The abomasum is capable of moving and can be displaced from the normal position in the lower right abdomen to the left side (left displacement of the abomasum or LDA) or upper right side of the abdomen (right displacement of the abomasum or RDA).
RDA is often followed by rotation of the abomasum on its mesenteric axis (abomasal volvulus or torsion).
LDA and RDA only partially obstruct the digestive tract - digestion, passage of digesta and blood supply to the organ are generally reduced but the condition may not be fatal.
Abomasal volvulus leads to complete obstruction and ischaemic necrosis of the abomasum, and is rapidly fatal without emergency surgery.
A combination of reduced rumen fill and reduced contractility (hypomotility) of the abomasum lead to increased risk of displacement. Contributing factors include stress, inadequate dietary fibre, indigestible content such as sand or phytobezoar, concurrent disease (such as hypocalcaemia, mastitis or metritis), sudden space in the abdomen following parturition, and possibly a genetic predisposition in large, deep-bodied dairy cows.
Abomasal displacement is known mostly as a disease of high producing, grain-fed adult dairy cattle, especially in early lactation. However, it may occur in non and early pregnant dairy cattle including unjoined heifers and bulls, and hence may be a cause of illthrift in individual dairy cattle in the live export process and occasionally, rapid death from abomasal volvulus. Increased risk could be expected in dairy cattle changing rapidly from a pasture or hay based diet on land to a pellet ration at sea. Displacement of the abomasum is rarely diagnosed in beef cattle.
With LDA and RDA, scanning of left flanks during pen inspection will detect hollowing and prominence of transverse processes reflecting reduced rumen fill and loss of condition from reduced appetite. An individual examination may additionally detect faeces that is pasty or fluid. Heart rate, temperature, respiration and demeanor are usually normal. Lifting of hind legs and looking at the flank are signs of abdominal pain that may be observed.
With an abomasal volvulus, the animal will likely be found recumbent, weak and depressed during a pen inspection. An individual examination will detect elevated heart rate, sunken eyes and cold clammy skin, all signs reflecting shock, dehydration and toxaemia. Deterioration will be rapid and death will occur within hours.
A displaced or torsed abomasum will be distended with gas and fluid enabling its detection with a stethoscope on the left or upper right side of the abdomen. Gas tinkling sounds and fluid sloshing can be heard if the area is pushed in and released a number of times with a fist, a process known as ballottement. A pinging sound will be heard when the area is flicked with a finger (percussed). The gas tinkling, sloshing and pinging should occur over a discrete area matching the size of the distended abomasum. These sounds must be differentiated from fluid and gas in the rumen or caecum.
With abomasal volvulus these sounds will be elicited from a very large area on the right side, the right flank will be grossly distended and faeces will be tar-like and mucoid.
Left and right displaced abomasa must be differentiated from other causes of illthrift such as mild ruminal acidosis, liver abscess, low grade pneumonia and vagus indigestion.
Cases of abomasal volvulus may look similar to other causes of gastrointestinal obstruction such as intestinal volvulus (mesenteric torsion), intussusception, dilatation or torsion of the caecum, acute diffuse peritonitis and intestinal foreign body such as a phytobezoar.
In animals dead from abomasal volvulus, necropsy findings include oedema and purple to black discolouration of the abomasum (from strangulated blood flow). The abomasum may be hugely distended with fluid and gas if it hasn't ruptured. A twist may be palpable at the root.
Immediate surgery is required for correction of RDA because the condition can result in severe disruption of gastrointestinal function, and may develop into abomasal volvulus which is a rapidly life-threatening condition. Affected animals will also require supportive care including fluid therapy (oral or intravenous) and possibly antibiotics. If skills and resources are unavailable, euthanasia should occur without delay.
LDA is generally not life threatening. If diagnosed at sea, surgery for LDA may be delayed until destination if facilities and expertise are available. It may be possible to correct LDA by using ropes to cast the animal on its right side and rolling it into dorsal recumbency for a few minutes and then into left lateral recumbency. Note that recurrence is common after rolling.
Increasing the amount of dietary fibre and ensuring the fibre is of adequate length is recommended to prevent abomasal displacement on dairy farms. On this basis, in the export of dairy cattle, the feeding of rough cut chaff or hay at 0.5% bodyweight daily as a supplement to pellets is recommended. Minimising periods of feed deprivation and providing pellets that are fibrous, low in starch and physically hard (causing the animal to chew, salivate and ruminate) are also recommended.