New approach to the fed pattern: feeding evokes the specific spike burst setting in the small bowel of non-fasted sheep

As feeding is not a factor disrupting the migrating motor (myoelectric) complex (MMC) in sheep, it is presumed that the fed pattern is absent in this animal species. In turn, feeding may stimulate ovine gastrointestinal motility. To verify this discrepancy the myoelectric activities of the antrum and duodeno-jejunum were recorded in seven adult sheep. Additionally, the relationship between electrical and mechanical activity was tested in four of these animals by means of strain gauge force transducers mounted near the duodenal electrodes. Chronic experiments were conducted in fasted and non-fasted sheep before, during, and after standard feeding. Fodder was offered during the duodenal phases 1, 2a, or 2b of the MMC. Two types of responses to feeding (an unspecific and a specific fed pattern) were denoted. A simple increase in spike burst intensity, i.e. without their special deployment and assessed as the myoelectric activity index (unspecific fed pattern), was observed in the abomasal antrum and small bowel during and after feeding in the course of phase 2b of the MMC in non-fasted and fasted sheep. In the abomasal antrum its duration was longer than in the small intestine. In non-fasted animals the unspecific fed pattern was more pronounced in the abomasal antrum than in the small bowel, while its duration was longer in fasted animals. The specific fed pattern was evoked in the duodeno-jejunum during feeding initiated in the course of phase 2b of the MMC exclusively in non-fasted animals. During this pattern, the spike burst series were significantly reduced compared with those which appeared during phase 2b of the MMC and dispersed single spike bursts predominated. The average duration of the specific fed pattern was 3-4 min and it arrived 2-7 min after feeding onset. In the remaining periods during feeding, the spike burst pattern resembled that often observed during phase 2b of the MMC. Thus the confined fed pattern is present in sheep and its character depends upon the gastrointestinal region and feeding habits.     

Influence of various feeding conditions, the migrating myoelectric complex and cholinergic drugs on antral slow waves in sheep.

The presented study was designed to elucidate whether the cholinergic mechanisms control ovine antral slow waves in various physiological conditions, including feeding and various phases of migrating myoelectric complex (MMC). The investigations were carried out on six adult sheep of Polish Merino breed with seven bipolar electrodes surgically implanted onto the antral and small intestinal wall. In the course of chronic experiments, the myoelectric activity was recorded from these regions using the multichannel electroencephalograph. Experiments were performed on 48 h fasted and non-fasted animals. During some of these experiments, sheep were fed with standard fodder. During control experiments 0.15 M NaCl was slowly administered i.v. through the indwelling catheter and during other experiment, hexamethonium bromide (2.0 and 5.0 mg/kg). atropine sulfate (0.02; 0.1; 0.5 and 1.5 mg/kg) and pirenzepine dihydrochloride (0.02; 0.5 and 2.0 mg/kg) were administered i.v. during phase 1-2a or 2b MMC. The drugs were also given in combinations. The recordings were analysed and the antral slow wave amplitudes and frequencies were calculated. Unlike the slow wave amplitude, either feeding or the anticholinergic drugs significantly increased slow wave frequency, especially when the given procedure was started during phase 2b MMC. The most pronounced effects were observed after hexamethonium given alone or in combinations. Thus, the cholinergic system modulates antral slow wave frequency in sheep.     

Regional differences in the effects of various doses of cerulein upon the small-intestinal migrating motor complex in fasted and non-fasted sheep

There are no precise data concerning the effect of cerulein on the small-intestinal migrating motor complex (MMC) in sheep. Thus, the effort was directed towards the elucidation of the role of cerulein, a cholecystokinin (CCK) amphibian analogue, in the regulation of MMC cycle in conscious fasted and non-fasted sheep in various regions of the small intestine. In six sheep, equipped with bipolar electrodes in the entire small intestine and with one duodenal strain gauge force transducer in four of these animals, the continuous myoelectric and motor activity recordings were performed. During control period, two normal consecutive MMC cycles were recorded in fasted and non-fasted animals and then cerulein was slowly injected at the dose 1 (during 30 s), 10 (during 30 s or 60 s) or 100 ng/kg (during 30 s, 60 s or 120 s) or infused at the dose 0.5 or 1.5 ng/kg/min during 60 min. After cerulein administration at least two consecutive MMC cycles were also recorded. It was found that cerulein in moderate and higher doses injected in both fasted and non-fasted animals, especially during phase 2a or 2b MMC, inhibited phase 3 in the duodenum in at least one-third of the experiments and significantly increased the MMC cycle duration. The application of 100 ng/kg of cerulein during 120 s in the course of phase 2b MMC prolonged cycle duration from 70 +/- 21 to 113 +/- 19 min (p < 0.05) or from 51 +/- 18 to 113 +/- 19 min (p < 0.01) in fasted and non-fasted sheep respectively. The first phase 3 MMC arriving after cerulein administration at the highest dose was usually abnormal in approximately 60% of the experiments. The second phase 3 observed following the hormone injection was abnormal much less frequently and to the lesser extent. Furthermore, both cerulein doses significantly shortened the duration of phase 3 MMC either in fasted (from approximately 5.5-6.5 cpm to 4-5 cpm) or in non-fasted sheep (from approximately 4.5-5.5 to 3-4.5 cpm). The effects of cerulein exhibited the dose-response character. They were more pronounced when cerulein was injected during phase 2b or 2a MMC when compared with phase 1 MMC. The effects of cerulein on the ileal MMC were less evident, although the inhibition of the ileal phase 3 in response to both higher injected doses was observed occasionally. Infusions of cerulein in non-fasted sheep exerted similar effects as cerulein injections. It was stated that cerulein exerts marked regulatory effect upon the small-intestinal MMC in sheep. Although it remains uncertain whether the efficient doses of cerulein used in the present study correspond to physiological or pharmacological doses of CCK it seems likely that most of these doses were physiological. Thus, it is concluded that cerulein participates in the control of MMC cycles in the digestive and interdigestive states in sheep. It is possible that CCK is a physiological regulator of the ovine small-intestinal MMC.     

The effect of cholecystokinin peptides on ovine duodeno-jejunal slow waves with and without pretreatment with proglumide

Cholecystokinin exerts a composite influence on gastrointestinal motility but little is known about its effect on small-intestinal slow waves. Thus, six rams were implanted with four bipolar serosal electrodes onto the duodeno-jejunal wall. In the course of chronic experiments the myoelectric activity was continuously recorded in the non-fasted animals. After recording of the full normal migrating myoelectric complex (MMC), 0.15 M NaCl or CCK peptides were injected intravenously during various phases of the next MMC cycle. Five ml of saline was injected over 30 s during phases 1, 2a, or 2b of the MMC. Cerulein was administered at doses of 1 (over 30 s), 10 (over 30 or 60 s), or 100 ng/kg (over 30, 60, 120 or 300 s) and cholecystokinin octapeptide (CCK-OP) at doses 20 times higher. CCK peptides were applied during early or late phase 1 of the MMC and during phases 2a and 2b of the MMC. In the course of additional experiments, saline and hormone administration was directly preceded by infusion of proglumide, an unspecific CCK receptor antagonist, at a dose of 10 mg/kg. The myoelectric recordings were continued until the arrival of a subsequent regular phase 3 of the MMC. In the duodenal bulb, slow waves were occasionally observed. In the duodenum the slow-wave frequency oscillated between 20 and 24 cpm and in the jejunum between 19 and 22 cpm before or after CCK peptides and proglumide. In the duodenum the slow-wave amplitude increased significantly after all doses of cerulein injected during phase 2b of the MMC. After administration of CCK-OP changes in duodenal slow-wave amplitude were not significant but exhibited a tendency similar to those after cerulein. In the jejunum, injection of cerulein and CCK-OP during phase 2 of the MMC increased the slow-wave amplitude significantly and the duration of these changes was longer than in the duodenum. After infusion of proglumide, administration of cerulein at the low dose over 30 s and at the high dose over 300 s in the course of late phase 1 and phases 2a and 2b of the MMC, significantly increased the duodenal slow-wave amplitude. Cerulein injection during phase 2b of the MMC at the high dose over 30 and 60 s, preceded by proglumide infusion, significantly inhibited the duodenal slow-wave amplitude. In the jejunum these changes were even more pronounced and their duration was much longer. It is concluded that CCK peptides affect slow-wave amplitude in the duodeno-jejunum in non-fasted sheep. This effect is stronger in the jejunum and is altered but not abolished by pretreatment with proglumide. Cerulein evokes more pronounced alterations in the slow-wave amplitude than CCK-OP in conscious sheep.     

Gallbladder motility in sheep: effects of cholecystokinin and related peptides

Gallbladder motility was recorded as tonic and small amplitude (rhythmic) contractions in conscious sheep fitted with miniaturized strain-gauge force transducers located in the corpus and fundus. Nichrome wire electrodes were chronically implanted in the gastroduodenal area. Both tonic and superimposed rhythmic gallbladder contractions were increased during feeding. They decreased during the periodic phases of antroduodenal quiescence. The excitatory effects on gallbladder and antroduodenal motility were mimicked by pilocarpine and blocked by atropine. Cholecystokinin (CCK-OP) and caerulein elicited motor responses of the gallbladder in a dose-related manner without antroduodenal stimulation. In contrast, pentagastrin induced gallbladder motor responses with concomitant stimulation of the antroduodenal area. The results suggest that feeding may act to trigger gallbladder motor activity through a mechanism related to the increased antroduodenal activity. Direct effects of CCK-OP and caerulein confirm that gallbladder motor function is also mediated through specific receptor sites.     

Effects of an abrupt increase of starch-rich concentrates in the diet of dairy cows on concentrations of volatile fatty acids in the rumen and large intestine and on myoelectric activity of the spiral colon

OBJECTIVES: To describe the effects of an abrupt increase of concentrates in the diet of dairy cows on myoelectric activity of the spiral colon and on fermentation patterns in the rumen and large intestine. ANIMALS: 6 healthy lactating Simmental x Red-Holstein cows. PROCEDURES: The diet of 6 cows implanted with bipolar electrodes in the spiral colon was changed from hay only to a ration of 50% hay:50% starch-rich concentrates during a period of 60 hours. Myoelectric activity of the spiral colon, concentrations of absolute and undissociated volatile fatty acids (VFA), and pH of ruminal and large intestinal contents were monitored before, during, and after the dietary change. RESULTS: Significant changes in patterns of myoelectric activity of the spiral colon were restricted to phases III and IV of the bovine migrating myoelectric complex and to propagation velocity. Significant alterations were not observed in pH or VFA concentrations in ruminal fluid, but pH decreased and VFA concentrations increased significantly in fecal specimens after the change of diet. CONCLUSIONS AND CLINICAL RELEVANCE: Although rumen fluid is of limited value for measurement of certain indicators of fermentation, fecal samples can be used for measurement of pH and VFA concentrations, which serve as indicators of fermentation patterns in the large intestine. Increased concentrations of VFA and low pH in large intestinal digesta have a minimal influence on myoelectric activity of the spiral colon. Increased luminal VFA concentrations are unlikely to play an important role in the etiopathogenesis of motility disorders of the large intestine in cattle.     

Myoelectric activity in the intestine of cows with strangulating obstruction of the distal small intestine

Myoelectric activity in 2 cows instrumented with permanent electrodes in the ileum, cecum, proximal loop of the ascending colon (PLAC), and spiral colon was analyzed after an obstruction developed in the distal small intestine. Results were compared with patterns from a group of 7 normal cows. Myoelectric activity in the ileum immediately orad to the occlusion was characterized by abolition of the migrating myoelectric complex (MMC) and a constant pattern of strong spike bursts of long duration. Cyclic activity was present in all parts of the large intestine, and propagation of phase III activity was evident from proximal to distal. A slight degree of disorganization in phase III propagation was restricted to the spiral colon. Activity cycles tended to be shorter in the cecum and PLAC of both cows with colic than in normal cows, and the intensity of spiking activity was generally lower. Changes in duration of the MMC in the spiral colon (bovine colonic MMC, bcMMC) were inconsistent, but the intensity of spiking activity tended to be lower in phases I and II of both cows compared to controls. The organization of phase III in several spindles typical of the bovine spiral colon was not disrupted, but phase IV of the bcMMC occurred only infrequently. Organized cyclic activity occurred in the large intestine of both cows despite complete disruption of the small intestinal MMC, indicating the presence of mechanisms able to initiate and regulate coordinated myoelectric patterns in the large intestine independent of the small intestine.     

Effect of anticholinergic drugs on the electrical activity of the antrum and duodeno-jejunum in sheep

The changes induced in the electrical activity of the small intestine by atropine sulphate, diphemanil methylsulphate, hyoscine butylbromide and prifinium bromide were studied in conscious sheep fitted with chronically implanted electrodes. Increased spike potential activity was induced by carbachol. The mean slow-wave frequency of the antrum was 7.35 ± 0.18/min with burst of spike potentials randomly superimposed on about 63% of the slow waves. The occurrence of the spike bursts was inhibited for 18—30 min after an intravenous injection of atropine (0.75 mg/kg) and during its infusion at the rate of 0.05 mg/kg/min. The activity of the proximal part of the small intestine, which is characterized by migrating myoelectric complexes moving down slowly at hourly intervals, was replaced by irregular series consisting of spike bursts of about 3 min duration, at intervals of about 12 min for a total of 110 min. Such an effect, in which the level of spike activity was reduced, was also observed with hyoscine, diphemanil and prifinium during 80, 120 and 180 min periods respectively. The injection of carbachol was followed by continuous spike activity in which the mean spike level was nearly doubled, as occurs at the onset of diarrhoea. An inhibitory effect was observed at both antral and duodeno-jejunal levels with the four drugs used, that of hyoscine being least marked. The effect of prifinium was more pronounced than that of atropine or diphemanil, especially on the jejunum. The results suggest that the ability of these drugs to reduce the level of spike activity accompanying disruption of migrating myoelectric complexes and to inhibit the carbachol-induced increased level of spiking may account for the antispasmodic effects observed after the use of anticholinergic drugs in gastrointestinal disorders. Prifinium had the longest lasting effect at both antral and duodeno-jejunal levels and seemed to be a good atropine substitute to alleviate gastro-intestinal hypermotility.     

Metabolism of prostaglandin F2alpha during fasting in prepubertal gilts

The study was conducted to investigate a possible mechanism behind earlier observations of fasting-induced increases of blood concentrations of prostaglandin (PG) F2alpha metabolite (P-PG) in gilts. Six animals were fasted for 28 h, then administered i.v. PGF2alpha (500 ng/kg body weight). Blood samples were withdrawn at 1, 3, 5, 7, 10, 15, 20, 30, 40, 60 min, 2 and 3 h after the injection. A control group followed an identical protocol, except that they were fed during the corresponding 28 h-period. P-PG increased as previously observed during the 28 h of fasting. The P-PG increase in terms of area under the concentration time curve (AUC) following injection was significantly larger in the fasted than in the non-fasted gilts. In the fasted animals, the mean P-PG maximum concentration (Cmax) was 7145 pmol/L, the corresponding value for the non-fasted animals was 4566 pmol/L. PGs are metabolised through beta-oxidation in the liver. The results of this study imply that reduced 15-ketodihydro-PGF2alpha breakdown in the liver might contribute to the fasting-induced increases in P-PG.     

Myoelectric activity of the ileum, cecum, and right ventral colon in ponies during interdigestive, nonfeeding, and digestive periods

Myoelectric activity of the ileum, cecum, and right ventral colon (RVC) was studied in 4 mature ponies. Eight Ag-AgCl bipolar recording electrodes were sutured to the seromuscular layer of the ileum (2 electrodes), cecum (4 electrodes), and RVC (2 electrodes). Myoelectric activity was studied beginning 10 days after surgery. Eight, 60-minute recording sessions were performed in each pony during the interdigestive period, which was the period 3 to 7 hours after the morning feeding. On separate days, food was withheld for 24 hours, and 90-minute recordings were obtained during the nonfeeding period. Ponies were then fed a normal ration, and recordings were continued to obtain data for the digestive (feeding) period. All phases of the migrating myoelectric complex were seen at both ileal electrodes during the interdigestive period, including the periods of no spiking activity (phase 1), irregular spiking activity (phase 2), and regular spiking activity (phase 3). Phase 2 occupied 77% of the total recording time, and the mean duration of phases 1, 2, and 3 was 3.4 +/- 0.2, 12.8 +/- 1.2, and 6.7 +/- 0.7 min, respectively. Frequency of ileal slow waves was 11.8 +/- 0.1/min, and spike burst conduction velocity was 4.7 +/- 0.3 cm/s. A complete migrating myoelectric complex was seen in 11 of 32 tracings (34%) and had a mean duration of 24.2 +/- 2.6 min. The ileal migrating action potential complex, most often seen in phase 2, had a frequency of 4.8 +/- 0.5 spike bursts/h and a conduction velocity of 13.6 +/- 0.4 cm/s.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of propofol and fentanyl on duodenal motility activity in pigs

To investigate the effects of propofol and fentanyl on the postprandial duodenal motility the intraluminal impedance technique was used. Six pigs were instrumented with a central venous catheter, a percutaneous enterogastrostomy (PEG), and an impedance catheter, which was introduced via the PEG into the duodenum through endoscopy. Over the following 3 d, duodenal motility was measured for 8-hour periods. Measurements were taken on each subject under 3 different sets of conditions: in the conscious unrestrained pig, during propofol sedation, and during sedation with propofol-fentanyl. Both, after morning feeding and during gastric nutrition via the PEG, duodenal feeding patterns and duodenal phase II of the migrating motor cycle were shortened during propofol and propofol-fentanyl sedation. In contrast, the duration of phase I was prolonged by propofol and propofol-fentanyl. In conclusion, either propofol or propofolfentanyl sedation shortens duodenal feeding patterns, as well as phase II of the migrating motor cycle.     

Effect of enteral feeding on gallbladder function in dogs

Nutritional support in critically ill patients is a fundamental principle of patient care. Little is known about gallbladder motility during the interdigestive phase and in response to enteral feeding. The objective of this study was to investigate the effect of enteral feeding on gallbladder function in dogs. The cholagogue meal (Lipofundin infusion) was applied in four anatomical positions (jejunum, duodenojejunal junction, descending duodenum, stomach) in five healthy Beagle dogs. Gallbladder volume (GBV) was monitored by ultrasonography. Lipofundin infusion given through the feeding tube caused a maximal gallbladder contraction of 9.2% (range 3.7-13.9%) in the jejunum, 16.5% (9.1-22.1%) at the duodenojejunal junction and 26.3% (22.8-29.5%) in the descending duodenum. When the cholagogue meal was given through the mouth, it caused a mean 33.8% (28.6-46.5%) maximum gallbladder contraction in the same animals. In conclusion, we can establish that the ultrasound-guided gallbladder emptying method proved to be a useful technique for monitoring the cholagogue effect of Lipofundin meal applied in different anatomical positions of the intestine. The deeper the position of application, the smaller and shorter gallbladder contraction was evoked.     

Myoelectric activity of the spiral colon in dairy cows

OBJECTIVE: To describe myoelectric activity of the spiral colon in healthy cows. ANIMALS: 7 lactating Simmental X Red-Holstein crossbred cows. PROCEDURE: Cows were implanted with 7 pairs of bipolar silver electrodes (4 in the spiral colon and 1 each in the cecum, distal part of the ileum, and proximal loop of the ascending colon [PLAC]). Myo-electric activity was recorded during 4 days for each cow. Patterns were analyzed, using computer-based methods. RESULTS: Myoelectric activity of the spiral colon was closely associated with motility of the ileum and PLAC and showed the typical organization of migrating myoelectric complexes (MMC). The MMC in the bovine spiral colon (bcMMC) had a mean +/- SD duration of 188.6 +/- 30.8 minutes and was divided into 4 phases. Phases I and II lasted 11.3 +/- 1.4 and 159.4 +/- 33.3 minutes, respectively. Phase III (duration, 5.4 +/- 1.2 minutes) was characterized by 5.2 +/- 0.9 regular spindles (35.4 +/- 5.4 seconds) and 1 final elongated spindle (137.2 +/- 56.4 seconds). Phase III most commonly (73.8 +/- 16.1%) was followed by phase IV (duration, 173 +/- 3.6 minutes). Propagation velocity of phase III was 4.4 +/- 0.5 cm/min, and 13.6% of bcMMC were incompletely propagated through the spiral colon. CONCLUSIONS: Myoelectric activity of the bovine spiral colon is composed of a recurring cyclic pattern similar to MMC of the small intestine. Data of colonic myoelectric activity in healthy cows will serve as a basis for studies on cecal dilatation and dislocation in cattle.     

Influence of time of food administration on daily rhythm of total locomotor activity in ponies

The activity rhythm can be entrained by nonphotic cues, especially food availability. Daily feeding schedules can act as “Zeitgeber” to synchronize the circadian system. In this study, the authors evaluated the influence of different feeding schedules on the daily rhythm of total locomotor activity in ponies. Six clinically healthy Shetland ponies were kept under natural 12/12-h light/dark cycle and monitored during 4 different feeding schedules: fed twice (at 8 am and 8 pm), fasted, fed at 8 pm, fed at 8 am, and fed twice a day again. Water was available ad libitum. To record total activity, we equipped the animals with actigraphy-based data loggers (Actiwatch-Mini). Two-way analysis of variance revealed a significant main effect of the time of day and no effect of feeding schedules on the amount of total locomotor activity. Locomotor activity showed daily rhythmicity in all experimental conditions, with diurnal acrophase. The amplitude of the rhythms and their robustness statistically changed across all experimental conditions. Our findings support the theory that when given essentially free choice hay, the time of feeding did not entrain activity, and suggest that feeding behavior can influence the distribution of locomotor activity during a 24-hour period in ponies, with changes in the amplitude and robustness of the rhythm.     

Effects of medetomidine on intestinal and colonic motility in the dog

The motor responses of the jejunum and colon to stimulation of α₂-adrenoceptors by medetomidine and clonidine were investigated in four dogs. In fasting dogs, medetomidine, at a dose rate of 30 μg/kg i.v., disrupted the migrating myoelectric complex (MMC) pattern of the small intestine for about 2 h. Similar, but shorter-lasting effects were also induced by clonidine (30 μg/kg i.v.) on the jejunum. The administration of α₂-agonists inhibited colonic motility in fasting dogs, although medetomidine-induced inhibition was preceded by a short period of increased muscle tone. All these effects were reversed by the α₂-antagonists atipamezole (0.15 mg/kg i.v.) and yohimbine (0.20 mg/kg i.v.). In fed dogs, medetomidine (30 μg/kg i.v.) induced a strong increase of the tone on the proximal colon, while the activity of the medium and distal colon was completely suppressed. Yohimbine (0.50 mg/kg i.v.) immediately restored the activity of the colon and induced a propagated giant contraction and defaecation by the animal. These data confirm the importance of a₂-adrenergic receptors in the control of intestinal and colonic motility in the dog.     

Relationships between electromyographic ileal and colonic motility patterns in cats during fasting and feeding.

The relationship between ileal and colonic electromyographic motility patterns were investigated in six awake cats chronically fitted with subserosal electrodes implanted in the smooth muscles of the ileum and colon. Smooth muscle electrical activity (electromyogram) was recorded in both fed and fasted conditions under a 12-12 hours dark-light schedule. It consisted of electrical long spike bursts having two different patterns for each condition. Short sequences of three to five long spike bursts were propagated either aborally or orally from any part of the colon; they were most frequent during the interdigestive or fasting period and no relationship was observed between these long spike bursts and the electrical activity of the ileum. During the digestive or feeding period, the colonic activity was organized in long sequences of 10-15 long spike bursts, termed migrating spike bursts, which started near the caecal junction and propagated aborally to the distal colon. These migrating spike bursts were correlated with the ileal motility. This relationship demonstrated between ileum and colon after feeding is dependent upon the amount of food intake.     

Effects of erythromycin on myoelectric activity of the spiral colon of dairy cows

The effects of erythromycin on myoelectric activity of the spiral colon of dairy cows were investigated in a prospective study. Four Simmental x Red-Holstein crossbred cows of similar body weight and condition with seven pairs of bipolar electrodes implanted in the intestine (one each in the distal ileum, caecum and proximal colon, and four in the spiral colon) were included. Erythromycin lactobionate (1 mg kg(-1)) and 0.9% sodium chloride solution (NaCl) were administered to each cow in a random order. Erythromycin was diluted with NaCl and both treatments were administered slowly intravenously over a period of 5 min 1 h after onset of a phase III of the bovine colonic migrating myoelectric complex (bcMMC). A 3-6-day washout period was scheduled between trials. Significant differences between the results of the treatments were observed for spike duration in phase I as well as for spike duration and duration of spiking activity during phase II of the second bcMMC, which were significantly higher after erythromycin treatment than after NaCl. These findings suggest an indirect effect of erythromycin on colonic motility in cattle.     

Myoelectric activity of the small intestine in enterotoxin-induced diarrhea of calves.

Electrodes were surgically implanted at 15-cm intervals in the jejunum and ileum of 4 healthy neonatal calves so that myoelectric activity could be recorded on 2 consecutive days. On the first day, each calf received a control treatment, and myoelectric activity was recorded for 340 minutes. Phase I was recorded for a mean of 175.8 +/- 22.8 minutes (51.5%), phase II for 124 +/- 27.4 minutes (36.5%), and phase III for 40.3 +/- 6 minutes (11.9%). On the second day, each calf was treated with approximately 200 micrograms of heat-stable enterotoxin (STa) of Escherichia coli orally. All calves developed diarrhea after the administration of STa. Phase I was recorded for a mean of 92.5 +/- 42.3 minutes (27.2%), phase II for 227.3 +/- 52.5 minutes (66.9%), and phase III for 20.3 +/- 11.4 minutes (6.0%). Increase in phase II and decrease in phases I and III after STa administration were significant (P less than 0.05). Duration of the migrating myoelectric complex was longer after STa administration (median, 64 minutes), compared with the control treatment (median, 54 minutes). Minute rhythms, recorded on the day of toxin administration, ranged from 49 to 153 minutes. There was no difference between the number of migrating action potential complexes on the control days (range, 1 to 10), compared with those on treatment days (range, 1 to 14). These findings are suggestive that enterotoxin-induced diarrhea of calves is accompanied by increased total spiking activity and minute rhythms in the distal portion of the jejunum and ileum.     

Temporal patterns of growth hormone, prolactin and thyrotropin secretion in Targhee rams selected for rate and efficiency of gain

Thirteen Targhee rams selected for rate and efficiency of gain for 4 yr (1.5 generations) were compared with 10 rams from a Targhee line with no selection for over 20 yr to determine if selection for these traits would be associated with changes in the secretion of growth hormone (GH), thyrotropin (TSH) and(or) prolactin (PRL). Selected rams exhibited greater birth weight, average daily gain (ADG) and feed consumed/day during a 6-wk individual feeding regimen, and exhibited greater overall ADG during a 16-wk feeding trial as compared with the unselected rams. Temporal blood plasma samples were collected at 15-min intervals for 8 h from each of the 23 rams for hormone analysis. Selected rams exhibited greater overall mean GH (6.1 +/- .4 vs 4.6 +/- .5 ng/ml), overall mean TSH (8.6 +/- 1.2 vs 6.2 +/- .7 ng/ml) and baseline mean TSH (8.0 +/- 1.1 vs 5.6 +/- .5 ng/ml) than the unselected rams. Although the adjusted GH spike amplitude value was higher in the selected line (12.1 +/- 3.0 vs 7.4 +/- .8 ng/ml), this difference was not significant. No differences were observed with any of the variables of PRL secretion. In addition, there were no significant correlations between any of the hormone variables and any of the feed or gain data. These data support the hypothesis that Targhee rams selected for rate and efficiency of gain exhibit higher plasma levels of GH and TSH than unselected rams of the same breed.     

A dynamic model of protein digestion in the small intestine of pigs

A dynamic mathematical model of the digestion of proteins in the small intestine of pigs was developed. The model integrates current knowledge on the transit of digesta along the small intestine, endogenous secretions, digestion of proteins, and absorption of amino acids into a mechanistic representation of digestion. The main characteristics of the model are the following: the small intestine is divided into several segments of variable length but with equal digesta retention time; the rate of transfer of digesta between segments is based on the progression of myoelectric migration complexes; pancreatic and biliary secretions are poured into the first segment, whereas intestinal secretions enter all intestinal segments; protein hydrolysis is described by first-order equations; and an intestinal absorption capacity is used to estimate absorption of hydrolyzed protein. Simulation results are consistent with observed data, although more information is needed to represent reality more closely. The sensitivity analysis shows that parameters for protein hydrolysis largely determine protein digestibility. The absorption capacity of the small intestine limits the absorption of amino acids at the beginning of a meal and modulates the appearance of amino nitrogen in the portal vein. It also shows that amino acid absorption can be limiting to protein digestibility when large amounts of protein are eaten in a single daily meal. The model is useful in evaluating the dynamics of protein digestion and absorption of feedstuffs. The model can be used in evaluating protein digestion of different feedstuffs and feeding strategies.