A radiological study of gastric (abomasal) emptying in calves before and after vagotomy

Factors Affecting the Welfare of Unweaned Dairy Calves Destined for Early Slaughter and Abattoir Animal-Based Indicators Reflecting Their Welfare On-Farm

In many dairy industries, but particularly those that are pasture-based and have seasonal calving, "surplus calves," which are mostly male, are killed at a young age because they are of low value and it is not economically viable to raise them. Such calves are either killed on farm soon after birth or sent for slaughter at an abattoir. In countries where calves are sent for slaughter the age ranges from 3-4 days (New Zealand and Australia; "bobby calves") to 3-4 weeks (e.g., Ireland); they are not weaned. All calves are at the greatest risk of death in the 1st month of life but when combined with their low value, this makes surplus calves destined for early slaughter (i.e., <1 month of age) particularly vulnerable to poor welfare while on-farm. The welfare of these calves may also be compromised during transport and transit through markets and at the abattoir. There is growing recognition that feedback to farmers of results from animal-based indicators (ABI) of welfare (including health) collected prior to and after slaughter can protect animal welfare. Hence, the risk factors for poor on-farm, in-transit and at-abattoir calf welfare combined with an ante and post mortem (AM/PM) welfare assessment scheme specific to calves <1 month of age are outlined. This scheme would also provide an evidence base with which to identify farms on which such animals are more at risk of poor welfare. The following ABIs, at individual or batch level, are proposed: AM indicators include assessment of age (umbilical maturity), nutritional status (body condition, dehydration), behavioral status (general demeanor, posture, able to and stability while standing and moving, shivering, vocalizations, oral behaviors/cross-sucking, fearfulness, playing), and evidence of disease processes (locomotory ability [lameness], cleanliness/fecal soiling [scour], injuries hairless patches, swellings, wounds], dyspnoea/coughing, nasal/ocular discharge, navel swelling/discharge); PM measures include assessment of feeding adequacy (abomasal contents, milk in rumen, visceral fat reserves) and evidence of disease processes (omphalitis, GIT disorders, peritonitis, abscesses [internal and external], arthritis, septicaemia, and pneumonia). Based on similar models in other species, this information can be used in a positive feedback loop not only to protect and improve calf welfare but also to inform on-farm calf welfare management plans, support industry claims regarding animal welfare and benchmark welfare performance nationally and internationally.

IMAGING DIAGNOSIS-TRAUMATIC ABOMASITIS CAUSED BY FOREIGN BODIES IN A COW

A 2-year-old Holstein cow presented with a history of colic signs of 3 days' duration that had not responded to routine medical therapy. Physical examination findings were consistent with tachycardia and colic. Ultrasonographic examination of the abomasum revealed a thin hyperechoic line producing a cone shadow. Radiography of the cranial abdomen revealed two radiopaque objects within the abomasum. Right paracostal laparotomy and abomasotomy permitted palpation and manual removal of two metallic foreign bodies and a small quantity of gravel. The animal recovered well after surgery and no signs of colic were observed. Her appetite and rumination were also improved.

Pre-slaughter mortality and post-slaughter wastage in bobby veal calves at a slaughter premises in New Zealand

AIMS

To determine the reasons for pre-slaughter mortality and post-slaughter wastage in New Zealand bobby veal calves, and to assess compliance with the national animal welfare codes at a slaughter premises in New Zealand.

METHODS

The study was conducted at a single slaughter premises in Southland, New Zealand, during the 2011 bobby veal processing season. Calves that died during the pre-slaughter period underwent post-mortem examination to identify the reasons for death and notable secondary findings. Data from calves condemned at official post-mortem meat inspection were also analysed.

RESULTS

The mortality risk in the pre-slaughter period was 0.7% (288/42,494) and post-slaughter condemnation losses were 0.4% (180/42,206), resulting in a total loss to food production of 1.1%. Of the calves that were examined after dying in the pre-slaughter period (n=247), digestive tract disorders (41%) and omphalitis (23%) were the most common primary diagnoses. Secondary findings in these calves included absence of curd in the abomasum (25%), immaturity (21%) and emaciation (9%). Omphalitis (54%) and septicaemia (37%) were the most common causes of post-mortem wastage.

CONCLUSIONS AND CLINICAL RELEVANCE

Digestive tract disorders, omphalitis and septicaemia were the most common reasons for pre-slaughter mortality and post-mortem wastage. Further investigation of pre-transportation husbandry and feeding practices is indicated to determine compliance with animal welfare codes by farmers that supplied calves that had no curd in the abomasum, or were immature or emaciated on arrival at the slaughter premises.

Electrical bioimpedance and other techniques for gastric emptying and motility evaluation

The aim of this article is to identify non-invasive, inexpensive, highly sensitive and accurate techniques for evaluating and diagnosing gastric diseases. In the case of the stomach, there are highly sensitive and specific methods for assessing gastric motility and emptying (GME). However, these methods are invasive, expensive and/or not technically feasible for all clinicians and patients. We present a summary of the most relevant international information on non-invasive methods and techniques for clinically evaluating GME. We particularly emphasize the potential of gastric electrical bioimpedance (EBI). EBI was initially used mainly in gastric emptying studies and was essentially abandoned in favor of techniques such as electrogastrography and the gold standard, scintigraphy. The current research evaluating the utility of gastric EBI either combines this technique with other frequently used techniques or uses new methods for gastric EBI signal analysis. In this context, we discuss our results and those of other researchers who have worked with gastric EBI. In this review article, we present the following topics: (1) a description of the oldest methods and procedures for evaluating GME; (2) an explanation of the methods currently used to evaluate gastric activity; and (3) a perspective on the newest trends and techniques in clinical and research GME methods. We conclude that gastric EBI is a highly effective non-invasive, easy to use and inexpensive technique for assessing GME.

A mechanism of excessive accumulation of abomasal gas in vagotomized cattle determined using fluoroscopy

To better understand the mechanism of excessive gas accumulation in the abomasum in bovine abomasal displacement, we performed gastric fluoroscopy in vagotomized cattle. Fifteen 6-month-old Holstein steers were divided into three groups: a non-vagotomized control group (Group C; n=5), a ventral thoraco-vagotomized group (Group V; n=5), and a dorsal and ventral thoraco-vagotomized group (Group DV; n=5). These groups were examined by fluoroscopy before and during a 5-week observation period after surgery. In Group C, no change was observed throughout the observation period. In Group DV, immediately after surgery, reticuloruminal motility was completely absent and ruminal distention was seen. Two weeks after surgery, abnormal reticulum motility and increased gas accumulation in the abomasal body were noted. Abomasal dilatation was also observed. In Group V, 1 week after surgery, gas inflow into the abomasum and relatively normal reticulum motility were observed along with a rapid increase in abomasal gas. Abomasal dilatation was also observed. In addition, left-displaced abomasum occurred in one of the steers in this group. From these results, we concluded that one of the mechanisms of excessive gas accumulation in the abomasum is reticulum-mediated gas inflow from the rumen combined with vagotomy-induced hypomotility.

Digestive processes in ruminal drinkers characterized by means of the acetaminophen absorption test

The aim of the present study was to measure transit patterns of nutrients and the absorptive ability in ruminal drinkers (RDs) compared with healthy unweaned calves. The acetaminophen (paracetamol) absorption test was used to characterize the oroduodenal transit rate. Clinical examination and the analysis of various blood parameters provided supplementary information on digestive processes. Three unweaned bucket-fed calves (one RD and two healthy controls) each from seven Swiss dairy farms were included in the study. Measurements (tests 1 and 2) were performed twice at an interval of 10 days. Between tests, the feeding technique of the RDs and one control calf per farm was changed to feeding with a nipple instead of by bucket (without nipple). Acetaminophen appearance in the blood was delayed and reduced in RDs compared with the controls. Acid-base metabolism and several haematological and metabolic parameters differed markedly between RDs and healthy controls. The characteristics of the oroduodenal transit rate, absorptive abilities and clinical status in RDs were nearly normalised within 10 days of reconditioning.

Intrinsic neuronal control of the pyloric sphincter of the lamb

To better understand the local neuronal network of the gastro-duodenal junction in ruminants, we identified the components of the enteric nervous system (ENS) innervating the pyloric sphincter (PS) of the lamb abomasum. The neurons were labelled after injecting the tracer Fast Blue (FB) into the wall of the PS, and the phenotype of the FB-labelled neurons was immunohistochemically investigated using antibodies against nitric oxide synthase (NOS), choline acetyltransferase (ChAT), tachykinin (substance P) and tyrosine hydroxylase (TH). The FB-labelled abomasal myenteric plexus (MP) neurons, observed up to 14cm from the PS, were NOS-immunoreactive (IR) (82+/-12%), ChAT-IR (51+/-29%), SP-IR (61+/-33%), and also TH-IR (2%). The descending nitrergic neurons were also SP-IR (64%) and ChAT-IR (21%); the cholinergic descending neurons were SP-IR (3%). The FB-labelled duodenal neurons were located only in the MP, up to 8cm from the sphincter and were ChAT-IR (79+/-16%), SP-IR (32+/-18%), NOS-IR (from 0 to 2%), and also TH-IR (4+/-3%). The cholinergic ascending neurons were also SP-IR (60%) whereas no ChAT-IR cells were NOS-IR. The findings of this research indicate that the sheep PS is innervated by long-projecting neurons of the abomasal and duodenal ENS.

Characteristics of Acetaminophen Absorption in Healthy Unweaned Calves as an Indirect Measurement of the Oroduodenal Transit Rate of Liquid Meals

Abomasal emptying plays an important role in the incidence of digestive problems in calves. Our aim was to evaluate the acetaminophen absorption test (APAT) for characterization of the oroduodenal transit (ODT) of liquid meals in unweaned calves. Six healthy, unweaned Simmental x Red Holstein crossbred calves were involved in the project. The study was performed in three blocks at 3, 6 and 9 weeks of the calves' age. Within blocks, APAT was performed twice at an interval of at least 24 h. Once per each block, liquid transit was carried out with non-coagulating electrolyte solution (NES). The second test within a block was performed either while atropine sulphate was administered (block I), or by feeding a coagulating milk replacer (block II), or by administration of NES by ruminal tube (block III). Data were compared within and among blocks. Significant differences of several APAT traits were present for the different types of feeding, the different types of meals, the administration of atropine sulphate and the different ages of the calves. The emptying index T(max)/C(max) was suggested to be a valuable kinetic parameter for the characterization of ODT in these calves. We conclude that APAT represents a valid technique for characterization of ODT of liquid meals in healthy unweaned calves and may be a valuable tool for the evaluation of the reticular groove mechanism, the abomasal emptying and the absorption capacity of the duodenum.

Ultrasonographic measurement of abomasal volume, location, and emptying rate in calves

OBJECTIVE

To develop and validate an ultrasonographic method for measuring abomasal volume, location, and emptying rate in suckling calves.

ANIMALS

9 male Holstein calves < 40 days of age.

PROCEDURE

Before and after calves were fed different volumes of milk replacer or 2 L of oral electrolyte solutions, ultrasonographic measurements of abomasal dimensions (width, length, and height) were obtained by applying a 3.5-MHz sector probe to the ventral aspect of the abdomen in the transverse and sagittal planes. Abomasal volume was calculated from the ultrasonographic measurements by modeling the abomasum as an ellipsoid and by use of a power exponential equation to calculate the half-time of abomasal emptying (t1/2).

RESULTS

Preprandial abomasal volume was 20 to 137 mL. All 3 abomasal dimensions increased during feeding and after suckling, and the abomasum was symmetrically located about the midline of the ventral aspect of the abdomen. Strong linear relationships were identified between ultrasonographic and suckled volumes, between ultrasonographic and scintigraphic heights, and between ultrasonographic and scintigraphic lengths. Ultrasonographic t1/2 was linearly related to scintigraphic t1/2; the latter is regarded as the gold standard measure of gastric emptying rate.

CONCLUSIONS AND CLINICAL RELEVANCE

Ultrasonographic evaluation of the abomasum appears to provide a practical, rapid, noninvasive, and accurate method for determination of abomasal volume, location, and emptying rate in suckling calves.

Determination of abomasal emptying rate in suckling calves by use of nuclear scintigraphy and acetaminophen absorption

OBJECTIVE

To develop nuclear scintigraphic and acetaminophen absorption methods for measuring abomasal emptying rate in suckling calves.

ANIMALS

9 male Holstein-Friesian calves < 30 days old.

PROCEDURE

Calves were fed 2 L of milk replacer, fresh cow's milk, or an isoosmotic (150mM) solution of NaCl, NaHCO3, or sodium acetate containing technetium TC 99m-diethylenetriamine-pentaacetic acid (370 MBq) and acetaminophen (50 mg/kg). Right lateral scintigraphic images and venous blood samples were obtained periodically after feeding. Two power exponential equations were fitted to the scintigraphic data, and 3 pharmacokinetic models were fitted to the acetaminophen concentration-time data.

RESULTS

Data from 32 feedings were analyzed, with half emptying time for scintigraphic evaluation ranging from 29 to 202 minutes. Siegel's modified power exponential equation provided a better description of the scintigraphic data than did Elashoff's power exponential equation. The first derivative of Siegel's modified power exponential formula provided the best pharmacokinetic model for the acetaminophen absorption data. Time to maximal acetaminophen concentration (Tmax) provided the most accurate index of abomasal emptying rate from the acetaminophen concentration-time data.

CONCLUSIONS AND CLINICAL RELEVANCE

Abomasal emptying rate is best determined in healthy suckling calves by use of Siegel's modified power exponential equation to model the scintigraphic data. Pharmacokinetic calculation of Tmax from the acetaminophen absorption curve provides an alternative method for determining abomasal emptying rate in healthy suckling calves that is accurate, inexpensive, practical, and safe. However, it is unclear whether diarrhea would alter the acetaminophen absorption curve in calves.

Modifiers of gastrointestinal motility of cattle

Little clinically relevant, evidence-based data about the effect of motility modifiers on the GI tract of cattle are currently available. Additionally, some of the published results seem to be contradictory. Three main facts explain this apparent discrepancy: (1) Results may not be transferred from one species to another, because presence, concentration, location, distribution, and function of specific receptors may differ significantly among species. (2) The lack of a significant effect on smooth muscle preparations in vitro does not necessarily exclude a certain drug's motility-modifying property on affected animals in vivo. Certain drugs bind to receptors outside the myenteric plexus. Others, such as lidocaine and adrenergic-, dopaminergic-, and opioid-antagonists increase only GI motility, if inhibitory reflexes or a hyperactive state of the inhibitory sympathetic nervous system preexists. (3) Effects of motility modifiers as found in healthy experimental animals in vivo may not be similar to those found in spontaneously diseased animals. Accurate and reliable data on the effect of modifiers of GI motility of cattle will be obtained only from double-blinded, evidence-based, in vivo studies on spontaneously affected animals. Because well-documented results from such studies are extremely rare, intensive research in this field is warranted in the future.

Cholinergic and noncholinergic innervation of the smooth muscle layers in the bovine abomasum

The intrinsic innervation of muscle layers in the mammalian gastrointestinal tract has been mainly studied in nonruminants. The aim of this study was to identify intrinsic motor neurones in the bovine abomasum that innervate the circular and longitudinal muscles. Circular (CMN) and longitudinal muscle motor neurones (LMN) were selectively labeled by application of the retrograde tracer 1,1'-didodecyl-3,3,3',3'-tetramethyl indocarbocyanine perchlorate (DiI) onto the muscle layers. The transmitter phenotype was determined by immunohistochemical detection of choline acetyltransferase (ChAT), nitric oxide synthase (NOS), and neurone-specific enolase (NSE). On average, the myenteric ganglia contained 61 +/- 19 NSE-positive cell bodies, of which 89% were ChAT-positive and 10% were NOS-positive. Only 0.7% of NSE-positive neurones (41 of 5,777) contained both ChAT and NOS. Application of DiI onto the circular and longitudinal muscles revealed on average 60 +/- 27 (n = 4) and 68 +/- 36 (n = 4), respectively, labeled cell bodies in the myenteric plexus. For the circular and longitudinal muscles the proportions of ascending to descending neurones were 76 : 24% and 54 : 46%, respectively. While most ascending CMN were ChAT-positive (96%), 51% of the descending CMN were ChAT-negative. All ascending and 95% of descending LMN were ChAT-positive. It was concluded that cholinergic excitatory innervation is predominant in both muscle layers of the abomasum. Whereas the circular muscle receives cholinergic excitatory and nitrergic inhibitory innervation, the longitudinal muscle is only innervated by cholinergic pathways. This innervation pattern is different from that in gastric muscle layers in monogastric animals.

An immunohistochemical study of endocrine cells in the abomasum of vagotomized calf

The effect of thoraco-vagotomy on the distribution and frequency of chromogranin-, serotonin-, somatostatin- and gastrin-immunoreactive cells in the abomasum of the calf were investigated by immunohistochemistry. Calves were vagotomized at 1 week old and sampled 2 and 4 weeks later. The endocrine cells generally decreased in number in vagotomized calves as compared to non-operated control calves. However, the detailed responses of endocrine cells to vagotomy varied depending on the endocrine cell type, region of gastric mucosa, and period after vagotomy. The present result suggests that the vagus nerve has an influence on the intrinsic regulatory system by endocrine cell control in the ruminant abomasum.

The effects of vagotomy on the abomasum in calves: radiography and protein gene product 9.5 immunohistochemistry

Abomasal disorders of calves with total vagotomy, operated on at 1 week old, were investigated with radiography and protein gene product (PGP) 9.5 immunohistochemistry. Radiographic findings indicated abomasal atony with dilatation in all calves 2 weeks after vagotomy, while 4 weeks after vagotomy abomasal dilatation was detected in 2 calves and another 2 calves showed dilatation and impaction. The densities of PGP 9.5-immunoreactive nerves in the tunica muscularis decreased significantly in the corpus region of the greater curvature 2 weeks after vagotomy and in the pyloric region of the lesser curvature 4 weeks after vagotomy, and it was at its lowest 4 weeks after vagotomy in all regions examined. In conclusion, abomasal dilatation and/or impaction in vagotomized calves confirmed by radiography were related with a decreased frequency of nerves in the tunica muscularis of the abomasum.

The effects of age, weaning, drench volume and yarding on ruminoreticulum bypass in sheep, with reference to the anthelmintic efficacy of benzimidazole drenches

AIMS

To determine the incidence of ruminoreticulum bypass in lambs before and after weaning, following drenching with anthelmintic-equivalent volumes of fluid; to investigate the influence of withholding feed for 24 hours before drenching on the incidence of ruminoreticulum bypass; and to investigate the hypothesis that ruminoreticulum bypass occurs more frequently following drenching with large than with low volumes. The relationship between these factors and the efficacy of benzimidazole anthelmintic drenches has been widely promoted in New Zealand and Australia.

METHODS

Video-taped fluoroscopy, using barium sulphate suspension with a specific gravity of 1.38 as a contrast medium, was used to study closure of the reticular groove and ruminoreticulum bypass in sheep.

RESULTS

When lambs were drenched with 3 ml of barium sulphate suspension/10 kg liveweight soon after removal from pasture, ruminoreticulum bypass only occurred before weaning and during the first 8 weeks after weaning. However, when a low volume drench (1 ml/10 kg) was used in lambs soon after removal from pasture during the same period, ruminoreticulum bypass was not observed. When recently weaned lambs were yarded for 24 hours before drenching with barium sulphate suspension, substantial (> or = 20%) ruminoreticulum bypass occurred in 25-58% of the animals. When 8-9 month-old hoggets were yarded for 24 hours before drenching, substantial ruminoreticulum bypass occurred in 35% of the animals. Ruminoreticulum bypass was not observed in the same group of hoggets when drenched soon after removal from pasture, in a reversed crossover experiment. This effect of withholding feed for 24 hours on ruminoreticulum bypass was significant (p < 0.0001). In hoggets which had been yarded for 24 hours before drenching with barium sulphate suspension, the incidence of ruminoreticulum bypass was significantly lower (p = 0.0026) following the use of a low volume (1 ml/10 kg) when compared to high volume (3 ml/ 10 kg) of drench. Thus, the effect of withholding feed for 24 hours on ruminoreticulum bypass was largely overcome when the low volume drench was used.

CONCLUSIONS

These results support the use of low volume formulations of benzimidazole drenches for New Zealand pasture-fed lambs less than 6 months old. The results indicate that, in order to obtain the optimum efficacy of benzimidazole anthelmintics in New Zealand pasture-fed sheep, which have been yarded for 24 hours, low volume drench formulations should be used.

Surgery of the bovine abomasum

Intensive management of cattle has resulted in an increased incidence of abomasal disorders. Many of these disorders require surgical intervention for the best outcome. This article reviews the anatomy and physiology of the abomasum, abomasal disorders that may be treated by surgery, and the advantages and disadvantages of various surgical approaches to those disorders.

Gastric and intestinal release of vasoactive intestinal polypeptide in the milk-fed lamb

Vasoactive intestinal polypeptide (VIP) has been proposed as the neurotransmitter of the atropine-resistant relaxation of gastric structures in the lamb. To examine this proposal VIP concentrations in plasma from arterial, gastric venous and intestinal venous blood were measured in healthy conscious lambs before, during and after teasing with, and sucking of milk. Basal arterial plasma VIP concentrations were undetectable (less than 3 pmol/l) and remained so during and after feeding. Before feeding VIP was detected in only 2 of 12 gastric venous plasma samples (5 and 13 pmol/l). During teasing with food there were increments in VIP of 19 +/- 4 pmol/l and during feeding of 27 +/- 5 pmol/l. VIP concentration in gastric venous plasma rapidly returned to fasting levels after cessation of sucking. In contrast VIP in the intestinal venous plasma did not rise during teasing or upon commencement of sucking but a peak increment of 34 +/- 6 pmol/l occurred at 5 min after cessation of feeding. The results are consistent with the hypotheses that VIP is released in anticipation of and during sucking from inhibitory neurones involved in relaxation of gastric structures and that intestinal release of VIP is a consequence of entry of digesta into the small intestine.

Intestinal control of gastric function in the calf: the relationship of neural and endocrine factors

1. Gastric emptying and secretion were measured in conscious calves during alkaline or acid perfusion of the duodenum with simultaneous assessment of endogenous plasma somatostatin, gastrin and blood 5-hydroxytryptamine (5-HT).2. Alkaline duodenal perfusion (isotonic NaHCO(3)) caused rapid gastric emptying and increased gastric acid secretion without any affect on basal levels of somatostatin, 5-HT or gastrin.3. Duodenal perfusion of 60 mm-HCl caused complete inhibition of gastric emptying, reduced gastric acid secretion considerably, and an associated elevation of somatostatin basal levels from 123.8 +/- 11.2 to 281.9 +/- 23.0 pg/ml. (P < 0.01) occurred.4. These effects of duodenal perfusion were unimpaired by bilateral lumbar splanchnectomy.5. On bilateral cervical vagotomy of the splanchnectomized calves, the inhibition of gastric function evoked by duodenal acidification persisted, and plasma somatostatin showed a further significant elevation to 506.9 +/- 49.9 pg/ml. (P < 0.01) but gastrin and 5-HT remained unchanged. The increased gastric function caused by alkaline duodenal function was significantly reduced following vagotomy but basal somatostatin, gastrin and 5-HT in the blood remained unaffected.6. These results suggest that the stimulatory effect on gastric emptying and acid secretion of isotonic NaHCO(3) in the duodenum may be mediated, partially at least, through the vagal nerves but not the splanchnics.7. The complete inhibition of gastric function which ensued on acidification of the duodenum and which continues after splanchnovagotomy, is not mediated by the autonomic nervous system. This inhibitory process appears to involve the endocrine system only, with somatostatin (but not gastrin or 5-HT) fulfilling a main enterogastrone role.

Oesophageal and diaphragmatic activity during sucking in lambs

1. Buccal, pharyngeal, oesophageal and diaphragmatic movements during swallowing of saliva and sucking from a bottle were studied in lambs by recording electromyograms (e.m.g.s) from the mylohyoid, thyrohyoid and thyroarytenoid muscles, cervical and caudal thoracic oesophagus and vertebral and costal regions of the diaphragm. Buccal and pleural pressure recordings were also made.2. Swallows of saliva characteristically involved contraction of the mylohyoid followed sequentially by contraction of the thyrohyoid, cervical, and finally, caudal thoracic oesophagus.3. Sucking (indicated by the mylohyoid e.m.g.s and buccal pressure) was initially at rates up to 6 sec(-1), sustained at up to 4 sec(-1) for 30-45 sec and, once established, accompanied by swallows in a 1:1 association with sucking.4. Respiration ceased during the pharyngeal phase of swallowing. At the time the primary contraction (of swallowing) involved the caudal thoracic oesophagus vertebral fibres of the diaphragm forming the hiatus oesophageus became quiescent, although costal fibres continued to contribute to inspiration.5. During sucking, respiration was shallow and rapid, with diaphragm contractions sandwiched between swallows.6. Towards the end of an episode of sucking, contractions of the diaphragm became more intense and occurred in groups with pressure changes corresponding to both individual contractions and the grouped activity.7. Primary oesophageal contractions occurred only after single swallows or at the end of a series of swallows.8. During periods when sucking and swallowing were frequent, short episodes of oesophageal contraction occurred, each being between thyrohyoid contractions.9. Recording from contiguous sites of the caudal thoracic oesophagus confirmed a caudally progressive character of those short contractions of the oesophagus observed during sucking.10. Factors contributing to these changes in oesophageal activity and consequences of altered diaphragmatic activity in sucking have been discussed.

The effect of duodenal infusion of milk, casein, lactose and fat on gastric emptying and acid secretion in the milk-fed calf

1. The effect of infusion of the duodenum with milk, casein, lactose and fat on gastric acid secretion and abnormal emptying of a saline meal was studied in milk-fed calves. 2. Compared with sodium bicarbonate, infusion with casein or lactose, alone or together, caused a small but statistically significant slowing of gastric emptying but did not effect gastric acid secretion. 3. Infection of the duodenum with cows' milk replacer or bovine milk fat slowed gastric emptying markedly and reduced gastric acid secretion significantly below levels obtained with sodium bicarbonate infusion. 4. The experiments provide evidence for the existence of mechanisms which prevent the passage of substantial amounts of whole milk into the duodenum before it has been subjected to gastric digestion.