Af. Branco et al., Estimating true digestibility of nonstructural carbohydrates in the small intestine of steers, J ANIM SCI, 77(7), 1999, pp. 1889-1895
Four Angus steers (318 +/- 16 kg) fitted with ruminal, duodenal, and ileal
cannulas were used in a 4 x 4 Latin square design to determine carbohydrate
disappearance from the small intestine (SI). Steers were fed fescue hay at
1.8% of BW and abomasally infused with starch hydrolysate (SH) at 10, 20,
or 40 g/h or glucose (G) at 30 g/h. Starch hydrolysate was raw cornstarch d
igested by a heat-stable alpha-amylase. Experimental periods were 10 d with
6 d of adaptation, 3 d of digesta and feces collection, and 1 d of rest. G
lucose (% of infused) had greater (P < .001) apparent small intestinal and
postruminal disappearance (% of infused) compared with 20 and 40 g/h SH. St
arch hydrolysate infusion linearly increased (P < .001) apparent SI, large
intestinal (LI), and total intestinal starch disappearance (g/d) and quadra
tically increased (P < .003) apparent SI and total intestinal starch disapp
earance (% of infused). Ileal starch flow from infusion increased quadratic
ally (P < .03) as SH infusion increased. True SI and total intestinal starc
h disappearance increased linearly (P < .001; g/d) with SH infusion. Howeve
r, SH infusion quadratically decreased (P < .02) efficiency of true SI star
ch disappearance (% of infused). True LI starch disappearance (g/d and % of
infused) quadratically increased (P < .03) as SH infusion increased. These
data demonstrate that, even in animals fed all-forage diets, there is a si
gnificant flow of alpha-glucosides, and these need to be considered when ev
aluating intestinal carbohydrate digestion.