Intestinal Starch Research Articles

Dietary Influences on Carbohydrases and Small Intestinal Starch Hydrolysis Capacity in Ruminants , ,

Data describing the influence of diet composition and intake on amylolytic and disaccharidase activities in the ruminant small intestine are reviewed. Changing dietary components from forage to grain increased pancreatic α-amylase activities in most studies; however, when metabolizable energy intake was equalized, concentrations of α-amylase in the pancreas and the total quantities in the small intestinal lumen were greater in forage-fed than in grain-fed animals. Concentration of pancreatic α-amylase increased with dietary energy intake. Changing diet composition or metabolizable energy intake exerted a small effect on intestinal disaccharidase activities, with hydrolytic capacity altered principally through changes in intestinal length. Other studies suggest a small contribution of intestinal disappearance of carbohydrates to net portal appearance of glucose. The fate of large portions of intestinal carbohydrate disappearance have not been adequately defined. For the importance of intestinal carbohydrate supply to be understood, the quantity of carbohydrate undergoing both enzymatic hydrolysis and absorption must be determined.

Site of Digestion of Starch in the Gastrointestinal Tract of Dairy Cows and Its Effect on Milk Yield and Composition

Physical and chemical processing of feed ingredients and feeding management strategies are major instruments of manipulating amount and site of starch digestion in the gastrointestinal tract. Generally, as rumen escape of starch increases, postruminal starch digestion increases, and there does not appear to be a limitation to intestinal starch digestion. However, the efficiency with which postruminal starch is digested decreases, which represents a limitation that warrants investigation. Even though digestible dietary starch is presented to the intestine, there is no net glucose absorption at the portal vein, and plasma glucose levels remain relatively unaffected. This result may be associated with the large metabolic requirement for postruminally absorbed glucose, which is preferentially used for oxidative metabolism at the visceral tissue level. In addition, peripheral glucose concentration is highly regulated. A possible implication is that the exogenous glucose supply may spare endogenously synthesized glucose for gut metabolism, allowing more to be directed to the mammary gland. Amino acids also may be spared (less metabolism of dietary and tissue amino acids in the gut). Current production studies yield no clear evidence as to the benefits of postruminal digestion of starch to enhance milk yield or to change its composition. However, studies suggest that starch digested postruminally is used more efficiently for milk synthesis than that digested in the rumen.

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.

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.

Effects of Ruminal Undigested Fiber on Intestinal Starch Digestion in Sheep Fed Different Ratios and with Starch Infusion into the Abomasum

Effects of Ruminal Undigested Fiber on Intestinal Starch Digestion in Sheep Fed Different Ratios and with Starch Infusion into the Abomasum

Small intestinal starch, dextrin, and glucose digestion in steers (1988)

Three Holstein steers (930 lb) were surgically fitted with abomasal and ileal cannulae, portal and mesenteric venous catheters, and an elevated carotid artery and used to study small intestinal starch digestion. Water, corn starch (66 g/hr), corn dextrin (66 g/hr), or glucose (66 g/hr) were continuously infused into the abomasum. Small intestinal disappearance of corn dextrin (57 g/hr) and glucose (57 g/hr) were higher (P<.05) than that of starch (48 g/hr). The percentage of carbohydrate disappearance accounted for as net portal glucose flux was 52, 54, and 72% for corn starch, corn dextrin, and glucose, respectively. Small intestinal starch utilization in the bovine may be limited by starch granular characteristics, enzyme activity, and glucose transport across the small intestine.; Dairy Day, 1988, Kansas State University, Manhattan, KS, 1988;

Limits to starch digestion in the ruminant small intestine.

Site and extent of starch digestion by ruminant animals varies with species, grain type and processing method. Based on a review of 40 different experiments with cattle, between 18 and 42% of the dietary starch from corn and sorghum grains fed to cattle reaches the small intestine for digestion. With more extensive grain processing, a smaller quantity of starch reaches the small intestine. In the small intestine, from 47 to 88% of the presented starch is digested, while in the large intestine, 33 to 62% of the presented starch is digested. Though limits to digestion in and absorption from the small intestine can be demonstrated by infusing starch and glucose into the duodenum, enzymatic capacity does not appear to limit intestinal starch digestion since no plateau in the amount of starch disappearing from the small intestine is detected with typical diets. Yet, extent of digestion is incomplete. Other factors, such as time and surface exposure may limit small intestinal digestion of starch. Processing methods to reduce particle size or alter the protein matrix, which cements starch granules together, will increase the extent of digestion both in the rumen and in the small intestine. Performance data from growing cattle fed processed corn and sorghum grains indicate that starch was used 42% more efficiently if it was digested in the small intestine rather than in the rumen. Though total tract starch digestibility is of primary concern, results support the concept that energetic efficiency of growing ruminants is greater if starch is digested in the small intestine rather than in the rumen.

Influence of Dietary Protein Degradability and Energy Concentration on Growth of Heifers and Steers and Intraruminal Protein Metabolism

Two studies with 4-mo old Holstein steers and heifers and one abomasal digesta collection study were used to determine the influence of altering the dietary energy content and crude protein escape on growth, intraruminal protein metabolism, and site of digestion of dry matter, starch, cellulose, hemicellulose, and protein. Dietary energy concentration was increased by tallow, and rumen protein escape was increased by dehydrated alfalfa and distillers dried grains with solubles substituted for soybean meal. Tallow appeared to depress intake and gain, but gain was increased by protein escape from the rumen. Total and particulate digesta crude protein reaching the abomasum was increased by protein escape; however, percentage crude protein digested was decreased in these treatments due to increased acid detergent insoluble nitrogen. Decreasing crude protein solubility decreased ruminoreticular digestion of dry matter, cellulose, hemicellulose, and starch; however, lower intestinal starch digestion compensated for decreased ruminoreticular digestion. In a third study, with growing steers and heifers, corn gluten meal provided the escape protein and soybean meal the degradable protein. Total and average daily gain were greater for the corn gluten meal diet, but intake was not influenced by energy concentration or protein escape.

Studies of mechanisms of diarrhea induced by fusarenon-X, a trichothecene mycotoxin from Fusarium species; the effects of fusarenon-X and various cathartics on the digestion and the absorption of the mouse intestine

The red mold toxicosis, the major symptoms of which are diarrhea, vomiting and nausea, has been suggested to be induced by trichothecenes produced by Fusarium fungi. Fusarenon-X (F-X) is one of the trichothecene mycotoxins. In this study, we measured the blood glucose level, intestinal glucose contents and intestinal starch contents after the mouse small intestine was loaded with starch, in order to observe the effect of F-X and various cathartics on the digestive and absorptive abilities of the mouse small intestine. Mannitol, castor oil and magnesium sulfate tended to inhibit the dietary increase of blood glucose, the increase of intestinal glucose contents and the decrease of intestinal starch contents after the administration of starch. These results suggest that these cathartics may slightly inhibit the digestion or the absorption in the intestine, but their inhibitory effects seem to be too weak to induce a significant increase of osmotic pressure in the intestinal lumen. Dioctyl sodium sulfosuccinate (DSS) significantly inhibited the increase of blood glucose level, the increase of intestinal glucose contents and the decrease of intestinal starch contents after the starch administration, suggesting that DSS may induce malabsorption and maldigestion in the intestine which may be one of the factors of induction of DSS-induced diarrhea. In contrast, F-X induced no change on blood glucose level, intestinal glucose and starch contents. Therefore, F-X-induced diarrhea can not be related to the increase of osmotic pressure of the intestinal lumen which is induced by malabsorption and maldigestion. Present results support the mechanism of F-X-induced diarrhea proposed previously by us that F-X causes diarrhea through increasing the permeability of intestinal epithelium cells and resulting in the exudation of plasma contents and an eventual increase in the intestinal fluids.

The rate of starch hydrolysis in vitro does not predict the metabolic responses to legumes in vivo

The aim of this study was to determine whether legumes in a physical form which is rapidly digested in vitro give rise to proportionately greater metabolic responses in vivo than legumes which are slowly digested in vitro. Samples of cooked whole and ground lentils were incubated in vitro with pancreatic amylase for 30 min and the percentage starch hydrolysis determined. Grinding the lentils before cooking resulted in a 5-fold increase in the rate of starch hydrolysis (whole lentils 12.1%, ground lentils 60.9%). For the in vivo studies six healthy, young, lean subjects consumed two test meals containing 50 g starch: whole lentils and lentils that had been ground finely before cooking. Postprandial glucose and insulin responses were measured over 4 h. Peak glucose and insulin responses occurred 60 min postprandially for the whole lentils and 30 min postprandially for ground lentils. Although the increase in plasma glucose after ground lentils (1.6 mM) was significantly higher (p < 0.025) than that after whole lentils (0.9 mM), there was no difference in the magnitude of the insulin responses. These results indicate that, unlike for cereals, the rate of intestinal starch hydrolysis is not the major factor determining the metabolic responses to legumes. By virtue of their low postprandial glucose and insulin responses, irrespective of their physical form and digestibility, legumes would appear to be ideal for inclusion in the diet of diabetics.

Effect of dietary corn starch intake on ruminal, small intestinal and large intestinal starch digestion in cattle.

In Exp. 1, 24 yearling Holstein steers averaging 340 kg were fed either an alfalfa hay diet at a maintenance level of metabolizable energy (ME) intake or corn silage-corn diets at one, two or three times maintenance ME intake. After a 42-day adjustment period, steers were fed individually, and digestibilities of total alpha-glucosides, starch oligosaccharides and glucose were determined at 2-week intervals, with chromic oxide used as an indicator. Steers fed the alfalfa hay diet had higher (P less than .05) total tract digestibilities of total alpha-glucosides and starch than steers fed the corn diets. Fecal starch (percentage of dry matter) in steers fed the corn diets increased (P less than .05) from approximately 11 to 31% as level of ME intake increased from one to three times maintenance. Starch digestibilities for the corn diets fed at one, two and three times maintenance were 81.4, 76.4 and 76.0%, respectively. However, these trends toward reduced starch digestibilities were not significant. There appeared to be no apparent adaption of alpha-glucoside digestibility in the total digestive tract among steers fed different levels of corn over the intervals observed. In Exp. 2, four Holstein steers (350 KH) were each fitted with duodenal and ileal reentrant cannulas and fed either a low or a high level of corn. Alpha-glucoside intakes for animals given the low and high levels of cord averaged 1.7 and 3.2 kg, respectively. Steers fed the high level of corn digested more (p less than .05) alpha-glucoside in the total tract (2.9 vs 1.6 kg), reticulo-rumen (2.3 vs 1.2 kg) and large intestine level of corn. Steers fed the high level of corn also digested more corn in the small intestine (.415 vs .221 kg) than steers fed the lower level; however, differences were not significant. Although there were trends toward lower partial digestion coefficients (expressed as a percentage of alpha-glucoside presented to that segment) in the total tract, reticulo-rumen and small intestine for steers fed the high corn diet, the magnitude of the differences was not significant.

Corn Particle Size and Site and Extent of Digestion by Steers

The site and extent of starch digestion by steers as influenced by corn particle size was studied in a 4 × 4 Latin square design. Steers (272 kg) fitted with permanent rumen cannulae were fed approximately 3.5 kg dry matter in eight portions daily (3-hr intervals). Site of digestion was estimated by withdrawing rumen samples and assuming such samples would be equivalent to abomasal samples if a constant flow of digesta was maintained by frequent feeding. Ruminal digestion of dry matter (DMD), organic matter (OMD) and starch was estimated by the ratio of permanganate lignin in feed to lignin in rumen digesta. Corn was fed whole or following grinding through 3.18, 4.76 or 7.94mm screens and comprised 72% of the diets. Geometric mean diameters (micrometers) of the four grains were as follows: whole (5978 $#x03BC;m), 3.18mm (509 μm), 4.76mm (588 μm) and 7.94mm (832 μm). In view of high and variable lignin digestibilities, ruminal digestibility estimates indicate trends rather than absolute values. Ruminal DMD was lower (P<.05) for whole corn (44.9%) than for that ground through 3.18mm (62.3%), 4.76mm (63.6%) and 7.94mm (60.8%) screens. This permitted intestinal DMD to be greater (P<.05) for whole corn and suggests increased quantitative importance of intestinal digestion for whole corn. Whole corn also had a lower (P<.05) ruminal starch digestibility (70.8%) than ground corn treatments (avg 91.7%). Moreover, total tract starch digestion was lower for whole 88.2%) than for 3.18mm (94.5%), 4.76mm (93.7%) and 7.94mm (93.5%) treatments. Intestinal starch digestion was generally low, particularly on ground corn treatments. Alteration of the whole kernel beyond mastication appears necessary to maximize total starch digestion. Rumen pH and liquid outflow rate were not greatly influenced by corn particle size, but tended to increase with particle size. Fecal pH was not related to starch content of feces and ruminal liquid dilution rate was not related to molar percentage acetate, propionate or butyrate.

The utilization of gelled maize starch in the small intestine of sheep.

1. A solution of gelled maize starch and Cr-EDTA was continuously infused for 4 weeks via the abomasum into sheep of different ages. The proportions of infused α-glucoside passing the terminal ileum as glucan (ethanol-precipitable α-glucoside), dextrins (ethanol-soluble glucose polymers) and glucose, and the glucan and over-all α-glucoside disappearances in the small intestine were determined. Ethanol-soluble α-glucoside compounds in ileal digesta were further separated by paper chromatography.2. Glucan was efficiently degraded, since little reached the terminal ileum. Most of the α-glucoside in ileal digesta consisted of glucose and dextrins (mainly short chain length oligosaccharides), suggesting that α-amylase activity was not limiting over-all starch utilization.3. No adaptation of intestinal starch utilization was evident except that the proportion of infused α-glucoside passing the terminal ileum as glucose decreased with time.4. A negative correlation existed between the pH and the total α-glucoside content of the ileal digesta, possibly relating to changes in the microbial activity.5. The advantages and disadvantages of feeding with starch so as to by-pass rumen fermentation are discussed.