Reticular Contractions Research Articles

Influence of dopamine on rumino-reticular motility and rumination in sheep.

The effects of intracerebroventricular (i.c.v.) and intravenous (i.v.) administration of dopamine and its antagonists (domperidone and metoclopramide) on forestomach motility were investigated in four sheep fitted with Nichrome electrodes and strain gauges implanted on the reticulum and the caudo-dorsal sac of the rumen. Infused by the i.c.v. route at a rate of 2 micrograms . kg-1 . min-1, dopamine inhibited the phasic contractions of the reticulo-rumen. A similar effect was obtained following i.v. administration of doses which were 10 times higher, but the effect was associated with an increased tone of the rumen wall. Prior i.v. administration of domperidone (0.5 micrograms . kg-1) blocked these effects and a selective blockade of the dopamine-induced inhibition of phasic contractions was obtained with higher dose of domperidone (2.5 micrograms . kg-1) administered centrally. When dopamine was infused alone ventricularly or intravenously after metoclopramide (40 micrograms . kg-1), it induced a transient (6-8 min) period of rumination, which could be blocked by a prior i.c.v. administration of tolazoline. It was concluded that dopamine acts on rumino-reticular motility in sheep through specific dopamine receptors (i) centrally by inhibiting the frequency of reticular contraction and (ii) peripherally by increasing the muscular tone of the rumen, and its effects on rumination involved alpha 2 adrenergic receptors located in the central nervous system.

Antagonistic effects of naloxone on CCK-octapeptide induced satiety and rumino-reticular hypomotility in sheep

Continuous intracerebroventricular (ICV) infusion of CCK-octapeptide (CCK 8) was performed in ewes fitted with a permanent cannula into the lateral cerebral ventricle and Nichrome electrodes on the reticulum in order to record its electrical activity. In the first series of experiments, subsequently repeated in 12 h fasted animals, CCK 8 was infused during the first hour of a 3 hour period of feeding at 2.5, 5 and 10 ng.kg −1 .min −1. The same series of infusion were performed 20 min after ICV injection of 2.4 and 10 μg.kg −1 of naloxone. CCK 8 reduced significantly in a dose related manner the food intake (r = 0.95; P < 0.01) and the frequency of cyclic spike bursts associated to biphasic contractions of the reticulum observed during feeding (r = 0.89 ; P < 0.01). At 5 and 10 ng.kg −1 .min −1, the reduction of food intake reached 46.2 and 52.6 % during the period of infusion ; the basal and stimulated (feeding) frequency of reticular contractions were nearly halved. Previous ICV administration of naloxone (2.4 μg.kg −1) partially blocked the effects of CCK 8 infusion on both food intake (72 %) and reticular frequency (54 % basal, 67 % stimulated). The CCK 8 induced effects on both food intake and frequency of reticular contraction were completely abolished after a previous 10 μg.kg −1 injection of naloxone. These results suggest that the central effects of CCK 8 on feeding behavior and forestomach motility involve similar central structures and are mediated through opiate receptor structures.

Factors affecting the voluntary intake of food by sheep. 3. The effect of intravenous infusions of gastrin, cholecystokinin and secretin on motility of the reticulo-rumen and intake.

1. Sheep given ground and pelleted lucerne hay (Medicago sativa) ad lib. were infused intravenously with pentagastrin, secretin, cholecystokinin (CCK) and its analogues to assess their effects on motility of the reticulo-rumen and on food intake. In the latter experiments the animals were deprived of their diet for periods of up to 6 h to induce hunger and the infusions were made before and during 3-10 min periods of feeding. 2. Pentagastrin, and analogue of gastrin, depressed intake by 35-50% (P less than 0.05) when it was infused at 9 microgram/kg per h during 30 min of feeding. The threshold may however be below 1 microgram/kg per h as this dose decreased intake of 12-17%. The frequency of reticular contractions decreased by 13, 35, 39 and 44% when 1, 3, 9, and 27 microgram pentagastrin/kg per h respectively was infused (P less than 0.025). 3. Secretin depressed food intake 38% after 30 min (P less than 0.025) when 8 Clinical Units (CU)/kg per h was infused but the threshold could be less than this dose since 0.5 CU/kg per h depressed intake by 12%. Contraction amplitude but not frequency decreased at 8 CU/kg per h. 4. CCK produced a 39% decrease in intake during the first 10 min of feeding (P less than 0.05) and the threshold was between 5 and 15 Ivy Dog Units (IDU) or 425 and 1276 pmol/kg per h. The frequency of reticular contractions was not affected by 1.7 IDU/kg per h but it was depressed 21 and 63% by 5 and 15 IDU/kg per h. Octapeptide at 1.5 and 3 microgram (1312 and 2624 pmol) kg per h depressed intake by 11 and 43% respectively after 10 min (not significant) and 1.5 microgram/kg per h depressed motility by 39% (P less than 0.01). Ceruletide at 810 ng (599 pmol)/kg per h depressed intake by 31% (not significant) after 10 min and decreased motility by 52% (P less than 0.05). The threshold dose for ceruletide on intake appeared to be about 90 ng or 66 pmol/kg per h which is considerably less than that for CCK or octapeptide. 5. The biological significance of gastrointestinal hormones as signals of satiety in normal sheep is not known since doses of pentagastrin and CCK that suppressed intake also interfered quite markedly with motility. However there is good reason to suspect that elevated concentrations of gastrin and CCK in blood of parasitized sheep may account at least in part for their symptoms of rumen atony and reduced food intakes.

X線透視像から見たウシの各種腹部消化管疾患について

Fluoroscopic examination was quite helpful for making an accurate diagnosis, selecting a proper treatment, including indication for surgery, and judging a prognosis in each cases.Characteristic fluoroscopic findings in the forestomach diseases were impaction and bloat of the rumen, atony, slow and weak contraction and foreign bodies in the reticulum, atony of the abomasum, and functional disorders of the colon. In 80% of the cows with these diseases, the reticulum had sharp foreign bodies. As the tips of these bodies touched the mucosae of the reticulum, reticular contraction became unclear or less marked. These bodies might act as triggers for functional disorders of the reticulum and other parts of the forestomach, finally causing reticular and abomasal atony.In 92% of the cows with abomasal displacement, the reticulum had sharp foreign bodies and showed the same movements as described above. These findings suggested that abomasal displacement might have some relations with such functional disorders in the fbrestomach as caused by traumatic reticulitis.

Effects of cold temperature and winter conditions on some aspects of behaviour of feedlot cattle

Behavioural responses were investigated in individually fed (maintenance to twice maintenance) feedlot steers housed inside (5 to 27°C) or outside (−40 to 19°C) from October to March (Experiment 1), and in steers exposed to temperatures of −20, 0 and 20°C in controlled temperature chambers in September and again in December (Experiment 2). Respiratory frequencies of the outside steers increased with increases in feeding level ( P<0.05) and temperature ( P<0.01). Steers in the outside lot increased the time spent ruminating as temperature decreased ( P<0.01). As the winter progressed the maximum temperature at which shivering was observed decreased from −9°C in November to −25°C in January, and shivering was not observed at −30°C in March. The outside feedlot steers increased the time spent lying down ( P<0.05) but decreased wet grooming (licking) behaviour ( P<0.05) as temperature decreased. Rumination activity by the steers in Experiment 2, while in temperature controlled chambers, was increased by exposure to −20°C ( P<0.01). The frequency of reticular contractions was greatest during periods of rumination ( P<0.01) and was inversely related to exposure temperature. The intensity of shivering was more severe in September than in December. Respiratory frequencies of steers in Experiment 2 increased with exposure temperature ( P<0.01). However, the increase with temperature was more pronounced in the December than in the September series of exposures ( P<0.05).

POST PRANDIAL CHANGES IN PAROTID SALIVARY SECRETION AND PLASMA OSMOLALITY AND THE EFFECTS OF INTRAVENOUS INFUSIONS OF SALINE SOLUTIONS

Parotid salivary secretion, reticular (gastric) contractions and blood osmolality were examined in conscious sheep prepared with re‐entrant parotid duct cannulae and given 1000 g of lucerne chaff daily. Osmolality of blood (portal, carotid and jugular) rose by 2–4 mosmoles. kg‐1 within 5 min of fresh food being given, continued to rise (up to 12–30 mosmoles. kg‐1) over the next 3 h and remained above levels detected before fresh food was given for up to 10 h. The greatest changes were in portal blood which was characteristically hyperosmolal to jugular and carotid blood; a difference which disappeared on fasting for 36 h. Parotid saliva which was 5–20 mosmoles. kg‐1 hyposmolal to jugular blood, increased to up to 6 ml. min—1 within 30 sec of the sheep starting to eat and although they continued to do so for some hours remained at these high levels for only about 30 min.Attempts were made to see whether parotid salivary secretion was affected by changing the osmolality of the blood. Reductions in the rate of parotid salivary secretions and sometimes in the rate of reticular contractions were produced in conscious, anaesthetized and decerebrate preparations by making intravenous infusions of hyperosmolal solutions. The effects were stronger, and the latency shorter, when the infusions were made into the portal vein than when made into the posterior vena cava or a jugular vein. They were reduced by vagotomy and splanchnotomy although not abolished by both.Increases in parotid salivary secretion and frequently, but not invariably, in the rate of reticular contractions followed intravenous infusions of isosmolal and hyposmolal solutions. In 6 experiments (of a total of 12) increases in parotid salivary secretion followed the intravenous injection of arginine vasopressin (0·06 mU.kg‐1), in none was saliva reduced by antidiuretic hormone.The possible involvement of peripheral osmoreceptors in the inhibitory effects, and of receptors sensitive to changes in blood volume in the excitatory effects, is raised in relation to post‐prandial changes which occur in blood composition.

EFFECTS OF COLD ON DIGESTIBILITY, RETENTION TIME OF DIGESTA, RETICULUM MOTILITY AND THYROID HORMONES IN SHEEP

In the first of two experiments, 12 closely shorn yearling wethers received grass hay either in the long form or pelleted form and were acclimated to temperatures of 0.8, 10.1 and 17.7 C. Feed was provided for each treatment at an equivalent intake level of approximately maintenance. The sheep receiving long hay consumed less water than those receiving hay pellets. Water consumption decreased with decreasing temperature. The apparent digestibilities of DM, E, N and ADF were lower for the pelleted hay than for the long hay (P &lt; 0.001). The digestibilities of DM, E and ADF were lower (P &lt; 0.05) when the sheep were at 0.8 C than at 17.7 C, but there were no significant ration × temperature interactions. In the second experiment, six closely shorn sheep receiving a pelleted hay ration at the maintenance level were exposed for 4–6 wk to temperatures of 21.2 and 1.3 C. DM digestibility was reduced (P &lt; 0.05) in the cold by 0.18 percentage units per degree (C) drop in temperature. Mean retention times, determined from the fecal excretion patterns of 144Ce following a single injection into the rumen, decreased (P &lt; 0.05) from 38.5 h in the warm environment (21.2 C) to 32.5 h in the cold (1.3 C). The mean number of reticulum contractions per hour was increased (P &lt; 0.001) from 60 at 21.2 C to 72.5 at 1.3 C. Serum thyroxine (T4) and triiodothyronine (T3) concentrations were significantly (P &lt; 0.05) higher in sheep exposed to the cold compared to the sheep in the warm temperature treatment. It is concluded that pelleting hay does not alter the depressing effect of cold environmental temperatures on digestibility and that the effect of temperature on digestibility is likely due to a change in rate of passage of digesta through the altimentary tract.

The cyclic motility of the omasum and its control in sheep.

1. The mechanical activity of different parts of the omasum was recorded by means of small balloons and/or strain-gauges in conscious sheep. These events were related to the electrical activity of the omasal body, the omasal groove and the leaves and to the changes in diameter of the reticulo-omasal orifice. Humoral, behavioural and nervous influences were examined.2. Two patterns of contraction of the omasum were found. One, confined to the oral and middle thirds of the organ, originated at the omasal groove and proceeded to the right and then the left surfaces of the body and ceased at the onset of reticular contraction. The other was limited to the aboral third of the organ near the abomasum; in this part the contractions were prolonged regardless of the reticular contraction and some gave rise to a reversed propagation over the organ. The characteristic cyclic motility of the omasum was slightly reduced in sheep fasted for 48 hr and in those fed on pelleted food, and it persisted after vagotomy.3. The reticulo-omasal orifice always dilated strongly during the second phase of reticular contraction. It also dilated noticeably during the extra-contraction associated with regurgitation. In each case alternating opening and closing movements at a frequency of 5-7/min followed. Contractions of the omasal leaves, which were independent of those of the omasal body, occurred at a rate of approximately 2-3/min. They passed from the free border to the base and travelled in an aboral direction. After local application of fatty acids the frequency of their contractions increased to approximately the same rate as that of the orifice.4. It is concluded that the motility of the omasum in sheep involves a wave of contraction starting at a point on the omasal groove just posterior to the reticulo-omasal orifice and passing slowly over the omasal body. With the exception of the occasional reversed contractions this pattern is closely associated with rumino-reticular cycles even though the omasal contractions and the movements of the leaves are partially independent of vagal innervation.

The sequential contractions of the rumen associated with eructation in sheep.

1. The orderly sequential movements of the reticulum and the rumen were studied in conscious sheep by electromyography using enamelled stainless-steel wires implanted in various regions of the stomach wall and by recording mechanical changes within the various parts of the organ. Electrical activity of the rumen and/or pressure changes were related to eructation when the animals were at rest, feeding or ruminating.2. Secondary contractions of the rumen were found to originate in the ventral blind sac immediately following a primary contraction or independently. The wave of contraction originating in the ventral blind sac was seen to pass in a circular manner to the dorsal blind sac, the dorsal sac, the ventral sac and finally once more to the ventral blind sac. Eructation occurs at the end of the contraction of the dorsal sac. In each case, the time required to initiate the secondary cycle depended on the strength of contraction of the ventral blind sac.3. Sustained gaseous distension elicited numerous secondary contractions of the rumen concurrent with a lower frequency of reticular contractions. Although some secondary contractions were incomplete, all began with contraction of the ventral blind sac and were associated with eructation.4. Chemical stimulation of the rumen by fatty acids at pH 5.5-5.9 increased the ratio of secondary to primary contractions of the rumen to a varying extent depending on their initial rate.5. It was concluded that the seemingly random occurrence of a secondary cycle of the rumen was dependent on the activity of the ventral blind sac and its pattern could be altered by both mechanical and chemical stimulation.

The locations and activities of medullary neurons associated with ruminant forestomach motility.

1. Neuronal activity bearing a temporal relationship with spontaneous reticulo-ruminal movements was recorded with micro-electrodes from the medulla oblongata in halothane-anaesthetized sheep. Recording sites were located histologically after causing electro-coagulation at the micro-electrode tip.2. One hundred and forty-four gastric units were recorded from the dorsal vagal nucleus and up to 1 mm dorsal and lateral to the nucleus between transverse planes 1 mm caudal, and 4 mm rostral, to the obex. It is considered that records were obtained from the regions of cell bodies.3. The discharges of thirty-two vagal preganglionic motoneurones were identified by an antidromic collision technique. Conduction velocities ranged from 10-26 m/sec. They were located in the dorsal vagal nucleus and up to 0.5 mm dorsal and lateral to the nucleus. The majority of motoneurones innervated either the reticulum or the rumen. One ruminal unit discharged during both primary and secondary cycle movements.4. One hundred and twelve units which were not orthodromically or antidromically activated by stimulating the vagus nerves were considered to be interneurones. Four types were distinguishable on the basis of their patterns of discharge during primary cycle movements.5. The discharges of Type A interneurones resembled those of gastric motoneurones, having no resting discharge between contraction cycles. Their discharges were temporally related to either reticular contractions or rumen contractions during primary and secondary cycle movements.6. Types B and C interneurones have resting discharges which, respectively, increased and either decreased or stopped during each primary cycle movement.7. Discharges of only three units identified as interneurones resembled the discharges of gastric vagal afferent units.

A Method for Recording the Motor Activity of the Reticulum in Cattle

A method for recording the motility of the reticulum in normal cattle has been devised. The method is based on measurement of the pressure variations occurring in connection with the reticular contractions. The pressure is transferred through open, water-filled catheters via a pressure transducer to an electromanometer, from which it is recorded with the aid of a mingograf. Mean values for the interval, duration and amplitude of the reticular contractions in 10 normal cows are given. The method permits recording in intact animals without any preliminary measures, and can therefore be used in clinical cases.

Movements of the stomach compartments of a young bull during sucking.

1. Gastric motility was studied in a young bull and two sheep which had retained their sucking behaviour. Pressure tracings or electromyograms were recorded from all compart-ments of the stomach.2. During the sucking of milk or water reticulum contractions either became more fre-quent but weak, or ceased altogether. After sucking, or after the introduction of fluid directly into the abomasum, reticulum contractions slowed down but retained their strength. The rumen and omasum were more fully inhibited than the reticulum.3. It is concluded that the inhibitory response to sucking has two phases, a cephalic phase dependent upon the eagerness of sucking which mainly influences the strength of the contractions of the forestomach, and an abomasal phase dependent on the degree of distension of the abomasum which mainly affects the frequency of the contractions.

Abomasal secretory responses to teasing with food and feeding in the sheep.

1. Secretion of acid and pepsin from abomasal pouches and contractions of the reticulum and rumen were studied in sheep. Observations were made in sheep after being fasted and when they had food available ad libitum.2. The abomasal pouches were of fundic regions alone and also of the fundic region with a rim of antral mucosa.3. The secretion from both types of pouch was continuous, was increased by feeding and decreased by fasting.4. The volume, pepsin concentration and acid concentration of the secretion from fundic pouches increased within 15-30 min of the sheep being teased with food or fed. These responses were observed in sheep which had food available ad libitum or had been fasted.5. Reticulum contractions and the rumen contractions associated with them (A sequences) increased in frequency when sheep with either type of pouch were teased with food or when they ate.6. Consistent associations between rumination and abomasal secretory activity were not established.7. Mixed fundic-antral pouches did not characteristically show responses to teasing with food and sustained secretory responses were delayed by up to 90 min after feeding commenced.8. It is suggested that a cephalic phase of gastric (abomasal) secretion was revealed in the studies on fundic pouches of the abomasum.

The dorsal nucleus of the vagus as a centre controlling gastric motility in sheep.

1. A preparation is described for investigating the central nervous control of gastric motility in decerebrate decerebellate sheep.2. The dorsal vagal nucleus has been electrically stimulated in thirty decerebrate sheep, and the effect on the mechanical responses of the different parts of the reticulo-rumen have been determined.3. In the absence of recurrent rhythmic gastric contractions, punctate electrical stimulation of the dorsal vagal nucleus did not elicit gastric contraction until the intensity of stimulation was sufficiently high to excite efferent vagal fibres.4. Direct stimulation of the vagus nerve, or of motor fibres running from the nucleus to this nerve, always caused contraction of the reticulum, and dorsal and ventral ruminal sacs.5. Electrical stimulation of certain points within the medulla oblongata, during rhythmic gastric motility, inhibited motility for one or more contraction cycles. These inhibitory points lay on a line commencing at the mid-point of the dorsal vagal nucleus, and extending forward and ventral to this.6. Excitatory responses were less frequent, and were seen along a line running parallel to, but about 1 mm below, the anterior half of the line of maximum inhibition. They usually followed a period of inhibition, were generally shorter in duration, and consisted of a series of small reticular contractions at a rate of about 1/10 sec.7. The presence of a powerful inhibitory influence on the dorsal vagal nucleus, mediated from an area lying anterior to the nucleus, is argued and its probable action at the level of the gastric motor nucleus is discussed.

Reticulo-ruminal mechanoreceptors in sheep.

1. The nervous activity in single afferent gastric vagal units was recorded electrophysiologically from halothane-anaesthetized sheep with spontaneous reticulo-ruminal movements present.2. Sixty-six afferent units innervating gastric mechanoreceptors were isolated from fifteen sheep. The receptors were located mainly in the medial walls of the reticulum and the cranial sac of the dorsal rumen, and also in the reticular groove, the reticulo-ruminal fold, the dorsal and ventral sacs of the rumen and the omasal canal.3. The mean conduction velocity (C.V.) for twenty-seven units was 12.4 +/- 1.0 m/sec (S.E.). For units with a pathway in the dorsal vagal trunk, the mean C.V. was 14.5 +/- 1.0 m/sec (S.E.) and for units with a pathway in the ventral vagal trunk the mean C.V. was 6.6 +/- 0.5 m/sec (S.E.).4. From the receptors a slowly adapting response was elicited by tangential lengthening. These were tension receptors in series with contractile elements, as they were excited by increased tensions developed both passively by inflation of the viscus and actively by muscular contractions.5. Receptors in the reticulum and the rumen appeared to be situated deep in the muscle layers, whereas those in the reticular groove structures seemed to be more superficial and gave the in series tension receptor response as well as a response to light pressure.6. A resting discharge in tension receptor units was usually absent at low levels of distension but appeared and increased as the level of distension was raised. Intermittency and fluctuations in the resting discharge were related to intrinsic local movement involving the receptive fields. Increasing distension enhanced the intrinsic movements.7. Even after the removal of the abomasum, reticular and ruminal (primary cycle) movements were evoked by distending the reticulum. It is possible that this manoeuvre enhanced intrinsic movements, which, in turn, caused an increased excitatory afferent input to the ;gastric centres' from in series reticular tension receptors.8. The enhanced afferent discharge from reticular tension receptors elicited by an isometrically recorded reticular contraction reflexly inhibited the subsequent (primary cycle) contraction of the rumen.9. Very few receptors were located in the caudal regions of the rumen whereas the cranial sac is richly supplied with tension receptors. The idea that the cranial sac may serve as the reflexogenic zone for secondary cycle movements of the rumen is discussed.

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.

Factors affecting the voluntary intake of food by cows. 8. Experiments with ground, pelleted roughages.

1. Two experiments were conducted to examine the effect of grinding and pelleting roughages on the voluntary intake of food, digestibility, time of retention of food in the digestive tract, amounts of digesta in the recitulo-rumen and eating and ruminating behaviour of adult, non-lactating, non-pregnant cows. The first experiment was with artificially dried grass and the second with oat straw; also, with a diet of ground, pelleted oat straw the effect was studied of giving a daily intraruminal infusion of 150 g urea. The size of the particles of the ground roughages are given. 2. The mean voluntary intakes of long and ground dried grass were similar, the voluntary intake of ground, pelleted oat straw was 26% greater than that of long straw and the daily infusion of urea increased the voluntary intake of ground, pelleted oat straw by 53%. 3. The digestibility of the ground roughages was lower than that of the long roughages, the lower digestibility of the ground roughages was due mainly to the poor digestibility of crude fibre in the reticulo-rumen. The rate of disappearance of cotton thread placed in the ventral sac of the rumen was slower with ground than with long roughages. 4. The mean times of retention of ground roughages were shorter than those of long roughages when equal and restricted amounts of each food were given; with food offered ad lib. there was little difference between the mean times of retention of long and ground roughages in the alimentary tract. 5. On average, the mean amounts of digesta dry matter in the reticulo-rumen immediately after a meal were about the same with long and ground dried grass, with long and ground oat straw the amounts of dry matter were similar, but when the intraruminal infusion of urea was given the amount of dry matter increased by 49%. 6. The rate of eating (min/kg food) ground, pelleted roughages was much faster than that with long roughages; when the cows received ground roughage rumination did not occur but during short periods triple reticular contractions were seen. 7. The relationship between the voluntary intake of food, the amount of digesta in the reticulo-rumen and the rate of disappearance of digesta from the alimentary tract is discussed.

ERUCTATION, REGURGITATION, AND RETICULORUMINAL CONTRACTION IN THE AMERICAN BISON.

Simultaneous pressure changes in four compartments of the reticulorumen of two young, female bison prepared with rumen fistulas were recorded during eating, ruminating, resting, and insufflation with nitrogen gas. Frequency, magnitude, and duration of contractions were measured in a series of 26 experiments during which the bison were tied in a stanchion. From these measurements it was concluded that reticuloruminal motility of American bison is similar to that of domestic cattle. Eructation occurred almost always during contraction of the posterior dorsal blind and dorsal sacs of the rumen. The frequency of eructation was similar to that which was reported previously in cattle and white-tailed deer. During rumination there was an extra reticular contraction during which regurgitation occurred.

The nervous control of the ruminant stomach. II. Movements of the partially exteriorized reticulum and rumen of a sheep.

Abstract Extract Successive sequences in the film showed: Diphasic contractions of the partially exteriorized reticulum of a sheep whilst eating. These normally recur in intervals of up to 120 sec. In the film the interval was 20 sec. The triphasic form of reticulum contractions during rumination. The first phase of the contraction is followed by the inspiratory movement which in turn is succeeded by the regurgitation of the bolus to be masticated. The otherphases of the contraction appear to correspond to normal diphasic reticulum contraction. After the mastication movements commence, the more liquid part of the bolus is swallowed. In the film, these events were emphasized by close-up and slow-motion sequences which showed in more detail the contractions of the reticulum, the inspiratory movement and cervical oesophageal movements during rumination. The two types of sequences of reticulum and rumen during fasting and feeding.

The production of rumen and reticulum contractions in decerebrate preparations of sheep and goats.

The production of rumen and reticulum contractions in decerebrate preparations of sheep and goats.