Chapter 6: Digestibility/Bioavailability (Hill) Flashcards
bioavailability *
the digestion, absorption, transport, utilization and excretion of a nutrient.
2 methods of measuring digestibility *
1) ileal
2) faecal
(via feeding trials)
enzyme activity is used to measure: *
how much is incorporated into a functional unit
urinary excretion is used to measure: *
how much food is stored
rank beans, keratin, meat, soy, and casein in order of digestibility of protein *
meat > casein > soy > beans > keratin
rank lactose, sucrose, uncooked potato starch, rice in order of digestibility of starch *
sucrose >rice > lactose > uncooked potato
least digestible protein sources *
feather meal/collagen, some veg. protein
least digestible carb sources *
root starches, pea, soybean carb, all fiber
benefits of cooking **
- destroys pathogens
- increases digestibility (by denaturing protein, solubilizing starch, allowing enzymes access to molecules, destroying anti-nutritional compounds, destruction of trypsin inhibitors)
effect of cooking on starch digestion *
allows enzymes access to molecules
resistant starch *
undigested starch. acts like fiber
disadvantages of cooking during processing **
- 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
Why cooked pet foods are ok *
- duration and temp of heat processing is carefully regulated
- B vitamins added in excess before cooking
- vit A added after extrusion
Is creatine added into pet food after cooking? *
no. Dogs can make their own
effect of age on digestibility in dogs/cats? *
dogs: no change
cats: some old cats digest fat poorly
rank protein, carb, and fat in order of digestibility *
fat > protein > carb
digestibility of most commercial pet foods = __% *
80-90%
What kind of diets are less digestible? *
generic and high fiber
Maillard Browning Rxn *
lysine cross-links carb with protein and blocks trypsin b/c lysine is site of trypsin attack on polypeptides
apparent digestibility (AD)
compares fecal excretion with intake of a nutrient. AD = (1-F)/I x 100 where F = nutrient excretion in feces and I = nutrient intake
100% AD means:
all nutrient was digested and none appeared in feces
Prececal (ileal) digestibility
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
what does 100% prececal or ileal AD mean?
all the nutrient was absorbed in the sm. intestine
difference between prececal and fecal AD represents:
the influence of the colon
the most accurate method of measuring the digestibility of poorly digested carbs which are well fermented in the large intestine.
prececal or ileal AD (fecal AD falsely suggests that such carbs are well digested because they are fermented in the large intestine)
how does adding carb t p food effect small intestinal digestibility of any protein?
decreases it
undigested protein is metabolized by large intestinal bacteria to:
VFA, ammonia, sulfur compounds
are by-products easily digestible?
yes
is visible fat in the stool abnormal? Cause?
yes. common cause = exocrine pancreatic insufficiency
pet foods high in fat are very digestible and tend to result in well formed feces
:)
why is fecal AD a poor indicator of carb digestibility?
indigestible fiber is fermented in the large intestine, which overestimates carb. digestibility
why is crude fiber analysis poor indicator of fiber and carb. digestibility?
most fiber in pet foods is soluble
Increasing carb –> feces
increased quantity, more moist/soft b/c carb is partially fermented
mineral and vitamin availability is influenced by what factors?
- nutritional status of animal
- source of nutrient
- other nutrients (that may inhibit or promote absorption)
- medications
