Downloaded from British Journal of Nutrition (1995), 73, 163-112 763 https://www.cambridge.org/core Abomasal glucose, maize starch and maize dextrin infusions in cattle : small-intestinal disappearance, net portal glucose flux and ileal oligosaccharide flow BY K. K. KREIKEMEIER U.S. Department of Agriculture, Agricultural Research Service, Roman L. Hruska US. Meat . IP address: Animal Research Center, Clay Center, Nebraska 68933, USA AND D. L. HARMON 170.106.35.93 Department of Animal Sciences, University of Kentucky, Lexington, 40546-1027, Kentucky, USA (Received 26 January 1994 - Revised 26 July 1994 - Accepted 24 August 1994) , on 23 Sep 2021 at 17:16:52 Three castrated male Holstein cattle (423 (SD 19) kg live weight) fitted with elevated carotid artery, portal, and mesenteric venous catheters, and abomasal and ileal cannulas were used to study small- intestinal starch digestion. The cattle were infused abomasally with water (275 ml/h), glucose (66 g/h), maize dextrin (66 g/h) or maize starch (66 g/h) in an incomplete Latin square design, with eight infusion periods. Infusion with carbohydrate resulted in higher arterial glucose concentrations and greater net portal glucose flux than when cattle were infused with water. Arterial glucose concentration and net , subject to the Cambridge Core terms of use, available at portal glucose flux were highest when glucose was infused. In the small intestine, 85 YO of abomasally- infused glucose, 78 YOof infused dextin, and 66 % of infused starch disappeared. Of the carbohydrate that disappeared in the small intestine, that which could be accounted for as net portal glucose flux was 73 YOfor glucose, 60 YOfor dextrin, and 57 YOfor starch. Ileal digesta contained unpolymerized glucose, and sbort-chain soluble a-glucoside. Of the infused dextrin flowing past the ileum (14 g/h), 03 g/h was glucose, 6.2 g/h was soluble a-glucoside, and 75g/h was insoluble a-glucoside. Of the infused starch flowing at the ileum (22.2 g/h), 0.9 g/h was glucose, 53 g/h was soluble a-glumside, and 159 g/h was insoluble a-glucoside. The average chain lengths of the soluble a-glucosides in ileal digesta were 2.07 and 236 for dextrin and starch infusions respectively, indicating mostly di- and to a lesser extent trisaccharides. We conclude that (1) when 66 g raw starch is presented to the small intestine per h, about half of the intestinal disappearance appears as glucose in the portal vasculature, and (2) a-1,4 glucosidase (EC 3.2.1.20) activity at the brush border is the rate-limiting step to small-intestinal starch digestion in cattle. Cattle: Starch digestion: Small intestine https://www.cambridge.org/core/terms Starch in the diet of ruminants is not completely fermented in the rumen and flow to the small intestine varies. When flow of maize starch or wheat starch to the small intestine was less than 600 g/d, apparent starch disappearance in the small intestine exceeded 90 Yo of duodenal starch flow in 300 kg cattle (Axe et al. 1987; Zinn, 1990; Kreikemeier et al. 1991). As maize starch flow to the duodenum increased to 900g/d, starch disappearance decreased to between 53 and 67% (Zinn, 1990; Kreikemeier et al. 1991). With sorghum- grain feeding, duodenal starch flows of 1300 g/d have been reported in cattle (Axe et al. 1987; Streeter et al. 1991), and 3500 g/d in lactating cows (Poore et al. 1993). In four recent . studies with sorghum-grain feeding, Streeter et al. (1989, 1990a, b, 1991) reported that 20 https://doi.org/10.1079/BJN19950079 to 40% of duodenal starch flow disappeared before the ileum. In the present experiment the objectives were (1) to evaluate the effect of abomasally infused maize starch, maize dextrin, and glucose on small-intestinal carbohydrate Downloaded from 764 K. K. KREIKEMEIER AND D. L. HARMON disappearance and net portal glucose flux, and (2) to determine the profile of infused carbohydrate escaping small-intestinal digestion. https://www.cambridge.org/core MATERIALS AND METHODS Animals and design Three castrated male Holstein cattle (423 (SD 19) kg live weight) were surgically prepared with permanent portal and mesenteric venous catheters, an elevated carotid artery, an ileal cannula (0.6 to 0.9 m anterior to the ileoxaecal junction), and a catheter (Bard Urological Division, size 36 FR., C. R. Bard, Inc., Murray Hill, NJ 07974, USA) which was fitted in . IP address: the mid-portion of the abomasum and exteriorized through the adjacent body wall as described previously (Kreikemeier et al. 1991). In an incomplete Latin-square design consisting of eight infusion periods, the three cattle 170.106.35.93 were continuously infused with either water (control), maize starch (66 g glucose/h), maize dextrin (66 g glucose/h), or glucose (66 g/h; U.S. Biochemical Corporation, Cleveland, OH44128, USA) into the abomasum. Infusion rates are expressed on a glucose basis , on assuming that the molecular weight of unpolymerized glucose is 180 and that of 23 Sep 2021 at 17:16:52 polymerized glucose is 162. Maize dextrin was prepared commercially under the following conditions. Roasting temperature was 138 to 140°, roasting time was 3-0to 6.5 h, HC1 served as the catalyst, and the pH was 1-9 to 2.0 (U.S. Biochemical Corporation). Animal management , subject to the Cambridge Core terms of use, available at Cattle were fed on chopped lucerne (Medicago sativa) hay (181 g crude protein (CP)/kg) at 15 g/kg live weight (LW) (dry matter basis) in two equal meals (08.00 and 17.00 hours). Fresh water and a trace-mineralized salt block (containing not less than 2 g Mn, 1 g Mg, 0.5 g S, 0.25 g Cu, 0.1 g Co, 0.08 g Zn and 0.07 g I/kg salt) were available continuously. Any feed refusals were collected, weighed, and discarded daily. The cattle were housed in a partly controlled environment. Temperature varied from approximately 18 to 28". The building was ventilated continuously with outside air and there was a combination of natural (06.00 to 21.00 hours) and supplemental (08.00 to 17.00 hours) fluorescent lighting provided. Cattle were tethered in tie stalls (1-5m wide) containing a rubber mat. Stalls were cleaned and cattle were washed daily. Experimental For the 10 h infusion period, cattle were infused with 275 ml solution/h, consisting of Cr-EDTA (50 ml/l; Binnerts et al. 1968), the appropriate carbohydrate and tap water. https://www.cambridge.org/core/terms Maize starch and maize dextrin were kept suspended in solution using an automatic stirrer during the infusion periods. The solutions were infused with a peristaltic pump (Haward Apparatus Model 1200, South Natik, MS 01760, USA) fitted with TygonR pump tubing (internal diameter 2.79 mm). From 3 to 10 hours of abomasal infusion, eight ileal digesta samples were collected at approximately 1 h intervals (10CL200 8). Ileal pH was recorded, and 10 M-NaOH was added (0.5 ml NaOH: 100 g digesta) to inactivate any residual carbohydrase activity in the digesta. This raised the pH above 10. The samples were mixed and frozen (- 20") for later analysis. When digesta was thawed it was divided into three portions. One portion was analysed https://doi.org/10.1079/BJN19950079 for dry matter (DM) (48 h at 65"). Another portion was centrifuged (20000 g) and the supernatant fluid was harvested. That fluid was analysed for Cr (atomic absorption spectroscopy), glucose (Gochman & Schmitz, 1972), and volatile fatty acids (VFA; Downloaded from ABOMASAL CARBOHYDRATE INFUSIONS IN CATTLE 765 Harmon et al. 1988). A third portion was analysed for starch (MacRae & Armstrong, 1968), and oligosaccharide chain length (described later). Digesta flow at the ileum was https://www.cambridge.org/core calculated as follows : Cr concentration in abomasal infusate (ppm) abomasal fluid fluid flow (g/h) = X Cr concentration in infusion rate (g/h)' ileal fluid (ppm) fluid flow (g/h) . IP address: total digesta flow (g/h) = (1 -&gesta DM)' = DM flow total digesta flow -fluid flow. 170.106.35.93 Ileal flows of glucose, ethanol-soluble oligosaccharides, and VFA were calculated as fluid flow multiplied by nutrient concentration. Ileal flows of starch and ethanol-insoluble oligosaccharide were calculated as DM flow multiplied by the nutrient concentration. , on At 25 h after the start of abomasal infusion, cattle were infused into the mesenteric 23 Sep 2021 at 17:16:52 venous catheter with a primed (15 ml), continuous infusion (0.7 ml/min) of para- aminohippuric acid (PAH; 100 g/l). From 3 to 9 hours of infusion, 10 ml arterial and portal venous blood were collected simultaneously into heparinized syringes at 1.5 h intervals (five sets of samples). Blood was transferred into 50 ml centrifuge tubes containing 30 mg NaF and put on ice. At the end of blood sampling the blood was centrifuged (20000 g), and the plasma was harvested and frozen (- 20'). Later the plasma was thawed , subject to the Cambridge Core terms of use, available at and it was analysed for PAH (Harvey & Brothers, 1962) and glucose (Gochman & Schmitz, 1972). Portal plasma flow was calculated as follows: PAH concentration in mesenteric infusate (ppm) mesenteric infusion plasma flow (ml/min) = X PAH concentration in rate (ml/min) ' portal plasma (pprn) Portal glucose flux was calculated by subtracting glucose concentration in arterial plasma from the glucose concentration in portal plasma and then multiplying that value by the portal plasma flow. The experiment took 11 d to complete. The eight infusion periods (10 h/infusion) were conducted on consecutive days with a 3 d break between period four and period five.