factors affecting digestibility
1) rate of passage
4) nutrient excess/deficiency
takes place in true stomach/abomasum/gizzard.
acid hydrolysis and enzyme breakdown
((weight feed X % nutrient in feed) - (weight feces X % nutrient in feces)) / (weight feed X% nutrient in feed)
sources of errors in digestibility trial
1) enzymes secreted into GI tract
2) nutrient of bacteria origin
3) nutrients from epithelium cells
4) feed waste and spillage
5) errors in proximate analysis
difference between intake and excretion.
doesn't take into account losses/gains from fermentation.
simple, fairly precise
difference between intake and excetion but collected at end of small intestine
bypasses microbial fermentation
surgery, more precise
measures enzyme and sloughed cell contribution
identical to ileal digestibility but also takes into account nutrients from digestive enzymes and slough intestinal cells
most precise, requires nutrient free diet.