The abomasum is the fourth compartment of the stomach in the cow. This compartment is most like the simple stomach of humans or the horse in that it is the only glandular portion of the stomach of cows secreting hydrochloric acid and enzymes. The abomasum must function normally for cows to maintain their health and production. Dysfunction of the abomasum, namely displacement, is one of the most common causes of a need for abdominal surgery in the bovine.
The abomasum typically resides in the right cranial abdomen. Certain conditions may predispose the abomasum to displace to an abnormal location. This displacement typically results in inhibition of normal digestion, stomach emptying and flow of ingesta. Three displacement syndromes are recognized in dairy cows including left displacement (LDA), right displacement (RDA) and volvulus (twisting) of the abomasum on the right side (RVA). The most common of these three syndromes is the LDA. In large population studies in dairy cows it has been shown to occur in about 4 percent of dairy cows and up to 15 percent in certain herds.
The vast majority of LDAs occur shortly after freshening with approximately 90 percent occurring within the first 6 weeks postpartum. For the dairy cow, freshening represents a major change in the cow’s system and production status. With the birth of the calf comes a dramatic change in abdominal space and orientation of abdominal contents, likely predisposing the cow to abomasal displacement. Additionally, the cow is typically transitioning to a diet much higher in concentrates. This sudden increase in concentrates can lead to abnormalities in abomasal outflow, excessive filling of the stomach and gas accumulation, all of which can cause displacement. It has also been shown that over 50 percent of cows with LDAs also have concurrent conditions that may play a role in upsetting normal abomasal function including hypocalcaemia, ketosis and mastitis or metritis.
Most producers notice that cows with left displacement of the abomasum have an abrupt decrease in milk production and drop in feed consumption. Often the best way to diagnose an LDA is with auscultation (with a stethoscope) and percussion of the cow over the area of suspected displacement. A classic ‘pinging’ noise can be heard due to the tightly gas-distended stomach. This is often described as being similar to the noise produced when flicking a basketball. RDAs can often be felt on rectal palpation. Certain characteristic changes can also be found on blood work to support the diagnosis. Cows with LDAs frequently have dark, pasty and scant feces as well.
Once the diagnosis of abomasal displacement has been made, the producer and veterinarian must together decide the best means of treatment. Medical therapy is often a necessary part of the overall treatment regimen, but alone, is generally not sufficient for correction. It is rare that a DA will revert to its normal location without some sort of surgical intervention. Rolling the cow has been used as a temporary means of correcting an LDA but about 75 percent of cows can be expected to displace again within a few days, and this procedure is not recommended except as a temporary means of correction. Two general categories of surgical correction are available. Minimally invasive techniques are popular due to their simplicity and the fact that they typically cost around half that of conventional open surgical approaches. The most common of minimally invasive techniques is the roll and toggle. The cow is rolled and the abomasum relocated to its normal position at which time toggle sutures are placed through the ventral abdominal wall to tack the stomach in place. The disadvantage to this procedure is that it is a blind tacking procedure and at times other abdominal structures are inadvertently punctured and the abomasum not successfully tacked. The most common conventional surgical technique is the right paralumbar omentopexy. An incision is made into the right side of the abdomen and the abomasum is manually relocated to its normal position. A portion of the stomach is tacked to the abdominal wall to prevent future displacement.
Many variables exist when comparing surgical options for correction of DAs and producers should consult with their farm veterinarian for case by case recommendations. With surgical correction upwards of 90 percent of cows are able to return to the herd and resume normal production levels.
Darren Loula, DVM, is a large animal veterinarian at Fair Grove Vet Service in Fair Grove, Mo.
