Chapter 6: Digestibility/Bioavailability (Hill)

Question 1

bioavailability *

Answer 1

the digestion, absorption, transport, utilization and excretion of a nutrient.

Question 2

2 methods of measuring digestibility *

Answer 2

1) ileal
2) faecal

(via feeding trials)

Question 3

enzyme activity is used to measure: *

Answer 3

how much is incorporated into a functional unit

Question 4

urinary excretion is used to measure: *

Answer 4

how much food is stored

Question 5

rank beans, keratin, meat, soy, and casein in order of digestibility of protein *

Answer 5

meat > casein > soy > beans > keratin

Question 6

rank lactose, sucrose, uncooked potato starch, rice in order of digestibility of starch *

Answer 6

sucrose >rice > lactose > uncooked potato

Question 7

least digestible protein sources *

Answer 7

feather meal/collagen, some veg. protein

Question 8

least digestible carb sources *

Answer 8

root starches, pea, soybean carb, all fiber

Question 9

benefits of cooking **

Answer 9

• destroys pathogens
• increases digestibility (by denaturing protein, solubilizing starch, allowing enzymes access to molecules, destroying anti-nutritional compounds, destruction of trypsin inhibitors)

Question 10

effect of cooking on starch digestion *

Answer 10

allows enzymes access to molecules

Question 11

resistant starch *

Answer 11

undigested starch. acts like fiber

Question 12

disadvantages of cooking during processing **

Answer 12

• destroys/reduces availability of nutrients (free aa such as taurine, B vitamins, creatine)
• excess decreases digestibility (cross links protein and carb which inhibits trypsin) -trypsin acts on lyseine

Question 13

Why cooked pet foods are ok *

Answer 13

• duration and temp of heat processing is carefully regulated
• B vitamins added in excess before cooking
• vit A added after extrusion

Question 14

Is creatine added into pet food after cooking? *

Answer 14

no. Dogs can make their own

Question 15

effect of age on digestibility in dogs/cats? *

Answer 15

dogs: no change
cats: some old cats digest fat poorly

Question 16

rank protein, carb, and fat in order of digestibility *

Answer 16

fat > protein > carb

Question 17

digestibility of most commercial pet foods = __% *

Answer 17

80-90%

Question 18

What kind of diets are less digestible? *

Answer 18

generic and high fiber

Question 19

Maillard Browning Rxn *

Answer 19

lysine cross-links carb with protein and blocks trypsin b/c lysine is site of trypsin attack on polypeptides

Question 20

apparent digestibility (AD)

Answer 20

compares fecal excretion with intake of a nutrient. AD = (1-F)/I x 100 where F = nutrient excretion in feces and I = nutrient intake

Question 21

100% AD means:

Answer 21

all nutrient was digested and none appeared in feces

Question 22

Prececal (ileal) digestibility

Answer 22

compares ileal chyme with nutrient intake in dogs implanted with ileal cannulae. Prececal AD = (I-IL)/I x 100 where IL is nutrient excretion in ileal chyme and I is nutrient intake

Question 23

what does 100% prececal or ileal AD mean?

Answer 23

all the nutrient was absorbed in the sm. intestine

Question 24

difference between prececal and fecal AD represents:

Answer 24

the influence of the colon

Question 25

the most accurate method of measuring the digestibility of poorly digested carbs which are well fermented in the large intestine.

Answer 25

prececal or ileal AD (fecal AD falsely suggests that such carbs are well digested because they are fermented in the large intestine)

Question 26

how does adding carb t p food effect small intestinal digestibility of any protein?

Answer 26

decreases it

Question 27

undigested protein is metabolized by large intestinal bacteria to:

Answer 27

VFA, ammonia, sulfur compounds

Question 28

are by-products easily digestible?

Answer 28

yes

Question 29

is visible fat in the stool abnormal? Cause?

Answer 29

yes. common cause = exocrine pancreatic insufficiency

Question 30

pet foods high in fat are very digestible and tend to result in well formed feces

Answer 30

:)

Question 31

why is fecal AD a poor indicator of carb digestibility?

Answer 31

indigestible fiber is fermented in the large intestine, which overestimates carb. digestibility

Question 32

why is crude fiber analysis poor indicator of fiber and carb. digestibility?

Answer 32

most fiber in pet foods is soluble

Question 33

Increasing carb –> feces

Answer 33

increased quantity, more moist/soft b/c carb is partially fermented

Question 34

mineral and vitamin availability is influenced by what factors?

Answer 34

• nutritional status of animal
• source of nutrient
• other nutrients (that may inhibit or promote absorption)
• medications