Abomasal pH Research Articles

Gastrin and gastrin-related responses to infection with Ostertagia ostertagi in the half

The effects of a single challenge with 60,000 infective Ostertagia ostertagi larvae on blood and gastrointestinal mucosal gastrin concentrations, gastrin-producing G-cell numbers in the pyloric mucosa and growth of different parts of the gut were investigated in 16, two-and-a-half-month-old calves. Infected calves exhibited a rise in abomasal pH which was accompanied by a 145 per cent increase in wet weight of the fundic mucosa (P<0·05) and a significant rise in blood total gastrin concentrations (P<0·01). Circulating little gastrin (G-17) was unaffected. Pyloric mucosal total gastrin concentrations remained unaltered in the infected calves until day 28 when levels fell to 36·9 per cent of control group values (P<0·01). Pyloric mucosal G-cell numbers declined during the experiment in the infected group. It is suggested that release of previously stored tissue gastrin and not a change in Gcell numbers contributes to the hypergastrinaemia associated with ostertagia infection in the calf.

Ancillary Tests for Assessment of the Ruminant Digestive System

This article reviews the ancillary tests that are available to evaluate disease and function of the gastrointestinal system. Procedures and tests such as abdominocentesis and peritoneal fluid cytology; rumen fluid analysis; abomasal pH and pepsinogen; upper digestive tract endoscopy; ultrasonography and radiology; hematologic and biochemical assessments; cytology, culture, and histopathology of aspirates; serology, liver function tests and biopsy; exploratory laparotomy; fecal examination; and microbiology are described.

Effect of ostertagiasis on copper status in sheep: a study involving use of copper oxide wire particles

Lambs infected with Ostertagia circumcincta larvae and uninfected controls were either dosed with 5 g copper oxide wire particles (cowr) or remained undosed. The change in abomasal pH was monitored from duodenal digesta and that in liver copper concentration from initial liver biopsy samples and liver obtained at necropsy after 22 days. Infection increased the pH of digesta from 2 · 5 to 4 · 5. The change in liver copper content in sheep not treated with COWP was +6-1 mg (12·6 per cent) and −6·8 mg (13·8 per cent) in control and infected sheep, respectively. Significantly greater amounts of COWP were recovered from the abomasa of infected than from control animals (3 · 6 ± 0 · 23 and 1 · 6 ± 0·55 g, respectively) and hepatic uptake of copper from COWP was 0 · 7 and 1 · 8 per cent of the dose, respectively. There were significant relationships between the pH of duodenal contents and cowr retained, soluble copper concentration in duodenal digesta and hepatic uptake of copper. It was concluded that, through causing an increase in pH in abomasal and duodenal digesta, gastrointestinal nematodes interfere with copper metabolism.

Hypergastrinaemia of sheep infected with Haemonchus contortus

Radioimmunoassay of plasma gastrin has shown that a hypergastrinaemia occurs in yearling sheep, after infection with 10(6) infective third stage larvae of Haemonchus contortus. Plasma gastrin concentrations began to rise two to four days after infection, that is, at about the same time as, or slightly before, the abomasal pH was observed to increase.

Observations at Slaughter in the Gastrointestinal Tract from Preruminant Calves Fed Different Milks and Milk Replacers

Abstract To investigate the content of the gastrointestinal tract a total of 21 Holstein calves (age 8 days) were killed 3 hours after fed one of 6 milk diets: Skim milk based replacer (S); as S, incubated with pancreatin to prevent clotting (SP); whey based replacer (V); as S, acidified with propionic acid (SA); whole milk (WM) and fermented colostrum (FC). Curd formation in the abomasum in groups S and WM delayed flow of protein and fat to the small intestine. Milk FC did not clot in the abomasum. pH in abomasal content was lowest in groups FC (3.8) and WM (4.1). There was no effect on abomasal pH by feeding the chemically acidified replacer (SA) relative to group S. After one fourth of the small intestine pH was identical in all groups. Protein proteolysis in abomasum was highest in groups S and WM and lowest in groups V and FC. In groups V and FC there was a higher content (g) and percentage of crude protein in the intestinal chymus.

Effect of sodium cromoglycate on the response to Ostertagia circumcincta in adult sheep

Serum pepsinogen concentrations rose more rapidly and to higher levels in adult sheep infected with Ostertagia circumcincta and treated orally with the mast cell stabilising agent sodium cromoglycate than they did in adult sheep infected with the parasite which remained untreated. Sodium cromoglycate did not affect the serum pepsinogen concentrations or abomasal pH in uninfected sheep.

Further studies on the response to transplanted adult Ostertagia ostertagi in calves

Calves infected by surgical transplantation of adult Ostertagia ostertagi had raised levels of plasma pepsinogen and those in which the largest number of worms established also had elevated plasma gastrin concentrations. Despite the elevated plasma pepsinogen values, the abomasal pH of the animals did not change significantly, and there was no significant difference in the percentage establishment of adult parasites in calves previously infected with O ostertagi third stage larvae and those which had been maintained parasite-naive before transplant.

Effects on plasma pepsinogen, gastrin and pancreatic polypeptide of ostertagia spp. transferred directly into the abomasum of sheep

Ostertagia spp. obtained at slaughter from the abomasa. of previously infected sheep and transferred via cannulae into the abomasa of previously worm-free sheep produced severe effects. This was shown with populations of mainly adult parasites given to three sheep and also when mixed populations of 4th stage larvae and adults were given to three other sheep. Although more severe effects were produced when both larval and adult worms were transferred, there were clearly effects when isolates composed predominantly of adults were transferred. Sheep of each group had reductions in food intake and elevations in plasma pepsinogen and gastrin within 24 h of transfer of the parasites. Further increase in plasma pepsinogen and gastrin occurred when abomasal pH rose 5–7 days after infection. Plasma pancreatic polypeptide varied but showed a general tendency to be markedly lower after infection. Ostertagia spp. eggs were detected in the faeces of infected sheep 48 h after transfer. The proportions of adults and inhibited larvae recovered from the abomasa were similar to those in the donor sheep, showing that inhibition, or arrested development of larvae, continued after their transfer to worm free sheep.

Initiation of migrating myoelectric complex in sheep by duodenal acidification and hyperosmolarity: role of vagus nerves.

Gastrointestinal motility was studied in conscious sheep by X-radiography and by electromyography from chronically implanted electrodes before and after total thoracic vagotomy. Duodenal infusion of 0.5-3 mmol HCl (0.035-0.1 M-HCl) induced premature duodenal regular spiking activity (r.s.a.) within 1-7 min in fifteen of seventeen sheep studied when infused at 20 min after a natural r.s.a. There was no correlation between abomasal pH and any phase of the migrating myoelectric complex (m.m.c.). Duodenal alkalinization by infusion of 0.3 M-Tris buffer (pH 10.2) or 0.1 M-NaHCO3 had no influence on the occurrence of the m.m.c. Duodenal infusion of 20-50 ml 0.5 M-NaCl induced a premature duodenal r.s.a. within 1-5 min in seven of eight sheep. Vagotomy did not prevent the initiation or migration of the m.m.c., but reduced the rate of propagation of the r.s.a. from 40.5 +/- 7.2 (mean +/- S.E. of mean) to 16.7 +/- 0.1 cm/min in the duodenum, from 27.3 +/- 4.1 to 16.6 +/- 0.8 cm/min in the jejunum, and from 21.4 +/- 1.1 to 13.7 +/- 0.7 cm/min in the proximal ileum. Initially the frequency of r.s.a. increased, especially in the duodenum where they recurred at an interval of 98.4 +/- 6.8 min before vagotomy; and at 23.4 +/- 1.8 min in the first 24 h after vagotomy; the interval had lengthened to 86.7 +/- 5.2 min 2-3 weeks after vagotomy. Premature duodenal r.s.a. was not induced by duodenal infusion of HCl in five, or by duodenal infusion of hyperosmolar NaCl in three chronically vagotomized sheep. It is concluded that the vagus nerves contribute to the regulation of the frequency and propagation of the m.m.c. in sheep; duodenal acidification is not essential nor is it the normal stimulus for initiation of r.s.a., but duodenal infusion of HCl or hyperosmolar NaCl can initiate a premature duodenal r.s.a. via the vagus nerves.

Effect of cimetidine on abomasal pH and Haemonchus and Ostertagia species in sheep

Cimetidine, a histamine H2-receptor blocking agent which reduces gastric acid flow in simple stomach animals was administered directly into the abomasum of sheep at 100 mg kg-1 twice daily for five consecutive days and again on the eighth day. The drug caused a significant increase in the pH values of the abomasal contents and was highly effective in reducing the adult population of Haemonchus contortus (100 per cent) and Ostertagia circumcincta (70 per cent) in the abomasum of sheep. The possibility of using cimetidine as a method of treating abomasal nematode parasitism is discussed.

Intake and digestion of mature Flinders grass (Iseilema spp.) by sheep and their response to the addition of urea and minerals

Studies were conducted of the voluntary feed consumption (VFC) and digestion by sheep offered mature Flinders grass hay containing, on a dry matter basis, 4.2% crude protein (CP), 71.8% cell wall constituents (CWC) and 12.6% total ash. The nutritive value of the hay was low, as indicated by the relatively low values for organic matter (OM) digestibility (40.9%), VFC (879 g OM/day) and CP digested in the intestines (5.8 g CP/100g feed OM intake). Digesta flows from the rumen and abomasum per unit OM intake, rumen and abomasal digesta pH, ammonia concentration in rumen liqour, and CP reaching the intestines relative to CP and digestible OM intakes were similar to values previously obtained with temperate grasses. Supplementation of the hay with urea increased VFC by 16%, and minerals in addition to the urea enhanced it by a further 6%. The supplements substantially increased OM and CWC digestibilities (by 16-17%) and CP digested in the intestines (DCPi) per unit hay intake (by 10%); these improvements could be attributed to changes in ruminal digestion. The higher levels of intake and digestion with the supplements were accompanied by increased concentrations of volatile fatty acids (VFA) in the rumen. It was calculated, by using the ad libitum feeding results, that the supplements of urea and minerals would have increased the intakes of digestible OM and DCPi by 44 and 36% respectively. However, with the supplements, DCPi per kg digestible OM remained low at 13.3 g. The data facilitate interpretation of previous animal production studies with Flinders grass hay and indicate that production may be limited by inadequate amino acids in the supplemented diet.

Haemonchus contortus: Egg laying influenced by abomasal pH in lambs

Abomasal and duodenal concentrations of Haemonchus contortus eggs were measured in four lambs fitted with permanent abomasal and duodenal cannulas and infected with 25,000 Haemonchus contortus larvae. During the period of maximal egg laying, i.e., when the abomasal H. contortus egg concentration was above 2000 eggs/ml, the animals received cimetidine (20 mg/kg) intravenously or pentagastrin (5 μg·kg −1·h −1) for 90 min and the changes in abomasal and duodenal egg concentrations were followed for 2.5 hr. Pentagastrin infusion reduced the abomasal and duodenal pH significantly and in less than 15 min decreased the abomasal and duodenal egg concentrations which represented only 21.4 and 12.0% of the control values at the end (90 min) of infusion. During pentagastrin infusion, both the abomasal ( r = 0.56, P ⩽ 0.01) and the duodenal ( r = 0.72, P ⩽ 0.01) egg concentrations correlated positively with the corresponding pH values. After cimetidine injection, the abomasal and duodenal pH had increased 150 min later to, respectively, pH 6.16 and 6.27. During the first 30 min for an abomasal pH lower than 4.5–5.0, egg production increased by 106%; then the abomasal and duodenal egg concentrations decreased progressively, representing, respectively, only 39.3 and 16.4% of the control values 120 min later. It is concluded that the level of egg laying of adult H. contortus was related to the abomasal acidity, the maximal egg production occurring when the abomasal pH was between pH 4 and 4.5.

Probantheline Bromide and Cimetidine in the Control of Abomasal Acid Secretion

Each of three cows fitted with a rumen cannula were maintained on a constant diet for two weeks prior to the experiment. Each cow was given 4, 8 and 16 mg/ kg cimetidine and probantheline bromide to determine the effects of these drugs on acid secretion. Samples were aspirated every 30 minutes from the abomasum and rumen for one hour prior to receiving the drug and for 5 ½ hours after the treatment. The pH measurements were completed in duplicate on a Model 5 Corning pH Meter. The samples were also analyzed for chloride concentration. Neither probanthelirie nor cimetidine had any significant effect on abomasal pH, suggesting neither drug would be of value in treating abomasal ulcers.

Haemonchus contortus: Abomasal transmural potential difference and permeability changes associated with experimental infection in sheep

Measurements of abomasal potential difference (PD), pH, and ionic concentrations of abomasal contents were made in four lambs fitted with permanent abomasal cannulae and infected twice at 39-day intervals with 25,000 Haemonchus contortus larvae. Within 10 to 15 min after intraruminal administration of larvae, the abomasal transmural PD increased from −12.9 ± 2.6 to −25 ± 3.1 mV and then returned progressively to basal values in 48 hr. A similar but slower increase was observed from 6 to 9 days after infection, the maximal PD values reaching −22.6 ± 0.8 mV. During the period of egg laying by the parasite, the transmural PD remained higher (55%) than normal. It returned to control levels following this period. After each infection, the transmural PD variations were positively correlated ( r = 0.82, P < 0.01) with the Na + concentration of abomasal contents but not with K + and Cl−. We conclude that H. contortus infection in sheep was characterized by an increase in the abomasal transmural PD occurring immediately after infection and we suggest that it was related to the changes in ionic permeability of the gastric wall.

Gastro-duodenal motor and transit disturbances associated with Haemonchus contortus infection in sheep.

Abomasal and duodenal motility was investigated by electromyography in 4 lambs fitted with permanent abomasal and duodenal cannulae and infected twice with 25,000 Haemonchus contortus larvae at an interval of 39 days. In addition, abomasal and duodenal pH, flow rate of digesta of the duodenum, and faecal water content were determined. The 80-90 min cycles of antral contractions were shortened for at least 3 weeks after infection. This was accompanied by a 26% increase in the number of duodenal migrating myoelectric complexes/day during the intraparietal development of the larvae (10-12 days). Concomitantly, the duodenal flow of digesta increased from 215 +/- 22 ml/h to 318 +/- 15 ml/h 4 days after infection and was associated with a higher water content of the faeces. The frequency of the migrating myoelectric complexes, but not the duration of antral motor cycles (or the duodenal flow rate), was correlated with both gastric (P less than 0.01) and duodenal (P less than 0.05) pH after the first and second infections. The duodenal flow rate was correlated with the Cl- concentrations of the abomasal contents (P less than 0.01) and with the duodenal pH (P less than 0.05). It is concluded that, (i) the duodenal motor disturbances associated with experimental H. contortus infection are related to the alterations in abomasal gastric acid secretion which occurs during the histotrophic phase of larval development and (ii) the increased duodenal flow is a consequence of ionic permeability changes of the gastro-intestinal mucosae.

Effects of Ostertagia circumcincta infections on plasma gastrin in sheep.

Radio-immunoassay of plasma gastrin showed that hypergastrinaemia developed in sheep during experimental infections with Ostertagia circumcincta. Elevations of plasma gastrin occurred within 8 days of the first dose of infective larvae, with the most marked increase being after 11-20 days when adult worms would be expected to be present in the abomasum. Increases of plasma gastrin levels from 69.0 +/- 7.6, 28.7 +/- 5.3, 48.7 +/- 5.9 and 60.6 +/- 9.4 pg/ml before infection to maxima of 650, 230, 900 and 750 pg/ml respectively were recorded in 4 sheep infected for the first time. In 2 others which had been previously infected and then treated with anthelmintic, plasma gastrin rose from 16.0 +/- 4.0 and 377 +/- 87 pg/ml to maxima of 260 and 900 pg/ml at 24 and 29 days after re-infection, respectively. The cause of hypergastrinaemia has not been established. The elevation of abomasal pH which occurs in ostertagiasis may result in increased gastrin levels but is thought not to be the only cause since plasma gastrin increased before the abomasal pH rose and developed in sheep infected for a second time although their abomasal contents remained at pH 4.0 or lower. The presence of the parasite is critical for development of hypergastrinaemia as shown by return of the gastrin level to normal following therapy with an anthelmintic. It was shown that the parasites do not depend on the hypergastrinaemia since O. circumcincta became established in antrectomized sheep in which hypergastrinaemia did not develop.

Abomasal function following injections of elfazepam and 9-aza-cannabinol

The feed intake stimulants elfazepam (E), a benzodiazepine, and 9-aza-cannabinol (9-AC) decrease rumen contractions and abomasal acid content in sheep and E increases rumen fluid volume, digestibility and overall nutrient availability. E has been hypothesized to decrease the propulsive activity of the entire GI tract. To further examine the effects of E and 9-AC on gastric function, 4 ewes were prepared with abomasal cannuals and 3 silver/silver chloride monopolar electrodes alternated with 2 strain gauges on the distal one-third of the abomasal serosa. Electromyographical (slow waves and action potentials) and contractile (rates and forces) activities and abomasal pH were measured. Treatments of 8 and 16 mg E had no effect on slow wave frequency, action potential rate, contraction rate, or contraction force. Abomasal content pH was decreased with 8 mg E. Treatments of 125 and 250 μg 9-AC depressed action potential and contraction rates and contraction force but had no effect on slow wave frequency or pH.

Herbage digestion in the stomach and intestines of weaner lambs at different stages of their maturity

Various parameters relating to digestion of a clover diet in the stomach and intestines were measured by marker techniques in the same weaner lambs at 15, 24 and 40 weeks of age when body weights averaged 18, 29 and 44 kg respectively. Significant small changes were observed with increasing age and body size in the values of several of the parameters measured. Thus at 40 weeks relative to 15 weeks values were higher for (i) crude protein digested in the intestines per unit feed intake (+ 10%), (ii) sodium content of rumen liquor and sodium flow from the rumen per unit feed intake (+ 9%, + 14%), (iii) potassium and chloride contents of abomasal liquor (+ 9%, + 7%) and (iv) pH of abomasal digesta (+ 0.3 pH unit). Values were lower for (v) digestibility of organic matter and cell wall constituents in the whole alimentary tract (c. – 1.8%), (vi) ammonia content of rumen liquor and ammonia flow from the rumen and abomasum per unit feed intake (– 15% to – 20%) and (vii) potassium content of rumen liquor (– 9%). No changes attributable to age or body size were observed with several paramefers, including (i) rate of production of volatile fatty acids in the rumen per unit feed intake, (ii) rate of absorption of volatile fatty acids from the rumen, (iii) rate of flow of digesta through the stomach per unit feed intake, and (iv) mean residence time of water-soluble marker in the rumen. The results indicate that care needs to be exercised in applying digestion data obtained with adult sheep to the nutrition of the growing weaner lamb.

Effects of intraruminal administration of zinc on gastric acid secretion in sheep

Intraruminal administration of zinc sulphate at 100 and 200 mg Zn/kg bodyweight resulted in central and peripheral effects in sheep. Feed intake was reduced, pH of the duodenal contents elevated and the secretion of acid from isolated pouches of the abomasum doubled. Suggested explanations include a local inhibitory effect of zinc on abomasal acid secretion elevating duodenal pH and a resultant increased release of gastrin stimulating secretion from the pouches.

Aspects of the physio-pathology of parasitic gastritis in the sheep.

Sheep and calves prepared with separated, innervated pouches made from the acid secreting region of the abomasum were given single or multiple infections of Ostertagia spp and comparisons were made of the secretory changes of parasitised and non-parasitised mucosa by means of cannulas placed in the abomasum and pouch. Contrary reactions of the parasite-free pouches and infected main part of the abomasum are described and explained in terms of a two-part hypothesis. The inhibitory effect on acid secretion of the abomasum (resulting in its contents being pH 5 to 7) was postulated to be due to the direct suppressive effects of substances released locally by parasites or injured host tissues, whereas increased secretion of the hormone, gastrin, was thought to account for the stimulatory effects of infection on acid secretion from the pouches. In sheep treated with anthelmintic and then reinfected the inhibitory effects on abomasal pH were not obtained. The hypersecretion from the pouches still persisted.