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The highest incidence of displaced abomasum (DA) is late winter and early spring (February and March). This phenomenon doesn't just occur in Minnesota, but throughout the U.S. and Scandinavian countries. Why? No one has been able to consistently explain why, but over the years some feeding and management practices have been identified as contributing factors to increasing the incidence of DAs.
A recent study in the United States looked at serum concentrations of nonesterified fatty acids (NEFA), beta hydroxybutyrate (BHBA), and calcium in relation to metabolic diseases. In this study, the average annual incidence of DA was 5.2 percent in Midwest study herds. Study herds in the Northeast had a similar incidence rate (5 percent) while those in the Southeast were slightly lower at 4.1 percent. In fewer herds, but higher cow numbers, the incidence rate in the West region was only 0.5 percent. Reason for the lower incidence rate in the West was not given, although other studies have reported lower incidences in the West also.
Over 80 percent of all DAs will be displacements to the left or left displaced abomasum (LDA) compared to the right (RDA). Most DAs occur within the first three weeks after calving. Mid to late lactation DAs are far fewer than early lactation DAs, but this year incidences in late lactation seem to have increased. In the past, a mid to late lactation DA was just as likely to be an RDA as LDA, but this year the LDA seems to be more prevalent.
While no specific nutrition or management factors have consistently been identified as causing a DA, there are some factors that are more commonly associated with a DA than others. Risk factors include feed intake depression, negative energy balance and increased NEFA's and/or BHBA, inadequate intake of effective fiber, high concentrate feeding both pre and post-calving, low serum calcium and empty feed bunks. The occurrence of other metabolic disorders such as milk fever, ketosis, retained placenta and metritis increase the risk of a DA in early lactation.

DAs in early lactation
Because most DAs occur within three weeks after calving, prevention starts in the dry period and needs to follow through the transition period (three weeks pre-calving to three week post-calving). There currently is interest in being able to predict cows at risk to DA and other metabolic diseases through blood metabolites pre and post-calving. Here are some of the findings from recent studies looking at blood metabolites and DAs.
• Body condition score (BCS). A recent study from Ontario found DAs tended to increase in cows with higher BCS around the time of calving. The risk or chance of having a DA was five percent in cows with a BCS of 3.75 of greater, 2.7 percent in cows with a BCS between 3.75 and 3.25 and only 1.3 percent in cows with a BCS of 3.25 or lower.
• Negative energy balance - post partum. In the same Ontario study, cows in the first week of lactation with a BHBA concentration greater than 1,000 micromoles (µmol) per liter (L) were 13.6 times more likely to develop a DA than cows with less than 1000 µmol/L. The recent US study on blood metabolites during the first week after calving indicated cows above 800 µmol/L of BHBA were at a greater risk to develop a DA than cows less than 800 µmol/L of BHBA. However, NEFA was found to be a better indicator of assessing risk for both DA and ketosis than BHBA in the US study herds. A cow with a pre-calving NEFA greater than 0.5 milliequivalents/L (mEq/L) and a post-calving NEFA greater than 1.0 mEq/L had a 2.7 times better chance of having a DA than cows with lower NEFA values per and post-calving.
• Hypocalcemia. In both the United States and Ontario study, cows with a low blood calcium (less than 9 mg/deciliter) were at much greater odds of developing a DA than cows that had higher blood calcium levels.
Application of this information into nutrition and management practices indicates we need to minimize negative energy balance in cows post-calving and maintain blood calcium levels. While feeding a low energy diet pre-calving has been a good nutrition program to minimize metabolic problems, too low of energy in the diet can create problems. Pre-calving diets containing 0.65 to 0.68 megacalories (Mcal) of net energy (NE) provide adequate, but not excessive, energy to the dry cow.
Some fine chopped straw in the pre-calving diet works well to provide effective fiber and keep energy levels low. If the straw or low quality hay used in pre-calving diets is not processed or only coarsely chopped, cows will separate it out and only consume the high energy corn silage and concentrates. Consumption of a high energy diet pre-calving is known to cause metabolic problems including DAs. In cows with an increased potential of getting a DA, fermented feeds, especially those with poor quality fermentation, can increase the likelihood of the DA as fermentation acids have been found to decrease abomasum muscle contractions. Haylages are generally not the best forage for pre-calving diets. Some haylage in the post-calving diet is okay, but avoid the wet, high butyric acid haylages. Poor quality, wet corn silages also can be a problem.
Some information suggests it is not how much feed a cow consumes in the close-up dry period, but how consistent her intake stays right up to the day of calving. Dry cows with high feed intakes that drop off sharply the week before calving are probably at a greater risk of developing a DA than cows with moderate, consistent intakes right up to the day of calving.
Fresh cow diets should be greater than 0.76 Mcal-NE with a good source and amount of effective fiber. Maximizing feed intake during this period increases rumen fill (decreasing the physical space available for the abomasum to move), decreases the mobilization of body fat for energy (NEFA and BHBA levels) and the length of time cows are in negative energy balance overall. Encourage feed intake during this time through adequate bunk space and a consistent supply of feed in the bunk. Fresh cows should never have an empty feed bunk.
To prevent hypocalcemia or milk fevers, I like to feed at least 1.5 percent calcium in the pre-calving ration and one percent calcium in the post-calving diet. Also, getting the DCAD in pre-calving diets to zero or lower helps stimulate release of calcium from bone during the high calcium demand for colostrum production and milk secretion immediately after calving. Try to keep sodium below 0.1 percent and potassium below 1.2 percent in pre-calving diets to achieve a low to negative DCAD.

Mid to late lactation DA
Determining the cause of DAs in mid to late lactation cows is very challenging. Cows usually have no predisposing condition to trigger the DA and their diets have been relatively stable over several weeks. However, some of the same factors and conditions which cause DAs in early lactation also apply to the mid and late lactation DAs. Things to watch for are an abrupt diet or management change that depresses feed intake. Moving cows between pens and overcrowding can trigger a DA in cows as they adjust to a new social order. Having an empty feed bunk for an hour or more limits feed intake, especially in timid cows. Slug feeding concentrates, over mixing a TMR, or adding excess grain into the TMR may cause a mild digestive upset which in turn can increase the risk of a DA as total and effective fiber in the diet decreases. Negative energy balance should not be a problem in a mid to late lactation cow unless she is restricted from feed or has a developing health condition that throws her off-feed.
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