Occurrence

LDA occurs most commonly in large, high-producing adult dairy cows immediately after parturition. Approximately 90% of cases occur within 6 weeks following parturition. Occasional cases occur a few to several weeks before parturition. The disease is common in the UK and North America, where dairy cattle are fed grain for high milk production and the animals are usually housed for part of the year or kept under confinement (zero grazing, loose housing). The disease is uncommon in Australia and New Zealand, where much less concentrate is fed to dairy cattle and the animals are usually on pasture for most of the year. However, it can occur in pasture-fed dairy cattle.² The importance of exercise in the etiology of LDA has not been explored. The incidence of LDA is higher during the winter months, which may be a reflection of either a higher frequency of calving or relative inactivity.

Risk factors

Economic importance and effects on production and survivorship

The economic losses from the disease include lost milk production during the illness and postoperatively, and the cost of the surgery. The effects of LDA on test-day milk yields from 12 572 cows from parities 1–6 over a 2-year period were evaluated.¹⁶ From calving to 60 days after diagnosis, cows with LDA yielded on average 557 kg less milk than cows without LDA and 30% of the losses occurred before diagnosis.¹⁶ Milk loss increased with parity and productivity and milk losses were greatest in highest-yielding cows. Cows with LDA were nearly twice as likely to have another disease as were cows without LDA. Cows with LDA are more likely to be removed from the herd at any point in time after the diagnosis than their herdmates.¹⁷ Cows with LDA survived a median of 18 months, and control cows survived a median of 27 months. Low milk production is a common reason for removal of cows with an LDA and the probability of removal increased as lactation number increased.

Abomasal luminal gas pressure, volume and perfusion in cows with LDA or abomasal volvulus

The luminal pressure in LDA is increased (median 8.7 mmHg; range 3.5–20.7 mmHg),²² which may contribute to the pathogenesis of abomasal ulceration. Abomasal luminal pressure and volume is higher in cattle with an abomasal volvulus than in cattle with an LDA.²³ Abomasal perfusion decreases as luminal pressure increases in cattle with an abomasal volvulus or LDA.

Perforating abomasal ulceration

Perforating abomasal ulceration and acute local peritonitis with fibrinous adhesions also occur in some cases of LDA.²⁴ Abdominal pain and pneumoperitoneum are common sequelae. The ulcers may perforate acutely and cause rapid death due to acute diffuse peritonitis. Duodenal ulceration has also been associated with LDA.

General appearance and ketosis

Usually within a few days or a week following parturition there will be inappetence, sometimes almost complete anorexia, a marked drop in milk production and varying degrees of ketosis, based on ketonuria and other clinical findings of ketosis. It is not uncommon to diagnose an LDA that was treated for ketosis, improved for a few days and then relapsed.

On inspection of the abdomen, the left lateral abdomen appears ‘slab-sided’ because the rumen is smaller than normal and displaced medially. The temperature, heart rate and respirations are usually within normal ranges. The feces are usually reduced in volume and softer than normal but periods of profuse diarrhea may occur.

Status of reticulorumen and spontaneous abomasal sounds

Ruminal movements are commonly present but decreased in frequency and intensity, and sometimes inaudible even though there are movements of the left paralumbar fossa indicating rumen motility. In some cases, the rumen pack is palpable in the left paralumbar fossa, and the rumen contractions and sounds can be detected in the fossa as in normal cows. However, the rumen sounds may not be audible over an area anterior to the fossa where they are also audible in normal cows. The absence of normal ruminal sounds in the presence of abdominal ripples suggests the presence of an LDA.

Auscultation of an area below an imaginary line from the center of the left paralumbar fossa to just behind the left elbow reveals the presence of high-pitched tinkling sounds, which often have a progressive peristaltic character. These are abomasal sounds and may occur several times per minute or infrequently (as long as 5 min apart). They are not related in occurrence to ruminal movements and this can be ascertained by simultaneous auscultation over an area between the upper third of the ninth and 12th ribs and palpation of the left paralumbar fossa for movements of the dorsal sac of the rumen. While auscultating over the same area and ballotting the left lower abdomen just below the fossa, high-pitched fluid-splashing sounds of the LDA are commonly audible.

Pings of the left-side displacement of the abomasum

Percussion, using a flick of the finger or a plexor, and simultaneous auscultation over an area between the upper third of the ninth and 12th ribs of the abdominal wall commonly elicits the high-pitched tympanitic sounds (pings) that are characteristic of LDA. These pings may not be present if the cow has just previously been transported to a clinic for surgery but they will commonly reappear in 24–48 hours. Occasionally, careful, repeated, time-consuming examinations using percussion and simultaneous auscultation are necessary to elicit the pings.

Acute left-side displacement of the abomasum

In rare cases there is initially a sudden onset of anorexia accompanied by signs of moderate abdominal pain and abdominal distension. These are the acute cases, which are uncommon. An obvious bulge caused by the distended abomasum may develop in the anterior part of the upper left paralumbar fossa and this may extend up behind the costal arch almost to the top of the fossa. The swelling is tympanitic and gives a resonant note on percussion. In acute cases the temperature may rise to 39.5°C (103°F) and the heart rate to 100/min but in the more common subacute cases the temperature and pulse rate are normal. The appetite returns but is intermittent and selective, the animal eating only certain feeds, particularly hay. There may be transitory periods of improvement in appetite and disappearance of these sounds, especially after transport or vigorous exercise.

Concurrent perforating abomasal ulceration

Perforating abomasal ulceration occurs concurrently in some cases of LDA, resulting in localized peritonitis and pneumoperitoneum.²⁴ Affected cattle have the ping over the left abdomen typical of an LDA, but a ping over both the right and left paralumbar fossae due to pneumoperitoneum is also common. Abdominal pain due to the local peritonitis is characterized by tensing of the abdominal wall, grunting and arching of the back on deep palpation over the abomasal area. The peritonitis is associated with a fever. The prognosis in these cases is unfavorable.

Other clinical features

Hemogram

There are no marked changes in the hemogram unless there is intercurrent disease, particularly traumatic reticuloperitonitis or abomasal ulcer. A moderate to severe ketonuria is always present but the blood glucose level is within the normal range. There is usually a mild hemoconcentration evidenced by elevations of the packed cell volume (PCV), hemoglobin and total serum protein. A mild metabolic alkalosis with slight hypochloremia and hypokalemia may also be present.

Serum biochemistry

Ketosis is the most common complication of LDA and severe cases of ketosis are commonly accompanied by fatty liver. The blood levels of AST and beta-hydroxybutyrate can be measured in dairy cows during the first and second weeks after parturition as possible tests to predict the subsequent diagnosis of LDA.¹⁴ AST values between 100–180 U/L and beta-hydroxybutyrate values between 1000–1600 μmol/L were associated with increased odds ratio and likelihood ratio of LDA.

In cows with fatty liver, plasmal lipoprotein concentrations are decreased. In addition to those of lipoprotein lipids, concentrations of apolipoprotein B-100 (apo-100), the major apoprotein in very low-density lipoproteins and low-density lipoproteins, and apolipoprotein A-1 (apoA-1), the predominant protein constituent of high-density lipoprotein, also are reduced in cows with fatty liver. Decreased serum levels of apo-100 and apoA-I occur in cows with ketosis and LDA and may be used during the stages of nonlactation and early lactation to predict cows susceptible to ketosis and LDA.²⁷ Dairy cows with LDA also have low plasma and liver α-tocopherol, and plasma vitamin E values may decrease in cows with increased liver triglyceride content.²⁸

A mild hypocalcemia is usually present but parturient hypocalcemia is uncommon.

Cowside tests of milk and urinary ketones

Milk ketone tests can also be used as predictors of LDA in dairy cows within 2 weeks of parturition.⁴ In the first week of lactation, the Pink test liquid and the Ketolac test strip were highly sensitive for the detection of subclinical ketosis when used in milk.²⁹ The Ketotest (a milk beta-hydroxybutyrate test strip) is also highly sensitive for the detection of subclinical ketosis.³⁰

Urine ketones: the Ketostix (urine nitroprusside strip detecting acetoacetate) can be used on a regular basis to detect subclinical ketosis.³⁰

Metabolic predictors of left side displacement of abomasum

Metabolic tests to predict the occurrence of LDA can be used strategically in the last week prepartum and the first week postpartum¹² (details under Metabolic predictors of left side displacement of abomasum, in Animal risk factors, under Epidemiology, above).

Liver function

Cows with LDA may have varying degrees of fatty liver.^31,32 In liver biopsy samples, more about 55% of cows with LDA, fatty degeneration may be present.³¹ In some cows with LDA, liver biopsies found 31% fat infiltration and in those same animals, serum AST and gamma-glutamyl transferase levels were increased.³²

Abomasocentesis

Centesis of the displaced abomasum through the 10th or 11th intercostal space in the middle third of the abdominal wall may reveal the presence of fluid with no protozoa and a pH of 2. Ruminal fluid will have protozoa and a pH of between 6 and 7. Fluid is not always present in appreciable quantity in the abomasum and a negative result on puncture cannot be interpreted as eliminating the possibility of abomasal displacement.

Open surgical techniques

Right paramedian abomasopexy and right paralumbar fossa omentopexy are the most widely used means of correcting left displacement of the abomasum. The right paralumbar fossa omentopexy is popular because the animal is standing and the surgeon can work alone without assistance. More skill is required than for the right paramedian abomasopexy. The right paramedian abomasopexy requires less manipulation because the abomasum usually returns to its normal position when the cow is placed in dorsal recumbency. The major disadvantage is the number of people required to restrain the animal in dorsal recumbency. There is little difference in the cost of doing a right paramedian abomasopexy compared to a right paralumbar fossa omentopexy, of which there are modifications from the original description. Based on field studies there is also no difference in either the reproductive performance or incisional complications following surgery. Based on milk yield at 1 month after surgery, some results indicate a slight preference for a right paramedian abomasopexy.

Closed suture techniques

A few closed suturing abomasopexy techniques have been advocated because they are rapid and inexpensive but the complications that can occur indicate that laparotomy and omentopexy are desirable. In the blind suture technique, the precise location of insertion of the sutures is unknown. Complications include peritonitis, cellulitis, abomasal displacement or evisceration, complete forestomach obstruction and thrombophlebitis of the subcutaneous abdominal vein.

Survivorship following surgery to correct left-side displacement of the abomasum

In a series of 564 cases of displaced abomasum (466 LDA, 98 RDA), survival after surgery was evaluated after 10 days and 15 months.³⁴ More LDA than RDA cows were discharged as cured (82% vs 74%). However, survival after the early postsurgical period was similar for RDA and LDA cows. In LDA cows, the factors associated with a favorable prognosis were a short duration of disease, an undisturbed general condition, good appetite, normal feces, a higher body weight, lower hematocrit, hemoglobin and erythrocyte counts, lower urea, AST and bilirubin, and higher serum sodium, potassium and chloride concentrations compared with cows with an unfavorable prognosis.³⁴ A thorough clinical and laboratory examination with special emphasis on general physical condition, liver function and dehydration status are important in determining the prognosis of abdominal surgery in LDA.

Treatment of ketosis

Parenteral dextrose and oral propylene glycol are necessary for treatment of the ketosis and to avoid fatty liver as a complication. Postsurgical convalescence of cows with LDA is clearly related to disturbances in energy metabolism and fatty liver.³⁵ During convalescence, in cows with no fatty liver or moderate fatty liver, the feed intake and daily milk production increases steadily. In cows with severe fatty liver feed intake remains low. This emphasizes the need for effective treatment of excessive lipomobilization, ketosis and fatty liver along with surgical correction of the LDA. All cases of LDA should be corrected as soon as possible to minimize the incidence of peritoneal adhesions and abomasal ulcers, which may perforate and cause sudden death.

Rumen transfaunation following surgery for left-side displacement of the abomasum

The administration of 10 L of rumen fluid via a stomach tube immediately after surgical correction of an LDA, and on the next day, resulted in a beneficial effect characterized by a greater feed intake, less degree of ketonuria and higher milk yield compared to control cows given water.³⁶

Prepartum nutrition and management

Reduction of the incidence of LDA in a dairy herd can be achieved by optimal nutrition and management during the dry period.^6,38 The following principles are important:

Every effort should be made to minimize dietary alterations near parturition that could result in indigestion. The amount of grain and corn (maize) silage fed prepartum should be kept at a minimum, while other forages are fed ad libitum.

Several experiments have shown no response in production to feeding large quantities of grain or concentrates (lead feeding) before parturition when cows were in good condition at drying-off and were fed well following parturition. Consequently, there seems little reason to continue the practice of steaming-up cows before parturition.

Crude fiber intake

Ensuring an adequate intake of a high-fiber diet to dairy cows during the ‘far-off’ and ‘close-up’ periods in late pregnancy and the immediate ‘postfreshening’ period is of critical importance to the prevention of this disease.⁶ The high-fiber diet will physically expand the rumen and provide a barrier against abomasal migration.⁸ The basic principle is to maintain adequate ruminal filling before and after calving.³⁸ This requires careful analysis and implementation of the dry cow feeding program.⁶ Readers are referred to National Research Council, 2001 (see Review literature) for details on feeding programs for dairy cattle.

The emphasis in the dry cow feeding program must be on increasing dry matter intake, increasing particle length and effective fiber content of the ration. Feeding a high-roughage diet is consistent with one of the most commonly recommended and successful management strategies for minimizing LDA during the postparturient period. This means insuring adequate fiber content of at least 17%. An adequate level of fiber will also aid in the control of subacute ruminal acidosis, which may occur when dairy cows are fed grain in the latter part of the dry period in preparation for lactation.

Monensin in controlled-release capsule prepartum

Monensin is an ionophore antibiotic that alters volatile fatty acid production in the rumen in favor of propionate, which is a major precursor for glucose in the ruminant. A monensin controlled-release capsule is available as an aid in the prevention of subclinical ketosis in lactating dairy cattle. The device delivers 335 mg of monensin per day for 95 days. A monensin controlled-release capsule has been shown to decrease the incidence of subclinical ketosis, displaced abomasum and multiple illnesses when administered to dairy cows 3 weeks before calving.³⁹ It is likely that these effects on clinical health are mediated by improved energy balance in monensin-supplemented cows. There are improvements in energy indicators such as increased glucose and decreased beta-hydroxybutyrate after calving.

The administration of a monensin controlled-release capsule to cows 3 weeks prepartum significantly decreased NEFA and beta-hydroxybutyrate and significantly increased concentrations of serum cholesterol and urea in the week immediately precalving.³⁹ No effect of treatment was observed for calcium, phosphorus or glucose in the precalving period. After calving, concentrations of phosphorus were lower and beta-hydroxybutyrate tended to be lower, and cholesterol and urea were higher in monensin-treated cows. There was no effect of treatment on NEFA, glucose or calcium in the first week after calving. Monensin treatment administered precalving significantly improved indicators of energy balance in both the immediate precalving and postcalving periods. The prevalence of subclinical ketosis as measured by cowside tests was lower in monensin-treated cows. These findings indicate more effective energy metabolism in monensin-treated cows as they approach calving, which is important for the prevention of retained placenta, clinical ketosis and displaced abomasum. In general, a 40% reduction in both LDA and clinical ketosis can be expected with precalving administration of monensin controlled-release capsules.⁴⁰ In addition, a 25% decrease in retained placenta may occur.

Genetic selection

There is some evidence that LDA is a moderately heritable trait and that the incidence may be lowered by genetic selection.⁴¹ However, this has not been explored on a practical basis.

Occurrence and incidence

Risk factors

There is little information available on the epidemiology of right-side displacement of the abomasum and abomasal volvulus. Most of the risk factors described for LDA are relevant to RDA and abomasal volvulus. The feeding of high levels of grain to high-producing dairy cows in early lactation is considered to be a major risk factor. However, there are no good reliable data to support this cause-and-effect relationship. Why the disease occurs in a small percentage of high-producing dairy cattle being fed high-level grain rations is unknown.

When this disease was originally described, the incidence appeared to be higher in Scandinavian countries than elsewhere. The risk factors in those situations were not identified but it was thought that indoor winter feeding and the shift of the acid–base balance to an alkalotic state during the winter months might be important factors. In Denmark, the ingestion of large quantities of soil particles on unwashed root crops used as feed is considered to be significant. This may be the reason for the higher incidence of the disease in the later part of the winter. However, attempts to reproduce the condition by feeding large quantities of sand have been unsuccessful. Because atony is often associated with vagus indigestion, a relationship between the two has been suspected but there are usually no lesions affecting the reticulum or vagus nerves.

A hospital-based epidemiological study of the risk factors for abomasal volvulus and FDA was performed using the medical record abstracts derived from the veterinary teaching hospitals of 17 North American veterinary schools.² The risk for abomasal volvulus increased with increasing age, with a greater risk in dairy cows 4–7 years of age. Dairy cattle were at a much higher risk than beef cattle. Approximately 28% of cases of abomasal volvulus occurred within the first 2 weeks and 52% within 1 month following parturition. This indicates that proportionately fewer cases of abomasal volvulus than left displacement occur during the first 2 weeks following parturition. The hospital case fatality rate for abomasal volvulus and LDA was 23.5%, and 5.6%, respectively.²

It is suggested that abomasal atony is a prerequisite for the development of right-side displacement and abomasal volvulus, and that following parturition the abdominal void facilitates such development. The direction of the displacement could be influenced predominantly by the volume of the forestomach. Immediately after parturition, displacement occurs to the left because of a reduction in the size of the rumen volume. Several weeks later the dilated abomasum moves caudally and dorsally in the right abdomen because the volume of the forestomach is much larger thereby providing an effective barrier (rumen barrier).

Abomasal volvulus has also occurred following correction of LDA by casting and rolling.⁴

Dilatation and displacement phase

In RDA, abomasal atony occurs initially, resulting in the accumulation of fluid and gas in the viscus leading to gradual distension and displacement in a caudal direction on the right side (dilatation phase). During the dilatation phase, which commonly extends over several days, there is continuous secretion of hydrochloric acid, sodium chloride and potassium into the abomasum, which becomes gradually distended and does not evacuate its contents into the duodenum. This leads to dehydration and metabolic alkalosis with hypochloremia and hypokalemia. These changes are typical of a functional obstruction of the upper part of the intestinal tract and occur in experimental RDA and experimental obstruction of the duodenum in calves.

The abomasal luminal pressure in naturally occurring abomasal volvulus is increased (median 11.7 mmHg; range 4.1–32.4 mmHg).⁵ Increased luminal pressure in abomasal volvulus could cause mucosal injury by local vascular occlusion and affect the prognosis. Among cattle with abomasal volvulus, the abomasal luminal pressure was significantly higher in those that died or were sold following surgery (median 20.6 mmHg) than in cattle that recovered and were retained in the herd (median 11.0 mmHg). Calculation of likelihood ratios suggest that selecting cattle with a value of 16 mmHg for luminal pressure optimized the distribution of cattle into productive and nonproductive groups.

The abomasal luminal gas pressure and volume were higher in cattle with an abomasal volvulus than in cattle with an LDA.⁶ As luminal gas pressure increases, abomasal perfusion decreases, resulting in varying degrees of ischemia to the abomasal mucosa. In cows with an abomasal volvulus, lactate concentration in the gastroepiploic vein was greater than that in the jugular vein, whereas no difference in lactate concentrations was detected in cows with an LDA. This indicates that cattle with a large and tensely distended abomasum associated with a volvulus or LDA should have the viscus decompressed as soon as possible to minimize the potential for ischemia-induced injury to the abomasal mucosa, which may result in ulcers and perforations.

An experimental model of hypochloremic metabolic alkalosis by diversion of abomasal outflow in sheep has been described.^7,8 A similar model in adult lactating dairy cows resulted in weakness and depression in 10–12 hours, dehydration, hypochloremia, hypokalemia, hypocalcemia and a milk alkalosis.⁹

Up to 35 L of fluid may accumulate in the dilated abomasum of a mature 450 kg cow, resulting in dehydration, which will vary from 5–12% of body weight. In uncomplicated cases, there is only slight hemoconcentration and a mild electrolyte and acid–base imbalance, with moderate distension of the abomasum. These cases are reversible with fluid therapy. In complicated cases there is severe hemoconcentration, hypovolemia and dehydration¹⁰ and marked metabolic alkalosis with a severely distended abomasum. The degree of dehydration is a reliable preoperative prognostic aid. The hypovolemia, compression of the caudal vena cava and stimulation of the sympathetic nervous system in response to distension and twisting of the abomasum results in tachycardia, which is also a reliable preoperative prognostic aid.¹⁰

In cattle with severe and prolonged abomasal volvulus, a metabolic acidosis may develop and be superimposed on the metabolic alkalosis, leading to a low base excess concentration of extracellular fluid. In the experimental disease in sheep, the metabolic acidosis observed terminally was associated with an increase in plasma lactate concentration probably due to hypovolemic shock and anaerobic metabolism.⁷ These severe cases require surgery and intensive fluid therapy. A paradoxic aciduria may occur in cattle affected with metabolic alkalosis associated with abomasal disease. This may be due to the excretion of acid by the kidney in response to severe potassium depletion or to the excretion of acid metabolites as a result of starvation, dehydration and impaired renal function. In the experimental model in sheep, renal net acid excretion decreases and sodium excretion increases initially, followed by increased net acid excretion and decreased sodium excretion resulting in aciduria and marked sodium conservation.⁸

Volvulus phase

Following the dilatation and displacement phase, the distended abomasum may twist in a clockwise or anticlockwise (viewed from the right side) direction in a vertical plane around a horizontal axis passing transversely across the body in the vicinity of the omasoabomasal orifice. The volvulus will usually be of the order of 180–270° and causes a syndrome of acute obstruction with local circulatory impairment and ischemic necrosis of the abomasum. Detailed examinations of necropsy specimens of volvulus of the abomasum indicate that the displacements can occur in a dual axial system. One system relates to displacements of the abomasum on a pendulum model, the point of suspension being situated on the visceral surface of the liver and the arms consisting of parts of the digestive tract adjacent to the abomasum. The other system comprises axes centered on the abomasum, about which this organ is able to rotate without changing its position in the abdomen. A theoretical analysis of the types of displacement of the abomasum that can occur is described.

In some cases the abomasum and omasum are greatly distended and form a loop with the cranial part of the duodenum. This loop may twist up to 360° in a counterclockwise direction as viewed from the rear or from the right side of the cow. The reticulum is drawn caudally on the right side of the rumen by its attachment to the fundus of the abomasum. The probable mode of rotation is in a sagittal plane. Abomasal volvulus with involvement of the omasum and reticulum does occur but represents only about 5% of cases. Pressure and tension damage to the ventral vagal nerve trunk and to the blood vessels are in part responsible for the poor prognosis in severe cases, even after successful surgical correction.

There is speculation that violent exercise and transportation may be contributory factors in the pathogenesis of acute abomasal volvulus, which occurs occasionally in mature cows and young calves without a history of immediate previous illness associated with the dilatation phase. The metabolic changes that occur are similar to those described above.

Postsurgical complication in right-side displacement of the abomasum or abomasal volvulus

A vagus-indigestion-like syndrome may occur in cattle treated for RDA or abomasal volvulus.¹¹ Possible mechanisms include: vagus nerve injury, overstretching of the abomasal wall during prolonged distension resulting in neuromuscular junction alterations and autonomic motility modification, thrombosis and abomasal wall necrosis, and peritonitis.

Dilatation and displacement phase

In right-side dilatation and displacement there is usually a history of calving within the last few weeks with inappetence and decreased milk production; the feces are reduced in amount and are abnormal. The cow may have been treated for an uncertain disorder of the digestive tract within the last several days. Anorexia is usually complete when the abomasum is distended. There is usually depression, dehydration, no interest in feed, perhaps increased thirst and sometimes muscular weakness. Affected cows will commonly sip water continuously. The temperature is usually normal, the heart rate will vary from normal to 100/min, and the respirations are usually within the normal range. The mucous membranes are usually pale and dry. The reticulorumen is atonic and the rumen contents (the rumen pack) feel excessively doughy. The distended abomasum may be detectable as a tense viscus on palpation immediately behind and below the right costal arch. Ballottement of the middle third of the right lateral abdomen immediately behind the right costal arch along with simultaneous auscultation will reveal fluid-splashing sounds suggesting a fluid-filled viscus. In many cases the dilatation continues and after 3–4 days the abdomen is visibly distended on the right side and the abomasum can be palpated on rectal examination. It may completely fill the right lower quadrant of the abdomen and feel tense and filled with fluid and gas. Percussion and simultaneous auscultation over the right middle to upper third of the abdomen commonly elicits a characteristic high-pitched ping.

Volvulus phase

Abomasal volvulus usually develops several days after the onset of dilatation of the abomasum but it is usually not possible to distinguish precisely the stages of the disease. However, in abomasal volvulus, the clinical findings are usually much more severe than during the dilatation phase. The abdomen is visibly distended, depression and weakness are marked, dehydration is obvious, the heart rate is 100–120/min and respirations are increased. Recumbency with a grossly distended abdomen and grunting may occur and represents a poor prognosis. A rectal examination is very important at this stage. In the dilatation stage the partially distended abomasum may be palpable with the tips of the fingers in the right lower quadrant of the abdomen. It may not be palpable in large cows. In the volvulus phase, the distended tense viscus is usually palpable in the right abdomen anywhere from the upper to the lower quadrant.

The feces are usually scant, soft and dark in color. The soft feces must not be mistaken for diarrhea, as is commonly done by the owner of the animal. Cattle with abomasal volvulus usually become recumbent within 24 hours after the onset of the volvulus. Death usually occurs in 48–96 hours from shock and dehydration. Rupture of the abomasum may occur and cause sudden death.

Acute abomasal volvulus (adult cattle)

In acute abomasal volvulus in adult cattle there is a sudden onset of abdominal pain with kicking at the abdomen, depression of the back and crouching. The heart rate is usually increased to 100–120/min, the temperature is subnormal and there is peripheral circulatory failure. The animal feels cool and the mucous membranes are pale, dry and cool. The abdomen is grossly distended on the right side and auscultation and percussion reveal the tympanitic sounds of a gas-filled viscus. Fluid-splashing sounds are audible on percussion. Paracentesis of the distended abomasum will usually reveal large quantities of blood-tinged fluid with a pH of 2–4. The distended abomasum can usually be palpated on rectal examination but the torsion may have moved it in a cranial direction and not uncommonly these are not as readily palpable as when only dilated. The feces are scant, soft and dark in color and become blood-stained or melenic in the ensuing 48 hours if the cow lives long enough. In some cases there is profuse watery diarrhea.

Acute abomasal volvulus (calves)

In calves with acute abomasal volvulus, there is a sudden onset of anorexia, acute abdominal pain with kicking at the belly, depression of the back, bellowing and straining. The heart rate is usually 120–160/min, the abdomen is distended and tense, and auscultation and percussion over the right abdomen reveal distinct high-pitched pings. Palpation behind the right costal arch reveals a tense viscus that is painful on even moderate palpation.

Abomasal displacement and volvulus in beef cattle

Abdominal distension, anorexia and colic are common historical findings.³ Clinically, there is abdominal distension, tachycardia and colic, and a high-pitched ping is audible on percussion over the right side of the abdomen. A distended gas-filled viscus is commonly palpable on rectal examination. The course of the disease in beef cattle appears to be more protracted than in dairy cattle.

Postsurgical complication in abomasal volvulus

The most frequent complication encountered following surgical correction of RDA and abomasal volvulus resembles vagus indigestion, which occurs in 14–21% of cases.¹¹ The case fatality rate is high, with only 12–20% of affected animals returning to normal production. In affected cattle, there is ruminal distension, rumen hypermotility or atony, and abnormal feces (usually scant and dry).

Serum biochemistry

There are varying degrees of hemoconcentration (increased PCV and total serum proteins), metabolic alkalosis, hypochloremia and hypokalemia.

The severity of volvulus can be classified, and the prognosis evaluated, according to the amount of fluid in the abomasum and the concentration of serum chloride and the heart rate:

The serum chloride levels and heart rates before surgery are also valuable prognostic aids. Cows classified as group 3 or 4 or those having presurgical chloride levels equal to or below 79 mEq/L (79 mmol/L)or pulse rates of 100/min or more have a poor prognosis.

The base excess concentration of the extracellular fluid can be a useful prognostic and diagnostic indicator in cows with abomasal volvulus or right displacement of the abomasum. In one retrospective study cows with a base excess of ± 5.0 mEq/L (5.0 mmol/L) had abomasal torsion rather than displacement. The survival rate of cows with abomasal volvulus was 50% with a base excess ± 0.1 mEq/L (0.1 mmol/L), whereas it was 84% if the base excess was + 10.0 mEq/L (10.0 mmol/L).

A cross-sectional study of the serum electrolyte and mineral concentrations in dairy cows with abomasal displacement or volvulus at the time of on-farm diagnosis found lower serum calcium, phosphorus, magnesium, potassium and chloride levels and an increase in the anion gap compared to controls.¹²

Urinalysis

Paradoxic aciduria may also be present.

Hemogram

The total and differential leukocyte count may indicate a stress reaction in the early stages, and in the later stages of volvulus there may be leukopenia with a neutropenia and degenerative left shift due to ischemic necrosis of the abomasum and early peritonitis.

Abomasocentesis

Centesis of the distended abomasum will yield large quantities of fluid without protozoa and a pH of 2–4. The fluid may be serosanguineous when volvulus is present.

Medical therapy for mild cases

In mild cases of dilatation and minimal displacement with a mild systemic disturbance, empirical treatment with 500 mL of 25% calcium borogluconate intravenously may yield good results. The rationale for the calcium administration is to improve abomasal motility. Affected cows are also offered good-quality hay but no grain for 3–5 days and monitored daily. Surgical correction may not be necessary if the appetite and movements of the alimentary tract return to normal in a few days. The ping in the right abdomen may gradually become smaller in 2–3 days and eventually disappear.

In mild cases of dilatation with only slight hemoconcentration and metabolic alkalosis, early treatment with fluids and electrolytes intravenously and orally will often yield good results. The fluid therapy is essential to restore motility of the gastrointestinal tract, particularly the abomasum, which is distended with fluid and must begin evacuating its contents into the duodenum for absorption of the electrolytes to occur. The cow will usually not regain her appetite until the abomasal atony has been corrected.

A combination of hyoscine–butyl bromide and dipyrone and fasting has been recommended based on field experience.¹⁷ Recovery occurred in about 77% of affected cows within 48 hours.

Deflation of distended abomasum in calves

Gas can be removed from a grossly distended (bloated) abomasum of calves as an emergency measure prior to surgical correction¹⁸ by laparotomy. The calf is placed in dorsal recumbency and the abdomen is punctured with a 16-gauge 12 cm hypodermic needle at the highest point of the distended abdomen between the umbilicus and the xiphoid. After the distension is relieved and fluid therapy is begun, the need for a laparotomy can be assessed and performed if necessary.

Surgical correction

In the more advanced cases of dilatation, displacement and volvulus, a right flank laparotomy for drainage of the distended abomasum and correction of the volvulus if present is necessary. The surgical techniques in common use have been described. Intensive fluid therapy is usually necessary preoperatively and for several days postoperatively to correct the dehydration and metabolic alkalosis and to restore normal abomasal motility. Electromyographic studies of the postoperative abomasal and duodenal motility reveal loss of motility, some retrograde motility and loss of spike activity. Cholinergics have been used to help restore motility but are not reliable. Rumen transplants to restore rumen function and appetite will provide a more effective stimulus to restore gastrointestinal tract motility.

Postsurgical complications resembling a vagus-indigestion-like syndrome have been described¹¹ (see under Clinical findings, above).

Fluid and electrolyte therapy

The composition of the fluids and electrolyte solutions that are indicated in RDA and abomasal volvulus has been a subject of much investigation. There are varying degrees of dehydration, metabolic alkalosis, hypochloremia and hypokalemia. With the aid of a laboratory it is possible to monitor the serum biochemistry during administration of the fluids and electrolytes and to correct certain electrolyte deficits by adding (‘spiking’) the appropriate electrolytes to the fluids. Without a laboratory, the veterinarian has no choice but to use the solutions that are considered safe and judicious. Balanced electrolyte solutions containing sodium, chloride, potassium, calcium and a source of glucose will commonly suffice. A mixture of 2 L of isotonic saline (0.85%), 1 L of isotonic potassium chloride (1.1%) and 1 L of isotonic dextrose (5%) given at the rate of 4–6 L/h intravenously is also recommended and reliable. Experimentally induced hypochloremic, hypokalemic metabolic alkalosis in sheep has been corrected using 0.9 (300 mosmol/L), 3.6 (1200 mosmol/L) and 7.2% (2400 mosmol/L) of sodium chloride solutions given intravenously¹⁹ over a 2-hour period with the administered volume determined by the estimated total extracellular fluid chloride deficit. Significant difference was not found among treatments, with all solutions resulting in return of clinicopathologic variables to pre-experimental values within 12 hours. It is suggested that rapid intravenous replacement of chloride with small volumes of hypertonic saline solution is safe and effective for correction of experimentally induced hypochloremic, hypokalemic metabolic alkalosis in sheep. Clinical trials are needed to evaluate the efficacy of hypertonic saline solution (7.2%) for the correction of naturally occurring right-side displacement and volvulus of the abomasum.

Acidifying solutions

Isotonic solutions of potassium chloride and ammonium chloride (KCl 108 g, NH₄Cl 80 g, H₂O 20 L) will provide a source of potassium and chloride and will correct the alkalosis. This solution can be given intravenously at the rate 20 L over 4 hours to a 450 kg cow. This may be followed by the use of balanced electrolyte solutions at the rate of 100–150 mL/kg BW over a 24-hour period. However, acidifying solutions such as potassium chloride and ammonium chloride must be used carefully and ideally the serum biochemistry should be monitored every hour to insure that acidosis does not occur. The above solutions are considered safe when given as described. Normal saline is also effective and potassium solutions may not be necessary unless there is severe hypokalemia.

Oral therapy

Oral electrolyte therapy has been recommended, particularly in the postoperative period following surgical drainage of the distended abomasum. A mixture of sodium chloride (50–100 g), potassium chloride (50 g) and ammonium chloride (50–100 g) is given orally daily postoperatively along with the parenteral fluids as necessary. Treatment with potassium chloride (50 g/day) orally can be continued daily until the cow resumes her normal appetite.

Salvage or treatment?

The challenge in treatment is to be able to recognize the cases that will respond to treatment and those that will not and should therefore be slaughtered immediately for salvage. Those that have a severely impacted abomasum and are weak with a marked tachycardia (100–120/min) are poor treatment risks and should be slaughtered. Rational treatment would appear to consist of correcting the metabolic alkalosis, hypochloremia, hypokalemia and dehydration and attempting to move the impacted material with lubricants and cathartics, or surgically emptying the abomasum. Balanced electrolyte solutions are infused intravenously on a continuous basis for up to 72 hours at a rate of 100–150 mL/kg BW over a 24-hour period. Some cases will respond remarkably well to this fluid therapy and begin ruminating and passing feces in 48 hours. The use of acidifying isotonic solutions of mixtures of ammonium chloride and potassium chloride at a rate of 20 L per 24-hour period for a 450 kg animal as described under the treatment for RDA is also recommended.

Dioctyl sodium sulfosuccinate is administered into the rumen by stomach tube at a dose rate of 120–180 mL of a 25% solution for a 450 kg animal repeated daily for 3–5 days. It is mixed with 10 L of warm water and 10 L of mineral oil. The amount of mineral oil can be increased to 15 L/d after the third day and for a few days until recovery is apparent. A beneficial response cannot be expected in less than 24 hours and most cattle that do respond will show improvement by the end of the third day after treatment begins. Cholinergics such as neostigmine, physostigmine and carbamylcholine have been used but appear not to alter the outcome.

Surgery

Surgical correction consists of an abomasotomy through a right paramedian approach and removal of the contents of the abomasum. The results are often unsuccessful, probably because of abomasal atony that exists and that appears to worsen following surgery.⁷ An alternative approach may be to do a rumenotomy, empty the rumen and infuse dioctyl sodium sulfosuccinate directly into the abomasum through the reticulo-omasal orifice in an attempt to soften and promote the evacuation of the contents of the abomasum. The placement of a nasogastric tube into the omasal groove and into the abomasum through a rumenotomy procedure is described. Mineral oil can then be pumped into the abomasum at the rate of 2 L/day for several days. Recovery should occur within 5–7 days. A rumenotomy and emptying of the rumen is necessary in the case of severe straw impaction of the rumen.

The induction of parturition using 20 mg of dexamethasone intramuscularly may be indicated in affected cattle that are within 2 weeks of term and in which the response to a few days’ treatment has been unsuccessful. Parturition may assist recovery as a result of a reduction in intra-abdominal volume. In sand impaction, affected cattle should be moved off the sandy soil and fed good hay and a grass mixture containing molasses and minerals. Severely affected cattle should be treated with large daily doses of mineral oil – at least 15 L/d.

Gravel obstruction of the abomasum and duodenum can be corrected surgically by right flank laparotomy.⁶

Provision of nutrient requirements during cold weather

Prevention of the disease is possible by providing the necessary nutrient requirements for wintering pregnant beef cattle with added allowances for cold windy weather when energy needs for maintenance are increased. When low-quality roughage is to be used for wintering pregnant beef cattle, it should be analyzed for crude protein and digestible energy. Based on the analysis, grain is usually added to the ration to meet the energy and protein requirements.¹ Pregnant beef cows fed a diet of 94% barley straw for 83 days during the cold winter months may consume only 70% of their energy requirements.¹ Such straw-based diets must be supplemented with protein and energy.¹ During prolonged periods of cold weather, wintering pregnant beef cattle should be given additional amounts of feed to meet the increased feed requirement for maintenance, which has been estimated to be 30–40% greater during the colder months than during the warmer months. These increased requirements are due almost equally to the effects of reduced feed digestibility and the increased maintenance requirements.⁸

Nutrient requirements for beef cattle

The published nutrient requirements of beef cattle are guidelines for the nutrition of cattle under average conditions and higher nutrient levels than those indicated may be necessary to provide for maintenance requirements, particularly during periods of cold stress.⁹ Adequate amounts of fresh drinking water should be supplied at all times and the practice of forcing wintering cows to obtain their water requirements from eating snow while on low-quality roughage is extremely hazardous. The question of whether or not low-quality roughages should be chopped or ground for wintering pregnant beef cattle is controversial. The daily voluntary intake of low-quality roughage can be increased by chopping or grinding but neither processing method increases quality or digestibility; in fact digestibility is usually decreased. If increased consumption during cold weather exceeds physical capacity and the nutrient requirements are still not satisfied, impaction of the abomasum may occur. Thus during the coldest period of the winter low-quality roughages must be supplemented with concentrated sources of energy such as cereal grains.¹⁰

Avoid excessive fiber

Omasal and abomasal impaction due to the provision of excessive poor-quality roughage is preventable by supplementation with appropriate sources of energy and protein.

Primary ulceration

While many different causes of primary abomasal ulceration have been suggested the cause is unknown. Possible causes that have been considered but for which there is no reliable evidence of a cause and effect relationship include:

Secondary ulceration

Abomasal ulceration secondary to other diseases occurs. Examples include lymphoma of the abomasum and erosions of the abomasal mucosa in viral diseases such as bovine virus diarrhea, rinderpest and bovine malignant catarrh.

Primary abomasal ulcers

Primary abomasal ulcers occur in lactating dairy cows, mature bulls, hand-fed calves, veal calves and sucking beef calves. The epidemiological circumstances for each of these groups are presented here.

Secondary abomasal ulcers

Abomasal ulcers occur secondary to left- and right-side abomasal displacements, abomasal impaction or volvulus, lymphomatosis and vagus indigestion, or unrelated to other diseases.

Type 1: Nonperforating ulcer

There is incomplete penetration of the abomasal wall resulting in a minimal degree of intraluminal hemorrhage, focal abomasal thickening, or local serositis. Nonbleeding chronic ulcers commonly cause a chronic gastritis.

Type 2: Ulcer causing severe blood loss

There is penetration of the wall of a major abomasal vessel, usually in the submucosa, resulting in severe intraluminal hemorrhage and anemia. In acute ulceration with erosion of a blood vessel there is acute gastric hemorrhage with reflex spasm of the pylorus and accumulation of fluid in the abomasum, resulting in distension, metabolic alkalosis, hypochloremia, hypokalemia and hemorrhagic anemia. Usually within 24 hours there is release of some of the abomasal contents into the intestine, resulting in melena. The ruminal chloride level may increase in about 40% of cows with bleeding ulcers, which suggests abomasal reflux of acid into the rumen.¹⁵

Plasma gastrin activity increases significantly in cattle with bleeding abomasal ulcers.¹⁶

Type 3: Perforating ulcer with acute, local peritonitis

There is penetration of the full thickness of the abomasal wall, resulting in leakage of abomasal contents. Resulting peritonitis is localized to the region of the perforation by adhesion of the involved portion of abomasum to adjacent viscera, omentum or the peritoneal surface. Omental bursitis and empyema may develop, with the accumulation of a large quantity of exudate and necrotic debris in the omental cavity.

Abomasal–pleural fistula associated with cranial displacement of the abomasum and abomasal ulceration has been described in a 11-month-old bull.¹⁷

Type 4: Perforating ulcer with diffuse peritonitis

There is penetration of the full thickness of the abomasal wall, resulting in leakage of abomasal contents. Resulting peritonitis is not localized to the region of the perforation; thus digesta is spread throughout the peritoneal cavity.

In nursing beef calves, about 90% of perforated abomasal ulcers occur in the body of the abomasum, with a propensity for the greater curvature.¹²

In some calves the ulcers are subclinical and the factors that determine how large or how deep an ulcer will become are unknown. Based on abattoir studies it is evident that abomasal ulcers will heal by scar formation.

Perforation of ulcer

Perforation of an ulcer is usually followed by acute local peritonitis unless the abomasum is full and ruptures, when acute diffuse peritonitis and shock result in death in a few hours. With the development of local peritonitis, with or without omental adhesions, there is a chronic illness accompanied by a fluctuating fever, anorexia and intermittent diarrhea. This is common in dairy cows in the immediate postpartum period. Pain may be detectable on deep palpation of the abdomen and the distended, fluid-filled abomasum may be palpable behind the right costal arch. Periabomasal abscess formation from a perforated ulcer also occurs and is similar to local peritonitis.

In calves with a perforated abomasal ulcer, abdominal distension and abdominal pain are common.⁵

Perforation of an abomasal ulcer and the development of an abomasal–pleural fistula has been described in an 11-month-old bull.¹⁷ Pleuritis, pericarditis, unilateral pneumothorax and pulmonary abscessation were present.

Nursing beef calves

Calves with abomasal ulceration may have a distended gas-filled and fluid-filled abomasum that is palpable behind the right costal arch. Deep palpation may reveal abdominal pain associated with local peritonitis due to a perforated ulcer. Unless an abomasal ulcer has extended to the serosa it is unlikely that it can be detected by deep palpation. Many cases of abomasal ulcers, particularly in calves, cause no apparent illness.

Melena

The dark brown to black color of the feces is usually sufficient indication of gastric hemorrhage but tests for occult blood may be necessary. Results from experiments simulating abomasal hemorrhage indicate that the transit time for blood to move from the abomasum to the rectum ranges from 7–19 hours. The available fecal occult blood tests may not detect slow abomasal hemorrhage at any one sampling. This can be overcome by testing several fecal samples over a 2–4-day period and reading multiple smears per specimen. The sensitivity of the occult blood tests increases after the fecal samples have been stored at room temperature for 2 days. The predictive value of the occult blood test may be a more reliable diagnostic indicator of abomasal disease than abdominal pain or the presence of anemia. When perforation has occurred, with acute local peritonitis, there is neutrophilia with a regenerative left shift for a few days, after which time the total leukocyte and differential count may be normal.

Hemogram

In acute gastric hemorrhage there is acute hemorrhagic anemia.

Plasma gastrin activity

Plasma gastrin concentration increases significantly in cattle with bleeding abomasal ulcers. The mean plasma gastrin concentration in healthy cattle was 103.2 pg/mL; in cattle with bleeding abomasal ulcers the mean was 1213 pg/mL.¹⁶

Blood transfusions

Blood transfusions and fluid therapy may be necessary for acute hemorrhagic ulceration. The most reliable indication for a blood transfusion is the clinical state of the animal.¹⁵ Weakness, tachycardia and dyspnea are indications for a blood transfusion. A hematocrit below 12% warrants a transfusion. In the case of severe blood loss, a dose of 20 mL/kg BW may be necessary.

Coagulants

Parenteral coagulants are used but are of doubtful value.

Antacids

The goal of antacid treatment is to create an environment that is favorable to ulcer healing. This can be done by decreasing acid secretion (oral or parenteral administration of histamine type-2 receptor antagonists [H₂ antagonists] and proton pump inhibitors) or neutralizing secreted acid (oral administration of magnesium hydroxide and aluminum hyroxide).¹⁹ The elevation of the pH of the abomasal contents would abolish the proteolytic activity of pepsin and reduce the damaging effect of the acidity on the mucosa.

Histamine type-2 receptor antagonists

These compounds increase gastric pH through selective and competitive antagonism of histamine at the H₂-receptor on the basolateral membrane of parietal cells, thereby reducing acid secretion. H₂-receptor antagonists are characterized pharmacologically by their ability to inhibit gastric acid secretion and kinetically by their similarity in absorption, distribution and elimination.

Cimetidine and ranitidine are synthetic H₂ antagonists that inhibit basal as well as pentagastrin- and cholinergic-stimulated gastric acid secretion. Both have been used extensively to treat gastric ulcers in many species, including horses, dogs and humans. Oral and parenteral administration of cimetidine and ranitidine increases abomasal pH in sheep and cattle. High doses of cimetidine (20 mg/kg BW intravenously, or 50–100 mg/kg orally) increase abomasal pH in weaned lambs for more than 2 hours. Daily oral administration of cimetidine (10 mg/kg BW for 30 d) to veal calves may facilitate healing of abomasal ulcers. Because ranitidine is three to four times more potent than cimetidine, results of studies in ruminants suggest that oral administration of cimetidine (50–100 mg/kg) and ranitidine (10–50 mg/kg) should increase abomasal pH in milk-fed calves.

Experimentally, the oral administration of cimetidine (50 or 100 mg/kg every 8 h) and ranitidine (10 or 50 mg/kg every 8 h) to normal calves fed milk-replacer caused a significant dose-dependent increase in mean 24-hour abomasal luminal pH.¹⁹ However, the effects of these agents have not been examined in calves with known abomasal ulcers.

Alkalinizing agents

Compounds such as magnesium hydroxide and aluminum hydroxide are weak bases that have a direct effect on gastric acidity by neutralizing secreted acids. Aluminum hydroxide directly absorbs pepsin, thereby decreasing the proteolytic activity of pepsin in the stomach. Both compounds bind bile acids, thereby protecting against ulceration induced by bile reflux.

Experimentally, the oral administration of commercially available preparations containing aluminum hydroxide and magnesium hydroxide to calves being fed milk-replacer resulted in a short-term increase in abomasal luminal pH.²⁰ However, as with the synthetic H₂ antagonists, the efficacy of these weak bases to aid in the treatment of calves with abomasal ulcers has not been determined.

Magnesium oxide (500–800 g/450 kg BW weight daily for 2–4 d) has been successful empirically in some cases of abomasal ulceration in mature cattle. The injection or infusion of the antacid directly into the abomasum would probably be much more effective but injections of the abomasum through the abdominal wall are not completely reliable. An abomasal cannula placed through the abdominal wall may provide a means of ensuring the infusion of antacids directly into the abomasum.

Kaolin and pectin

Large doses of liquid mixtures of kaolin and pectin (2–3 L twice daily for a mature cow) to coat the ulcer and minimize further ulcerogenesis have been suggested, and used with limited success.

Surgical excision

Surgical excision of abomasal ulcers has been attempted, with some limited success. The presence of multiple ulcers may require the radical excision of a large portion of the abomasal mucosa and hemorrhage is usually considerable. A laparotomy and exploratory abomasotomy are required to determine the presence and location of the ulcer. The diagnostic criteria for deciding to do surgery have not been described, which makes it difficult to select cases with a favorable prognosis. Valuable animals with clinical evidence of chronic ulceration or those that relapse should be considered for surgical correction. Surgical correction of perforated abomasal ulcers in calves is possible and may be successful.

Ultrasonographic examination of the cecum

The cecum and proximal and spiral ansa of the colon can be visualized ultrasonographically using a 3.5 MHz linear transducer in mature cows.¹¹ The cecum can be visualized from the middle region of the abdominal wall. It extends caudocranially, varies in diameter from 5.2–18.0 cm and is situated immediately adjacent to the abdominal wall. The lateral wall of the cecum appears as a thick, echogenic, crescent-shaped line. It can be visualized as far cranially as the 12th intercostal space. Although its junction cannot be identified, the proximal ansa of the colon is recognizable on the basis of its anatomical position and its diameter, which is smaller than that of the cecum. The spiral ansa of the colon and the descending colon are situated dorsal to the cecum and can be identified by moving the transducer horizontally along the abdominal wall to the last rib. The spiral ansa of the colon is situated ventral to the descending colon, and its walls appear as thick echogenic lines. In a contracted state, the spiral colon has the appearance of a garland.

The ultrasonographic findings in cows with dilatation, torsion and retroflexion of the cecum have been described and compared with the findings on laparotomy.¹² The wall of the proximal ansa of the colon and of the dilated cecum closest to the abdominal wall is visible in all cows and appears as an echogenic semicircular line immediately adjacent to the peritoneum. The contents of the cecum and of the proximal and spiral ansa of the colon are not always visible because of gas. In some cows, the contents are hypoechogenic to echogenic in appearance. The dilated cecum can be imaged from the right abdominal wall at the level of the tuber coxae. The cecum can be imaged from the 12th, 11th and 10th intercostal spaces in some cows, and in other cows the cecum and proximal ansa of the colon are situated immediately adjacent to the right abdominal wall by the liver and/or gall bladder. The diameter of the cecum, measured at various sites, varies from 7.0–25.0 cm. Cecal dilatation can be diagnosed on the basis of the results of rectal examination in most cows but in all cows ultrasonographically. Dilatation and caudal displacement of the cecum and dilatation and craniodorsal retroflexion of the cecum can be visualized. In some cows, the direction of the retroflexed cecum cannot be determined.

Medical therapy

Mild cases of uncomplicated gaseous dilatation may be treated conservatively by feeding good-quality hay and recovery can occur in 2–4 days. The use of parasympathomimetic drugs such as neostigmine given subcutaneously every hour for 2–3 days has been recommended¹⁴ but controlled trials were not done. Xylazine is contraindicated for the abdominal pain associated with cecal dilatation because it reduces myoelectrical activity of the cecum and proximal loop of the ascending colon.¹⁵ Cisapride at 0.08 mg/kg BW shows some promise.¹⁵ Bethanechol at 0.07 mg/kg BW and neostigmine at 0.02 mg/kg BW increased the frequency of cecocolic spike activity, the duration of cecocolic spike activity and the number of cecocolic propagated spike sequences every 10 minutes.¹⁶ Bethanechol is considered superior to neostigmine because it induces more pronounced coordinated and aborally propagated spike activity.¹⁶

Surgical correction

For torsion and volvulus with the accumulation of ingesta and the possibility of necrosis of the cecum, the treatment of choice is surgical correction and the prognosis is usually good.^5,14 The recurrence rate of cecal dilatation and displacement ranges from 11–13% within the first week after surgery, whereas the long-term recurrence rate is about 25%.⁹ In severe cases with necrosis of the cecum, partial resection or total typhlectomy may be necessary. Extensive cecal necrosis requires total typhlectomy, which can be successful and lactating dairy cows may thrive and their milk production may be excellent in the current lactation.¹⁷

Intestinal accidents

Luminal blockages

Functional obstructions

Peritonitis and hypocalcemia are two common causes of functional obstruction in cattle.

Physical obstruction

Physical obstruction of the small intestines of cattle results in an absence of feces, distension of the intestine cranial to the obstruction with fluid and gas, acute abdominal pain and a hypochloremic, hypokalemic metabolic alkalosis and dehydration. The alkalosis results from small-intestinal and abomasal reflux into the rumen, with chloride and hydrogen ion sequestration in the abomasum. Ileus of the small intestines is one of the most common consequences of obstruction, resulting in distension and hypomotility cranial to the obstruction. The myoelectric activity patterns occurring during small intestinal obstruction are disorganized in the segment orad to the obstruction, characterized by rapidly migrating, prolonged, high-amplitude spikes that sometimes occur in clusters.¹⁴ This probably accounts for the intermittent abdominal pain.

Ileal impaction in Swiss Braunvieh cows in Switzerland is characterized clinically by anorexia, sudden drop in milk production and some evidence of colic, including shifting of weight from leg to leg and occasional kicking at the abdomen. The ventral aspect of abdomen was enlarged and pear-shaped, and a tense abdominal wall was present in some cows. A ping could be elicited over the right abdomen in most cows. The feces in the rectum may be reduced in amount or there may be none. On rectal palpation, dilated loops of both small and large intestine are usually palpable. On laparotomy, the impaction was situated at the ileocecal valve, and the ileum proximal to ileocecal junction was impacted with ingesta for up to 15 cm in length. The color of the serosa of the ileum and distal part of the jejunum was normal.

Volvulus and intussusception

Volvulus of the small intestine is a rotation of the entire small intestine, with or without the cecum and spiral colon, or of only the distal third of the jejunum and the proximal portion of the ileum about its mesenteric axis. The volvulus results in intestinal distension, vascular compromise, intestinal necrosis and eventually death unless surgically corrected.¹

Intussusception is the invagination of one portion of the intestine into the lumen of an adjacent segment of intestine. Jejunojejunal intussusception is the most common form in cattle, although isolated cases of ileocecal, ileocecocolic, cecocolic and colocolic intussusception also occur. In most cases the intussusception is single, but doubles do occur. There are reports of cattle surviving after sloughing of an intussusceptum but these are rare and death usually occurs 5–8 days after the onset of clinical findings if surgical correction is not carried out.

In general, the effects of intestinal accidents in cattle are not as remarkable as in the horse. Neither the abdominal pain nor the cardiovascular collapse is as severe in adult cattle as in horses with similar lesions. The exception is in calves, in which the effects are more marked and more rapid. Distension of the abdomen occurs much more frequently in calves than in adult cattle.¹⁵ Involvement of large segments of intestine as in torsion of the root of the mesentery may result in metabolic acidosis because of the rapid onset of shock. Ischemic necrosis of the intestinal wall results in various degrees of severity of peritonitis and abnormal peritoneal fluid containing erythrocytes, leukocytes and increased serum proteins.

Hemorrhage into the intestinal tract at the level of the obstruction results in the passage of small quantities of dark blood, which may be almost black if the obstruction is high up in the small intestinal tract. Distension of intestines with fluid and gas cranial to the obstruction may cause some mild distension of the abdomen but primarily if the large intestine is obstructed as in torsion of the coiled colon. The longer duration of the disease and the profound depression that develops suggest that endotoxemia, as in horses, may be the lethal agent, but the course is much slower than in the horse.

The effect of myoelectric activity of the cecum and proximal loop of the ascending colon on motility of this segment of intestine in experimental obstruction of the large intestine in cattle has been examined.¹⁴ Obstruction of the colon results in prestenotic hypermotility (colic motor complex) or prolonged propulsive peristaltic waves directed toward the obstruction site. This may represent an effort of the intestine to overcome the obstruction in order to re-establish the continuity of the passage of ingesta.

Patterns of myoelectric activity in the small and large intestine of cows orad and aborad to an obstruction site have been measured.¹⁶ Myoelectric activity in the ileum immediately orad to the occlusion was characterized by abolition of the migrating myoelectric complex and a constant pattern of strong bursts of long duration. Organized cyclic activity occurred in the large intestine despite complete disruption of the small-intestinal migrating myoelectric complexes, indicating the presence of mechanisms able to initiate and regulate coordinated myoelectric patterns in the large intestine independently of the small intestine.¹⁶

Duodenal ileus

In duodenal ileus caused by obstruction of the lumen by phytobezoars or compression of the duodenum by a liver abscess associated with traumatic reticuloperitonitis in mature cows, there is abomasal and duodenal reflux into the rumen resulting in metabolic alkalosis with hypochloremia and increased ruminal chloride.¹³ The obstruction caused by phytobezoars and liver abscesses may occur at almost any segment of the duodenum.¹³ The ileus results in a marked reduction in gastrointestinal motility and distension of the forestomach and abomasum due to the accumulation of excessive quantities of fluid, which results in dehydration. Abdominal pain is associated with the distension of the duodenum. The ileus results in marked decrease in movement of ingesta and the feces are markedly reduced in quantity. Duodenal obstruction caused by malposition of the gallbladder in a heifer has been described.¹⁷

Functional obstruction

In functional obstruction, there is paralytic ileus and an increase in the transit time of ingesta and feces. The feces are scant and do not contain blood.Sequestration of fluids in the intestines may result in varying degrees of dehydration and a metabolic alkalosis with hypochloremia and hypokalemia.

General findings

There is an initial attack of acute abdominal pain in which the animal kicks at its abdomen, treads uneasily with the hindlegs, depresses the back and may groan or bellow from pain. The pain occurs spasmodically and at short, regular intervals and may occasionally be accompanied by rolling. This stage of acute pain usually passes off within a few (8–12) hours and during this time there is anorexia and little or no feces are passed. The temperature and respiratory rates are relatively unaffected and the heart rate may be normal or elevated, depending on whether or not blood vessels are occluded. If there is infarction of a section of intestine there will be signs of endotoxic shock, including low blood pressure, very rapid heart rate, and muscle weakness and recumbency. These signs are absent in cases where the blood supply of the intestine is not compromised. For example, in cecal torsion the heart rate may be normal. In all cases, as the disease progresses and dehydration becomes serious the heart rate rises and may reach as high as 100/min just before death.

When the acute pain has subsided, the cow remains depressed, does not eat nor ruminate and passes no feces. The circulation, temperature and respirations are usually within normal limits and ruminal activity varies. In most cases there is complete ruminal stasis but, in exceptional cases, movements will continue, though they are usually greatly reduced. The rumen pack feels dry and firm on palpation through the abdominal wall.

Abdomen

The abdomen is slightly distended in all cases. Where there is distension of loops of intestine, as in ileus due to dietary error, there may be some distension of the right abdomen. Fluid-splashing sounds can be elicited by ballottement and simultaneous auscultation over the right abdomen in most cases and in a minority of cases over the left abdomen. With obstruction of the pylorus the splashing sounds can be elicited only on the right side, just behind the costal arch and approximately halfway down its length. Regurgitation of fluid ingesta through the nose is common.

Feces

The character of the feces is highly variable. In the early stages they will be normal but passed frequently and in small amounts. It may be necessary to carry out a rectal examination because the feces may not be passed from the anus. In some cases they will be hard, turd-like lumps, usually covered with mucus. Blood is often present, not as melena but as altered red blood, in the form of a thick red slurry, leaving dried flakes of it around the anus, especially in intussusception. The last fecal material is more mucoid and may consist entirely of a plug of mucus. In some cases of obstruction caused by fiber balls the fecal material is pasty, evil-smelling and yellow-gray in color.

Rectal examination

When there is intussusception or volvulus of the small intestine, the affected segment is usually felt in the lower right abdomen but the site varies with the nature of the obstruction. It is important to appreciate that not all intestinal obstructions can be palpated on rectal examination. It depends on the location of the affected segment of intestine: those in the anterior part of the abdomen are not palpable, those in the caudal part of the abdomen may be palpable. In addition, the affected segment may or may not be palpable, and the adjacent segments cranial to the obstruction may be palpable as distended segments of intestine.

In intussusception the affected segment may be palpable, usually as an oblong, sausage-shaped mass of firm consistency, but if a long length of intestine is involved a spiral develops and is palpable as such. In volvulus the intestinal loop may be small, soft and mobile. In many cases, it is possible to follow tightly stretched mesenteric bands coursing dorsoventrally in the middle part of the abdomen.¹ Palpation of distended loops of intestine may cause distress, especially in the early stages, and distension of a number of loops may increase intra-abdominal pressure to the point where entry of the hand beyond the pelvis is difficult. Within a few days, the rectum is empty except for tarry mucus and exudate and insertion of the arm usually causes pain and vigorous straining. Distension of loops of intestine is not nearly as obvious as in horses with intestinal obstruction and may not occur unless the colon or cecum is involved.

Serum biochemistry

Hypochloremia, hyponatremia, azotemia, and hyperglycemia are common.¹

Hemogram

Hemoconcentration, a mild left shift and an inverted neutrophil-to-lymphocyte ratio are common in cases of intussusception.⁴

Surgical correction

Surgical correction of physical obstructions of the intestine is the only method of treatment for animals in which survival and recovery are desirable. Right side paralumbar fossa celiotomy is the most common approach. The methods for surgical correction are presented in textbooks dealing with large-animal surgery. Survival rates for correction of volvulus of the entire small intestine have been 44%; 86% for volvulus of the distal jejunum and ileum.¹ Survival rates were much higher in dairy cattle (63%) than beef cattle (22%).¹ Survival rates for intussusception in cattle were about 50%.⁴ In ileal impaction in cattle, the postoperative outcome following laparotomy and massage of the contents of the impacted ileum into the cecum is excellent.¹¹

Fluid therapy

Fluid and electrolyte therapy given intravenously may be necessary preoperatively and always postoperatively (see Ch. 2). Multiple electrolyte solutions or normal saline are effective even though metabolic alkalosis with hypochloremia and hypokalemia may be present.

Antimicrobials

Antimicrobials pre- and postoperatively are recommended for the control of peritonitis, which is inevitable.

Nonsteroidal anti-inflammatory drugs

NSAIDs have also been used for their anti-inflammatory and antiendotoxic effects.

Hematology

The hemogram is variable and not diagnostic. Leukocytosis and mature neutrophilia with increased band neutrophils and increased fibrinogen concentrations are common but neutropenia with a left shift may also occur.⁷ The PCV and plasma protein concentrations are variable.

Serum biochemistry

Metabolic alkalosis with compensatory respiratory acidosis, hypokalemia and hypochloremia are common, which is consistent with abomasal outflow obstruction due to the obstruction caused by the clotted blood or ileus.⁷