Reticulo-ruminal Contractions Research Articles

Evaluation of an indwelling bolus equipped with a triaxial accelerometer for the characterisation of the diurnal pattern of bovine reticuloruminal contractions.

This observational study aimed to describe the diurnal pattern of reticuloruminal contraction rate (RRCR) and the proportion of time spent ruminating by cattle, using two commercial devices equipped with triaxial accelerometers: an indwelling bolus (placed in the reticulum) and a neck collar. The three objectives of this study were firstly to determine whether the indwelling bolus provided observations consistent with RRCR as determined by clinical examination using auscultation and ultrasound, secondly to compare estimates of time spent ruminating using the indwelling bolus and a collar-based accelerometer, and finally to describe the diurnal pattern of RRCR using the indwelling bolus data. Six rumen-fistulated, non-lactating Jersey cows were fitted with an indwelling bolus (SmaXtec Animal Care GmbH, Graz, Austria) and a neck collar (Silent Herdsman, Afimilk Ltd. Kibbutz Afikim, Israel), and data were collected over two weeks. Cattle were housed together in a single straw-bedded pen and fed ad libitum hay. To assess the agreement between the indwelling bolus and traditional methods of assessing reticuloruminal contractility in the first week, the RRCR was determined over 10 min, twice a day, by ultrasound and auscultation. Mean inter-contraction intervals (ICI) derived from bolus and ultrasound, and from auscultation were 40.4 ± 4.7, 40.1 ± 4.0 and 38.4 ± 3.3 s. Bland-Altmann plots showed similar performance of the methods with small biases. The Pearson correlation coefficient for the time spent ruminating derived from neck collars and indwelling boluses was 0.72 (highly significant, P < 0.001). The indwelling boluses generated a consistent diurnal pattern for all the cows. In conclusion, a robust relationship was observed between clinical observation and the indwelling boluses for estimation of ICI and, similarly, between the indwelling bolus and neck collar for estimating rumination time. The indwelling boluses showed a clear diurnal pattern for RRCR and time spent ruminating, indicating that they should be useful for assessing reticuloruminal motility.

Effect of forage types differing in undigested neutral detergent fiber concentration and forage inclusion rate on reticulo-ruminal motility and fermentation, total tract barrier function, and blood metabolites of finishing beef heifers.

This study evaluated the effects of forages (BarS vs. STR) that differ in the uNDF concentration and FI rate on ruminal fermentation, total tract barrier function, reticulo-ruminal motility, and blood metabolites of beef heifers. Six ruminally cannulated Hereford × Simmental heifers (699 ± 69.1 kg BW) were used in a 6 × 6 Latin square (26 d periods) with a 2 × 3 factorial treatment arrangement. However, 1 heifer was removed from the study after period 2 due to health problems unrelated to treatment, resulting in an incomplete 6 × 6 Latin square design. Barley grain-based diets were formulated using BarS or wheat STR to alter uNDF (7.1% vs. 8.5% DM) with FI rates of 5%, 10%, or 15% of DM. There were limited interactions between the forage type and FI. DM intake was not affected (P ≥ 0.10) by forage type or FI. Use of STR vs. BarS increased uNDF intake (P < 0.001). Increasing FI increased (P < 0.001) uNDF intake for those fed 15% forage. Ruminal pH was not affected (P ≥ 0.10) by forage type; however, cattle fed 5% FI had lesser (P = 0.017) mean ruminal pH and maximum pH (P = 0.018) than those fed 10% and 15% of forage. The total SCFA concentration was not affected by forage type (P = 0.84) but cattle fed the 5% FI rate had lesser (P < 0.001) molar proportion of acetate when compared with cattle fed 10% and 15% forage. Increasing the FI rate decreased the molar proportion of propionate (P < 0.001). Feeding STR relative to BarS decreased (P = 0.041) the reticulo-ruminal contraction duration. In contrast, cattle fed the 10% and 15% FI rates had a greater (P = 0.028) contraction frequency with lower (P = 0.048) contraction area than those fed 5% forage. Plasma glucose, serum insulin, and serum amyloid A were not affected by forage type or FI rate (P ≥ 0.10). Cattle fed 15% forage had lesser (P = 0.040) concentration of serum haptoglobin when compared with cattle fed 5% or 10% forage. In conclusion, forage type used to affect the dietary uNDF concentration, and FI rate act independently suggesting that the provision of STR to increase uNDF reduces reticulo-ruminal contraction duration and total tract permeability but may not affect ruminal pH. Increasing the FI increased dietary uNDF, stabilized ruminal pH, stimulated more frequent reticulo-ruminal contractions, and may decrease the permeability of the gastrointestinal tract and systemic inflammation.

PSX-B-10 Effect of undigested neutral detergent fiber concentration and forage inclusion rate on ruminal pH, reticular motility, and total tract permeability for finishing beef heifers

Abstract This study evaluated the effects of undigested neutral detergent fiber (uNDF) concentration and forage inclusion (FI) rate on dry matter (DM) intake, ruminal pH, reticular contractions, and gastrointestinal permeability for finishing beef cattle. Five ruminally cannulated Hereford′Simmental heifers (699±69.1 kg) were used in an incomplete 6×6 Latin square (26-d periods) with a 2×3 factorial treatment arrangement. Barley grain-based diets were formulated using barley silage or wheat straw to provide low or high uNDF (7.1 vs. 8.5% DM) with forage proportions of 5, 10, or 15% of dietary DM. Dry matter intake (P ≥ 0.10) and eating time (P ≥ 0.13) were not affected by uNDF, FI, or uNDF′FI. With low uNDF diets, increasing FI numerically (P = 0.02) increased rumination time (min/d); while, with high uNDF diets, rumination time increased with 5 to 10% FI, but not thereafter (P = 0.03). Mean ruminal pH was not affected by uNDF (6.17 vs. 6.19; P = 0.08), but increased with increasing FI (6.04b, 6.23a, and 6.28a; P = 0.02). Duration of ruminal pH &amp;lt; 5.5 was not affected by uNDF but tended (P = 0.07) to be reduced with increasing FI. High uNDF diet tended to increase the frequency of reticular contractions (1.43 vs. 1.51 contractions/min; P = 0.07) but decreased the contraction duration (13.2 vs. 14.1 sec; P = 0.04). Increasing FI increased contraction frequency (1.39b, 1.50a, and 1.53a contractions/min; P = 0.03) and tended to reduce contraction duration as forage increased from 5 to 10 and 15% (14.3, 13.1, and 13.6 sec; P = 0.07). Feeding high uNDF decreased (P = 0.05) permeability of the gastrointestinal tract based on the appearance of Cr-EDTA in urine following an intra-ruminal dose. Increasing FI tended to reduce gastrointestinal tract permeability (P = 0.06). Limited interactions indicate that uNDF and FI act independently suggesting that increasing dietary uNDF, without increasing FI rate, can stimulate frequency of reticulo-ruminal contractions and reduce gastrointestinal permeability for finishing cattle.

Contrasting effects of high-starch and high-sugar diets on ruminal function in cattle.

The experiment reported in this research paper aimed to determine whether clinical and subclinical effects on cattle were similar if provided with isoenergetic and isonitrogenous challenge diets in which carbohydrate sources were predominantly starch or sugar. The study was a 3 × 3 Latin square using six adult Jersey cows with rumen cannulae, over 9 weeks. In the first 2 weeks of each 3 week experimental period cows were fed with a maintenance diet and, in the last week, each animal was assigned to one of three diets: a control diet (CON), being a continuation of the maintenance diet; a high starch (HSt) or a high sugar (HSu) diet. Reticuloruminal pH and motility were recorded throughout the study period. Blood and ruminal samples were taken on day-1 (TP-1), day-2 (TP-2) and day-7 (TP-7) of each challenge week. Four clinical variables were recorded daily: diarrhoea, inappetence, depression and ruminal tympany. The effects of treatment, hour of day and day after treatment on clinical parameters were analysed using linear mixed effects (LME) models. Although both challenge diets resulted in a decline in pH, an increase in the absolute pH residuals and an increase in the number of minutes per day under pH 5.8, systemic inflammation was only detected with the HSt diet. The challenge diets differentially modified amplitude and period of reticuloruminal contractions compared with CON diet and both were associated with an increased probability of diarrhoea. The HSu diet reduced the probability of an animal consuming its complete allocation. Because the challenge diets were derived from complex natural materials (barley and molasses respectively), it is not possible to assign all the differential effects to the difference in starch and sugar concentration: non-starch components of barley or non-sugar components of molasses might have contributed to some of the observations. In conclusion, substituting much of the starch with sugar caused no substantial reduction in the acidosis load, but inflammatory response was reduced while feed rejection was increased.

Automated system for characterizing short-term feeding behavior and real-time forestomach motility in cattle

The objectives of this study were to develop instrumentation for measuring feed intake and forestomach motility for individually housed cattle and create data analysis algorithms to characterize feeding behavior and reticuloruminal contractions. Feed bunks were mounted onto S-beam load cells and suspended outside the animal stalls. Load cells were connected to a data logger which recorded bunk weight at 1-min intervals. Thus, periods of feed disappearance from the bunk could be equated to meals. A meal detection script was developed in MATLAB to import the weight data, filter the weight to reduce noise, detect meals by evaluating the difference between consecutive measurements, and export the meal start time, duration, and size of each meal. Evaluation of the meal detection script by visual review resulted in a combined error rate of 1.8%. A water-filled (2 L) balloon attached to a catheter was placed into the ventral sac of the rumen through the rumen cannula and connected to a disposable pressure transducer. The transducers were connected to a PowerLab data acquisition system via bridge amplifiers, and the ruminal pressure signal was visualized in real-time using LabChart computer software. A script was prepared in MATLAB for filtering pressure data, detecting contractions using the findpeaks function within the Signal Processing Toolbox of MATLAB, and evaluating contraction amplitude, duration, and frequency. Evaluation of the ruminal contraction script by visual review resulted in a combined error rate of 4%. After successful evaluation of the algorithms, an experimental application of these systems characterized meals and ruminal contractions for 8 animals in response to an increase in grain in the diet. This trial produced average daily results for feeding behavior and ruminal motility that were within the range of other published studies. With the low error rate and biologically acceptable values, the instrumentation and data analysis algorithms are appropriate means of characterizing feeding behavior and ruminal motility. These systems and algorithms could have important applications for ruminant physiology and behavior research.

Hot topic: Automated assessment of reticulo-ruminal motility in dairy cows using 3-dimensional vision

Reticulo-ruminal motility is a well-established indicator of gastrointestinal health in dairy cows. The currently available methods for assessing motility are labor-intensive, costly, and impractical to use regularly for all cows on a farm. We hypothesized that the reticulo-ruminal motility of dairy cows could be assessed automatically and remotely using a low-cost 3-dimensional (3D) camera. In this study, a 3D vision system was constructed and mounted on the frame of an automatic milking robot to capture the left paralumbar fossa of 20 primiparous cows. For each cow, the system recorded 3D images at 30 frames per second during milking. Each image was automatically processed to locate the left paralumbar fossa region and quantify its average concavity. Then, the average concavity values from all images of 1 cow during 1 milking process were chronologically assembled to form an undulation signal. By applying fast Fourier transformation to the signal, we identified cyclic oscillations that occurred in the same frequency range as reticulo-ruminal contractions. To validate the oscillation identification, 2 trained assessors visually identified reticulo-ruminal contractions from the same 3D image recordings on screen. The matching sensitivity between the automatically identified oscillations and the manually identified reticulo-ruminal contractions was 0.97. This 3D vision system can automate the assessment of reticulo-ruminal motility in dairy cows. It is noninvasive and can be implemented on farms without distressing the cows. It is a promising tool for farmers, giving them regular information about the gastrointestinal health of individual cows and helping them in daily farm management.

Identification of the Rumination in Cattle Using Support Vector Machines with Motion-Sensitive Bolus Sensors.

The reticuloruminal function is central to the digestive efficiency in ruminants. For cattle, collar- and ear tag-based accelerometer monitors have been developed to assess the time spent ruminating on an individual animal. Cattle that are ill feed less and so ruminate less, thus, the estimation of the time spent ruminating provides insights into the health of individual animals. pH boluses directly provide information on the reticuloruminal function within the rumen and extended (three hours or more) periods during which the ruminal pH value remains below 5.6 is an indicator that dysfunction and poor welfare are likely. Accelerometers, incorporated into the pH boluses, have been used to indicate changes in behaviour patterns (high/low activity), utilised to detect the onset of oestrus. The paper demonstrates for the first time that by processing the reticuloruminal motion, it is possible to recover rumination periods. Reticuloruminal motion energy and the time between reticuloruminal contractions are used as inputs to a Support Vector Machine (SVM) to identify rumination periods with an overall accuracy of 86.1%, corroborated by neck mounted rumination collars.

Influence of centrally administered diltiazem on behavioural responses, clinical symptoms, reticulo-ruminal contractions and plasma catecholamine level after experimentally induced duodenal distension in sheep

A different role of L-type antagonists for voltage-gated calcium channels (VGCC) has been previously identified in different types of experimental and clinical pain in man and animals. Present study examined the role of VGCC blocker – diltiazem administered icv (0.25, 0.5, 1.0 and/or 2.0 mg in toto) on the development of pain related symptoms, clinical signs, plasma catecholamine level and the inhibition of reticulo-rumen motility caused by 5 min lasting mechanical duodenum distension (DD) in the sheep. Experimental DD was conducted by insertion (during surgery) of rubber balloon into the duodenum and the distension by 40 ml of warm water. Duodenal distension resulted in a significant increase of behavioural pain responses, tachycardia, hyperventilation, inhibition of reticulo-rumen contractions rate (from 85% to 45% during 15–20 min), an increase of plasma catecholamine concentration (over sevenfold increase of epinephrine during 2 h following DD, two-times norepinephrine and 84% increase of dopamine). Diltiazem infusion given 10 min before DD decreased intensity of visceral nocifensive responses such as: behavioural changes, tachycardia, hyperventilation, reticulo-rumen motility and efficiently prevented appearance of catecholamine release. These data demonstrated that the development and persistence of acute duodenal pain depends on the activation of Ca 2+ ion flux leading to neurotransmitters release and modulation of membrane excitability. It seems that diltiazem given icv 10 min prior to DD (as a source of acute visceral pain), inhibited specific receptors α 1 subunits of VGCCs in target tissues, prevent depolarization of cell membranes and release of neurotransmitters responsible for pain sensitivity in sheep. The observed antinociceptive action of VGCCs type-L blockers suggests that these channels play a crucial role in the modulation of acute visceral pain in sheep.

The inhibition of experimentally induced visceral hyperalgesia by nifedipine – A voltage-gated Ca 2+ channels blocker (VGCCs) in Sheep

Present study examined the effect of VGCC L-type blocker – nifedipine given i.c.v. (0.25, 0.5, 1 and/or 2 mg in toto) on the development of nociceptive behavior, clinical symptoms, plasma catecholamin concentration and reticulo-rumen motility following 5 min lasting mechanical duodenal distension (DD) in sheep. After 24 h of fasting, all animals received i.m. ketamine analgesia (20 mg kg −1 B.W) and anesthetized with pentobarbital (20 mg kg −1 B.W., i.v. infusion) The permanent stainless steel cannula 29 mm in length and 2 mm in diameter was inserted into the lateral cerebral ventricle (controlled by cerebro-spinal efflux) 10 mm above the bregma and 5 mm laterally from the midline sutures using stereotaxic method. Under the same general anesthesia/analgesia a T-shaped silicon cannula (inside diameter of 21 mm), was inserted into the duodenum (12 cm from pylorus). Second identical cannule was inserted into the dorsal sac of the rumen, a previously described. After surgery each animal was kept in individual boxes for 10 days prior to experiment and was treated i.m. with benzyl procaine penicillin 30,000 I.U kg −1 B.W.) + dihydrostreptomycine sulfate (10 g kg −1 B.W.) + prednisolone acetate (1.2 mg kg −1 B.W.) combination and i.m. ketamine (20 mg kg −1 B.W.) every day by seven consecutive days. Experimental DD was conducted by insertion and then distension of rubber balloon (containing 40 ml of warm water) inserted into sheep duodenum. Duodenal distension produced a significant increase in behavioral pain manifestations, tachycardia, hyperventilation, inhibition of reticulo-ruminal contractions rate (from 87.2 to 38.0% during 15–20 min), an increase of plasma catecholamine concentration (over 6.4-fold increase of epinephrine during 2 h following DD, 2-times norepinephrine and 84% increase of dopamine). Nifedipine infusion administered 10 min prior to DD decreased intensity of visceral pain manifestations such as: behavioral changes, hyperventilation, reticulo-rumen motility and efficiently prevent appearance of catecholamine release. These data demonstrated that the development and persistence of duodenal hyperalgesia depends on the activation of Ca 2+ ion flux leading to neurotransmitters release and modulation of membrane excitability. It seems that nifedipine given i.c.v. 10 min prior to DD (as a source of visceral pain), inhibited specific receptors 1 subunits of VGCCs in target tissues, prevented depolarization of cell membranes and release of neurotransmitters responsible for pain sensitivity in sheep. The observed antinociceptive action of VGCCs type L blockers suggest that these channels play a crucial role in the modulation of acute visceral hyperalgesia in sheep.

Centrally administered verapamil prevents the autonomic reaction to visceral pain in sheep

The significant role of voltage gated calcium channels (VGCC) L-type antagonists used concomitantly with opioids in attenuation of clinical pain has been confirmed. The aim of this study was to evaluate the effect of centrally administered verapamil on behavior and biochemical parameters in sheep that have undergone experimental duodenal distension (DD) and to determine whether verapamil exerts any anti-nociceptive effects under these conditions. The study was carried out using 24 mature crossbred ewes, each weighing 38–43 kg. Verapamil, a VGCC blocker, was administered through an intracerebroventricular cannula at the following doses: 0.25, 0.5, 1.0 and 2.0 mg in toto. Ten minutes later experimental DD was conducted by insertion and the distension of rubber balloon (containing 40 ml of warm water) inserted into sheep duodenum. After 5 min of mechanical DD the following reactions were then observed: the significant increase in behavioral pain responses, i.e. tachycardia, hyperventilation, inhibition of reticulo-ruminal contractions (70% approximately, during 15 min), an increase of plasma catecholamine concentration (over 7-fold increase of epinephrine during 2 h following DD, 2-times norepinephrine and ±80% increase of dopamine). Verapamil infusion administered 10 min prior to DD decreased intensity of visceral pain responses, such as: behavioral changes, tachycardia, hyperventilation, inhibition of the reticulo-rumen motility and efficiently prevented the appearance of catecholamine release. These data demonstrated that the development and persistence of duodenal hyperalgesia depends on the activation of Ca 2+ ion flux leading to neurotransmitters release and modulation of membrane excitability. The observed antinociceptive action of VGCCs type-L blockers suggests that these channels play a crucial role in the modulation of acute visceral hyperalgesia in sheep.

Comparison of two ruminoscopy techniques in calves

Two different techniques were tested in nine calves to describe endoscopically the visible structures of the rumen and the reticulum. Ruminoscopy using an orally introduced flexible endoscope proved to be unsatisfactory, but when the endoscope was introduced through a ruminal fistula in the left flank into the dorsal and ventral ruminal sacs, the blind sacs, ruminal pillars, the atrium of the rumen, the reticulum and the reticular groove could all be displayed effectively. Indentations of the ruminal wall caused by the left kidney, the spleen and the abomasum could be seen with the endoscope as could reticulo-ruminal contractions. The technique allowed visual evaluation of the mucosal surfaces and movement of the rumen, reticulum and reticular groove. The advantages and disadvantages of ruminoscopy in bovine medicine are discussed.

Cholecystokinin does not act on the efferent pathway of cholinergic and adrenergic nerves to inhibit ruminal contractions in sheep (Ovis aries).

The effect of exogenous cholecystokinin-octapeptide (CCK-8) on ruminal contractions and the role of efferent pathways of cholinergic and adrenergic nerves on the effect were studied in sheep. Intravenous infusion of CCK-8 at 11.4 and 45.6 pmol/kg/min significantly inhibited the frequency and amplitude of ruminal contractions in conscious sheep. After bilateral cervical vagotomy, intravenous infusion of CCK-8 at 45.6 mol/kg/min had no detectable effect on amplitude of ruminal contractions induced by electric stimulation to the cervical vagus nerve (1 msec, 20 Hz, 5 mA, for 10 sec at 1-min intervals) in anesthetized sheep. The amplitude of contractile responses of ovine ruminal muscle strips to acetylcholine at 5 x 10(-5) M was not inhibited by CCK-8 applied simultaneously at 1 x 10(-9) M. Intravenous infusion of phentolamine at 53.0 nmol/kg/min, propranolol at 101.4 nmol/kg/min, or their combined infusion did not alter the inhibitory action of CCK-8 at either dose on ruminal contractions in conscious sheep. These results suggest that CCK-8, which does not act on the efferent pathway of cholinergic and adrenergic nerves, may reflexively inhibit reticuloruminal contractions via vagal afferent fibers in sheep.

Influence of dietary particle size on chewing activity and reticulo-ruminal motility in goats and sheep fed wheaten ( Triticum aestivum) hay

Wheaten hay, prepared into two physical forms was used to formulate four diets for goats and sheep. Hay was either chopped into 1 cm lengths or ground (3.2 mm screen) and pelleted and fed in either form or as a 2:1 or 1: 2 ratio, respectively. Responses in chewing activity and reticulo-ruminal motility were compared in a replicated 4 × 4 Latin square design. Goats ate 14% less DM than sheep (28.8 g/kg bodyweight vs. 33.5) yet spent 55% more time eating (251 min/d vs. 162), and 15% more time ruminating (635 min/d vs. 552). Frequency of primary and secondary reticulo-ruminal contractions were similar in both species when corrected for intake and digestible DM intake, respectively, but there were fewer secondary contractions in goats during eating and rest. Eating was associated with the highest frequency of both contraction types. There were no significant species by treatment interactions. In both species, feed intake and number of primary contractions increased linearly as the particle size of the diet decreased. In contrast, frequency of secondary contractions was not affected by physical form of the diet but was highly correlated ( r=0.97) with digestible DM intake. The digestive physiology of the two species appears to differ in regard to feed intake and chewing activity but goats did not clear digesta from the rumen as rapidly as sheep and, therefore, the extra particle size reduction of feed and rumen digesta did not enhance intake or digestion of the wheaten hay. However, these characteristics may provide a survival advantage for goats when limited to very poor quality roughage.

Inhibition of reticulo-rumen motility by gammaendorphin in sheep

Effects of gamma-endorphin, the mu- and delta-opioid receptor's agonist on amplitude and frequency of reticulo-ruminal contractions of conscious sheep were determined. Gamma-endorphin (1.0 and 2.0 μg kg −1 BW) administered into the third cerebral ventricle caused significant decreases in frequency of reticulo-ruminal contractions. Gamma-endorphin (2.0 μg kg −1 BW) depressed frequency and amplitude, and caused general neuroleptic-like action. A 1.0 μg kg −1 BW dose increased amplitude of contractions and provoked psychomotor-excitability action. Naloxone (12.5 μg kg −1 BW) prevented response to gamma-endorphin. Results suggest that an inhibitory mu- and delta-opioid system is involved in the control of forestomach motility and general behavior in sheep.

Vagal Influences on the Phasic and Tonic Components of the Motility of the Ovine Stomach and Gastroduodenal Area

Both the phasic and tonic components of gastric motility including the gastroduodenal junction were recorded after section or cooling blockade of the vagus nerves in conscious sheep. The phasic contractile activity was monitored using electromyography, strain gauges, and intraluminal manometry. The changes in the tone of the stomach (abomasum) were assessed by an electronic barostat. The cyclical contractions of the reticulorumen ceased immediately after bilateral vagotomy, whereas the activity of the antral part of the abomasum was strongly enhanced. Two weeks after vagotomy, the abomasal hypermotility persisted while reticuloruminal movements developed from a local nervous network. Vagal cooling at 5°C of one of the vagus nerves after section of the contralateral vagus similarly inhibited reticuloruminal contractions in contrast to the occurrence of abomasal hypermotility. During vagal cooling, both the abomasal and pyloric tone were lowered. We conclude that vagal cooling impairs excitatory input to the reticulorumen and inhibitory input to the gastroduodenal junction. The decreased smooth muscle tone at the abomasal and pylorus levels during vagal cooling suggests that vagal stimulatory influences are abated.

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)

The effect of roughage quality on intake, digestion and rumen function in sheep

In a previous experiment (Hovell et al. (1987)) it was found that with two roughages, one of good (hay) and the other of poor (straw) degradability, both ground and pelleted, that the voluntary intake of the hay was (60% greater than that of the straw. This was despite the fact that rumen DM pool sizes were very similar. The outflow of undegraded material from the rumen was much greater with the hay although particle size should not have been a constraint to outflow with either roughage (Poppi et al. (1980)), and indeed their particle size distributions were very similar. It was suggested that there might have been an effect of roughage quality on rumen outflow rate, possibly mediated through an effect on reticulo-rumen contractions.The objective of the experiment reported here was to examine the effect of roughages with different degradabilities on voluntary intake, rumen volume, rumen outflow rate, and on reticulo-ruminal contractions.

Inhibition of reticulo-ruminal motility by volatile fatty acids and lactic acid in sheep.

1. A study was made of the influence on reticulo-ruminal motility, recorded by electromyography, of ruminal infusions of volatile fatty acids (VFAs) and lactic acid in twenty-four sheep maintained by intragastric infusion of a complete liquid diet, in three sheep fed grass pellets, and in nine chronically vagotomized sheep; abomasal and duodenal infusions of VFA and lactic acid were tested in five sheep fed grass pellets. 2. Ruminal infusions of VFAs and lactic acid progressively inhibited the amplitude of the reticulo-ruminal contractions. In many experiments there was no effect on contraction frequency until the cessation of all reticulo-ruminal contractions at which point the maximal concentration of VFA recorded in the abomasum was 28 mM, and that of lactic acid was 20 mM. 3. The concentrations of undissociated VFAs causing cessation of reticulo-ruminal contractions in the vagus-intact sheep were very similar to the concentrations causing abolition of the organized intrinsic motility of the chronically vagotomized sheep. 4. The inhibition of reticulo-ruminal motility with ruminal infusions of mixtures of VFAs and of lactic acid together with VFAs could largely be explained by the sum of the effects of the individual acids present. 5. Abomasal infusion of VFA or lactic acid inhibited the amplitude of ruminal, especially primary ruminal, contractions at concentrations of undissociated acid of 60 mM and above and increased the frequency of reticulum and primary ruminal contractions at about 80 mM. 6. Duodenal infusion of VFAs and lactic acid (100 mM, 5 ml/min) strongly inhibited abomasal motility without affecting reticulo-ruminal motility, and at a higher rate (100 mM, 10 ml/min) abolished motility and inhibited both the amplitude and frequency of reticulo-ruminal contractions. 7. It is concluded that the initial inhibition of reticulo-ruminal motility in ruminal acidosis is unlikely to involve any significant influence from duodenal, or abomasal receptors. The final cessation of reticulo-ruminal motility with ruminal acidosis could involve local effects of VFAs in the reticulo-rumen as well as through excitation of acid-sensitive reticulo-ruminal receptors.

MODULATION OF RETICULO-RUMINAL MOTILITY IN GOATS AND SHEEP BY OPIOID MECHANISMS

Normorphine and naloxone were administered via selective routes in sheep and goats. The results with normorphine indicate the presence of both (1) a central action depressing frequency and amplitude and, (2) a peripheral action — probably on the intramural plexus — depressing only the amplitude of the cyclical reticulo-ruminal contractions. Key words: Sheep, goat, normorphine, naloxone, forestomach motility

An electrophysiological study of some reticulo‐ruminal and abomasal reflexes in sheep

1. In halothane-anaesthetized sheep in which reticulo-ruminal (gastric) contractions were present, nervous discharges have been recorded electrophysiologically in sixty-four single efferent gastric units (grouped in seven types) dissected from the mid-cervical region of the left vagus. An examination was made of the reflex effects on the efferent discharges of the procedures given in paragraphs 2-5.2. Under isotonic recording conditions the total discharge was reduced but the peak frequency of most types of unit was enhanced compared with the discharge recorded under control isometric conditions.3. Abolition of reticular contractions by the use of preganglionic and post-ganglionic blocking agents resulted in an efferent discharge pattern similar to that recorded under isotonic conditions.4. Sudden deflation or inflation of the reticulum at the start of a reticular contraction had an effect that depended on the initial volume of the reticulum. It could be either excitatory and/or inhibitory.5. Acidification of the abomasal contents reflexly enhanced the discharge in three of ten efferent gastric vagal units. An abomasal pH less than 1.0 appears to be less important in providing an excitatory drive to the ;gastric centres' in halothane-anaesthetized sheep than in decerebrate sheep.6. It is estimated that the total reflex time is > 1.3 sec for reticulo-reticular reflexes and > 2.1 sec for reticulo-ruminal reflexes. The central reflex time is > 370 msec.7. It is concluded that a tonic afferent input from ;in series' reticular tension receptors during the quiescent period of the primary (reticulo-ruminal) cycle provides a reflex drive to the ;gastric centres' and largely determines the rate and amplitude of the reticular and ruminal contractions.8. The enhanced afferent input, during a reticular contraction under isometric recording conditions, modifies the size, form and duration of the later phases in the contraction sequence of the reticulum and rumen. The reflex effects are predominantly excitatory at low and moderate levels of reticular tension and inhibitory at high levels.