Digesta Flow Research Articles

A multicompartmental model to describe marker excretion patterns in ruminant faeces.

A multicompartmental model, which assumes first-order kinetics, is proposed to describe digesta flow along the gastrointestinal tract of ruminants. Solution of the model yields a multiplicative equation, containing a single-exponential term and a double-exponential term, for describing faecal outflow rate. The logarithmic transformation of the equation was fitted to eighty-two excretion curves obtained after the administration of marker into the rumen of cattle and sheep, and compared with other published models. It was found to be superior to the other models in that it fitted all the data sets successfully.

Effect of Ileal Infusion of Intralipid on Gastrointestinal Transit, Ileal Flow Rate, and Carbohydrate Absorption in Humans After Ingestion of a Liquid Meal

The effects of ileal infusion of Intralipid on the time required for a radiolabeled liquid starch meal to empty from the stomach and reach a point in the ileum that was 230 cm from the teeth and on the ileal flow rates and the degree of carbohydrate absorption were measured in 5 normal volunteers. The subjects were intubated with a four-lumen polyvinyl tube. Studies were carried out on consecutive days in random order. Infusion of fat into the ileum (a) slowed the transit of a liquid meal through the stomach, (b) delayed the arrival of the liquid meal in the ileum and increased its residence in the upper small intestine, (c) reduced the average flow of digesta through the upper small intestine and altered the pattern of flow, (d) reduced the volume of the meal entering the ileum, and (e) reduced the degree of carbohydrate absorption in the upper small intestine. These results suggest that the presence of fat in the ileum may have a profound influence on the digestion and absorption of a meal.

On the mathematics of digesta flow kinetics

A unifying mathematical analysis of the use of compartmental models with and without time lags is given, with particular reference to the use of such models for digesta movement along the gastro-intestinal tract of the ruminant. First the generalized compartmental model without time lags is developed, and then it is shown how discrete time lags may be incorporated into this formalism. The important relationship between distributed lags, especially the gamma-distributed time lags, and the equivalent compartmental scheme, is emphasized. It is shown how distributed time lags can be included in a general compartmental model. The treatment covers, as special cases, some widely used models, and shows their relationship to each other and to other possible models. Finally a compartmental interpretation is outlined for a recently proposed double-exponential model.

The relation between food intake and abomasal emptying and small intestinal transit time in sheep.

The relation between the level of food intake and gastrointestinal motility and digesta flow in the abomasum and small intestine was studied in sheep fitted with nichrome-wire electrodes in the gut wall, an abomasal and a duodenal catheter and a terminal ileal cannula. Abomasal volume and outflow were calculated from CrEDTA dilution in six sheep and small intestinal transit time by the passage of Phenol Red in ten sheep. The frequency of the migrating myoelectric complex of the small intestine was not altered by the level of food intake but the duration of the periods of irregular spiking activity, the amplitude of abomasal activity and the frequency of duodenal rushes were decreased as the level of food intake was decreased. There was a linear relation between the level of food intake (FI) and abomasal outflow (mean with SEM: 327 (69) ml/h for each kg FI/d; P less than 0.01), and abomasal volume (mean with SEM: 344 (50) ml/kg FI per d; P less than 0.001), without any significant change in the half-time of marker dilution in the abomasum. Small intestinal transit time decreased with an increase in food intake (mean with SEM: -54.9 (5.6) min/kg FI per d; P less than 0.001). It is concluded that abomasal volume and the rate of digesta flow from the abomasum and along the small intestine are linearly related to the level of food intake.

Influences of cold exposure on digestion of organic matter, rates of passage of digesta in the gastrointestinal tract, and feeding and rumination behaviour in sheep given four forage diets in the chopped, or ground and pelleted form.

Sixteen sheep, each fitted with cannulas in the rumen and proximal duodenum, were given four diets in the chopped or ground and pelleted form, at fixed intakes at intervals of 2 h. The sheep were closely shorn and exposed to temperatures of 22-25 degrees or 1-4 degrees for four periods of 45 d. Flow of duodenal digesta by reference to the markers CoEDTA and 103Ru-phenanthroline, chewing behaviour and particle size of rumen and duodenal digesta were measured. Apparent digestibility of organic matter (OM) in the gastrointestinal tract was depressed (P less than 0.05) by grinding and pelleting the diet, and by exposure of sheep to cold ambient temperatures. This was attributable to depression (P less than 0.01) by 0.1 of OM digestion in the reticulo-rumen. No effects on intestinal digestion of OM were observed. Cold ambient temperatures did not affect the content, but increased the rate of digestion for pelleted diets but not for chopped diets, of potentially-degradable cell-wall constituents of ground dietary material incubated in nylon-bags in the rumen. Retention times of markers of the particulate and liquid phases of rumen digesta were not significantly (P less than 0.05) affected by ambient temperature, despite significant (P less than 0.001) increases in the rate of contraction of the reticulum. Retention time of 103Ru-phenanthroline in the intestines was not affected by cold exposure. Cold exposure was associated with depression (P less than 0.05) of volatile fatty acids concentration in the rumen and elevated (P less than 0.05)pH. Molar proportions of acetic and isovaleric acid were reduced (P less than 0.01), accompanied by increased (P less than 0.001) proportions of propionic acid during cold exposure. Cold exposure and pelleting of the diets were both associated with reduction in digesta particle size in the rumen. Duodenal particle size was not affected by cold exposure. Pelleting of the diet markedly reduced (P less than 0.001) duration of chewing and number of chews/d during eating and rumination. Cold exposure of sheep resulted in a faster (P less than 0.01) rate of eating of the diets. When allowed to express their voluntary feed consumption during a 10 d period, intakes of chopped diets were increased by 0.13 (P less than 0.01) by cold exposure, in contrast to lack of significant change in sheep given pellets.(ABSTRACT TRUNCATED AT 400 WORDS)

DOUBLE INTESTINAL CANNULATION FOR STUDY OF DIGESTA FLOW IN RUMINANTS

Two simple cannulae (proximal and distal) are placed respectively in the proximal duodenum just beyond the pylorus, and distal to the pancreatic duct. The established optimal diameters of cannulae and distance between them allow direct measurements of the flow of digesta in the proximal duodenum without the use of traumatic re-entrant cannulation. Key words: Duodenum, cannula, proximal, distal, digesta flow

COMPOSITION CHANGES IN PANCREATIC JUICE IN SHEEP CAUSED BY PREVENTION OF ENTRY OF DIGESTA INTO THE DUODENUM

The temporary prevention of entry of digesta into the duodenum of sheep increased the specific activities of amylase and lipase in pancreatic juice by 35% and 42%, respectively, and decreased that of protease by 52%. In this preparation, intravenous infusion of caerulein increased the specific activity of protease but did not change amylase activity. Key words: Pancreas, digesta flow, amylase, lipase, protease

Magnesium absorption in mature ewes infused intrarumenally with magnesium chloride.

The effects of magnesium supplementation on Mg absorption proximal and distal to the pylorus in ewes maintained on a grass diet were investigated using a combination of balance, digesta flow and electropotential measurements. Three mature ewes each received by intrarumenal infusion a supplement of 0, 1, 2 and 3 g Mg/d in sequence over four 10-d periods. Net Mg absorption distal to the pylorus took place down its electrochemical gradient, although the quantity absorbed remained small during the control and first infusion periods. The bulk of Mg absorption occurred before the pylorus and, during the control and first infusion periods, took place against its electrochemical gradient. The net Mg absorption proximal to the pylorus rose with declining efficiency as Mg intake was increased. It is suggested that saturation of the absorption process at this site was occurring.

Bloat in cattle: 43. Resting level and vertical displacement of the cranial pillar and other structures in the ruminoreticulum of cattle of known bloat susceptibility

Abstract The resting level and vertical displacement during ruminoreticular contractions, of the cardia, reticulo-omasal orifice, ruminoreticular fold, cranial pillar (CP), dorsal and ventral coronary pillars, roof of the main dorsal rumen, floors of the reticulum, cranial sac of the rumen, main ventral rumen, and caudal dorsal blind sac were measured in 4 cows. The rumen was 56 cm deep and the cardia 22 cm ventral to the roof of the rumen. The CP exhibited the greatest vertical displacement during contractions (15 cm) of the structures examined. The CP partitioned digesta into cranial and caudal pools and was able to partially restrain cranial flow of digesta during B sequences (BS). The movement of the CP was examined in greater detail in cows of high and low susceptibility to bloat. Significant differences were observed between cows in resting level and vertical displacement of the CP, and some differences were correlated with differences in bloat susceptibility. Fewer BS contractions were evident in c...

Site and Extent of Protein Digestion in Lactating Cows Fed Alfalfa Silage or Baled Alfalfa Hay

Four lactating Holstein cows fitted with T-type cannulae in the proximal duodenum and terminal ileum were in a three-period switchback experiment to monitor nitrogen digestion and sites and extent of nutrient digestion when alfalfa, preserved as hay or as silage (47.9% dry matter), was served as the forage and major source of nitrogen in the ration. Cows were fed four times daily, and diets contained 65% forage and 35% grain. Lanthanum and samarium served as indigestible markers for calculating digesta flow rates and nutrient digestibilities. Apparent digestibility of organic matter tended to be greater for the silage diet, primarily due to increased disappearance of organic matter in the small and large intestine. Nonammonia nitrogen flows to the duodenum were 79 and 74% of nitrogen intake for hay and silage diets. The apparent degradability of dietary crude protein in the rumen was 80% for both forage sources. This indicates that alfalfa hay and alfalfa low-moisture silage were equal in ability to supply protein to the small intestine, even though nitrogen solubilities for hay and silage were 40 and 63%. Digestibilities of amino acids in the small intestine were not affected by source of forage and were 62.3 and 58.1% for hay and silage diets. Apparent digestibilities of individual amino acids in the small intestine differed.

Pattern of motility and flow of digesta in the forestomach of the Llama (Lama guanacoe f.glama)

A study of the pattern of stomach motility was made in five conscious llamas. Motility was recorded continuously by X-radiography, electromyography and/or balloons with pressure transducers, and correlated with outflow of fore-stomach contents measured by a thermistor. The llama forestomach showed a rhythmic pattern of contractions (motility cycle). A single cycle lasted about 82 s. Evidence is presented that each cycle comprises a single A- and numerous B-contraction sequences. Each motility cycle started with an A-sequence which began with a contraction of the canal between compartment 2 (C2) and compartment 3 (C3). A vigorous contraction of C2 followed, as the pressure in the canal fell below the baseline, then a contraction of the caudal sac of compartment 1 (C1) and another contraction of the canal occurred. The B-sequence of contractions began with a contraction of the cranial sac of C1 at the same time as the second canal contraction, followed by a weak contraction of C2 and finally a contraction of the caudal sac of C1. This B-sequence was repeated a number of times in each motility cycle. Passage of contents from C2 to C3 only occurred as the canal relaxed during the A-contraction. Continuous aborally-directed segmention and peristaltic-like movements were recorded in C3. These contractions occurred at 10 min−1 in the proximal part, and at 5 min−1 in the distal part where they were strongest. In the hind stomach mixing movements could be seen. At the border between C3 and the hind stomach, within a length of 10 cm the pH fell from 6 to less than 2. No reflux of contents was observed from the hind stomach to C3.

Microbial protein synthesis in cattle given roughage-concentrate and all-concentrate diets: the use of 2,6-diaminopimelic acid, 2-aminoethylphosphonic acid and 35S as markers.

Three steers, each fitted with a rumen cannula and a re-entrant cannula in the proximal duodenum, were offered diets consisting of a barley-based concentrate and chopped hay at a daily intake of 61 g/kg live weight0.75 given in three equal meals. The ratio, concentrate: hay was changed from 50:50 to 90:10 and then to 100:0 in successive periods of 12-18 weeks and the flow and composition of digesta at the duodenum was measured over 48-h periods on each dietary treatment. Samples of bacteria and protozoa were separated from rumen contents and the proportions of bacterial and protozoal nitrogen (N) in duodenal digesta were estimated using 2,6-diaminopimelic acid (DAPA) and 2-aminoethylphosphonic acid (AEP) as markers. On separate occasions, radioactive sulphur (35S) was infused into the rumen for 48 h and digesta collected over the final 24 h; the specific radioactivity of S in microbial and digesta fractions was used to estimate the proportions of microbial N. 35S gave reproducible and apparently reliable estimates of microbial protein formation: the proportion of microbial N in digesta was significantly higher (P less than 0.05) for the 50:50 diet than for the other treatments but the energetic efficiency of microbial protein formation did not differ significantly between diets. Estimates of bacterial N based on DAPA concentrations were highly variable and frequently impossibly high. It is suggested that many of the anomalous values were the result of non-representative sampling of the rumen microbial population and that this is particularly likely to occur when conditions within the rumen are unstable. AEP was found to be unsuitable as a marker for rumen protozoa as considerable concentrations of this substance were found also in rumen bacteria.

Nutritional availability of amino acids from protein cross-linked to protect against degradation in the rumen.

Casein was labelled with pairs of radioactive amino acids, lysine, tyrosine and leucine, one with 14C and the other with 3H, by jugular infusion into lactating goats followed by isolation of the double-labelled casein from the milk. Total milk protein was similarly labelled by jugular infusion of [35S]cystine. U-14C-labelled fraction-1 leaf protein was isolated from lucerne (Medicago sativa) grown in an atmosphere of 14CO2. The proteins were treated with different levels (333 and 667 mmol/kg protein) of formaldehyde, glutaraldehyde and glyoxal. Absorption from the small intestine was measured in sheep with fistulas in the abomasum and terminal ileum, using Cr-EDTA as the digesta flow marker, by introducing radioactive casein into the abomasum. Lysine, tyrosine and cystine became increasingly unavailable for absorption from the small intestine of sheep with increasing levels of aldehyde. At the lower level (333 mmol/kg) the proportions of the amino acids that were unavailable were 0.192, 0.051 and 0.123 respectively. At the higher level of formaldehyde (667 mmol/kg) the corresponding values were 0.335, 0.201 and 0.432 respectively. Leucine was not made unavailable with formaldehyde. The proportions of lysine, tyrosine and leucine that were unavailable were higher, on a molar basis, after treatment of the proteins with the dialdehydes glutaraldehyde and glyoxal than after treatment with formaldehyde. However, the extent of protein protection provided by the dialdehydes in the rumen, measured using an in vitro procedure, was lower.

The effect of variation in phosphorus intake on net intestinal phosphorus absorption, salivary phosphorus secretion and pathway of excretion in sheep fed roughage diets.

Mature sheep fitted with rumen and duodenal cannulae and fed either pelleted hay or grass diets were given supplements of Na2HPO4 by continuous infusion into the rumen and the effects on salivary phosphorus secretion, intestinal phosphorus absorption and pathway of excretion were studied. Little phosphorus was excreted in the urine in control periods and little increase was seen in response to phosphorus supplementation, most of the extra phosphorus given being recovered in the faeces. Infusion of phosphorus into the rumen led to an increase in the flow of phosphorus to the intestine, an increase in absorption, a rise in plasma phosphate level and an increase in salivary phosphorus secretion while withdrawal of supplementary phosphorus was seen to have the opposite effects. In separate studies short sections of the upper small intestine temporarily isolated from the normal flow of digesta were perfused with solutions containing NaH2PO4 (5-50 mmol.l-1). Phosphorus absorption increased with increasing concentration though the relationship was curvilinear such that absorptive efficiency fell from around 0.7 at 5 mmol.l-1 to around 0.35 at a concentration of 50 mmol.l-1. The significance of these results in relation to the control of phosphorus balance in ruminants is discussed.

Effect of intake and feeding frequency on feeding behaviour and quantitative aspects of digestion in sheep fed chaffed lucerne hay

SummaryChaffed lucerne hay of 64% apparent organic matter (OM) digestibility was fed to wether sheep under four feeding regimens: two levels of dry matter (D.M.) intake (700 (L) and 1050 (H) g/day) and within each level two feeding frequencies (once a day (daily) and once an hour (hourly)). Three separate groups of sheep were used concurrently: a slaughter group was used to obtain feeding behaviour data and to measure pool sizes and obtain samples from the reticulo-rumen; a digestion group, in which each sheep was prepared with a rumen and a duodenal cannula, was used to measure duodenal digesta flow, rumen microbial growth and reticulo-rumen motility; a balance group was used to measure digestibility and nutrient balances.High D.M. intake increased reticulo-rumen pool sizes and flow rates but it did not affect apparent digestibilities or the proportions of OM, fibre, cellulose, hemicellulose, lipid and nitrogen digested in the stomach and intestines. Increased feeding frequency had a major effect on reticulo-rumen pool sizes but did not affect apparent digestibilities or partition of digestion of non-nitrogenous constituents. Daily feeding resulted in increased total-N flow to the duodenum; however, N retention was significantly greater with frequent feeding. It is suggested that this was due to a more efficient tissue utilization of N.The kinetics of digesta flow within the reticulo-rumen, expressed as fractional flow rates, were studied with data from sheep fed hourly. The fractional inflow, outflow and disappearance rates for OM, fibre, cellulose and hemicellulose did not change with an increase in intake because of an equivalent increase in reticulo-rumen volume. Increasing D.M. intake by 50% resulted in a 24% increase in water intake, a 19% increase in reticulo-rumen water volume, and a 49% increase in water outflow rate. The data suggest that the increased outflow of water was achieved by increasing the net flow of water across the mucosa into the reticulo-rumen, rather than by increasing salivation.There was no difference between treatments in the frequency of reticulo-rumen contractions. It was calculated that for each A sequence contraction, OM flow was 0·26 and 0·37 g and water flow was 4·38 and 0·36 g on L and H intakes respectively. A 50% increase in intake resulted in a 42% increase in OM passage per A sequence contraction. This increased passage with intake was not accompanied by an increase in reticulorumen contraction frequency.

The role of condensed tannins in the nutritional value of Lotus pedunculatus for sheep. 2. Quantitative digestion of carbohydrates and proteins.

Primary growth vegetative Lotus pedunculatus containing 46 and 106 g/kg dry matter (DM) of total condensed tannin and 3 and 14 g/kg DM of free condensed tannin, was cut and fed fresh at hourly intervals (750 g DM/d) to sheep fitted with permanent cannulas into the rumen and duodenum. Low- and high-tannin lotus contained respectively 41.3 and 31.6 g total nitrogen/kg DM and 132 and 152 g lignin/kg DM. The two forms of lotus were similar in carbohydrate composition. Nutrient intake was recorded and faecal output measured by direct collection. Digesta flow to the duodenum was estimated by measuring dilution at the duodenum of inert ruthenium phenanthroline (Ru-P) and chromium-EDTA markers continuously infused into the rumen. Effects attributable to condensed tannins were assessed by comparing the digestion of the two diets, and by comparing the digestion of each with predicted values for non-tannin-containing fresh forages fed at similar intakes. Apparent digestibility of all nutrients measured was less for high- than for low-tannin lotus (P less than 0.01). The levels of cellulose digested ruminally and post- ruminally in both forms of lotus were similar to predicted values. However, less hemicellulose and readily fermentable carbohydrate (RFC; soluble carbohydrate + pectin) was digested in the rumen in sheep given both forms of lotus than would be predicted for non-tannin-containing fresh forage diets, but this was compensated for by greater post-ruminal absorption of both nutrients. Total N gains across the rumen (duodenal N flow--total N intake) were 1.8 and 10.5 g/d for low- and high-tannin lotus v. predicted losses of 3.7 and 2.1 g/d for non-tannin-containing fresh forages given at the same total N intakes. Post-ruminal digestion of non- amonia -N (NAN; proportion NAN flowing at duodenum) was 0.71 and 0.67 for low- and high-tannin lotus respectively v. 0.76 for comparable non-tannin-containing fresh forages. Energy absorbed as amino acids from the small intestine was calculated to be 0.29 of metabolizable energy for both forms of lotus, compared with 0.17 and 0.21 for perennial ryegrass and white clover. It was concluded that the presence of condensed tannins in lotus markedly increased post-ruminal NAN absorption compared with non-tannin-containing fresh forage diets, but depressed ruminal digestion of RFC and hemicellulose.

UTILIZATION OF SUGAR CANE FINAL MOLASSES BY THE PIG: COMPOSITION OF ILEAL DIGESTA

Castrated male pigs of 30-kg live weight were fitted with re-entrant ileal cannulae using a surgical procedure which minimized disruption of digestive tract function. Three diets were investigated: sugar cane final molasses, a mixture of molasses and torula yeast, 3:1 on a dry weight basis, and a mixture of molasses and processed food industry by-products: (garbage), 3:1 on a dry weight basis. The pigs were trained to consume their diet in a single daily meal period of 30 min. The ileal digesta were collected, measured and sampled every 30 min for 24 h following the meal. Two collections were made for each diet, using a group of four pigs for both the first and second diets, and another group of four pigs for the third diet. Food and water intake, and ileal digesta flow varied greatly between pigs but there were linear relationships between the volume of ileal digesta and the dry matter intakes: the regression coefficient being 11,6 and 3 mL/g dry matter consumed for the molasses, molasses plus yeast, or molasses plus garbage, respectively. Regression analysis of digesta flux and digesta composition showed that the ash content of the digesta was directly related to the water flux through the terminal ileum. Carbohydrate constituted almost half of the organic matter in the ileal digesta from the molasses diet, and 41% of this was sucrose, 57% fructose and 2% glucose. This indicated incomplete hydrolysis of the sucrose and incomplete absorption of the fructose, within the small intestine. Key words: Swine, molasses, ileal cannulation, digesta composition, torula yeast, garbage

A comparison of particulate markers for the estimation of digesta flow from the abomasum of sheep offered chopped oaten hay

Five sheep with simple cannulae in the rumen and abomasum were given a diet of chopped oaten hay at 95-98% of ad libitum intake from continuously moving belts. Flows of digesta from the abomasum were estimated by a double marker method by reference to 51Cr-EDTA as the fluid marker, and either 103Ru-P, lignin, or acid insoluble ash (AIA) as the particulate marker. Estimates were also made by reference to lignin as a single marker. Estimates of the weight of digesta leaving the abomasum daily were unaffected by the choice of particulate marker when used with 51Cr-EDTA, but were 25% lower when lignin was used alone. The estimated flows of dry matter and acid detergent fibre (ADF) were dependent upon the choice of markers. Compared with estimates of ADF flow given by 51Cr-EDTA and lignin, estimates given by AIA were lower (-24.6%) and those given by 103Ru-P were higher (+26.2%). Lignin alone gave estimates 1.6% higher. Observations on the distribution of 103Ru-P in digesta dry matter indicated a markedly higher concentration on fine than on large particles. It is concluded that lignin may be preferable to 103Ru-P as a particulate marker when certain coarsely chopped roughages are given to sheep, and when samples of digesta from the abomasum are obtained through a simple cannula.

A Method of Intestinal Cannulation for Collection and Return of Digesta

An intestinal re-entrant cannulation technique was devised which did not necessitate gut transection. The technique provides for the total collection and return of digesta, but restores a comparatively uninterrupted flow of digesta between collection periods. The technique involves the displacement of a short section of intestine to a subcutaneous site between two simple T-shaped cannulae. The procedure has been shown to cause some disturbance to the flow of digesta when not in use, but this was less than when a divided intestine was connected by rigid cannulae.

Effect of feed intake on digesta flow and myoelectric activity in the gastrointestinal tract of the preruminant calf.

The effect of feed intake on abomasal digesta outflow and gastrointestinal motility of preruminant calves given whole milk was studied. Digesta collections were made from calves fitted with re-entrant duodenal cannulas. In other calves myoelectric activity was recorded from electrodes implanted on the abomasum and proximal small intestine, sometimes concurrently with recordings from an electromagnetic flow sensor on the duodenum. After a feed of 2-8 kg milk recurring patterns of intestinal myoelectric activity associated with fasting were temporarily interrupted by a period of continuous irregular spike activity; the duration of the post feeding activity increased with intake of milk. Patterns of abomasal digesta flow were characterized by alternating periods of rapid and slower flow with a frequency that corresponded to cyclic change in myoelectric activity of the small intestine. Hourly rates of abomasal emptying of digesta during a 6-h collection period were significantly greater (P less than 0.05) after giving feeds of 6-8 kg milk compared with measurements of flow rate when 2 kg feeds were given. It is concluded that myoelectric activity of the proximal small intestine exercises control over abomasal emptying of digesta by a mechanism which adjusts the mixing and propulsive functions of gut motility in accordance with the amount of milk consumed.