Small intestinal starch digestion in steers: effect of various levels of abomasal glucose, corn starch and corn dextrin infusion on small intestinal disappearance and net glucose absorption.

Abstract

Eight Holstein steers (four at 300 kg, four at 406 kg) fitted with an elevated carotid artery, hepatic portal and mesenteric venous catheters, and abomasal and ileal cannulas were used in several 4 x 4 Latin square experiments to evaluate small intestinal starch digestion. They were fed alfalfa hay at 1.5% of BW and abomasally infused with water or glucose, corn starch or corn dextrin (one carbohydrate per Latin square) at 20, 40 or 60 g/h, with subsequent determination of small intestinal disappearance and net portal glucose absorption. Increasing the amount of all three carbohydrates infused abomasally increased the amount of carbohydrate disappearing in the small intestine. Increased infusion of glucose caused a continual increase (linear, P less than .01) in net glucose absorption, whereas net glucose absorption for starch and dextrin was maximal at the 20 g/h infusion (quadratic, P less than .05). With the 60 g/h infusion, 94% of the glucose but only 38% of starch and 29% of small intestinal dextrin disappearance could be accounted for as net glucose absorption, leaving a large portion of starch and dextrin disappearance unaccounted for. Of the infused starch and dextrin passing the ileum, 5.8 and 7.3%, respectively, was unpolymerized glucose, indicating that, at least in the distal small intestine, complete starch hydrolysis exceeded the capacity for glucose disappearance. It is concluded that only about 35% of the raw corn starch disappearing in the steer's small intestine resulted in net portal glucose absorption.

A titration approach to identify the capacity for starch digestion in milk-fed calves

“…Abomasal infusion of corn starch in steers resulted in an ileal disappearance of starch of 66% and the remaining sugars in the ileum contained only 4% free glucose (Kreikemeier and Harmon, 1995). Abomasal infusion of glucose in steers resulted in a higher portal glucose uptake compared with starch or dextrin infusion (Kreikemeier et al, 1991;Kreikemeier and Harmon, 1995). We suggest that maltase activity probably limits starch digestion in milkfed calves.…”

“…An inverse linear relation was found between abomasal starch or dextrin infusion and ileal digesta pH in steers (Kreikemeier et al, 1991) and between ileal glucoside content and ileal pH in sheep (Mayes and Ørskov, 1974). This linear decline indicates that the enzymatic capacity for starch digestion is already low at low inclusion levels of starch and suggests that fermentation may contribute substantially to SP disappearance.…”

“…However, a high oral glucose load could lead to osmotic diarrhoea, not necessarily coinciding with a decrease in faecal pH. Indeed, infusion of glucose in the abomasum of steers at 80 g/h (Kreikemeier et al, 1991) and feeding a glucose solution of 4.8 g/kg BW to calves by nipple bottle (Sen et al, 2006) resulted frequently in diarrhoea. Comparing glucose to maltose feeding in a titration approach, as in the current study, would therefore be difficult because osmotic diarrhoea is likely to occur.…”

“…faecal starch concentration, blood reducing sugar response) in ruminants (Huber et al, 1961;Ørskov et al, 1970). Furthermore, a linear decrease was found in ileal pH when infusing starch or dextrin in the abomasum of steers (Kreikemeier et al, 1991;Branco et al, 1999). This decreased pH may indicate that starch is fermented rather than enzymatically hydrolysed.…”

The effect of replacing lactose by starch on protein and fat digestion in milk-fed veal calves

“…Diets, GIT digesta and faeces were analysed in duplicate for content of DM (ISO 1999a and1999b), CP (Kjeldahl method (ISO 2005)) for SI1 and SI2 samples and Dumas combustion method for ileal samples due to a small amount of digesta. (AOAC 990.03, using a Thermo Quest NA 2100 Nitrogen and Protein analyzer of Interscience, Troy, NY, USA) and crude fat with acid hydrolysis for faeces and without hydrolysis for SI1 and SI2 (ISO 1999a and1999b). Cobalt (faeces and ileal digesta) and chromium (GIT samples) were measured by atomic absorption spectrophotometry using a SpectrAA300 (Varian, B.V., Middelburg, the Netherlands).…”