Abomasal Outflow Research Articles

Pharmacokinetics and efficacy of intravenous famotidine in adult cattle.

BackgroundAbomasal ulceration is recognized in neonatal and adult cattle, but research regarding treatment is limited. Histamine‐2 receptor antagonists (H2RA), such as famotidine, are used clinically with little evidence‐based research about efficacy in adult cattle.Hypothesis and ObjectivesIntravenous famotidine administered at 0.4 mg/kg will increase the pH of abomasal outflow digesta compared to saline control in adult cattle. The objectives were to assess the effect of famotidine, administered as a single dose and as multiple doses, on abomasal outflow fluid pH in adult cattle. A third objective was to describe the pharmacokinetic parameters of IV famotidine in cattle.AnimalsFour clinically healthy adult Angus‐cross steers previously fitted with duodenal cannulae placed orad to the biliary and pancreatic ducts.MethodsRandomized, 2‐way cross‐over clinical trial. Steers received IV famotidine (0.4 mg/kg) as a single and 3‐dose regimen (every 8 hours) versus saline control. Blood for analysis of serum famotidine concentration was collected intermittently for 12 hours, and abomasal outflow fluid pH was measured at intervals for a 24‐hour period. After a 34‐hour washout period, the opposite treatments were administered and the sampling repeated.ResultsAbomasal outflow fluid pH was higher in steers treated with famotidine for up to 4 hours after a single dose but the effect decreased with subsequent doses. The median (range) elimination half‐life was 3.33 (3.21‐3.54) hours.Conclusions and Clinical ImportanceFamotidine may be useful for treatment or prevention of abomasal ulceration in adult cattle, but the duration of effect may decrease with time.

Abomasal emptying defect in two British Toggenburg goats

ABOMASAL emptying defect (aed) is a sporadic cause of dysfunction of the alimentary tract of sheep. The condition has also been described as functional pyloric stenosis ([Naerland and Helle 1962][1]), abomasal impaction ([Kline and others 1983][2]) and abomasal outflow defect ([Scott 2004][3]).

Determination of Intestinal Disappearance of Lysine and Methionine Derived from Ruminally Protected Lysine and Methionine in Holstein Heifers

In order to estimate the availability of ruminally-protected Lys (RPLys) and Met (RPMet), quantitative changes of free Lys and Met in the total abomasal outflow and feces were determined in three Holstein heifers with a T-shaped duodenal cannula. RPLys was prepared by coating Lys with fat and RPMet with a pH-sensitive polymer. RPLys and RPMet containing 30 g of each amino acid were supplied together to heifers, and total abomasal outflow was collected hourly from the T-shaped duodenal cannula for a 48 h period. Collected abomasal outflows were fractionated into liquid and solid phases to measure free Lys and Met concentration. At 2 wk after total abomasal outflow sampling, heifers were supplied RPLys and RPMet together again, and total feces were collected every 12 h for a 3 d period to estimate excreted RPLys and RPMet in feces. The amounts of Lys and Met recovered from the liquid fractions of abomasal outflow were estimated to be 23.9±8.3% and 68.6±3.6% (p=0.008) of RPLys and RPMet ingested, respectively. Final intestinal disappearances of Lys and Met were estimated to be 49.5±2.6% and 78.2%±6.5% (p=0.015) of ingested RPLys and RPMet, respectively. (Asian-Aust. J. Anim. Sci. 2003. Vol 16, No. 4 : 549-554)

The effect of the plasma glucose level on the abomasal function in dairy cows.

We have studied the effect of plasma glucose level on the abomasal outflow rate of fluid using a hyperinsulinemic glucose clamp technique in dairy cows. Four nonpregnant, nonlactating cows were subjected to one of the following treatments: hyperinsulinemic normoglycemic clamp; hyperinsulinemic hypoglycemic clamp; hyperinsulinemic hyperglycemic clamp; or, as a control, an intravenous infusion of .9% sodium chloride in a Latin square design. The cows were previously fitted with a permanent fistula in the abomasum and the outflow rate of abomasal fluid was determined using Co-EDTA as a marker assuming that the outflow followed first-order kinetics. The abomasal pH was also registered. Insulin was infused continuously through a jugular catheter at a rate of 4.8 mU. kg(-1)min(-1) for 2.5 h in the three clamp treatments. A glucose solution was infused through the catheter at a variable rate to achieve a circulating concentration, near the preinfusion glucose level (approximately 4.1 mmol/L), 2 mmol/L below the preinfusion level, and 2 mmol/L above the preinfusion level for the three hyperinsulinemic treatments, respectively. There was a significant effect of treatment on the rate of abomasal outflow (P < .001). The rate of abomasal outflow was highest for the control treatment (7.8%/min). The slowest outflow was observed in the hyperglycemic cows (3.40%/min). The hypoglycemic and normoglycemic cows showed intermediate rates (6.0%/min and 5.2%/min, respectively). The rate of outflow for the hyperglycemic cows was significantly lower than for all the other treatments (P < .01). Abomasal pH was affected by treatment (P < .05). The highest pH was observed in the hyperglycemic cows (pH 2.3). The values for the other three treatments ranged from pH 1.9 to 2.0. These results show that hyperglycemia reduced the rate of outflow and increased the pH of abomasal fluid in dairy cows. An elevated plasma glucose level thus can be considered as a potential risk factor in the pathogenesis of left-displaced abomasum.

Immunochemical studies on gastric and intestinal digestion of soybean glycinin and beta-conglycinin in vivo.

Two experiments were conducted to study gastric and small intestinal digestion of soybean glycinin and beta-conglycinin in preruminant calves fed milk replacers containing a mixture of skim milk powder and antigenic heated soybean flour. In experiment 1, duodenal passage of immunoreactive beta-conglycinin lasted for a much longer time after the morning meal than that of glycinin. Western blotting revealed the early abomasal outflow of glycinin subunits that associated nearly intact basic polypeptides to partially degraded acidic polypeptides. Intact beta-conglycinin was evidenced at most sampling times. In experiment 2, intact basic glycinin (M(r) = 21000) associated with partially digested acidic glycinin (7000 < M(r) < 25000) was demonstrated in ileal digesta up to 8-10 h after the meal. beta-Conglycinin immunoreactivity could not be evidenced by Western blotting in ileal digesta.

Radionuclide imaging of abomasal emptying in sheep

A liquid radionuclide tracer was administered to nine sheep in order to visualise the abomasum with a gamma camera computer system. The aim was to develop a method of studying gastric emptying, with minimal surgical intervention. Oral administration of the tracer gave good images of the whole complex stomach, but quantifying abomasal emptying was not possible because of the superimposition of the stomach compartments. When the reticular groove reflex was stimulated with oral copper sulphate the radionuclide bypassed the reticulorumen, allowing quantitative analysis of abomasal activity. However, the repeatability of the reflex activation was low. Radionuclide administered directly into the abomasum produced good images of abomasal outflow and provided digital data which were analysed quantitatively. A wide range of emptying rates was observed, generally with a stepped pattern.

Comparison of 0.9, 3.6, and 7.2% NaCl for correction of experimentally induced hypochloremic, hypokalemic metabolic alkalosis in sheep

Summary Nine adult female sheep were each surgically fitted with an Ivan and Johnston reentrant cannula in the cranial part of the duodenum just distal to the pylorus. By diversion (loss) of abomasal outflow, this model has been shown to consistently induce hypochloremic, hypokalemic metabolic alkalosis, accompanied by hyponatremia and dehydration. Each sheep was subjected to 3 treatment trials, each preceded by a 24-hour prediversion period, and a diversion period during which a syndrome of hypochloremia (68 ± 2 mEq/L), hypokalemia, hyponatremia, and metabolic alkalosis was induced. Development of this syndrome was attributable to losses of large amounts of acid and electrolytes in the abomasal effluent. Mean total electrolyte contents of the effluent were: Cl−, 650 ± 27 mEq; Na+, 388 ± 23 mEq; and K+, 123 ± 12 mEq, with total volume loss ranging from 3.6 to 10.0 L of gastric contents and pH ranging from 3 to 5. Decreases in plasma electrolyte concentrations also can be attributed to decreased intake, because anorexia developed shortly after the onset of diversion. Electrolyte losses in urine during diversion were minimal for Cl− (mean ± sem, 12.0 ± 5.1 mEq), but were greater for Na+ (124.2 ± 14.5 mEq) and K+ (185.1 ± 31.2 mEq). Treatments consisted of 0.9% NaCl (300 mosm/L), 3.6% NaCl (1,200 mosm/L), and 7.2% NaCl (2,400 mosm/L) administered over a 2-hour period, with the administered volume determined by the estimated total extracellular fluid Cl− deficit. Significant difference was not found among treatments, with all solutions resulting in return of clinicopathologic and physical variables to prediversion values within 12 hours of treatment. We concluded that rapid iv replacement of Cl−, with small volumes of hypertonic saline solution, is safe and effective for correction of experimentally induced hypochloremic, hypokalemic, metabolic alkalosis in sheep.

Replacement of chloride deficit by use of 1.8% NaCl to correct experimentally induced hypochloremic metabolic alkalosis in sheep

SUMMARY Five adult 40- to 50-kg female sheep were surgically fitted with a reentrant cannulae placed in the proximal part of the duodenum just distal to the pylorus. By diversion of abomasal outflow, this model has been shown to produce hypochloremic metabolic alkalosis accompanied by dehydration, hypokalemia, and hyponatremia. Each sheep was subjected to 3 separate, 12-hour iv treatment trials, in each case preceded by a control period of 48 hours, and a diversion period of 36 to 96 hours, during which a hypochloremic (Cl− ≤ 60 ± 2 mEq/L) metabolic alkalosis with hypokalemia and hyponatremia was produced. Treatment 1, consisting of 6 L of isotonic Na gluconate, was designed to replace volume without replenishing the Cl− deficit. Although hydration improved, plasma Cl− decreased further, and the sheep became increasingly weak and depressed. Treatment 2, consisting of 2 L of 1.8% NaCl, was designed to replace the Cl− deficit without replacing total volume. Plasma Na+ and Cl− concentrations returned to normal during the 12 hours of treatment; acid-base balance and plasma K+ concentrations returned to normal within 36 hours of treatment. During treatment 3 (control, no treatment), measured metabolic values changed minimally. We concluded that the iv replacement of Cl− without K+ is effective in the correction of experimentally induced hypochloremic metabolic alkalosis in sheep.

Experimental model of hypochloremic metabolic alkalosis caused by diversion of abomasal outflow in sheep

SUMMARY Hypochloremic metabolic alkalosis accompanied by hypokalemia and hyponatremia was induced experimentally in 7 adult sheep by diversion (loss) of gastric contents through an Ivan and Johnston cannula placed in the cranial part of the duodenum just distal to the pylorus. Cannula placement was easily accomplished, and cannulae were tolerated well by the sheep. Volume of effluent produced during the 60- to 120-hour period of diversion ranged from 7.7 to 14.9 L and tended to be greatest during the first 24 hours. All sheep became dehydrated, with mean pcv and plasma total protein concentration increases of 94.2 and 61.7%, respectively. Plasma chloride concentration decreased in linear fashion from a prediversion mean of 113 mEq/L (range, 111 to 117 mEq/L) to an end-point mean of 54 mEq/L (range, 45 to 65 mEq/L). Plasma sodium and potassium concentrations also decreased, though potassium concentration increased terminally. There were rapid increases in arterial blood pH and bicarbonate and base excess concentrations during the first 48 hours after diversion. However, during the final stages of diversion, sheep developed superimposed metabolic acidosis with increased plasma lactate concentration and high anion gap.

Inhibition of Abomasal Outflow and Feed Intake by Intra-duodenal Infusion of Acetic Acid in Sheep

Inhibition of Abomasal Outflow and Feed Intake by Intra-duodenal Infusion of Acetic Acid in Sheep

Influence of duodenal digesta composition on abomasal outflow, motility and small intestinal transit time in sheep.

1. A study was made of the influence of duodenal infusion of some of the components of the digesta on gastrointestinal motility, abomasal outflow and small intestinal transit time in seven sheep fed 1500 g grass pellets/day. Gastrointestinal motility was recorded by electromyography. Abomasal outflow was estimated according to the rate of dilution of CrEDTA injected and sampled via an abomasal catheter. Small intestinal transit time was measured by the passage of Phenol Red from the duodenum to the terminal ileum. 2. Abomasal outflow was inhibited during 3 h infusions (5 ml/min) of 100 mM-acetic, propionic, butyric and lactic acids, of 50 mM-HCl, of 0.56 M-glucose, and of 2 and 4% protein hydrolysate. Abomasal motility was inhibited by these infusions and by infusion of 234 mM-oleic acid (0.75 ml/min), of a fat emulsion (Intralipid 20% 0.3 ml/min) and of 50 mM-L-tryptophan (7.5 ml/min). 3. Abomasal motility and, where tested, abomasal outflow, were not affected by duodenal infusion of 150 mM-NaHCO3 (5-10 ml/min), 0.28 M-NaC1 (5-7.5 ml/min), distilled water (5-7.5 ml/min), 25 mM-L-tyrosine (5 ml/min), and of 50 mM-acetic, propionic, butyric and lactic acids (5 ml/min). 4. At concentrations or rates of infusion above the threshold dose needed to inhibit abomasal motility, small intestinal motility was altered and the frequency and amplitude of the reticulo-ruminal contractions were inhibited. 5. The transit time through the small intestine was increased during infusion of 100 mM-acetic, propionic, butyric and lactic acids and decreased during infusion of 0.56 M-glucose and Intralipid. 6. Inhibition of abomasal motility and outflow in sheep receiving 1500 g/day grass pellets was calculated to require increases in the duodenal concentration of volatile fatty acids of about 150% and K+ of about 38%, and to require an increase in the rate of delivery to the duodenum of H+ of about 90%, nitrogen of about 22% glucose of about 2000% and fat of about 84%. 7. These findings are discussed in relation to the composition of abomasal and duodenal digesta in sheep fed different diets. 8. It seems likely that components of duodenal chyme, such as H+, volatile fatty acids, glucose and fat only affect abomasal outflow in sheep fed high-grain diets (glucose, volatile fatty acids), or diets highly supplemented with fat (fat), for short periods after meal feeding (volatile fatty acids) or under abnormal conditions (H+).(ABSTRACT TRUNCATED AT 400 WORDS)

Hyperphagia induced by pylorectomy in sheep

In the hay-fed sheep, gastric (abomasal) contents are delivered continously into the duodenal bulb at a mean flow rate of 210 ml per hour. The pylorus could behave as the site of origin of a feedback satiety signal by acting as a distal stomach sphincter limiting the abomasal emptying rate. This ability of the pyloric sphincter was confirmed by enhancement of abomasal outflow following either pylorectomy or pyloroplasty. In both cases, the subsequent reduction of the mean residence time of digesta in the abomasum was accompanied by an increase in the voluntary intake. The increase by 48% of food intake persisted several weeks after pylorectomy and was not only compensatory for the lower intake during recovery from surgery. Such an hyperphagia, obtained by removal of the ruminant herbivore pylorus, suggests the suppression at the antroduodenal junction level of a regulating factor affecting voluntary food intake by modulating the mean residence time of digesta in the abomasum.

Gastroduodenal motor activity associated with gastric emptying rate in sheep.

1. Gastric emptying rate was calculated from dye dilution and was measured as the net flow over periods of 5 days through an electromagnetic probe inserted into a T-cannula, 5 cm beyond the pylorus in conscious hay-fed sheep. The net aboral flow was related to the motor activity of the antrum and duodenal bulb which was recorded via chronically fixed strain-gauge transducers. Nichrome wire electrodes were also implanted in order to quantify the electrical activity of the musculature associated with the abomasal outflow in sheep sustained on a liquid diet infused at fixed rates. 2. The abomasal outflow occurred as gushes of 2.1-9.2 ml associated with antroduodenal contractions during 90-95% of the recording time. In the sheep eating 0.7 kg/day hay, the daily outflow of chyme was 5.1 l which increased to 7.5 l of less viscous chyme when the sheep was fed 1 kg/day lucerne hay. During gastric infusion of 3.9 and 7.9 l of the liquid diet, the outflow was 5.7 and 8.3 l/day respectively of low-viscosity chyme propelled as gushes of 5.9-6.9 ml during 95% of the recording time. 3. Increasing the viscosity of the liquid diet with guar-gum caused a reduction in both antroduodenal motility and flow. Dilution of the liquid diet with saline doubled the flow as a result of an increase in the amplitude of the antral contractions. Circadian variations in outflow were also related to concomitant variations in antral motility. 4. It is concluded that the minute-to-minute flow rate of chyme through the pylorus could be satisfactorily measured at the duodenal bulb level and related to the motor activity of the antrum and duodenum. The rate of abomasal outflow depended primarily upon the strength of antral contractions, while the viscosity of the chyme also appeared capable of exerting a major influence on the outflow rate.

The influence of a chronic subclinical infection of Trichostrongylus colubriformis on gastrointestinal motility and digesta flow in sheep.

The influence of a chronic subclinical infection of Trichostrongylus colubriformis, 2500 larvae/day for 12 weeks, on gastrointestinal motility and digesta flow was studied in 12 sheep supplied ad libitum with food and water. Motility was recorded by X-radiography and electromyography from chronically implanted electrodes; abomasal volume and outflow were estimated by dilution of CrEDTA; small intestinal transit time was estimated by passage of Phenol Red. The findings were compared with measurements made prior to infection at restricted food intake and reported separately. The first effects of infection were seen after 3-4 weeks. No animal developed diarrhoea, but food intake was progressively reduced. Small intestinal transit time, abomasal volume and half-time of marker dilution increased while abomasal outflow decreased during infection. These changes occurred both in absolute terms and when compared with values predicted from the observed level of food intake. As the animals became resistant to the parasites abomasal volume and digesta flow returned towards control values (weeks 10-12). The migrating myoelectric complex (MMC) was disrupted in only one sheep, and only transiently. In all sheep the frequency of the MMC was increased during infection and there was a progressive inhibition of abomasal, duodenal and jejunal motility. X-radiography showed there was prolonged pooling of digesta in the proximal small intestine which was cleared only at the phase of regular spiking activity. Two sheep given an anthelmintic drench recovered normal motility and clearance of digesta. It is concluded that subclinical infection of sheep with T. colubriformis alters the normal pattern of gastrointestinal motility in the absence of any diarrhoea, and causes inhibition of abomasal and proximal small intestinal motility and digesta flow. The increased frequency of MMCs helps to maintain digesta flow through the proximal small intestine.

Digestion, absorption and utilization of single-cell protein by the preruminant calf. Abomasal outflow and its composition from calves given milk-substitute diets containing varying amounts of either bacterial or yeast protein.

Two experiments of Latin square design, with four Friesian bull calves fitted with re-entrant duodenal cannulas at 4-10 d of age, were made to study the effect of giving varying levels of single-cell protein on the abomasal outflow and composition of digesta. In Expt 1, diets in which 0, 220, 440, and 660 g/kg milk protein were replaced by the bacterial protein Pruteen were compared from 14 d of age. In Expt 2, which began at about 61 d of age, a comparison was made of diets in which 0, 220, 440 and 660 g/kg milk protein were replaced by the yeast protein Toprina. Collection of abomasal outflow was made for 8 h after feeding for 2 d within each 6 d period of the Latin square design experiment. The amount of diet offered daily was 50 g dry matter/kg body-weight 0.75. Polyethylene glycol (PEG), which was used as an indigestible marker, total nitrogen (TN), protein-N (PN), fat, and potassium, sodium and chloride ion outflows were measured together with pepsin (EC 3.4.23.1) and chymosin (EC 3.4.23.4) activities, pH and titratable acidity. In Expt 1 there was little difference in the outflow of liquid digesta between diets and about 0.9 of the dietary PEG was recovered within the 8 h collection period. With increasing amounts of Pruteen in the diet, outflows of TN, PN, fat and Na+ increased, and the pH of digesta increased. However, the volume of 'apparent secretion' into the abomasum (outflow - intake), pepsin activity, chymosin activity, titratable acidity, (outflow of Cl- -outflow of Na+) as a measure of outflow of HCl, and outflows of K+ and of Cl- were reduced. All outflows decreased with the time interval after feeding, except (Cl- -Na+) outflow. In Expt 2, the same trends as in Expt 1 were apparent, but since one calf had to be slaughtered and the experiment had to be analysed as a randomized block, only PN and K+ outflows and pH were significantly affected by dietary treatment, with K+ outflow increasing, rather than decreasing, with increasing concentration of single-cell protein in the diet.(ABSTRACT TRUNCATED AT 400 WORDS)

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.

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.

Influence of the type of fat in milk replacers on hydrolysis and digestion by the pre‐ruminant calf

AbstractPre‐ruminant Friesian calves were fed milk replacers containing three different fat sources to observe their effect on abomasal outflow, triglyceride hydrolysis and nutritive value. The calves were fitted with re‐entrant cannulae in the duodenum and ileum. The milk replacers were prepared by homogenising 30% butterfat, tallow or soya‐bean oil with skim milk prior to spray‐drying. These milk replacers (500 g), and also skim milk, were fed once daily dissolved in 3500 ml of water. Total collections of abomasal and ileal outflow were made for 24 h periods. There were no appreciable differences in abomasal emptying of fresh matter, dry matter, total fat, or in the pH of the digesta when calves received milk replacers containing butterfat or tallow, but some inhibition of gastric emptying occurred when skim milk was fed. The extent of hydrolysis of the fats which occurred in the abomasum, as evidenced from free fatty acid concentrations in the abomasal fat, decreased in the order: butterfat &gt; soya‐bean &gt; tallow. There was an inverse relationship between the chain length of the fatty acids and their rate of hydrolysis. Extensive biohydrogenation in the large intestine appeared to occur only when the highly unsaturated soya‐bean oil was fed. The mean apparent digestibilities of the total dietary fats were: butterfat, 95.0%; tallow, 85.3% and soya‐bean oil, 93.9%. Between 4–16 g more fat than was ingested flowed from the abomasum during the period 0–24 h after calves received skim milk, which represented 1–4% of the total abomasal outflow. Metabolic faecal fat excretion was 5.93 ± 2.02 g 100 g−1 faecal dry matter.

Measurement of flow and sampling of digesta in the preruminant calf.

1. Methods of measuring and sampling the flow of digesta passing through intestinal cannulas in preruminant calves were studied and compared. 2. The effect of collecting digesta from a duodenal cannula on abomasal emptying in a calf given whole milk was determined. When digesta were collected and returned to the duodenum manually in large amounts (about 200 g) the outflow of abomasal contents was intermittent. When digesta were returned to the animal either manually or automatically in amounts of less than about 50 g abomasal emptying was smooth. 3. An automatic apparatus for measuring and sampling the flow of digesta continuously was developed. The device allowed effluent to be returned smoothly to an ingoing cannula at the same rate that digesta left the outgoing cannula. After a feed of whole milk abomasal contents were observed to enter the duodenum in an orderly series of gushes. Each gush consisted of about 5--30 g of digesta. 4. The apparatus was rearranged to measure the effects of composition of duodenal digesta on abomasal emptying. Replacement of duodenal digesta with a suspension containing heated soyabean flour slowed the abomasal outflow of a feed containing casein. 5. Automatic apparatus was used to collect digesta arriving at the distal ileum. Withholding effluent from the large intestine did not affect the movement of digesta from the ileum.

Concurrent studies of the flow of digesta in the duodenum and of exocrine pancreatic secretion of calves. 3. Further studies on the addition of fat to skim milk and the use of non-milk proteins in milk-substitute diets.

1. The flow of digesta through the duodenum and the concurrent secretion of the pancreas were studied in four Friesian calves given four milk-substitute diets. The diets were: reconstituted, "mildly" pre-heated, spray-dried skim-milk powder with (SKF) or without (SK) margarine fat or with 5o percent of the skim-milk powder in diet SKF replaced by soya-bean flour (ASKF) or fish-protein concentrate (BSKF), together with dried whey. The diets were given ad lib. twice daily from 13 to 37 d of age, each diet being given for 6 consecutive days. Collections of duodenal digesta and pancreatic secretions, from cannulas, were made for 12 h after feeding the 6th and 12th meals ("experimental" meals) for each diet. 2. The diets fed as "experimental" meals contained polyethylene glycol (PEG) as a fluid (whey) marker and goat's milk containing (3H)lysine as a marker for total protein; beta-carotene was added as a lipid marker to the three diets containing margarine fat. 3. Over the 12 h postprandial period, the patterns of duodenal digesta flow and secretion of pancreatic fluid did not differ markedly between the four diets. The abomasal outflow of both nitrogen and lipid in a 12 h postprandial period was related to their intakes from the "penultimate" (5th and 11th) meals for diets SKF and SK BUT TO THEIR INTAKES AT THE "EXPERIMENTAL MEALS" FOR DIETS ASKF and BSKF. Secretion of pancreatic enzyme activity was highest during the 1st hour after feeding but the main outflow from the abomasum of total N and lipid occurred 5-10 h after feeding. 4. The time required for all the whey marker (PEG) to pass through the duodenum was similar for diets SKF and SK, but only 53 and 42 percent respectively of the ingested protein marker passed through the duodenum in the 12 h after feeding. More acid appeared to be secreted by the abomasum when diet SK was given; also less undigested protein passed out of the abomasum after giving this diet. It is concluded that the physical absence of fat globules in the abomasal clot increases the degree of proteolysis. 5. The secretions of pancreatic fluid and pancreatic enzyme activity were all markedly lower for diet SK than for diet SKF. 6. With diets containing non-milk proteins (ASKF and BSKF), abomasal proteolysis was less efficient and the ingested protein passed out of the abomasum more rapidly than for diet SKF. There was no difference in the rate of abomasal outflow of the whey fluids between diets SKF, ASKF and BSKF. 7. In comparison with diet SKF, diets ASKF and BSKF tended to induce less pancreatic enzyme secretion over a 12 h postprandial period, with the exception of lipase. 8. There appeared to be no direct relationship between the quantities of any of the pancreatic enzymes secreted during a postprandial period and either the concurrent flow of duodenal digesta or the total quantities of dietary constituents passing through the duodenum.