how long should a requirement trial be for weight gain for pigs and chickens? and for N balance?

Answer 13

28 and 21 d, 5-7 d of adaptation + 5-7 for collection

Question 14

N balance, or growth requirement graph:

Answer 14

increases with higher intake and plateaus at requirement

Question 15

urinary or plasma urea requirement graph

Answer 15

decreases with higher intake and plateaus at requirement

Question 16

AA oxidation requirement graph

Answer 16

unique, it is low and increases when requirement is met

Question 17

Indicator AA oxidation requirement graph:

Answer 17

decreases with higher concentrations and plateaus at requirement

Question 18

what are the two statistical models that can be used to determine requirements?

Answer 18

quadratic model: describes the requirement for maximal response of all animals in population
Broken-line model: requirement for average animal of population, done by using two straight lines (slope and horizontal), when they intersect that is the requirement

Question 19

what constitutes obligatory losses?

Answer 19

inefficiency in protein turnover, gut endogenous losses (ileal losses * 1.1 = whole tract losses), synthesis of other compounds (non-protein N compounds(histamine, serotonin, glutathione) and irreversibly altered AA structure), integumental losses, urinary losses

Question 20

factorial requirement methods consider the requirements for :

Answer 20

Obligatory losses and tissue growth

Question 21

how may N balance be misestimated?

Answer 21

feed wastage and not collecting all feces, these lead to overestimation of N balance and underestimate the requirement